Laboratory Evaluation of EPA Methods 26 and 26A for Analysis of Halogens and Halides in Stack Gas

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1 Laboratory Evaluation of EPA Methods 26 and 26A for Analysis of Halogens and Halides in Stack Gas

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3 Laboratory Evaluation of EPA Methods 26 and 26A for Analysis of Halogens and Halides in Stack Gas Technical Update, December 2014 EPRI Project Managers N. Goodman C. Dene ELECTRIC POWER RESEARCH INSTITUTE 3420 Hillview Avenue, Palo Alto, California PO Box 10412, Palo Alto, California USA

4 DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES THIS DOCUMENT WAS PREPARED BY THE ORGANIZATION(S) NAMED BELOW AS AN ACCOUNT OF WORK SPONSORED OR COSPONSORED BY THE ELECTRIC POWER RESEARCH INSTITUTE, INC. (EPRI). NEITHER EPRI, ANY MEMBER OF EPRI, ANY COSPONSOR, THE ORGANIZATION(S) BELOW, NOR ANY PERSON ACTING ON BEHALF OF ANY OF THEM: (A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR IMPLIED, (I) WITH RESPECT TO THE USE OF ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT, INCLUDING MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, OR (II) THAT SUCH USE DOES NOT INFRINGE ON OR INTERFERE WITH PRIVATELY OWNED RIGHTS, INCLUDING ANY PARTY'S INTELLECTUAL PROPERTY, OR (III) THAT THIS DOCUMENT IS SUITABLE TO ANY PARTICULAR USER'S CIRCUMSTANCE; OR (B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY WHATSOEVER (INCLUDING ANY CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY EPRI REPRESENTATIVE HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES) RESULTING FROM YOUR SELECTION OR USE OF THIS DOCUMENT OR ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT. REFERENCE HEREIN TO ANY SPECIFIC COMMERCIAL PRODUCT, PROCESS, OR SERVICE BY ITS TRADE NAME, TRADEMARK, MANUFACTURER, OR OTHERWISE, DOES NOT NECESSARILY CONSTITUTE OR IMPLY ITS ENDORSEMENT, RECOMMENDATION, OR FAVORING BY EPRI. THE FOLLOWING ORGANIZATION, UNDER CONTRACT TO EPRI, PREPARED THIS REPORT: Clean Air Engineering This is an EPRI Technical Update report. A Technical Update report is intended as an informal report of continuing research, a meeting, or a topical study. It is not a final EPRI technical report. NOTE For further information about EPRI, call the EPRI Customer Assistance Center at or askepri@epri.com. Electric Power Research Institute, EPRI, and TOGETHER SHAPING THE FUTURE OF ELECTRICITY are registered service marks of the Electric Power Research Institute, Inc. Copyright 2014 Electric Power Research Institute, Inc. All rights reserved.

5 ACKNOWLEDGMENTS The following organization, under contract to the Electric Power Research Institute (EPRI), prepared this report: Clean Air Engineering 500 West Wood Street Palatine, IL Principal Investigators A. Milianti S. Evans This report describes research sponsored by EPRI. This publication is a corporate document that should be cited in the literature in the following manner: Laboratory Evaluation of EPA Methods 26 and 26A for Analysis of Halogens and Halides in Stack Gas. EPRI, Palo Alto, CA: iii

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7 ABSTRACT Acid gases are produced when fuels containing chlorine or other halogens are combusted. Hydrochloric acid (HCl) is produced during coal combustion and in lesser amounts from combustion of other fuels such as fuel oil or natural gas. Recent changes to U.S. environmental regulations will require many coal- and oil-fired power plants to monitor concentrations of hydrochloric acid in emitted stack gases on a regular basis. Two U.S. Environmental Protection Agency (EPA) methods are routinely used to measure hydrochloric acid and other halides in stationary source air emissions EPA Methods 26 and 26A. These methods can also be used to measure molecular halogens such as chlorine and bromine in emitted gases; however, past research raised questions about the ability of the EPA methods to correctly measure those chemicals. EPRI initiated a laboratory study to evaluate the performance of Methods 26 and 26A. Synthetic flue gases were generated in the laboratory with gas compositions similar to those expected from coal-fired power plant units complying with recently established U.S. emissions limits for existing electric generating units. This report presents the findings from a series of tests to determine the precision and accuracy of the two methods as well as the impact of changes to gas composition and sampling procedures on method performance. In addition to studying method performance, the project develops best-practice recommendations for accurate measurement of acid gases emitted by fossil-fuel-fired stationary sources. Keywords EPA Methods 26 and 26A Halogens Halides Emitted stack gas Hydrochloric acid Fuel combustion v

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9 EXECUTIVE SUMMARY Acid gases are produced when fuels containing halogens are combusted. Hydrochloric acid (HCl) is produced during coal combustion and in lesser amounts from combustion of other fuels such as fuel oil or natural gas. Because coal contains bromine, hydrobromic acid (HBr) may also be produced during combustion. Recent changes to U.S. environmental regulations will require many fossil-fuel-fired power plants to limit HCl emissions and to monitor concentrations in emitted stack gas on a regular basis. The concentration of HBr in stack gas is of interest because bromine may be added to the fuel or boiler in order to increase mercury oxidation and thereby improve the efficiency of mercury removal in pollution control devices. Power plant owners may therefore wish to measure levels of HBr for evaluating the efficacy of control measures. In addition to formation of halide compounds such as HCl, halogens could potentially be present in flue gas as molecular chlorine (Cl2) or bromine (Br2). Currently two U.S. Environmental Protection Agency (EPA) reference methods are used for sampling and analysis of halogens in stack gases: Method 26 and Method 26A. Method 26 a non-isokinetic, manual test method can only be used in dry stacks, meaning those that do not have suspended water droplets in the flue gas. Method 26A an isokinetic method can be used at any combustion source. Both methods collect halides by bubbling the flue gas through a series of impingers containing a sulfuric acid solution. Documentation for the two methods states that they can also be used to collect molecular halogens by adding an additional impinger containing sodium hydroxide. Ion chromatography is required to measure the halide concentration in the impinger liquids. The ability of these two methods to accurately and reliably measure HCl emissions from coalfired power plants at or below the emission limits mandated by the 2012 Mercury and Air Toxics Standards (MATS) rule is of interest to utility power plant owners/operators. EPRI initiated the laboratory study described in this report to evaluate the performance of Methods 26 and 26A when applied to synthetic flue gases in the laboratory. For the study, investigators used gas compositions similar to those expected of coal-fired power plant units complying with the MATS limit for existing units. The primary objective of this study was to determine the bias and precision of EPA Methods 26 and 26A (the study methods ) when used to measure HCl and HBr emissions from a typical coal-fired MATS-compliant electric utility stack. In addition to determining performance at a base set of conditions, the study also examined how the bias and precision of the study methods varied with respect to Sulfur dioxide (SO2) concentration in the flue gas Presence of free halogens namely chlorine (Cl2) and bromine (Br2) as well as free ammonia (NH3) and different types of fly ash in the flue gas Temperature at which ash filtration occurs Determination of whether the sample filter is pre-conditioned with flue gas Duration of sampling and total volume of gas collected during a sampling run vii

10 The study also examined the relative difference in bias and precision between the two study methods and the ability of Method 26 to differentiate between hydrogen halides (HCl and HBr) and free halogens (Cl2 and Br2). A parametric study was developed and executed to evaluate the above points. Synthetic flue gas representative of a coal-fired power plant was prepared and used to test method performance. Paired sampling trains run under identical conditions were used to determine method precision. Paired sampling trains differing in one or more respects (for example, test method and gas composition) were used to compare performance under various run conditions. Fourier transform infrared spectroscopy (FTIR) was used as the referee method for HCl and HBr analysis. The principal findings of the study were as follows: Method precision and bias: At the baseline conditions for this study, Method 26 appears to give more precise results than Method 26A, a relative standard deviation (RSD) of 11% vs. 22% at 0.5 ppmv HCl and 5% vs. 11% at 0.2 ppmv HCl. Method 26A exhibited no bias compared to the FTIR reference concentration at 0.5 ppmv or 0.2 ppmv HCl. Method 26 exhibited a 25% high bias compared to the reference concentration at 0.2 ppmv and no significant bias at 0.5 ppmv. Method performance in the presence of Cl2 and Br2: Method 26 (used as the base method for all subsequent test runs) was not able to speciate Cl2. All Cl2 was measured as HCl; thus HCl results were biased high. This result is consistent with previous studies reported in the literature, which showed that at SO2 to HCl ratios above ~8, all molecular chlorine converted to HCl. In this study, the ratios of SO2 to HCl were above 80 in all runs. Impact of bromine: Bromine (Br2) exhibited the same speciation characteristics as Cl2 all added bromine was measured as HBr. Br2 also appeared to have an effect on HCl concentration. When Cl2 was added, HCl results were biased high. When both Cl2 and Br2 were added, HCl results were still biased high but to a lesser degree. The study concludes that when bromine and/or HBr are present in the flue gas, even at low levels, it is difficult to predict speciation. Method performance in the presence of SO2, NH3, and HBr: It was not possible to determine the effect of sulfur dioxide (SO2) on bias and precision due to the overwhelming bias resulting from Cl2. The presence of ammonia (NH3) did not appear to significantly influence either the precision or the bias of the HCl measurement. HBr appeared to cause the HCl results to bias high by about 12%. Impinger solution chemistry: Increasing the normality of the acidic impinger solution did not improve speciation of Cl2 under the conditions of this study. Effect of fly ash: Application of several fly ashes of different coal ranks to the particulate filter ahead of the Method 26 sampling train did not appear to significantly affect the results in a 30-min run. However, with a 180-min run, minor differences in method precision and in bias (ranging from 8% negative bias to 10% positive bias) were observed at some filter temperatures and with some fly ash types. viii

11 Effect of filter temperature: In this study, the filter temperature was much higher than the estimated acid gas dew point. As a result, variations in the filter temperature had no impact on the method performance. If the flue gas temperature were closer to the acid dew point, it is possible that these results would have been different. However, experience with the sample delivery system indicates that temperatures closer to the acid dew point result in sample loss. Pre-conditioning: Extending the pre-conditioning time beyond the five minutes required in Method 26 had no effect on HCl precision or bias. The following best-practice recommendations were identified in this study for accurate measurement of acid gases emitted by fossil-fuel-fired stationary sources: The probe material should be made of borosilicate glass, not Teflon. The filter holder and support should be made of borosilicate glass or quartz. The Teflon filter holders specified in the method are confirmed to be incompatible with the temperature of the filter box in which the holder should be placed, both by experience and by the manufacturer. The temperature of the probe should always be well above the acid dew point of the flue gas. The method currently specifies a probe temperature in the range of 120 C 134 C (248 F 273 F) in order to prevent condensation. A typical source today can very well be the outlet of a wet scrubber, where the flue gas is relatively cool and condensing. In this case, the probe acts as a heater to vaporize the flue gas prior to its passing through the filter and into the impinger train. In this study, the simulated probe in the system was set to be constantly above 200 C (392 F). This ensured that the simulated flue gas temperature (which is decidedly different than the probe temperature) would never drop below the acid dew point. Further research on the subject of optimum probe temperature in coal combustion source testing would be beneficial. Potential sampling biases resulting from improper or inadequate sampling train cleaning practices were investigated. Specific guidelines were developed for cleaning the sampling train impingers prior to the start of test program and between test runs. The cleaning procedures are intended to mitigate contamination from previous tests, cleaning materials, or interactions of analytes with cleaning material residue. Strict guidelines on quality control of the ion chromatography analytical method are required for accurate results. Audit samples of a known concentration of HCl were sent to three different laboratories for ion chromatography (IC) analysis. The results varied from -20% to +7% of the expected concentration. The analytical aspect of these methods may require further scrutiny. If stricter IC quality assurance/quality control guidelines are not incorporated into the method, then the bias associated with the analytical results could outweigh all other uncertainties in the method. In Method 26, a majority of the total chloride content is recovered in the knockout impinger prior to the first acidic impinger. Therefore an enhanced rinsing procedure is necessary to ensure high chloride recovery. In Method 26A, when the method is applied to a wet stack, the knockout impinger contains condensed water, resulting in lower chloride recovery in that impinger. While it is important to adequately rinse every piece of glassware, it is particularly essential that procedures for recovery of the Method 26A knockout impinger closely follow procedures for the other impingers. ix

12 Additional research into the impacts of fly ash and ammonia on method performance would be useful, as only limited testing was conducted with these flue gas components. Bromine addition to facilitate Hg removal is a growing trend in the power generation industry; thus, the observed conversion between Br2 and HBr and its effect on both method performance and control technology performance should be studied further. A study of varying Br2 and HBr concentrations, along with varying temperatures and flow rates, could help characterize typical kinetic behaviors of bromine in a flue gas stream. x

13 SI CONVERSION FACTORS English (U.S.) units X Factor = SI units Area: 1 ft 2 X 9.29 x 10-2 = m 2 Flow Rate: 1 gal/min X 6.31 x 10-5 = m 3 /s 1 gal/min X 6.31 x 10-2 = L/s Length: 1 ft X = m 1 in X 2.54 = cm 1 yd X = m Mass: 1 lb X 454 = g 1 lb X = kg 1 gr X = g 1 ton X = tonne Volume: 1 ft 3 X 28.3 = L 1 ft 3 X = m 3 1 gal X = L 1 gal X x 10-3 = m 3 Temperature: F-32 X = C Energy: Btu X = Joules Btu/hr X = Watts xi

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15 ADI ASTM Br2 BTU CCV CEMS CFR CPMS CTM DI DSCF DSI EGU EPA EPRI ESP FGD FTIR fpm GFC/IR IAS IC ICR IGCC ISO kwh L lb/mmbtu lb/mwh LEE ACRONYMS AND ABBREVIATIONS Air Dimensions, Inc. American Society for Testing and Materials Bromine British Thermal Unit Continuing Calibration Verification Continuous Emissions Monitoring System Code of Federal Regulations Continuous Particulate Monitoring System Conditional Test Method (USEPA) Deionized (Water) Dry Standard Cubic Feet Dry Sorbent Injection Electrical Generating Unit U.S. Environmental Protection Agency Electric Power Research Institute Electrostatic Precipitator Flue Gas Desulfurization Fourier-Transform Infrared Spectroscopy Filterable Particulate Matter Gas Filter Correlation Infrared Spectroscopy Inspire Analytical Systems Ion Chromatography Information Collection Request Integrated Gasification Combined Cycle International Organization for Standardization Kilowatt Hours Liter Pounds per Million Btu (Heat Input Basis) Pounds per Megawatt Hour (Output Basis) Low Emitting EGU xiii

16 LOQ M Limit of Quantitation Molarity (moles per liter) M26 U.S. EPA Method 26 M26A MATS MDL MFC mg ml U.S. EPA Method 26A Mercury and Air Toxics Standards Method Detection Limit Mass Flow Controller Milligram Milliliter µm Micrometer MW N NELAC NIST NOx PM ppmdv PRB QA QC R 2 RATA ReMAP RSD SCR SF6 SW-846 SI VLE Megawatt Normality (Equivalent per liter) National Environmental Laboratory Accreditation Conference National Institute of Standards and Technology Nitrogen Oxides Particulate Matter Parts Per Million (dry volume) Powder River Basin Quality Assurance Quality Control Coefficient of Determination Relative Accuracy Test Audit Reference Method Accuracy and Precision Relative Standard Deviation Selective Catalytic Reduction Sulfur Hexafluoride Test Methods for Evaluating Solid Waste, Physical/Chemical Methods (USEPA) International System of Units Vapor-liquid Equilibrium xiv

17 CONTENTS 1 INTRODUCTION Summary of Past Research on Methods 26/26A Project Objectives STUDY DESIGN Flue Gas Simulation Description of Test Program Condition 1 Bias and Precision, Method Condition 2 Bias and Precision, Method 26A Condition 3 Bias and Precision, Inter-Method Comparison Condition 4 Br 2, Cl 2, Ash Interactions Condition 5 SO 2 and Cl 2 Effects on Halogen Speciation Condition 6 Train Pre-Conditioning Effects Condition 7 Run Duration Effects Condition 8 Ammonia and Filter Temperature Effects EXPERIMENTAL METHODOLOGY Synthetic Gas Stream and Sample Delivery System Description of the Principal System Components Gas Delivery System Hovacal Bromine Generation Permeation Devices Fly Ash Particulate Matter Used in Study Description of Test Methods EPA Reference Methods for Halogens and Halides Referee Method (FTIR) for Acid Halides Sampling Quality Control Measures Used in the Study Halide Analysis by Ion Chromatography RESULTS AND DISCUSSION Conditions 1 and 2 Bias and Precision, Inter-Method Comparison Condition 3 Bias and Precision, Inter-Method Comparison Condition 4 Br 2, Cl 2, Ash Interactions Effect of Cl 2 on M26A/M26 HCl Recovery Effect of HBr and Br 2 on M26A/M26 HCl Recovery Effect of Fly Ash on HCl Effect of Br 2 on HBr When Cl 2 is Not Present Effect of Br 2 on HBr When Cl 2 is Present Condition 5 SO 2 and Cl 2 Effects on Halogen Speciation Condition 6 Train Pre-Conditioning Effects Condition 7 Run Duration Effects xv

18 Condition 8 Ammonia and Filter Temperature Effects Discussion of Method Performance Comparison of Method Precision with Literature Values Impinger Chloride Collection Efficiency Ion Chromatography Method Evaluation SUMMARY AND CONCLUSIONS Method Precision and Bias Speciation of HCl and Chlorine Speciation of HBr and Bromine Method Performance in the Presence of SO 2, Ammonia, and HBr Impinger Solution Chemistry Effect of Fly Ash Effect of Filter Temperature Effect of Sampling Train Preconditioning Evaluation of Best Practices for Methods 26 and 26A Recommendations for Future Research REFERENCES A LITERATURE REVIEW... A-1 B DELIVERY SYSTEM AND FTIR TEST PROTOCOL... B-1 C FLY ASH SIZING AND SEEDING... C-1 Sample Preparation... C-1 Particle Density... C-1 Size Distribution Analysis... C-1 D QA/QC GRAPHS AND FIGURES... D-1 E EVALUATION OF EQUIPMENT CLEANING AND FIELD BLANK PROCEDURES... E-1 F DATA TABLES... F-1 Condition 1 Method 26 Baseline Tests... F-2 Condition 2 Method 26A Baseline Tests... F-4 Condition 3 Methods Bias, Precision and Comparison... F-6 Condition 4 Hydrogen Bromide, Bromine and Chlorine... F-8 Condition 5 Chlorine and Variable Sulfur Dioxide...F - 10 Condition 6 Preconditioning Times... F-13 Condition 7 Extended Run Times...F - 15 Condition 8 Ammonia and High Filter Box Temperatures...F - 17 xvi

19 LIST OF FIGURES Figure 3-1 Flue Gas Simulator Diagram Figure 3-2 Flue Gas Simulator Figure 3-3 Glass Gas Mixing Manifold (With Heat Wrap Removed) Figure 3-4 HCl Gas Cylinder Concentration as a Function of Time Figure 3-5 Diffusion Vial for Bromine Permeation Figure 3-6 EPA Method 26A Sampling System Figure 3-7 EPA Method 26 Sampling System Figure 3-8 Filter Box Drawing for Method Figure 3-9 Port Comparisons (HCl) Figure 3-10 Example IC Calibration Curve Figure 4-1 Comparison of Results from Conditions 1, 2, and Figure 4-2 Condition 3 Results Figure 4-3 Effect of Cl2 on Method 26A/26 HCl Measurement Figure 4-4 Effect of Br 2 on Method 26A/26 HBr Measurement Figure 4-5 Effect of Varying SO 2 on HCl Figure 4-6 Effect of Preconditioning Figure 4-7 Effect of Extended Run Time Figure 4-8 Method 26 Ammonia and Elevated Filter Box Temperature Runs Figure 4-9 Duplicate Train %RSD Compared to Literature Values Figure 4-10 Method 26 Impinger Collection Efficiency Low HCl Concentrations (0-5 ppm) 4-16 Figure 4-11 Method 26A Impinger Collection Efficiency Low HCl Concentrations (0-5 ppm) Figure 4-12 Comparison of Analytical Laboratory IC Audit Results Figure A-1 Effect of SO 2 /HCl Ratio on Cl 2 Speciation (from Sun et al., 2000)... A-5 Figure A-2 ReMAP %RSD Correlation with HCl Concentration... A-6 Figure C-1 Flowchart for Seeding Fly Ash on the Filter... C-2 Figure D-1 Mass Flow Controller Calibration Curve... D-1 Figure D-2 Water Concentration Port Confirmations... D-2 Figure D-3 Sampling System Confirmation with SF6, Performed on Different Days... D-2 Figure D-4 A Cracked Filter Holder Made of Teflon and Tefzel... D-3 Figure D-5 An Attempt to Leak Check an Individual Filter Holder... D-3 Figure E-1 HCl Concentrations in Equipment Blank Rinses... E-1 xvii

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21 LIST OF TABLES Table 1-1 Summary of MATS Rule HCl Emission Limits for New and Existing Units Table 2-1 Summary of Test Conditions Table 2-2 Design Base Composition of Synthetic Flue Gas Table 2-3 Condition 1 Test Run Matrix Table 2-4 Condition 2 Test Run Matrix Table 2-5 Condition 3 Test Run Matrix Table 2-6 Condition 4 Design Matrix Table 2-7 Condition 4 Test Run Matrix Table 2-8 Condition 5 Test Run Matrix Table 2-9 Condition 6 Test Run Matrix Table 2-10 Condition 7 Test Run Matrix Table 2-11 Condition 8 Test Run Matrix Table 3-1 Fly Ash Types and Particle Sizes Table 4-1 Condition 3: Test Conditions and Results Table 4-2 Condition 4: Test Conditions and Results (Zero Cl 2 Runs) Table 4-3 Condition 4: Test Conditions and Results (2 ppmv Cl 2 Runs) Table 4-4 Condition 5: Test Conditions and Results Table 4-5 Condition 6: Test Conditions and Results Table 4-6 Condition 7: Test Conditions and Results Table 4-7 Condition 8: Test Conditions and Results Table A-1 Literature Reviewed for this Study... A-1 Table F-1 Condition 1 Run Data... F-2 Table F-2 Condition 1 Data Calculations... F-3 Table F-3 Condition 2 Run Data... F-4 Table F-4 Condition 2 Data Calculations... F-5 Table F-5 Condition 3 Run Data... F-6 Table F-6 Condition 3 Data Calculations... F-7 Table F-7 Condition 4 Run Data... F-8 Table F-8 Condition 4 Data Calculations... F-9 Table F-9 Condition 5 Run Data...F - 10 Table F-10 Condition 5 Data Calculations...F - 11 Table F-11 Condition 6 Run Data...F - 13 Table F-12 Condition 6 Data Calculations...F - 14 Table F-13 Condition 7 Run Data...F - 15 Table F-14 Condition 7 Data Calculations...F - 16 Table F-15 Condition 8 Run Data...F - 17 Table F-16 Condition 8 Data Calculations...F - 18 xix

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23 LIST OF TABLES Table 1-1 Summary of MATS Rule HCl Emission Limits for New and Existing Units Table 2-1 Summary of Test Conditions Table 2-2 Design Base Composition of Synthetic Flue Gas Table 2-3 Condition 1 Test Run Matrix Table 2-4 Condition 2 Test Run Matrix Table 2-5 Condition 3 Test Run Matrix Table 2-6 Condition 4 Design Matrix Table 2-7 Condition 4 Test Run Matrix Table 2-8 Condition 5 Test Run Matrix Table 2-9 Condition 6 Test Run Matrix Table 2-10 Condition 7 Test Run Matrix Table 2-11 Condition 8 Test Run Matrix Table 3-1 Fly Ash Types and Particle Sizes Table 4-1 Condition 3: Test Conditions and Results Table 4-2 Condition 4: Test Conditions and Results (Zero Cl 2 Runs) Table 4-3 Condition 4: Test Conditions and Results (2 ppmv Cl 2 Runs) Table 4-4 Condition 5: Test Conditions and Results Table 4-5 Condition 6: Test Conditions and Results Table 4-6 Condition 7: Test Conditions and Results Table 4-7 Condition 8: Test Conditions and Results Table A-1 Literature Reviewed for this Study... A-1 Table F-1 Condition 1 Run Data... F-2 Table F-2 Condition 1 Data Calculations... F-3 Table F-3 Condition 2 Run Data... F-4 Table F-4 Condition 2 Data Calculations... F-5 Table F-5 Condition 3 Run Data... F-6 Table F-6 Condition 3 Data Calculations... F-7 Table F-7 Condition 4 Run Data... F-8 Table F-8 Condition 4 Data Calculations... F-9 Table F-9 Condition 5 Run Data... F-10 Table F-10 Condition 5 Data Calculations... F-11 Table F-11 Condition 6 Run Data... F-13 Table F-12 Condition 6 Data Calculations... F-14 Table F-13 Condition 7 Run Data... F-15 Table F-14 Condition 7 Data Calculations... F-16 Table F-15 Condition 8 Run Data... F-17 Table F-16 Condition 8 Data Calculations... F-18 xxi

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25 1 INTRODUCTION Acid gases are produced when fuels containing halogens are combusted. Hydrochloric acid (HCl) is produced in coal combustion, and in lesser amounts from combustion of other fuels such as fuel oil or natural gas. Coal also contains bromine; thus, hydrobromic acid (HBr) may also be produced during combustion. Recent changes to United States (U.S.) environmental regulations will require many fossil-fuel fired power plants to limit emissions of HCl and to monitor concentrations in emitted stack gas on a regular basis. The concentration of HBr in stack gas is of interest because bromine may be added to the fuel or boiler to increase oxidation of mercury, to improve the efficiency of mercury removal in pollution control devices. Power plant owners may therefore wish to measure levels of HBr, to evaluate the efficacy of control measures. In addition to forming halide compounds such as HCl, halogens could potentially be present in flue gas as molecular chlorine (Cl2) or bromine (Br2). The adequacy of test methods to measure molecular halogen species has not been determined. The U.S. Environmental Protection Agency (EPA) has promulgated two reference methods for sampling and analysis of halogens in stack gases: Method 26 and Method 26A. Method 26 is a non-isokinetic method that can only be used in dry stacks, i.e., those that do not have suspended water droplets in the flue gas. Method 26A is an isokinetic method that can be used at any combustion source. Both methods collect halides by bubbling the flue gas through a series of impingers containing a sulfuric acid solution. The two methods state that they can also be used to collect molecular halogens by adding an additional impinger containing sodium hydroxide. Ion chromatography is used to measure the halide concentration in the impinger liquids. Over the past 30 years, there have been a number of studies conducted to evaluate the performance of EPA Methods 26 and 26A for measuring halogens and halogenated acids. The earliest studies guided the development of the methods as they are currently formulated. However, some questions were raised in those early studies as to limitations and inherent biases to the methods, especially at low concentrations (usually below 5 parts per million dry volume HCl). The limitations of the methods are of concern, as the U.S. Mercury and Air Toxics Standards (MATS) limit for existing coal-fired electrical generating units is approximately 1.9 parts per million dry volume (ppmdv); the limit for new or reconstructed units is approximately 0.9 ppmdv. Most previous research has focused on HCl; a few studies have also looked at chlorine (Cl2), hydrogen bromide (HBr), and bromine (Br2). Flue gas components that have been identified as potentially causing bias in the methods include particulate matter (PM), ammonia, SO2, Cl2, and Br2. Condensed water droplets, materials of construction in the sampling apparatus, pre-conditioning, and operating practices are also potential sources of inaccuracy. To verify that the methods are measuring the target species accurately, all possible interferences from the source, through the sampling apparatus, and all the way to the final sample analysis need to be identified, quantified, and mitigated to the fullest extent possible. 1-1

26 EPRI initiated the study described in this report to evaluate the performance of Methods 26 and 26A in synthetic flue gases in the laboratory, using gas compositions similar to those expected of coal-fired power plant units complying with the MATS limit for existing units. In addition to studying likely interferences, the project develops best-practice recommendations for the methods. The recently promulgated MATS Rule regulates power generating units at both major and area sources. The mercury and air toxics standards will affect Electric Generating Units (EGUs) that burn coal or oil for the purpose of generating electricity for sale and distribution through the national electric grid to the public. The final rule identifies four subcategories of coal-fired EGUs, five subcategories of oil-fired EGUs, and a subcategory for units that combust gasified coal or solid oil (integrated gasification combined cycle (IGCC) units) based on the design, utilization, and/or location of the various types of boilers at different power plants. The rule includes emission standards for each subcategory. The MATS Rule HCl emission limits are summarized in Table 1-1. Table 1-1 Summary of MATS Rule HCl Emission Limits for New and Existing Units Subcategory HCl (lb/mwh) HCl (lb/mmbtu) HCl 3% O2) Existing Not Low Rank Virgin Coal d 1.9 a Existing Low Rank Virgin Coal d 1.8 b Existing IGCC e 4.6 a Existing liquid oil c Existing - solid oil-derived d 4.9 c New Not Low Rank Virgin Coal d 0.9 a New Low Rank Virgin Coal d 0.9 b New IGCC e 0.20 a New solid oil-derived d 0.04 c New liquid oil continental d 0.04 c New liquid oil (non-continental) c Notes: a Converted to concentration using F-factor of 9,780 dscf/10 6 (bituminous coal). b Converted to concentration using F-factor of 9,860 dscf/10 6 (lignite coal). c Converted to concentration using F-factor of 9,190 dscf/10 6 (oil). d Converted to lb/mmbtu using heat rate of 10,000 Btu/kWh e Converted to lb/mmbtu using heat rate of 8,425 Btu/kWh lb/mwh = pounds pollutant per megawatt-electric output (gross). lb/mmbtu = pounds pollutant per million British thermal unit fuel input. 1-2

27 HCl emissions from coal-fired utility boilers will vary depending on coal rank (which determines the alkalinity of the fly ash) and the chlorine content of the fuel. Flue gas HCl levels ranging from single digits to 100 ppmv are typically expected. The addition of wet scrubbers or alkaline sorbent injection systems can reduce these levels to below the MATS limits listed in Table 1-1. The MATS Rule (40 CFR Parts 60 and 63, February 12, 2012) requires owners of coal and oil (both solid and liquid) fired boilers that are used to generate electricity to conduct regular monitoring to verify compliance with the HCl limit. Owners of coal units equipped with wet or dry flue gas desulfurization (FGD) systems may continuously monitor SO2 as a surrogate for HCl. The use of SO2 as a surrogate places additional emissions restrictions on the unit. The MATS Rule also has exemptions from this monitoring requirement for units that meet the low emitting EGU (LEE) requirement listed in the rule. If neither of the above listed exemptions is met, then the unit must either install an HCl CEMS or perform quarterly stack testing for HCl to comply with the standards (ICAC 2013). For quarterly testing at units with dry stacks, the Rule allows the use of Method 26A or a Fourier Transform Infrared Spectroscopy (FTIR) method: EPA Method 320 or American Society for Testing and Materials (ASTM) D (Reapproved 2010). For units with wet stacks, only Method 26A can be used. In the past, power companies have generally used Method 26 or 26A due to the higher cost and higher level of expertise required for FTIR testing. The EPA estimates that there are approximately 1,400 units affected by the MATS rule, approximately 1,100 existing coal-fired units and 300 oil-fired units at about 600 power plants (EPA, 2011). The MATS compliance deadline for existing units is April 16, 2015; however, facility owners may request a one-year extension. The primary drivers for speciation are related to operations and/or engineering considerations for pollution control equipment. Acid gas and mercury control technologies require accurate knowledge of flue gas concentrations of HCl and Cl2. Accurate knowledge of flue gas HCl concentrations are necessary to design and operate dry sorbent injection (DSI) control technologies. HCl concentrations provide an important input parameter which determines and/or controls sorbent injection rates. HCl and Cl2 are also oxidizing agents that play a key role in mercury control processes via the oxidation of elemental mercury (Hg 0 ) to oxidized mercury. The oxidized form of mercury (e.g., HgCl2) is water soluble, and is much more readily removed in wet scrubbers and/or by adsorption on unburned carbon in fly ash captured by ESPs or baghouses. Summary of Past Research on Methods 26/26A Laboratory and field studies have been conducted over the past 30 years, documenting the precision, bias and general performance characteristics of Methods 26 and 26A. A literature search was conducted to identify and review recent and historical research. Detailed reviews of each of the principle studies are provided in Appendix A; summaries of the main findings are provided here. The earliest work with a major influence on the development of the EPA methods was reported by Cheney and Fortune (1979). This study investigated the collection of HCl in NaOH solutions of varying concentration using four different analytical titration procedures. A mercuric nitrate titration after collection in 0.1M NaOH was ultimately recommended. Cheney and Fortune (1984) followed their earlier work with a second study which investigated reaction and sorption 1-3

28 losses of HCl during sampling. Use of disc filters made of quartz was recommended to minimize losses to the filter material, and relatively high flow rates were recommended to minimize interactions with collected alkaline particulate material. Stern, et al. (1984) reported on the development and laboratory evaluation of a sampling and analysis system for collection and speciation of halogens and halogen acids. The sampling equipment was essentially the midget impingers currently used in Method 26. Ion chromatography was chosen for the analysis because of its high selectivity, low detection limit, and multiple ion capability. Collection and quantitation of HCl (130 ppmv) and Cl2 (19 ppmv) were successful in the presence of 250 ppmv SO2 and 600 ppmv NOx. It was demonstrated that dilute H2SO4 was a superior collection medium for the halogen acids as compared to water. When water was used, some retention of the halogen compounds in the acidic impingers resulted, presumably from redox reactions. The presence of the dilute acid suppressed these types of reactions and resulted in excellent speciation. Poor recovery was obtained with HBr (10 ppmv). The authors speculated that the poor performance for HBr was due to sorption or line losses. The fact that virtually all of the collected HBr was found in the first impinger is consistent with that hypothesis, and would rule out poor impinger collection as the problem. DeWees et al. (1989) and Steinsberger et al. (1989) constitute the principal evaluation base for the measurement of HCl and Cl2 using Methods 26 and 26A. Both laboratory evaluation and field testing were carried out. During the laboratory phase of the project, a ruggedness test was conducted to evaluate the effect of six variables on HCl results. Within the ranges tested, the method was shown to be insensitive to low reagent volume, increased first impinger ph, longer sampling times, elevated impinger temperatures, higher sampling rate, and elevated Cl2 levels up to 50 ppmv. Earlier experiments showed that only a 3.4% positive bias of the HCl result was caused by 197 ppmv of Cl2 in a gas stream containing 221 ppmv of HCl. The methodology was field tested using dynamic spiking of gaseous HCl standards and a test protocol that included dual sample trains. Key conclusions of the field test were: The precision of the method for HCl ranged from ± ppmv at flue gas HCl levels of 3.9 to 15.3 ppmv. The bias of the method was <8% for HCl cylinder gases of 9.7 and 34.3 ppmv. The manual method agreed within 7% with a continuous HCl monitor based on gas filter correlation infrared spectroscopy (GFC/IR). Flue gas CO2 absorption by alkaline impinger reagents was insignificant with either the midget impinger train or the Method 5 type train. The midget impinger train and the Method 5 type train (now Method 26A) showed similar results at a flue gas HCl concentration of 21.2 ppmv. However, at lower concentrations the Method 5 type train produced results with a negative bias of about 50% compared to the midget impinger train and the continuous monitor, both of which averaged 4.8 ppmv. Steger et al. (1994) looked at three potential sources of error in Proposed Method 0050 (which became SW-846 Method 0050, EPA 2007a) and Method 26A. They investigated possible negative bias related to purging of the optional cyclone catch, negative bias at low ppmv concentrations previously reported, and potential positive bias due to the presence of ammonium chloride (NH4Cl). Key findings were: 1-4

29 A negative bias at low HCl concentrations was confirmed. The bias was variable and seemed to correlate better with gas stream moisture content than with HCl concentration. Higher probe and filter temperatures improved accuracy. NH4Cl caused a positive bias under all test conditions by penetration of the filter as a vapor and subsequent interference in the analysis. Lower probe and filter temperatures were beneficial for this interference, but detrimental from a sorption standpoint, as described above. When high moisture levels force the use of the cyclone, a post-sampling cyclone purge is essential to drive any trapped HCl into the impinger catch. However, when the volume of aqueous solution in the cyclone exceeded 25 ml, the 45-minute purge required in Method 0050/26A was not sufficient to complete the task. Sun, et al. (2000) conducted bench-scale experiments using simulated combustion flue gas designed to validate the ability of Method 26A to speciate low levels of Cl2 accurately. The effect of various flue gas components was discussed. The results indicate that SO2 is the only component in coal combustion flue gas that has an appreciable effect on Cl2 distribution in Method 26A impingers, and that Method 26A cannot accurately speciate HCl and Cl2 in coal combustion flue gas without modification. This was reported to be related to the presence of SO2, which reacts with and traps chlorine in the acidic impinger, which results in the chlorine being reported as HCl. However, it was found that if the SO2/HCl ratio in the flue gas is sufficiently low (i.e., < 1), then speciation of HCl and chlorine is feasible; however, a coal combustion source is not likely to have a ratio low enough for speciation. Before simulation of an entire flue gas matrix, testing was done to prove that the method can speciate chlorine when only chlorine (balance nitrogen) is present. Subsequent testing introduced different species of the flue gas. Lanier and Hendrix (2001) conducted a study to estimate the standard deviation of selected EPA Measurement Reference Methods as a function of average stack concentration. His program was called Reference Method Accuracy and Precision (ReMAP). The ReMAP program performed a careful assessment of the statistical analysis procedures required to estimate the precision of Manual Reference Methods using multi-train sampling data. To assure the quality of data used in the statistical analysis, an extensive effort was expended in gathering data from the original sources and carefully evaluating them to assure that consistent data reduction procedures were used. Regression analysis was performed on multiple data sets from multiple sources. Results from the regression analysis represent the best estimate available on the standard deviation of the measurement method at any given concentration. Based on the regression line and the confidence intervals, the various precision metrics were determined for each method as a function of concentration. The ReMAP analysis of Method 26 data showed that the relative standard deviation (RSD) was typically in the range of 5% to 10% at HCl concentrations in the range of 1.5 to 3.5 ppmdv, with increasing RSD as the method was applied to stacks with very low concentrations. The lowest HCl concentration tested was 0.2 ppmdv. At this low concentration, the RSD varied between 7% and 27%, and the average RSD was approximately 17%. 1-5

30 EPRI (2010) evaluated the procedures and results of Method 26 and 26A measurements of hydrochloric acid (HCl), hydrofluoric acid (HF) and hydrogen cyanide (HCN) tests of coal-and oil-fired EGUs conducted in response to EPA s Information Collection Request (ICR) for the Electric Utility Steam Generating Units MACT rulemaking (EPA, 2009). Most of the field testers used Method 26A. The most significant quality issues affecting these measurements were noted as: (1) very high detection limits for HCl and HF in some samples and (2) inability of testers to maintain a high ph in the alkaline impingers. The high detection limits were due to matrix interferences in ion chromatography associated with EPA s requirement (later reversed) that testers collect HCN using the same sampling train as the halogens, i.e., combine Conditional Test Method CTM-33 with Methods 26/26A. Because the ICR procedures do not reflect normal sampling practice, the ICR data are of limited use for evaluating method performance for acid halides. Subsequent to issuance of the ICR, EPA added a requirement to report Cl2 measured from the alkaline impinger catch. Many of the units included in the ICR had already tested, and therefore did not perform those measurements. EPRI (2014) reviewed laboratory data packages from several of the chlorine tests. Two quality problems were identified: 1) an interfering peak in the ion chromatographs of the sodium hydroxide solutions that coelutes with chloride, causing a positive bias for Cl2, and 2) excessive dilution of the impinger liquid that caused the chloride peak to be indistinguishable from the coeluting peak. Project Objectives The purpose of this laboratory study was to determine the effectiveness of EPA Reference Methods 26 and 26A for halogen and hydrogen halide measurements at low concentrations. The study examines the effects of gas composition and sampling system conditions on the bias and precision (repeatability) of the methods. The study was designed to answer the following specific performance-related questions regarding EPA Methods 26 and 26A: What is the bias and precision (repeatability) of the methods at HCl concentrations typical of coal-fired EGUs in compliance with MATS limits for existing units (<1 ppmdv)? How is the method performance (i.e., bias, precision, and speciation) affected by the presence of SO2, NH3, and HBr in the flue gas? How does the impinger solution chemistry (e.g., ph, ion concentrations) vary with flue gas composition? Does the presence and composition of fly ash on the filter influence the results? Is there a difference in performance between Method 26 and Method 26A? How is the method performance affected by filter and probe temperature? Does the addition of a sampling train conditioning run improve the method performance? How is chloride speciation affected by flue gas composition and sampling conditions? How is method performance affected by the simultaneous presence of HCl, Cl2, HBr, and Br2? Can HBr and Br2 be speciated using the current methods and impinger chemistry? 1-6

31 2 STUDY DESIGN The study involved measurement of simulated flue gas following EPA Methods 26 and 26A protocols ( subject methods ) and comparing these results against the expected flue gas composition and/or reference measurements ( referee method ) using Fourier Transform Infrared (FTIR) spectroscopy. Over the course of this study a procedure for proper operation of the FTIR and delivery system was developed (see Appendix B). The composition of the simulated flue gas was formulated to mimic the combustion gas from in subbituminous coal combustion. The concentrations of key components in the flue gas were varied to set up a parametric study. Variation in operational or equipment configurations of Methods 26 and 26A provided insight into the effects these modifications had on method performance. Finally, side-by-side operation of the subject methods allowed comparison of the performance of the two methods. The experimental design of the study consisted of paired measurement runs of the flue gas using either or both of the subject methods (or modifications of the methods). Each unique combination of the two methods or modifications represented a test condition. The study consisted of eight conditions, referred to as Test Conditions 1 through 8. The objectives and parameters varied for each of these test conditions are shown in Table 2-1. Table 2-1 Summary of Test Conditions Condition Objective Parameters Varied 1 Method 26 precision/bias HCl concentration 2 Method 26A precision/bias HCl concentration 3 Method 26 vs Method 26A; Test method; HCl concentration 4 Effect of Br 2, Cl 2 on HCl HBr, Br 2, Cl 2 concentrations; fly ash on filter 5 Effect of SO 2 on speciation SO 2 concentration; Cl 2 present/absent 6 Effect of sampling train preconditioning Preconditioning; HCl concentration 7 Effect of sampling duration Run duration; fly ash type 8 Effect of NH 3 and filter temperature Ammonia concentration; filter temperature; fly ash type Each test condition included two or more test series in which one or more flue gas components was varied. A test series represents a specific condition and flue gas composition, and is referred to by its associated condition number followed by a numerical designator, i.e., Test No. 1-1 represents the first test series conducted under Test Condition 1. Each test series consisted of multiple replicate runs during which the flue gas was sampled and measured over a prescribed period of time. The run times were either 30 minutes (most runs) or 180 minutes (Test Condition 7) in duration. 2-1

32 Flue Gas Simulation The flue gas simulator used a combination of compressed gas cylinders, mass flow controllers, evaporative gas standards generators, and gas permeation tubes to generate the simulated flue gas. The flue gas consisted of three categories of components. A mixture of base components of O2, CO2, N2, NO, and NO2 comprised the background matrix of the gas and was intended to be fixed throughout the study at levels typically encountered at the stack flue of a unit firing sub-bituminous coal. However, due to the large number of gases used, levels of certain components had to be varied over the course of the program to meet targeted levels of other gas species. The base mixture composition is summarized in Table 2-2. Table 2-2 Design Base Composition of Synthetic Flue Gas Component Concentration (ppm) CO 2 12 O 2 6 NO 2 10 NO 200 SO 2 50 H 2 O 10% The second category of components was comprised of the controlled variable components of water (H2O), sulfur dioxide (SO2), ammonia (NH3) and fly ash. Levels of these compounds and fly ash loadings on the Method 26/26A particulate filter were varied to define certain test conditions. The levels of these parameters were intended to represent emissions from units firing sub-bituminous coal, with ranges of H2O and SO2 selected to represent units with and without wet scrubber FGD, and levels of ammonia selected to represent units with and without SCR. The third category of components was study analytes, consisting of HCl, Cl2, HBr, and Br2. These are compounds that were measured directly by the study methods. Levels of these compounds also defined specific test conditions. The HCl concentrations used in the study were selected to represent the range of expected concentrations after the MATS compliance deadline. Description of Test Program Condition 1 Bias and Precision, Method 26 Condition 1 was designed to measure the bias and precision of Method 26 at two different HCl levels. Table 2-3 lists the design parameters for the Condition 1 tests. Duplicate Method 26 samples were compared against the FTIR measurements. Condition 1 was comprised of eleven 30-minute test runs, with seven runs conducted under the Low-HCl condition and four runs conducted under the High-HCl condition. 2-2

33 Since Method 26 cannot be used in the presence of entrained water droplets, this method is generally not performed on stacks located downstream of wet scrubbed FGD. Therefore, the simulated flue gas used for all of the runs under this condition was mixed to SO2 and H2O levels that would comparable to emissions from sub-bituminous coal combustion without FGD. A particulate filter was not used in any of the Method 26 trains studied under Condition 1. Table 2-3 Condition 1 Test Run Matrix Condition-Series_Train(s) 1-1_AB 1-2_AB Description M26, Low HCl, High SO2, Bias/Precision M26, High HCl, High SO2, Bias/Precision Number of Runs* 5/5 6/6 Method SO2 (ppm) HCl (ppm) HBr (ppm) Cl2 (ppm) Br2 (ppm) NH3 (ppm) Ash (Y/N) N N Filter Temp ( F) Run Duration (min) Filter Pre- Conditioned N N Acid Impinger Normality *Number of runs represented as A train/b train. Condition 2 Bias and Precision, Method 26A Condition 2 was similar to Condition 1 except that Method 26A was evaluated instead of Method 26, and the SO2 and H2O levels in the simulated flue gas were representative of wet scrubbed FGD emissions. Condition 2 was comprised of seven 30-minute test runs, with four runs conducted under the Low-HCl condition (target concentration at 0.5 ppm) and three runs conducted under the High-HCl condition (target concentration at 1 ppm). Table 2-4 lists the design parameters for the Condition 2 tests. 2-3

34 Table 2-4 Condition 2 Test Run Matrix Condition-Series+Train 2_1_AB 2-2_AB Description M26A, Low HCl, Low SO 2, Bias/Precision M26A, High HCl, Low SO 2, Bias/Precision Number of Runs* 4/4 3/3 Method 26A 26A SO 2 (ppm) HCl (ppm) HBr (ppm) Cl 2 (ppm) Br 2 (ppm) NH 3 (ppm) Ash (Y/N) N N Filter Temp ( F) Run Duration (min) Filter Pre- Conditioned N N Acid Impinger Normality *Number of runs represented as A train/b train. Condition 3 Bias and Precision, Inter-Method Comparison Condition 3 was designed to compare the results of Methods 26A versus Method 26 at Low- and Mid-HCl levels. Due to problems with the synthetic flue gas preparation that impacted the first two sets of tests, the program objectives for measuring method bias and precision from Conditions 1 and 2 were also incorporated into the Condition 3 tests. Table 2-5 lists the design parameters for the Condition 3 tests. Condition 3 consisted of two series of runs at two HCl levels. Test Series 3-1 targeted a low-hcl level (0.2 ppmv) and Test Series 3-2 studied a mid-hcl level (0.5 ppmv). Seven 30-minute test runs were conducted for each HCl level, with each run consisting of a Method 26 train paired with a Method 26A train. The targeted flue gas mixture was representative of wet scrubbed FGD emissions. Both methods always used clean particulate filters (no spiked fly ash). 2-4

35 Table 2-5 Condition 3 Test Run Matrix Condition-Series+Train 3-1A 3-1B 3-2A 3-2B Description M26A Base, Low Level HCl, no ash M26 Base, Low Level HCl, no ash M26A Base, High Level HCl, no ash M26 Base, High Level HCl, no ash Number of Runs Method 26A 26 26A 26 SO 2 (ppm) HCl (ppm) HBr (ppm) Cl 2 (ppm) Br 2 (ppm) NH 3 (ppm) Ash (Y/N) N N N N Filter Temp ( F) Run Duration (min) Filter Pre- Conditioned N 5 min N 5 min Acid Impinger Normality Condition 4 Br2, Cl2, Ash Interactions Condition 4 was designed to study the effects of Br2 and Cl2 on HCl and HBr measurements with and without fly ash present in the sample. The Condition 4 tests were conducted as a full factorial 2 3 experimental design with replicates for a total of 16 test runs. The design matrix is shown in Table 2-6. Table 2-6 Condition 4 Design Matrix Run Cl2 Target (ppm) Br2 Target (ppm) Ash Run Yes Run No Run Yes Run No Run Yes Run No Run Yes Run No Each test condition consisted of a 30-minute test run using paired Method 26 trains. Each run was replicated once for a total of 16 runs. All of the ash used to simulate the dust cakes was from Ash Sample 081. Table 2-7 lists the design parameters for the Condition 4 tests. 2-5

36 Table 2-7 Condition 4 Test Run Matrix Condition- Series+Train 4-1AB 4-2AB 4-3AB 4-4AB 4-5AB 4-6AB 4-7AB 4-8AB Description M26, Low Level HCl, Ash 1, +HBr, +Br 2 M26, Low Level HCl, No Ash, +HBr, +Br 2 M26, Low Level HCl, Ash 1, +HBr, +Br 2, +Cl 2 M26, Low Level HCl, No Ash, +HBr, +Br 2, +Cl 2 M26, Low Level HCl, Ash1, +HBr M26, Low Level HCl, No Ash, +HBr M26, Low Level HCl, Ash1, +HBr, +Cl 2 M26, Low Level HCl, No Ash, +HBr, +Cl 2 Number of Runs* 2/2 2/2 2/2 2/2 2/2 2/2 2/2 2/2 Method SO 2 (ppm) HCl (ppm) HBr (ppm) Cl 2 (ppm) Br 2 (ppm) NH 3 (ppm) Ash (Y/N) Y 081 N Y 081 N Y 081 N Y 081 N Filter Temp ( F) Run Duration (min) Filter Pre- Conditioned Acid Impinger Normality *Number of runs represented as A train/b train. 5 min 5 min 5 min 5 min 5 min 5 min 5 min 5 min Condition 5 SO2 and Cl2 Effects on Halogen Speciation Condition 5 was designed to study the ability of Method 26 to differentiate between HCl and Cl2 in the presence of SO2. This study also examined the effects of absorbing solution ph on the resulting distribution of HCl/Cl2 in the impingers. Table 2-8 lists the design parameters for the Condition 5 tests. Three series of triplicate runs were conducted at SO2 concentrations ranging from approximately 50 ppmv to 450 ppmv. HCl and Cl2 concentrations of 0.5 and 2 ppmv, respectively, were targeted. Two additional runs constituting a fourth series were conducted without HCl present. Each run was 30 minutes in duration and involved operation of paired Method 26 trains with simulated filter cakes composed of ash from sample 081. For each pair of trains (except the fourth series), the ph of the absorbing solution in the acidic impingers for one of the trains was lowered using higher strength sulfuric acid reagent (0.25 N versus 0.1 N) in order to measure whether acid impinger ph has any effect on Cl2 recovery. 2-6

37 Table 2-8 Condition 5 Test Run Matrix Condition- Series+Train Description 5-1A 5-1B 5-2A 5-2B 5-3A 5-3B 5-4A 5-4B M26 with Cl 2, Low SO 2, ash M26 with Cl 2,Low SO 2,ash, fortified acidic impinger M26 with Cl 2, Mid SO 2, ash M26 with Cl 2, Mid SO 2, ash, fortified acidic impinger M26 with Cl 2, High SO 2, ash M26 with Cl 2, High SO 2, ash, fortified acidic impinger M26 with Cl 2, Low SO 2, ash, No HCl Number of Runs M26 with Cl 2, Low SO 2, ash, No HCl Method SO 2 (ppm) HCl (ppm) HBr (ppm) Cl 2 (ppm) Br 2 (ppm) NH 3 (ppm) Ash (Y/N) Y 081 Y 081 Y 081 Y 081 Y 081 Y 081 Y 081 Y 081 Filter Temp ( F) Run Duration (min) Filter Pre- Conditioned Acid Impinger Normality min 5 min 5 min 5 min 5 min 5 min 5 min 5 min Condition 6 Train Pre-Conditioning Effects The objective of Condition 6 was to study the effects of pre-conditioning the particulate filter according to the requirements of ASTM Method D6735. Pre-conditioning involves exposing the filter to sample gas prior to using it to collect a sample. Two series of test runs were performed at different HCl levels (0.5 ppmv and 1.6 ppmv). Three runs were conducted at the 0.5 ppmv HCl level and four runs were conducted at the 1.6 ppmv level. Table 2-9 lists the design parameters for the Condition 6 tests. Each test run was 30 minutes in duration and consisted of a standard Method 26 train paired with a Method 26 train in which the filter was pre-conditioned with the sample flue gas mixture for 30 minutes. The filters of each train contained a simulated dust cake comprised of ash from Ash Sample 081. The flue gas mixture was representative of wet scrubbed FGD emissions. 2-7

38 Table 2-9 Condition 6 Test Run Matrix Condition-Series+Train 6-1A 6-1B 6-2A 6-2B Description M26 Base, High Level HCl, ash 1 M26 with preconditioned filter, High Level HCl, ash 1 M26 Base, Low Level HCl, ash 1 M26 with preconditioned filter, Low Level HCl, ash 1 Number of Runs Method SO 2 (ppm) HCl (ppm) HBr (ppm) Cl 2 (ppm) Br 2 (ppm) NH 3 (ppm) Ash (Y/N) Y 081 Y 081 Y 081 Y 081 Filter Temp ( F) Run Duration (min) Filter Pre- Conditioned 5 min 30 min 5 min 30 min Acid Impinger Normality Condition 7 Run Duration Effects Condition 7 examined the impacts of different sampling durations on Method 26 results. Sampling durations of 180 minutes and 30 minutes were compared. Two series of tests were done at this condition using two different ashes to simulate dust cakes on the filters (Ash Samples 118 and 119). Three test runs were conducted for each ash, and each run consisted of a Method 26 train operated for 30 minutes paired with one operated for 180 minutes. The targeted flue gas mixture contained 0.5 ppmv HCl and was representative of wet scrubbed FGD emissions. Table 2-10 lists the design parameters for the Condition 7 tests. 2-8

39 Table 2-10 Condition 7 Test Run Matrix Condition-Series+Train 7-1A 7-1B 7-2A 7-2B Description M26 Base, Low Level HCl, ash 3 M26, Low Level HCl, ash 3, extended run M26 Base, Low Level HCl, ash 4 M26, Low Level HCl, ash 4, extended run Number of Runs Method SO 2 (ppm) HCl (ppm) HBr (ppm) Cl 2 (ppm) Br 2 (ppm) NH 3 (ppm) Ash (Y/N) Y 118 Y 118 Y 119 Y 119 Filter Temp ( F) Run Duration (min) Filter Pre- Conditioned 5 min 5 min 5 min 5 min Acid Impinger Normality Condition 8 Ammonia and Filter Temperature Effects Condition 8 examined the impacts of ammonia and elevated filtration temperature on Method 26 results. Two series of tests were done at this condition using two different ashes to simulate dust cakes on the filters (Ash Samples 081 and 117). Table 2-11 lists the design parameters for the Condition 8 tests. Three 30-minute test runs were conducted for each ash, and each run consisted of a Method 26 train operated with a nominal filtration temperature of 250 F and one operated at a temperature of 350 F. The targeted flue gas mixture contained nominally 5 ppmv NH3, 0.5 ppmv HCl, and was representative of wet scrubbed FGD emissions. 2-9

40 Table 2-11 Condition 8 Test Run Matrix Condition-Series+Train 8-1A 8-1B 8-2A 8-2B Description M26, Low Level HCl, with NH 3, ash 1 M26, Low Level HCl, with NH 3, ash 1, 350F filter M26, Low Level HCl, with NH 3, ash 2 M26, Low Level HCl, with NH 3, ash 2, 350F filter Number of Runs Method SO 2 (ppm) HCl (ppm) HBr (ppm) Cl 2 (ppm) Br 2 (ppm) NH 3 (ppm) Ash (Y/N) Y 081 Y 081 Y 117 Y 117 Filter Temp ( F) Run Duration (min) Filter Pre- Conditioned 5 min 5 min 5 min 5 min Acid Impinger Normality

41 3 EXPERIMENTAL METHODOLOGY This section describes the methods used to prepare and deliver synthetic flue gas, the test methods used to collect and analyze samples, and the measures implemented to ensure data quality. Synthetic Gas Stream and Sample Delivery System Figure 3-1 shows a process flow diagram of the synthetic gas stream generator and sample delivery system. In order to conduct the parametric study of the performance characteristics of EPA Methods 26 and 26A using paired runs, it was necessary to develop a consistent, reliable simulated flue gas source. The simulated flue gas delivery system setup had eight possible dry gas entry ports, two wet reagent standard ports, and two permeation device ports, which are possible through two wet gas standard generators, one independent mass flow controller (MFC), and one dual-port permeation oven. Figure 3-1 Flue Gas Simulator Diagram Two Hovacal gas mixing systems were used to allow precision blending of the sample gases. Liquid analyte solutions were used for HCl, HBr and water. Evaporators with liquid mass flow control valves were used to achieve the desired liquid flow rates. A computer interfaced to the gas mixing system controlled the mass flow valves, and continuously recorded their positions and flow rates. The Hovacals delivered the requisite gas stream constituents to a heated mixing manifold. Downstream of the mixing manifold, the blended gas stream was delivered to a heated distribution manifold where the gas streams were divided equally and distributed (metered) to the Method 26/26A sample trains and the referee method (FTIR). Excess gas was vented. 3-1

42 During the early part of the test program, inclusive of the Shakedown Testing (Test Condition 0) and Test Conditions 1 and 2, the mixing manifold consisted of a 316L stainless steel tube. This system element had long equilibration times and occasionally experienced sample losses. In the interest of improving equilibration time and optimizing the delivery system in general, the sample delivery system was modified by changing all mixing manifold, distribution manifold components and ports to glass. The testing for Condition 3 through Condition 8 was performed with this glass configuration, including checks to ensure that the main analyte, HCl, exhibited excellent recovery through all ports. Figure 3-2 shows the laboratory flue gas simulator set-up, and Figure 3-3 shows the re-designed glass gas mixing manifold. Figure 3-2 Flue Gas Simulator Figure 3-3 Glass Gas Mixing Manifold (With Heat Wrap Removed) 3-2

43 Description of the Principal System Components This subsection describes the equipment used to generate synthetic flue gas for the study. Gas Delivery System The primary simulated flue gas constituents, consisting of air, SO2, CO2, NO, NO2, Cl2, N2, and NH3, were supplied via calibration gas cylinders. Each cylinder used an appropriate 2-gauge regulator and was connected to its mass flow controller using unheated, uninsulated ¼-inch Teflon tubing with stainless steel fittings. All regulators and Teflon tubing were leak checked and periodically inspected for data quality and safety purposes. The N2 mass flow controller worked independently of the other mass flow controllers and only controlled total flow. The nitrogen was used as dilution gas for the other components to the flue gas and to provide a means to augment the gas volume to allow for high flow sampling. The design of the mass flow controller limited the input pressure to the controller to a maximum of 40 pounds per square inch (psig). The digital display on the mass flow controller was used to develop a calibration curve in conjunction with a NIST-traceable Bios calibrator. All other mass flow controllers were part of the two Hovacals. One Hovacal blended up to four dry gases and one liquid reagent. The second Hovacal blended up to three dry gases and one wet reagent. All MFCs in each device were controlled via mass balance calculations and component concentration set points through the instrument s software package. Each individual dry gas concentration was confirmed via FTIR measurement. All dry mass flow controllers required a minimum regulator pressure of 20 psig, and were calibrated through the software and with a Bios calibrator. The calibration curves generated by the software were applied automatically to the internal calculations of the instrument, so no correction factors were needed. Originally, HCl calibration gas cylinders were to be used to deliver HCl to the system. However, it became apparent early into the project that there were significant issues with this approach. During quality checks (see Delivery System Quality Checks section) there were found to be significant differences between listed HCl cylinder concentrations and measured HCl concentrations (by FTIR). The measured HCl concentrations were checked with multiple FTIR instruments, which all were in relative agreement with each other and all reported accurate SF6 measurements. As much as 12 hours were given to reach equilibrium using various Teflon and stainless steel tubing at various lengths. It was determined that the HCl cylinder concentration was not reliable, and was therefore not used as the HCl delivery to the system. Figure 3-4 shows the FTIR output for an HCl cylinder having a listed concentration of 49.5 ppmv, but whose measured HCl concentration was approximately 29.1 ppmv. 3-3

44 Figure 3-4 HCl Gas Cylinder Concentration as a Function of Time Hovacal The Hovacal is a calibration gas generator manufactured by Inspire Analytical Systems (IAS). It is an instrument made up of several mass flow controllers (MFCs) and a liquid flow meter. Using the internal software on the display interface or with software on a computer, the operator can accurately blend several gas cylinders into one composite gas stream, dilute a pure component with zero gas, vaporize a liquid reagent (water or aqueous solution) and incorporate it into the gas stream. It is possible to continuously deliver a composite gas sample and make adjustments to the targets in near real-time. In addition, the computer software can log data in 30-second average data points. HCl Generation HCl was generated through the Hovacal by vaporizing a liquid reagent of known concentration at a known rate. A NIST-traceable HCl reagent was diluted to the desired molarity and confirmed by IC analysis. Using the Hovacal software, the molarity of the reagent and the desired vapor concentration output were set by the user. The internal mass flow controller maintained a constant feedback loop to the peristaltic pump to achieve and maintain the user-desired target. The mass flow meter output was recorded in grams per minute and was confirmed for accuracy gravimetrically with a calibrated and certified mass balance. All conversions and calculations used in achieving the target HCl concentration in the composite gas stream were done internally by the Hovacal using known liquid and vapor parameters specific to HCl. HBr Generation HBr was generated using the Hovacal in a manner very similar to that used for HCl, except that the liquid and vapor parameters for HBr were not included in the software package. The Hovacal is currently limited in that only a handful of reagents have parameter values pre-loaded in the software package. It is not possible to add new reagents to the pre-loaded list. Thus, the target HBr concentration was achieved by manual calculation, converting the desired HBr target concentration into an equivalent HCl concentration. The Hovacal logged the HBr generation as HCl, but the actual HBr generation was confirmed by mass flow. 3-4

45 Moisture and Liquid Reagents Generation The liquid MFCs in the two Hovacals were used to generate water vapor, HCl, and, in some runs, HBr. The two liquid MFCs used a peristaltic pump to pull liquid from a blanked Nalgene TM container with a known concentration of the reagent of interest. The liquid pulled into the port was then vaporized and blended with the dry MFC ports in that instrument. The amount of liquid (mass flow rate in g/min) was controlled and calculated through the internal instrument software and confirmed gravimetrically with a NIST traceable laboratory scale. In addition, the two liquid gas standard generator instruments received their annual maintenance and calibration service from the manufacturer during the project (laboratory results before and after servicing are noted as such). Any differences in reagent concentrations between the software and gravimetric calculations during individual test runs were assigned a correction factor to reflect the effect on component concentrations in the simulated flue gas. Bromine Generation Permeation Devices In order to safely and effectively deliver bromine (Br2) to the system, a permeation device (diffusion vial) housed inside of a permeation oven was used. A pure component that exists in a vapor-liquid equilibrium (VLE) can emit or diffuse the vapor fraction out of the oven at a known mass flow rate (usually in nanograms per minute). Given a known mass flow rate and known flow rate of zero dilution gas (in this case N2) a known concentration of the pure component in nitrogen can be delivered and blended into the simulated flue gas. Figure 3-5 shows a bromine diffusion vial. Figure 3-5 Diffusion Vial for Bromine Permeation Fly Ash Particulate Matter Used in Study Several test conditions included the addition of particulate matter to the filter substrates to simulate fly ash dust cakes. EPRI provided fly ash samples, which were obtained from utility ESP hoppers. Four different ash samples were used, representing a variety of coal types. Each of the four ash samples was sized in accordance with ASME Power Test Code 28 using a Bahco Centrifugal Classifier. This process divides the samples into various particle fractions based on 3-5

46 size, shape, and weight using centrifugal force. For more detail on fly ash sizing and seeding procedures used in this study, see Appendix C. Table 3-1 identifies the types of coals represented and the particle size distributions for each of the ash samples. Table 3-1 Fly Ash Types and Particle Sizes Upon completion of the sizing analysis, each fraction was saved for seeding. To seed a Method 26 filter, all fractions less than four microns in diameter were combined and a 5 mg aliquot was extracted. The aliquot was loaded onto a 47 mm Method 26 filter by pulling a vacuum behind the filter, which allowed the ash to distribute evenly on the filter surface. The loaded filter was placed in a dessicator and periodically weighed until a constant weight was observed. A 5 mg ash loading is equivalent to an emission rate of approximately lb/mmbtu for a 1-hour test. Description of Test Methods The test methods used in this project were the two EPA Reference Methods 26 and 26A and FTIR, which was used as a referee method for HCl and HBr, since it is not impacted by the same biases as the impinger-based methods. FTIR cannot detect molecular chlorine or bromine. EPA Reference Methods for Halogens and Halides The principal EPA Reference Methods for HCl measurement from stationary sources are Methods 26 and 26A. Diagrams and descriptions of each of these methods are provided in this section. EPA Methods 26 and 26A can be found in the Code of Federal Regulations (CFR) at 40 CFR 60 Appendix A. Method 26A The full title of Method 26A is: Determination of Hydrogen Halide and Halogen Emissions from Stationary Sources, Isokinetic Method. EPA Method 26A (EPA, 1994a) is found in 40 CFR 60, Appendix A. The method is available at: The Method 26A sampling train, shown in Figure 3-6, is an isokinetic sampling method in which the impingers are charged with dilute acidic absorbing solution (sulfuric acid) and alkaline absorbing solution (sodium hydroxide). The sample train captures gaseous hydrogen halides (e.g., HCl and HBr) in the acidic solution and halogens (Cl2 and Br2) in the alkaline solution. This method collects the emission sample isokinetically and is therefore the preferred method for sampling at sources controlled by wet scrubbers that emit acid particulate matter (e.g., hydrogen halides dissolved in water droplets). 3-6

47 Figure 3-6 EPA Method 26A Sampling System Gaseous and particulate pollutants are withdrawn isokinetically from the source and collected in an optional cyclone, on a particulate filter, and in absorbing solutions. The cyclone collects any liquid droplets and is not necessary if the source emissions do not contain them; however, it is preferable to include the cyclone in the sampling train to protect the filter from any liquid present. An additional empty impinger may be included upstream of the sulfuric acid impinger if excessive moisture condensation is anticipated. The filter collects particulate matter including fly ash and halide salts; the filter is not routinely recovered or analyzed. Acidic and alkaline absorbing solutions collect the gaseous hydrogen halides and halogens, respectively. Halogens (Cl2 and Br2) have a low solubility in an acidified solution and hence theoretically will not be captured to a large extent in the first set of impingers containing 0.1 N sulfuric acid (H2SO4). In principle, halogens will be captured in the 0.1 N NaOH impinger solution. Meanwhile, the halides (HCl, HF, and HBr) are intended to be captured in the 0.1 N H2SO4 and hence removed before they can get to the NaOH solution. If particulate mass emissions are to be determined, then the recovery of the probe and filter follow EPA Method 5 recovery procedures (EPA, 1991). The contents of the empty impinger (if used) and the two acidic impingers are combined in a suitable storage container. If flue gas moisture is to be calculated, the volume or mass of the acidic impinger contents is determined. These impingers and connecting glassware (including the back portion of the filter holder) are rinsed with deionized (DI) water, and the rinses are added to the storage container. This first container is the hydrogen halide sample. The container is sealed, and the liquid level of the container is marked. The contents of the two alkaline impingers are combined in a second 3-7

48 suitable storage container. These impingers and connecting glassware are rinsed with DI water, and the rinses are added to the storage container. If flue gas moisture is to be calculated, the volume or mass of the alkaline impinger contents is determined. This container is the halogen sample. Approximately 25 mg of sodium thiosulfate per ppmv of halogen anticipated is added to the halogen container; the thiosulfate reacts with the hypohalous acid to form a second halide ion; two halide ions are formed for each molecule of halogen gas. Analysis of both sets of solutions is by ion chromatography (IC) of halide ions (Cl -, F -, or Br - ), using standards prepared in the appropriate solution matrix. In Method 26A, if the optional cyclone is used, or if moisture condensation is observed, then it is necessary to conduct a post-test purge to evaporate the halogens, halides, and the condensed moisture from the filter so it can be captured and recovered in the impinger solutions. Failure to dry the train completely can result in significant negative bias. Method 26 The full title of Method 26A is: Determination of Hydrogen Halide and Halogen Emissions from Stationary Sources, Non-Isokinetic Method. EPA Method 26 (EPA, 1994b) is contained in 40 CFR 60, Appendix A. It is available at: Figure 3-7 shows a schematic of the Method 26 sampling train. EPA Method 26 is a single-point, non-isokinetic test conducted at a relatively low sample flow rate of 2 liters per minute. The low flow rate is accommodated by substituting midget impingers in place of the standard impingers used in Method 26A. EPA Method 26 is the preferred methodology in flue gas streams with the following characteristics: 1) clean flue gas streams, i.e., downstream of particulate removal devices, 2) flue gas streams containing low reactivity particulate matter, and 3) flue gas streams where the HCl is not stratified. In EPA Method 26, an integrated sample is extracted from the source and passed through a pre-purged heated probe and filter into 30-ml midget impingers containing dilute sulfuric acid (0.1 N H2SO4) and dilute sodium hydroxide (0.1 N NaOH) solutions which collect the gaseous hydrogen halides and halogens, respectively. The filter collects particulate matter including halide salts but is not routinely recovered and analyzed. The hydrogen halides are solubilized in the acidic solution and form chloride (Cl - ), bromide (Br - ), and fluoride (F - ) ions. The halogens have a very low solubility in the acidic solution and pass through to the alkaline solution where they are hydrolyzed to form a proton (H+), the halide ion, and the hypohalous acid (HClO or HBrO). The contents of the empty impinger (if used) and the two acidic impingers are combined in a suitable storage container. These impingers and connecting glassware are rinsed with DI water, and the rinses are added to the storage container. This container is the hydrogen halide sample. The container is sealed, and the liquid level of the container is marked. The contents of the two alkaline impingers are combined in a suitable storage container. These impingers and connecting glassware are rinsed with DI water, and the rinses are added to the storage container. This container is the halogen sample. Approximately 25 mg of sodium thiosulfate per ppmv of halogen anticipated is added to the halogen container to assure reaction with the hypohalous acid to form a second halide ion; two halide ions are formed for each molecule of halogen gas. The halide ions in the separate solutions are measured by ion chromatography (IC). 3-8

49 Figure 3-7 EPA Method 26 Sampling System Principal Differences between Method 26 and 26A The following are the principal differences between EPA Methods 26 and 26A: Method 26 is a single point, non-isokinetic test conducted at relatively low sample flow rate of approximately 2 liters per minute. A Method 26 test would collect approximately 10% of the sample volume of a comparable 1-hour Method 26A test. Method 26A can provide a concurrent filterable particulate mass emission rate measurement, provided the Teflon matte filter used meets EPA Method 5 s 99.95% collection efficiency requirement and the probe and filter temperatures are maintained between 249 F and 274 F. Method 26 cannot be used on sources where there are entrained water droplets in the flue gas, e.g., downstream of wet scrubbers. Method 26 uses midget (30-ml) impingers, while Method 26A uses 500-ml impingers. Method 26 requires a pre-purge of the probe and filter at 2 liters per minute for at least five minutes; Method 26A does not require the pre-purge. The purpose of the pre-purge is to condition probe and filter with stack gas. Method 26 does not discuss post-test purging while Method 26A has an option post-test moisture removal purge procedure in section If moisture condensation is present, then this purge step is critical to the recovery of HCl that may be in the moisture. The HCl will evaporate only after the water is all evaporated. Method 26A sampling equipment can be used to perform a Method 26 test. The converse is not true. 3-9

50 Precision and Bias The term precision refers to the repeatability of a measurement. If a measurement is taken several times and the results are all clustered closely together, the method is said to be precise for that application. The term bias refers to how far a measurement is to the true value of the measured parameter. In all cases, the true value is unknown so a generally accepted standard (e.g., calibration gas, check weight, or calibrated standard pitot) is used as a comparison. EPA Method 26 reports the within-laboratory relative standard deviations (precision) to be 6.2% and 3.2% at HCl concentrations of 3.9 and 15.3 ppmv, respectively. EPA Method 26A does not report a method precision. Steinsberger (1989) reports a positive bias to HCl in the presence of Cl2 when sampling at Cl2 concentrations less than 50 ppmv. Steinsberger also reports a possible negative bias below 20 ppmv HCl perhaps due to reaction with small amounts of moisture in the probe and filter. Similar bias for the other hydrogen halides is possible. Detection Limits Methods 26 and 26A provide limited guidance on the method detection limit. Both methods report what is referred to as the analytical detection limit in the stack gas. For Method 26, the analytical detection limit in the stack gas is reported to be 0.1 ppmv for both HCl and Cl2. For Method 26A, the analytical detection limit in the stack gas is reported to be 0.04 ppmv for both HCl and Cl2. EPA arrives at these values by multiplying the analytical detection limit by the quantity of sample analyzed, divided by the volume of sample gas collected. Stack testing involves both field sampling and laboratory analysis. Most of the variability for a test method occurs with sampling, not with analysis. Detection limits based solely on the variability of laboratory analysis are, therefore, far lower than the actual in-stack detection limits. EPA s approach is likely to result in an unrealistically low detection limit, as the result will be highly dependent upon the analytical detection limit. Analytical labs are constantly working to control variables that will ultimately lower their detection limits. This may lead to an unrealistic expectation for the stack tester or the source owner as it pertains to the detection limit achievable in the stack. The method detection limit is fundamentally related to the measurement variability (precision) at or near zero. One must determine the variability which encompasses the entire method which includes sampling uncertainty and matrix effects. The best way to address this is by utilizing paired sampling trains. By comparing the variability in the differences between paired trains, the precision of the method can be determined. EPA Reference Method 26 and Method 26A are similar in principle. As detailed earlier, Method 26 involves constant rate sampling whereas Method 26A requires isokinetic sampling. Method 26 also uses smaller quantities of absorbing solutions and collects less than one-fifth the gas sample volume as does Method 26A. It is a common practice in the testing industry to operate a Method 26A train at a constant rate and call it Method 26. Because of its smaller sample gas volume requirements, Method 26 was selected as the base condition for this study, to reduce the volume of gases required. Therefore, with respect to intermethod comparisons, this report compares the performance of Method 26A relative to Method 26, and not vice versa. Specific tests to study the effects of fly ash, SO2/halogen interactions, filter pre-conditioning, ammonia interference, and filtration temperature were also limited to Method

51 Method 26/26A Filter Box The filter boxes used were typical of those used in field testing. The filter boxes were equipped with centrally placed thermocouples and a heating element capable of emitting adequate heat such that the filter setup inside is uniformly heated. Methods 26 and 26A require customized entry and exit ports about the walls of the box. The filter box design for Method 26A is used for heating the filter setup in other methods; however, the design needed to run Method 26 is unique, as it must allow for preconditioning of the filter prior to beginning a run. This bypass is achieved with a three-way borosilicate stopcock as shown in Figure 3-8. Figure 3-8 Filter Box Drawing for Method 26 Referee Method (FTIR) for Acid Halides FTIR was used as the referee method to verify the levels of HCl and HBr added to the simulated flue gas mixtures. A limit of system (LOS) study was conducted for each unique gas matrix to determine the lowest HCl concentration that can be differentiated from background noise. These studies were performed through serial dilution of the HCl concentration while holding the other gas parameters constant. A MKS Multigas TM 2030 FTIR was used for this program. There was a sampling port on the delivery system devoted to the FTIR instrument, as indicated in the Figure 3-1 above. Sample was pulled through the FTIR with an Air Dimensions Inc. (ADI) pump at approximately 400 F (~204 C). The closest spectral reference library in the FTIR was 191 C; data was quantified using this reference. A composite spectrum was collected from the hot, wet gas sample every 60 seconds using the normal combustion emission source recipe and method in the instrument software. An average of all spectra during a test run was the representative reference concentration of each flue gas component, including HCl. 3-11

52 Concentrations determined by FTIR and by the wet method trains were compared to each other and to the Hovacal HCl concentration; significant deviations in wet method HCl concentration from the FTIR HCl concentrations were considered a bias in the wet method. Significant deviations were defined as being differences larger than the calculated 95% confidence interval for the dataset. Since this project simulated flue gas from coal combustion, moisture was added to the system. The FTIR spectra of certain flue gas components (in particular HCl) are influenced by an effect known as collisional broadening or matrix broadening in the presence of polar compounds such as water. This effect changes the line shape of the spectrum and results in incorrect quantification. While this effect may be corrected by calibrating the instrument with the same gas components as found in the sampling matrix (including water), calibration with dry gas standards will not correct this effect. At the beginning of the project the FTIR method used for quantification did not take matrix broadening into account and the HCl concentrations measured were consistently biased low compared to the expected concentrations. After correcting for matrix broadening, the measured concentrations more closely corresponded with expected concentrations, in some cases changing the FTIR concentration by as much as 20%. Some conditions tested in this study included hydrogen bromide (HBr), which behaves similarly to HCl in that the same types of measures must be taken to ensure minimal line/system loss. HBr is also potentially affected by matrix broadening associated with the presence of water in the flue gas; however, there is currently no vendor-supplied correction for HBr. In accordance with the discussion in the Impinger Chemistry section on reactions between bromide ions and chlorine, a small series of points varying water and HBr concentrations must be collected by the FTIR in order to form a correction for HBr. FTIR Calibration The quantification of any collected spectrum requires comparison to an internal reference library. Thus, most gas species are calibrated on a range from ppb to 100%. Linearity and calibration can be checked in the field via a response check. There was never a problem with linearity throughout this study. FTIR Detection Limits The detection limit of a gas species is determined in FTIR by the signal strength, path length, scan time, and materials of construction. According to the MKS specifications sheet for the MultiGas 2030 FTIR Continuous Gas Analyzer, the lowest detectable limit with a one-minute scan for HCl is 0.20 ppmv. The detection limit for this study was calculated 7 replicate runs at 0.2 ppmv from Condition 3-1. The standard deviation of the FTIR results was ppmv. Three times this standard deviation is 0.08 ppmv. This will be considered as the FTIR detection limit for this study. 3-12

53 FTIR Analytical Interferences A persistent issue with FTIR technology is interference from water vapor. In the case of HCl, the latest Cement Kiln method by MKS compensates for the water interference; however, HBr currently does not have such compensation. The Cement Kiln method is a prebuilt software method and recipe for quantification of combustion sources, and supports quantification of all study analytes detectable by FTIR technology. As mentioned earlier, molecular chlorine and bromine are not detectable by FTIR. One of the most common types of infrared transmission window on an FTIR is a potassium bromide (KBr) window, due to its excellent signal throughput and relatively low cost. However, KBr windows can be easily damaged, and any slight scratch, crack, or coating dramatically interferes with the signal throughput. Acid gases (such as HCl and HBr) and NOx present in the gas stream will deteriorate the KBr windows over time. For these reasons, barium fluoride (BaF2) windows were chosen for this study. BaF2 windows have a very modest decrease in signal throughput relative to KBr, but are much more robust in any gas stream environment. The real drawback to BaF2 windows is that the spectral cut-off occurs at 690 cm -1 ; that is, some of the spectrum is not scanned and not quantifiable. If there is a gas species of interest that peaks on this part of the spectrum then it would be impossible to measure. Fortunately, all of the gas species measured in this study had peaks in other areas of the spectrum that could be readily quantified. Sampling Quality Control Measures Used in the Study Leak Checks Pre- and post-test leak checks were performed on all trains as defined by Method 26, Method 26A, and Method 5. As an additional QA/QC check during runs, an oxygen sensor was used to monitor the dry flue gas sample passing through the meter box housing the pump. If the oxygen concentration was greater than the expected target value, this was a positive indication of a leak in the train setup. Such a leak can dilute the gas being sampled, resulting in an under-measurement of HCl or other analytes. Delivery System Quality Checks In order to draw any definitive conclusions on method performance, there must be confirmation that the flue gas simulation delivery system was able to consistently deliver known and steady component concentrations to all three sampling ports. The concentration measured in the instrument port (FTIR) must be the same concentration being delivered to the two sampling train ports. Two categories of quality checks were performed on the system: 1) checks that directly measure and confirm analyte concentration, and 2) checks that indirectly confirm analyte concentration by measuring other parameters. Direct system quality checks performed included serial dilutions, port confirmations, cylinder and reagent comparisons, and zero concentration checks. Indirect system quality checks performed included pressures, temperatures, purge flow rates, spectrum analysis, signal losses, leak checks, liquid nitrogen level determinations, FTIR health check utility parameters, and Hovacal performance. 3-13

54 Serial Dilutions Throughout this project several checks were done to confirm that both the system and the FTIR instrument were functioning properly. One of the types of checks used is serial dilution of HCl. In a serial dilution, the analyte concentration is varied as the rest of the chosen matrix is held at steady concentrations. For this project, serial dilutions were performed in different gas matrices for the purpose of determining how different conditions can affect the detection limit of the FTIR. The chosen blend of gases was sent through the system at a flow rate of at least 5 liters per minute (LPM) and no more than 4 LPM of the delivered gas was pulled through the FTIR. The first serial dilution performed was with a dry gas cylinder of only HCl with a balance of nitrogen. Starting at a higher HCl concentration and stepping down to 0 ppmv HCl, five steadystate concentrations were maintained for at least 10 minutes. Although it appears the HCl concentrations were properly diluted for each point, the absolute concentrations did not always agree with the targeted HCl concentration. As previously stated, we concluded that this was due to the unreliability of the dry gas cylinders. In all other serial dilution tests, a NIST-traceable HCl solution was used to prepare the dilutions. In order to assess how the FTIR s performance with respect to HCl was affected by the presence of water vapor, a serial dilution was performed where HCl concentration was varied in the presence of moisture (between 10% and 12%). The absolute HCl concentration was in good agreement with the target; however, the noise band of the HCl concentration increased. This means that the presence of water increases the detection limit; that is, the minimum concentration of HCl that can be statistically distinguished from a zero reading. According to the data, the average detection limit was approximately 0.08 ppmv. It does not appear that any other components of the simulated flue gas affect the detection limit of the FTIR. Every test run in this study (with the exception of blank runs) targeted HCl concentrations at 0.2 ppmv and above; therefore, FTIR was concluded to be sufficiently sensitive for use in this study. Port Confirmations FTIR was used to verify that both ports were supplying the same composition of flue gas. Figure 3-9 shows the port confirmation runs for HCl. From the port confirmation runs, it was concluded that the three independent ports received HCl from the sample delivery system at equal concentrations. That is, at steady state, the average HCl concentrations sampled from the three ports were the same. 3-14

55 Figure 3-9 Port Comparisons (HCl) Method 26/26A Sampling System Temperature Because we are sampling acid gases, temperature plays an important role in the sample recovery. As the temperature drops below the acid dew point at any given condition, moisture (and subsequently, water-soluble components) will condense in the system. This results in a loss of analyte concentration. As a check to confirm that this condensation is not occurring prior to the impingers, several thermocouples were put into the system. The temperatures were verified several times during each day of testing; the actual gas temperature at the inlet to the mixing oven was recorded before and after each test run. Halide Analysis by Ion Chromatography IC analyses of the Method 26/26A impinger contents were conducted using a Dionex Model ICS-90 ion chromatograph. In ion chromatography, the sample is moved through a static phase (the column) by a mobile phase (the eluent solution). A specific analyte is identified by its characteristic retention time. The concentration is determined by instrument response as the peak area count. As discussed earlier, halogens in the alkaline impinger liquid were converted to halides by addition of sodium thiosulfate prior to analysis. The acidic impingers did not need the same addition of sodium thiosulfate prior to analysis since halogens are insoluble in acidic solutions. 3-15

56 Detection Limits The Method Detection Limit (MDL) for the IC method was determined in accordance with procedures in 40 CFR 136, Appendix B. The Limit of Quantitation (LOQ) was set to be the concentration of the lowest calibration point for each analyte. Values between these limits were quantified, but should be used with discretion as they were below the LOQ. Values that are below the MDL were indicated by a < where appropriate. The MDL range for chloride was mg/l to 0.01 mg/l, and the MDL range for bromide was mg/l to 0.02 mg/l. Instrument Calibration The calibration procedure is used to determine a linear relationship between the ion chromatograph s output and the concentration of the relevant ion. The procedures below outline CleanAir s IC calibration guidelines. Instrument calibrations follow regulations found in U.S. EPA Method and U.S. EPA Method 26A. Calibration standards were prepared from ACS grade, or better, dry salts as per section 7.3 of U.S. EPA Method As per Section of U.S. EPA CTM-027, a series of six diluted standards were prepared from the original calibration standard and run through the column in duplicate from lowest to highest concentration. The average peak area for each calibration point was plotted against the expected solution concentration. In accordance with section of U.S. EPA Method 9057, a least-squares regression with an R 2 value of or greater must be produced from the resulting curve. Figure 3-10 below shows a typical IC calibration curve. In accordance with U.S. EPA Method 26, a full post-test calibration was performed. The pre-test and post-test calibration average peak area for any standard must agree within 5% of any observed area. All calibration standards were prepared in a deionized water matrix. Documentation showing the validity of this deviation is available upon request. 3-16

57 Figure 3-10 Example IC Calibration Curve Ion Chromatography QA/QC The procedures followed in this study met and exceeded EPA requirements. The QA/QC procedures are as follows: Each analytical balance was calibrated and certified as accurate by an ISO calibration service on annual basis. A copy of this calibration data is available on request. Each balance was also calibrated prior to use on a daily basis using a minimum of three Class 1 weights. These daily calibrations must match the Class 1 weight values within ±0.2 mg in order to proceed. Periodic calibrations are also performed throughout the day if the analyst believes they are required. Before the first sample is analyzed and every twenty samples thereafter, a Quality Control (QC) sample was analyzed. The QC sample is created using ACS grade or better dry salts from a different manufacturer and or lot number than the salts used to create the calibration standards. The QC must show a regression concentration within 10 percent of the expected concentration. 3-17

58 After the first ten samples were analyzed and every twenty samples thereafter (and before the post-test calibration) a laboratory blank and a Continuing Calibration Verification (CCV) were analyzed. The CCV is prepared from the same calibration standard as used to create the eight standards that make up the calibration curve. The laboratory blank must show a regression concentration of zero, and the CCV must show a regression concentration within 10 percent of the expected concentration. A matrix spike analysis was performed on ten percent of the total number of samples. This sample was prepared with equal amounts of sample and a calibration standard whose concentration was known to be larger than that of the sample. The matrix spike was acceptable when the recovery is found to be 100 ± 10 percent. As a measure of precision, 20% of all matrix spikes were prepared and analyzed in duplicate. The average area count of two identical matrix spikes may not have a relative percent difference of more than 10 percent. Every sample was analyzed in duplicate and the mean area count used to determine the concentration. The duplicate area counts must not have a relative difference of more than five percent. In the event that the relative difference is more than five percent, the sample is reanalyzed in duplicate until a duplicate relative difference of less than five percent is obtained. Each point on the calibration curve should be within ± 2 percent of the calibration span of the curve used. The observed concentration value of each point on the calibration curve should have a relative percent difference of 10 percent from its expected concentration. Each calibration standard was prepared in accordance with EPA Method and EPA Method 26A and was been designated an original lot number. This number can be used to trace back to the original dry salts used in the preparation of these standards. In suppressed ion chromatography, eluent was defined as the carrier that moves chemicals through the column and regenerant was defined as a reagent used to remove ions opposite in charge of the specific analyte while reducing the overall conductivity of the eluent. 3-18

59 4 RESULTS AND DISCUSSION The results from each of the Conditions are presented below. Run-by-run measurements of matrix gases and analytes are provided in Appendix F. Conditions 1 and 2 Bias and Precision, Inter-Method Comparison The objectives for Conditions 1 and 2 were to measure baseline method bias and precision. Condition 1 was conducted using paired Method 26 trains and Condition 2 was conducted using paired Method 26A trains. After completion of the Conditions 1 and 2 tests, it became apparent that the data collected during these runs was not of sufficient quality to meet the study objectives. Deficiencies in the simulated flue gas delivery system compromised the ability to deliver flue gas with the targeted levels of the study analytes. This prompted a redesign of the sample delivery apparatus prior to execution of the testing for Condition 3. Figure 4-1 compares Condition 1 and 2 results to Condition 3 results. Note that the paired trains in Conditions 1 and 2 showed poor agreement with each other and with the FTIR. In addition the FTIR results were inconsistent. These deficiencies were corrected in Condition 3. The data from Conditions 1 and 2 were not used in formulating the conclusions and recommendations of this study. Figure 4-1 Comparison of Results from Conditions 1, 2, and 3 4-1

60 Condition 3 Bias and Precision, Inter-Method Comparison Condition 3 was designed to compare the results of Methods 26A versus Method 26 at low- (0.2 ppm) and mid-hcl (0.5 ppm) levels. The program objectives for measuring method bias and precision from Conditions 1 and 2 were also incorporated into the Condition 3 tests. The run duration was 30 minutes. The results from Condition 3-1 and 3-2 are shown in Table 4-1 and plotted in Figure 4-2. Table 4-1 Condition 3: Test Conditions and Results Condition/Train 3-1A 3-1B 3-2A 3-2B Number of Runs 7 7 Method 26A 26 26A 26 Target Input HCl (ppmv) Average Measured HCl by FTIR (ppmv) St. Dev. (ppmv) Relative St. Dev. (%) 14.8% 2.2% Average Measured HCl by Method by Train (ppmv) (0.51) 0.51 (0.52) Std Dev. (ppmv) (0.024) (0.015) Relative St. Dev. (%) 23.2% 14.5% 12.0% (4.6%) 4.6% (3.1%) Relative St. Dev. Corrected for HCl Input Variation (%) () values in parentheses are calculated without outlier value. 22.3% 10.7% 11.6% (5.0%) 5.0% (3.4%) Figure 4-2 Condition 3 Results 4-2

61 One data point in Condition 3-2 (Run 3) may be an outlier. The values in parentheses in Table 4-1 show the statistics with this potential outlier removed. The RSD (precision) of each method is corrected for HCl input variability. This correction is necessary since the HCl delivered to the sampling trains varied slightly from run to run. Method 26A exhibited greater variability (higher %RSD) than Method 26 at both the 0.2 ppmv and the 0.5 ppmv levels. The greater variability of Method 26A observed in this study is at odds with EPA s assessment of the methods. The in-stack detection limits stated in each method indicate that Method 26A has less variability. Bias between methods is determined by evaluating the difference between the two methods for each run. The differences are averaged and a 95% confidence interval is calculated. If zero is included within this interval, the methods are not significantly biased with respect to each other. There is no significant bias between the two methods at either the 0.2 ppmv or the 0.5 ppmv levels. There is no significant bias between Method 26A and the FTIR result at either the 0.2 ppmv or the 0.5 ppmv levels. However, the Method 26 results at the 0.2 ppm level are biased high by 25% compared to the FTIR. Method 26 shows no significant bias at the 0.5 ppmv level. The detection limit for Method 26A calculated as 3 times the standard deviation from the 0.2 ppmv target runs is 0.13 ppmv. The detection limit for Method 26 calculated in the same manner is 0.09 ppmv. Condition 4 Br2, Cl2, Ash Interactions Condition 4 was designed to study the effects of Br2 and Cl2 on HCl and HBr measurements, with and without fly ash present in the sample. The testing consisted of eight test series. Each series consisted of two 30-minute test runs with paired Method 26 trains. For half of the test runs, the sampling trains were operated with simulated dust cakes on the sample filters, while for the other half, the sampling trains used clean filters. All of the ash used to simulate the dust cakes was from Ash Sample 081, a fly ash from an 80:20 Powder River Basin (PRB)/lignite coal blend. Effect of Cl2 on M26A/M26 HCl Recovery Under the test conditions established for this project, all of the Cl2 in the flue gas hydrolyzed to HCl and was measured in the first impingers as HCl. This resulted in very high HCl biases for all of the test runs where chlorine was present. Stoichiometry of Cl2 is discussed below in the results of Condition 5. This very high HCl bias tended to overwhelm any smaller bias effects from other flue gas components. This result is consistent with other studies [Sun, et al. (2000)] and is related to the high SO2/HCl ratio. The results of the HCl measurements without chlorine in the flue gas are summarized in Table 4-2. Results of HCl measurements with chlorine in the flue gas are shown in Table 4-3. When Cl2 was present in the gas stream part of the Cl2 was converted to HCl prior to the impinger trains. This results in a positive bias in the FTIR results. 4-3

62 Table 4-2 Condition 4: Test Conditions and Results (Zero Cl2 Runs) Condition/Train 4-1A 4-1B 4-2A 4-2B 4-5A 4-5B 4-6A 4-6B Number of Runs Method Target Input HCl (ppmv) Target Input Cl 2 (ppmv) Target Input Br 2 (ppmv) Ash None PRB Blend None PRB Blend Average Measured HCl by FTIR (ppmv) St. Dev. (ppmv) Relative St. Dev. (%) 1.1% 0.2% 12.5% 0.4% Average Measured HCl by Method by Train (ppmv) Std Dev. (ppmv) Relative St. Dev. (%) 23.5% 10.9% 9.7% 7.4% 4.3% 11.5% 2.3% 0.7% Average Measured HCl by Method All Trains (ppmv) Std Dev. (ppmv) Relative St. Dev. (%) 15.2% 7.4% 7.1% 1.8% In the following figures showing Condition 4 results, Run was included graphically but was not used in the analysis of the data. Figure 4-3 shows that the paired train data from this run were not in agreement with its replicate run or with any other similar runs. The RSD of the train difference (A-B) for Run was approximately 12.5% compared to Run at 0.32%. Because Run was the first run in which Br2 was injected into the delivery system, it is believed that the system had not yet reached equilibrium when Condition 4 testing began. Since Br2 concentration could not be measured in real time, it was difficult to predict when equilibrium was reached. The results of the rest of the runs indicate that equilibrium was reached in those runs. 4-4

63 Table 4-3 Condition 4: Test Conditions and Results (2 ppmv Cl2 Runs) Condition/Train 4-3A 4-3B 4-4A 4-4B 4-7A 4-7B 4-8A 4-8B Number of Runs Method Target Input HCl (ppmv) Target Input Cl 2 (ppmv) Target Input Br 2 (ppmv) Ash None PRB Blend None PRB Blend Average Measured HCl by FTIR (ppmv) St. Dev. (ppmv) Relative St. Dev. (%) 5.2% 4.8% 1.7% 0.1% Average Measured HCl by Method by Train (ppmv) Std Dev. (ppmv) Relative St. Dev. (%) 0.3% 3.2% 0.7% 1.6% 14.5% 13.4% 1.0% 0.9% Average Measured HCl by Method All Trains (ppmv) Std Dev. (ppmv) Relative St. Dev. (%) 3.8% 1.3% 11.4% 2.9% Figure 4-3 Effect of Cl2 on Method 26A/26 HCl Measurement 4-5

64 The results from Run appear significantly lower than the corresponding runs. Investigation into this difference revealed no obvious causes. Therefore, this point was included in subsequent analyses. The results from Train A and Train B were essentially identical; therefore the data points overlap in Figure 4-3. Effect of HBr and Br2 on M26A/M26 HCl Recovery Because of a lack of HCl/Cl2 speciation for all test runs, it is not possible to determine the effects of HBr or Br2 on speciation of chlorides in the impingers. However, when examining the FTIR data effects may be seen. When Cl2 and HBr are present without Br2 (Runs 4-7 and 4-8), some Cl2 converts to HCl in the gas stream prior to the impingers. See Figure 4-3. When Br2 is added (Runs 4-3 and 4-4) this conversion is reduced. A dynamic equilibrium is present in stack gas between hydrogen halides and halogens: 2HBr + Cl 2HCl+Br When HBr and Cl2 alone (without Br2) are present in the gas stream, the equilibrium is shifted forward, resulting in increased conversion of Cl2 to HCl. When Br2 is added, the equilibrium is shifted backwards, resulting in decreased conversion of Cl2 to HCl. This effect may be seen by comparing the FTIR average from Run 4-7 and 4-8 to Runs 4-3 and 4-4 in Figure 4-3. The runs with Br2 added show a 0.5 ppmv reduction in HCl concentration compared to the same conditions without the presence of Br2. Figure 4-4 shows the HBr measurements from runs with and with Cl2 and Br2 added. It was noted that the paired train results for HBr during the first 8 runs of Condition 4 did not show agreement. The difference between trains is fairly consistent; however, no explanation for this trend was identified. Figure 4-4 Effect of Br2 on Method 26A/26 HBr Measurement 4-6

65 Effect of Fly Ash on HCl The presence of Fly Ash 1 (081 PRB:lignite blend) on the filter, had no effect on HCl concentration. This was true whether or not Br2 or Cl2 was present. These runs were conducted with a 30 minute sample duration. Runs with a longer sample duration (180 minutes) that had fly ash present did show a minor effect this is discussed below under Condition 7. Effect of Br2 on HBr When Cl2 is Not Present The result of test runs conducted with bromine in the absence of chlorine is shown in the two rightmost columns in Figure 4-4. For all runs without Cl2 in the gas stream there was no measurable effect on HCl concentration observed from the presence of Br2 or the presence of fly ash on the filter. Br2, however, did bias the HBr concentration. When Br2 was present, the HBr recovery on the Method 26 trains was biased high. When no Br2 was present, the HBr recovery was as expected. During all runs with no Br2 present, the HBr concentration measured by FTIR was much lower than the HBr delivered to the system. Under these conditions, HBr oxidizes SO2 without any equilibrium inhibition from Br2 since Br2 was not present. As the redox reaction moves forward, the HBr and SO2 concentrations decrease while Br2 and SO3 are created. Increased SO3 was measured by the FTIR under these conditions. This reaction reaches an equilibrium simultaneously with the equilibrium between all four main analytes (HCl, HBr, Br2, Cl2). Effect of Br2 on HBr When Cl2 is Present The result of test runs conducted with bromine in the presence of chlorine is shown in the two leftmost columns in Figure 4-4. As described above, when Cl2 is present in the flue gas stream under the condition of these tests, HCl is biased very high. However, if Br2 is also present, it mitigates this bias to some degree the bias for HCl is not quite as high. The Condition 5 discussion, below, has a thorough explanation of this effect. Condition 5 SO2 and Cl2 Effects on Halogen Speciation Condition 5 was designed to study the ability of Method 26 to differentiate between HCl and Cl2 in the presence of SO2. This study also examined the effects of absorbing solution ph on the resulting distribution of HCl/Cl2 in the impingers. Table 4-4 below summarizes the Condition 5 test conditions and results. Results of these runs are shown in Figure 4-5. Three series of triplicate runs were conducted, with different SO2 concentrations, ranging from approximately 50 ppmv to 450 ppmv. HCl and Cl2 concentrations of 0.5 and 2 ppmv, respectively, were targeted. Two additional runs constituting a fourth series were conducted without HCl present. Each run was 30 minutes in duration and involved operation of paired Method 26 trains with simulated filter cakes composed of ash from sample 081. For each pair of trains (except the fourth series), the ph of the absorbing solution in the acidic impingers for one of the trains was lowered using higher strength sulfuric acid reagent (0.25 N versus 0.1 N). As in Condition 4, no Cl2 speciation was observed under any of the test conditions. All Cl2 hydrolyzed to HCl and was measured as HCl in the sampling trains, resulting in a very high HCl bias. The fortification of the acidic impinger reagent and the varying concentrations of SO2 did not improve method performance. 4-7

66 Table 4-4 Condition 5: Test Conditions and Results Condition/Train 5-1A 5-1B 5-2A 5-2B 5-3A 5-3B 5-4A 5-4A Number of Runs Method Target Input HCl (ppmv) Target Input SO 2 (ppmv) Acidic Impinger Molarity Average Measured HCl by FTIR (ppmv) St. Dev. (ppmv) Relative St. Dev. (%) 23.0% 9.2% 7.7% 16.7% Average Measured HCl by Method by Train (ppmv) (4.7) Std Dev. (ppmv) Relative St. Dev. (%) 10.6% 10.4% 1.0% 1.7% 0.03% Average Measured HCl by Method All Trains (ppmv) 10.4% (1.2%) 0.7% 1.9% (4.7) 4.4 Std Dev. (ppmv) (0.032) Relative St. Dev. (%) 9.6% 1.4% 7.0% (0.7%) 1.6% Figure 4-5 Effect of Varying SO2 on HCl 4-8

67 The work by Sun et al showed that SO2/HCl ratios greater than or equal to eight would result in 100% Cl2 conversion to HCl (no speciation). The lowest achieved ratio in this study was 81, or approximately 10 times the ratio for 100% Cl2 conversion. The high SO2/HCl ratios had more impact on speciation than the above mentioned efforts to enhance the method for speciation. Since Cl2 is a homonuclear diatomic molecule, complete recovery in the acidic impinger results in double the amount of chloride ion measured compared to HCl (two chlorides form from every molecule of Cl2). At a target of 2 ppmv Cl2, the reported HCl concentration would be 4 ppmv. This concentration, added to the actual HCl in the system, accounts for all of the observed bias in these runs. The lack of speciation can be accounted for by the equilibrium reactions occurring in the impingers. When the moisture in the gas stream condenses in the first impinger, the Cl2 reacts with SO2 and water to form chloride ions, according to the following reaction: SO +Cl +2H O 4H +2Cl +SO Because the SO2 concentration is much higher than Cl2, all Cl2 reacts to form the products. In the absence of SO2 this reaction will not occur and Cl2 would remain unreacted, making speciation possible. As SO2 increases, the equilibrium shifts towards product (SO4-2 ), resulting in increased Cl2 conversion. As Sun et al observed, at a SO2/HCl ratio of eight, all Cl2 is converted (see Appendix A, Figure A-1). In an attempt to drive the equilibrium back to Cl2, the H2SO4 molarity was increased in the acidic impingers in several test runs. However, the limiting product in the reaction was HCl, since its concentration was only 0.5 ppmv. These concentrations resulted in a net forward reaction to completion. Thus all Cl2 was converted to HCl in the impingers, even at the higher impinger acid concentration. In Condition 5-4, no HCl was delivered to the sampling system but approximately 2 ppmv Cl2 was delivered. All chloride measured in the trains was collected in the acidic impingers and reported as HCl. This is in agreement with the other Condition 5 runs. However, since no HCl was delivered to the sampling system, no HCl should have been measured by FTIR. During this condition, however, the FTIR averaged 0.27 ppmv. A plausible explanation for this observation is that some of the Cl2 was being converted to HCl in the delivery system by hydrolysis, according to the reaction: The equilibrium between reactants and products reached by the system produced approximately 0.27 ppmv HCl as measured by FTIR. Further evidence of this is found in the rest of the Condition 5 runs, where a decreasing trend of HCl is found. During testing of Conditions 5-1, 5-2, and 5-3, HCl, Cl2 and the rest of the flue gas components were constantly flowing through the system, including between runs. SO2 was varied from run to run to achieve these three conditions. In the initial Condition 5 runs, HCl was approximately 0.2 ppmv higher than expected based on the FTIR results. Because HCl was being added to the system, the equilibrium shifted back towards the reactants, leading to a decrease in HCl with each subsequent run. Eventually the system reached equilibrium, with HCl concentration measured by FTIR being in agreement with the targeted HCl. 4-9

68 For most applications and sources, a small equilibrium shift of less than 0.3 ppmv is insignificant. However, at low HCl concentrations, this shift is significant. Therefore, the simultaneous presence of Cl2 and water in high temperature sources may produce a positive bias in HCl measurements when the HCl concentration is small. The bias will be a function of HCl concentration and Cl2 concentration, where bias is increased as the ratio of Cl2/HCl increases. Condition 6 Train Pre-Conditioning Effects The objective of Condition 6 was to study the effects of pre-conditioning the filter according to the requirements of ASTM Method D6735, compared to the normal 5-minute preconditioning required by Method 26. Pre-conditioning involves exposing the filter to sample gas prior to using it to collect a sample. Two series of test runs were performed at different HCl levels (0.5 ppmv and 1.6 ppmv). Three runs were conducted at the 0.5 ppmv HCl level and four runs were conducted at the 1.6 ppmv level. Table 4-5 summarizes the Condition 6 test conditions and results. Each test run was 30 minutes in duration and consisted of a standard Method 26 train paired with a Method 26 train in which the filter was pre-conditioned with the sample flue gas mixture for 30 minutes. In the pre-conditioning step, a steady state sample gas stream was flowed through the filter and impingers, in the same way a run would be conducted. At the end of the preconditioning step, the impingers were replaced with a fresh set. The run was then conducted with the pre-conditioned filter and the fresh set of impingers. The filters of each train contained a simulated dust cake comprised of ash from Ash Sample 081 PRB Blend. The flue gas matrix was intended to be representative of wet FGD emissions. Table 4-5 Condition 6: Test Conditions and Results Condition/Train 6-1A 6-1B 6-2A 6-2B Number of Runs 4 3 Method Target Input HCl (ppm) Precondition Time (min) Average Measured HCl by FTIR (ppm) St. Dev. (ppm) Relative St. Dev. (%) 0.9% 1.1% Average Measured HCl by Method by Train (ppm) Std Dev. (ppm) Relative St. Dev. (%) 4.6% 4.1% 5.9% 2.7% Relative St. Dev. Corrected for HCl Input Variation (%) 4.7% 3.8% 6.1% 3.8% 4-10

69 Figure 4-6 shows the results of the pre-conditioning runs. Extended pre-conditioning did not have a significant effect on the performance of either method. There was no significant difference in HCl concentration between the 5 minute pre-condition and the 30 minute pre-condition. Neither of the trains were biased compared to the FTIR results. In all trains for Condition 6, Fly Ash 1 (081) was pre-loaded onto the filter, but did not appear to affect the method performance. The only difference between Train B in Condition 3-2 (baseline runs) and Train A in Condition 6-2 was the presence of fly ash on the filter. Since the RSD was 5.0% in Condition 3-2 compared to 6.1% in Condition 6-2, we can conclude that the fly ash had no significant effect on method performance. Note that in Condition 6-1, the first run is included graphically but was not used in analysis of the results. This run was invalid because the filter holder broke during the run. An example of a broken filter holder is shown in Appendix D. Figure 4-6 Effect of Preconditioning Condition 7 Run Duration Effects Condition 7 examined the impacts of different sampling durations on Method 26 results. Sampling durations of 180 minutes and 30 minutes were compared. Two series of tests were conducted at this condition using two different ashes to simulate dust cakes on the filters Ash Samples 118 (Eastern Bituminous) and 119 (PRB). Table 4-6 provides a summary of the Condition 7 test conditions and results. Three test runs were conducted for each ash. Each run consisted of a Method 26 train operated for 30 minutes paired with one operated for 180 minutes. The targeted flue gas mixture contained 0.5 ppmv HCl and was representative of wet scrubbed FGD emissions. Runs at the longer sampling duration had better precision than the standard 30-minute runs but higher bias compared to FTIR. The trends were similar for both types of fly ash. The 180 minute runs were biased high by 0.05 ppmv (10%) and the RSD was lower than Condition 3 baseline tests. Figure 4-7 shows the Condition 7 results. During the 180 minute runs, it is possible that 4-11

70 any chloride buildup on the filter medium broke through due to the combination of high sampling time and high gas stream temperature. Chloride buildup can be from fly ash content or from HCl collected on the filter medium during the pre-run purge. Table 4-6 Condition 7: Test Conditions and Results Condition/Train 7-1A 7-1B 7-2A 7-2B Number of Runs 3 3 Method Target Input HCl (ppm) Fly Ash E. Bit. PRB Sampling Duration (min) Average Measured HCl by FTIR (ppm) St. Dev. (ppm) Relative St. Dev. (%) 7.5% 5.8% Average Measured HCl by Method by Train (ppm) Std Dev. (ppm) Relative St. Dev. (%) 8.7% 11.5% 6.8% 5.9% Relative St. Dev. Corrected for HCl Input Variation (%) 4.4% 8.8% 1.7% 6.0% Figure 4-7 Effect of Extended Run Time 4-12

71 For the 30 minute runs, there was not a significant difference between the trains and no significant bias compared to the FTIR. RSDs were nearly identical to the baseline runs. In addition to a high bias, extended run times were not favorable for the Teflon filter holders specified in Method 26. After 30 minutes at high temperature, the Teflon filter holders would sometimes break or crack. Glass filter holders were not affected by run time. Condition 8 Ammonia and Filter Temperature Effects Condition 8 examined the impacts of ammonia and elevated filtration temperature on Method 26 results. Two series of tests were performed at this condition using two different ashes to simulate dust cakes on the filters -- Ash Samples 081 (PRB Blend) and 117 (Central Appalachian). Table 4-7 provides a summary of the Condition 7 test conditions and results. Three 30-minute test runs were conducted for each ash. Each run consisted of a Method 26 train operated with a nominal filtration temperature of 250 F and one operated at a temperature of 350 F. The targeted flue gas mixture contained nominally 5 ppmv NH3, 0.5 ppmv HCl, and the matrix was representative of wet FGD emissions. Figure 4-8 shows the results from Test Condition 8. There was no significant difference in HCl concentrations between the 350 F train and 250 F train. There was also no significant difference between either train and the FTIR. However, the high temperatures runs in the first series of runs (with the PRB ash) had an RSD of 11.8%, about twice that of baseline runs, while the high temperature runs with the Central Appalachian ash had an RSD of 1.3%, much lower than the baseline runs (Condition 3). Table 4-7 Condition 8: Test Conditions and Results Condition/Train 8-1A 8-1B 8-2A 8-2B Number of Runs 3 3 Method Target Input HCl (ppm) Filter Temperature F Fly Ash PRB Blend Central App. Ammonia (ppm) 5 5 Average Measured HCl by FTIR (ppm) St. Dev. (ppm) Relative St. Dev. (%) 2.9% 0.1% Average Measured HCl by Method by Train (ppm) Std Dev. (ppm) Relative St. Dev. (%) 6.8% 10.6% 5.2% 1.2% Relative St. Dev. Corrected for HCl Input Variation (%) 7.2% 11.8% 5.0% 1.3% 4-13

72 Figure 4-8 Method 26 Ammonia and Elevated Filter Box Temperature Runs During Run 3 of Condition 8-2, condensation was noted in the sampling trains. Therefore, the data from this run is excluded. Since there are only 2 remaining runs, the confidence intervals used to determine bias are very large and therefore not sensitive to small bias effects. The temperature of the gas stream leaving the delivery system and entering the filter box was approximately 400 F. It is possible that if the gas stream temperature were lower, these tests might have been more sensitive to filter box temperature. Discussion of Method Performance Comparison of Method Precision with Literature Values Figure 4-9 compares the duplicate train relative standard deviation calculated from each test run plotted against the RSDs from the ReMAP Method 26 field data (Lanier, 2001). The ReMAP field data is also shown alone on Figure A-2 in Appendix A. For all but two runs, the duplicate train RSDs from this laboratory study are below the ReMAP correlation curve, showing that the methods were run with better duplicate train precision than measured in the field in A new correlation was developed using all runs from this study. It is not surprising that better precision is achievable under controlled laboratory conditions. 4-14

73 Figure 4-9 Duplicate Train %RSD Compared to Literature Values Impinger Chloride Collection Efficiency According to the EPA methods, the knockout and acidic impingers should be recovered together, and the alkaline impingers should be recovered together. In several test runs in our study, each impinger was recovered and analyzed separately, to gain a better understanding of where the analytes were ending up. In the Method 26 runs at low HCl concentrations (< 1 ppmv), the trains with the modified recovery procedure showed an average recovery of HCl of greater than 93% in the first (knockout) impinger. The recovery percentages are shown in Figure Essentially all of the remaining chloride content was collected in the first acidic impinger. For HCl concentrations above 1 ppmv (maximum of 8 ppmv), the collection efficiency of the first impinger dropped to 85%. The high recovery of chloride content in the knockout impinger shows that at low concentrations of HCl, Method 26 will capture all chlorides in the sample stream. In the Method 26A runs, shown in Figure 4-11, the first impinger collection efficiency averaged 31%; the second impinger collection efficiency averaged 66%. The collection efficiency of the impingers were not affected by HCl concentration for the range tested in this study (0-5 ppm). 4-15

74 Figure 4-10 Method 26 Impinger Collection Efficiency Low HCl Concentrations (0-5 ppm) Figure 4-11 Method 26A Impinger Collection Efficiency Low HCl Concentrations (0-5 ppm) 4-16

75 Ion Chromatography Method Evaluation In an attempt to confirm the ion chromatography results, a sample of known concentration was sent to three independent laboratories. All three laboratories were accredited by the National Environmental Laboratory Accreditation Conference (NELAC) and had recently passed audit sample testing. The audit sample had a concentration of 365 ppmv HCl (0.01N). All three laboratories performed IC analysis in accordance with Method 26 procedures. As can be seen in Figure 4-12, there was generally poor agreement between the lab results and the audit sample concentration. Lab A was asked to repeat the IC analysis a second time after they reported a result 23% lower than the expected concentration. The second result was somewhat higher but was still significantly lower than the expected concentration. These limited audit sample results raise a potential red flag as it relates to the bias and precision of analytical laboratory ion chromatography testing. If stricter ion chromatography QA/QC guidelines are not incorporated into the method, the bias associated with analytical results could far outweigh all other interferences in the method, other than speciation of HCl and Cl2. Figure 4-12 Comparison of Analytical Laboratory IC Audit Results 4-17

76

77 5 SUMMARY AND CONCLUSIONS The main objective of this study was to determine the performance of Method 26 at different testing conditions that simulate field conditions at a coal combustion source. The principal findings of the study were as follows: Method Precision and Bias At the baseline conditions for this study, Method 26 appears to give more precise results than Method 26A a relative standard deviation (RSD) of 11% vs 22% at 0.5 ppmv HCl and 5% vs 11% at 0.2 ppmv HCl. Method 26A exhibited no bias compared to FTIR at either concentration. Method 26 exhibited a 25% high bias compared to FTIR at 0.2 ppmv and no significant bias at 0.5 ppmv. It was expected that Method 26A should have better precision and a lower detection limit since the isokinetic flow rate was approximately 10 times the flow rate of Method 26 and the total metered sample volume was much higher. However, in contrast, Method 26A had a poorer precision and a higher detection limit based on the variability of the results. One possible explanation of this finding is that the sample stream might not have enough residence time inside of the impinger train for complete HCl molecular interaction with the liquid reagent due to the high flow rate. Because of an inadequate residence time, absorption of HCl into the liquid reagent will be limited by the random movement of the molecules in the sample gas, resulting in imprecision. In addition to high flow/low residence time, greater imprecision in Method 26A compared to Method 26 may also be explained by variation in the flow rates through the meter boxes. The flow rate for Method 26A is adjusted throughout the run to maintain isokinetic flow (±10%) and is therefore not constant. During testing, flow was set arbitrarily to approximately 19 LPM, but the manometer indicated that actual flow varied from run to run. In fact, it was frequently observed to change slightly during the run due to minor variation in pressure and temperature. Method 26 is a constant flow method. A calibrated orifice was used in conjunction with the meter box to ensure constant flow. The combination of higher flow and larger uncertainty in the total sample volume contributed to greater imprecision in Method 26A relative to Method 26. The duplicate train RSDs for every completed run were compared to field data from literature sources; the laboratory study RSDs had better precision than the field data. One possible explanation for this difference is that in our study, the sampling probe was kept well above the acid dew point, which minimized any HCl dropout due to condensation. Dropout in the field varies from train to train and cannot be predicted, so dropout would add to the scatter (noise) observed. 5-1

78 Speciation of HCl and Chlorine At the high SO2/HCl ratios (>80) examined in this study, Method 26 was not able to speciate Cl2. This result is consistent with previous studies, which found that at SO2: HCl ratios above 8, 100% of Cl2 was converted to HCl in the acidic impinger. All Cl2 was measured as HCl, resulting in HCl results biased high. Speciation of HBr and Bromine Bromine (Br2) exhibited the same lack of speciation as Cl2. It also appeared to have an effect on HCl concentration. When Cl2 is present, HCl is biased high. When both Cl2 and Br2 are present, the HCl is still biased high but to a lesser degree. The proposed mechanism for this observation is that all four species will exist in a dynamic equilibrium that is dependent on individual concentrations and temperature. This equilibrium shifted some HCl back to chlorine when bromine was added to the system. When bromine and/or HBr is present in the flue gas even at low levels, it is difficult to predict speciation. It appears that the system reaches an equilibrium before reaching the liquid phase in the impinger train, so all four species will be biased in some way. Method Performance in the Presence of SO2, Ammonia, and HBr It was not possible to determine the effect of SO2 alone on bias and precision due to the overwhelming bias resulting from Cl2. The presence of NH3 does not appear to significantly influence either the precision or bias of the HCl measurement. HBr appeared to cause the HCl results to be biased high by about 12%. In considering all trains in Condition 8 that used a normal temperature in the filter box, the presence of ammonia becomes the isolated variable. Based on these data, there is no measurable effect of the presence of ammonia on Method 26 performance. Upon isolation of temperature of the filter box, it appears that filter box temperature by itself does not affect the method performance. The only instance where Method 26 is biased versus FTIR in this condition is when the filter box temperature is high and eastern bituminous coal fly ash is pre-loaded onto the filter. Further investigation is required to confirm this bias. Impinger Solution Chemistry Since Cl2 was not successfully speciated during this test, the effect of impinger chemistry (acid normality) on Cl2 speciation could not be determined. When Cl2 was present, it reacted with SO2 in the flue gas to form HCl and H2SO4 in the acidic impinger. The simultaneous presence of Cl2 and water in high temperature sources may produce a positive bias in HCl measurements when the HCl concentration is small. The bias will be a function of HCl concentration and Cl2 concentration, where bias is increased as the ratio of Cl2/HCl increases, and will decrease as the ratio of Cl2/HCl decreases. Effect of Fly Ash The different types of fly ash tested did not appear to significantly affect the method results with a 30 minute run. However, with a 180 minute run, both a PRB ash and an Eastern Bituminous ash exhibited higher precision in results, but also a 10% high bias compared to the FTIR reference. In the high temperature runs, Central Appalachian ash showed a higher precision in results but also showed a potential low bias of about 8%. This result from Central Appalachian 5-2

79 ash was not statistically significant, however, due to the low number of runs at this condition. PRB blend ash did not exhibit a bias at high temperatures. Not all ashes were tested under all conditions. Effect of Filter Temperature During this study, the system temperature was much higher than the estimated acid gas dewpoints during all runs. As a result, variations in the filter temperature had no impact on the method performance. If the flue gas temperature were closer to the acid dew point, it is possible that these results would have been different. However, our experience with the sample delivery system indicates that temperatures closer to the acid dewpoint result in sample loss in Methods 26 and 26A. Effect of Sampling Train Preconditioning Extending the pre-conditioning time beyond the 5 minutes required in Method 26 (as for example in ASTM D ) had no effect on HCl precision or bias. The pre-conditioning runs in Condition 6 were effectively a longer pre-run purge than what is already required by Method 26. For PRB ash, there was no measurable effect in the bias or precision of Method 26. Also, preconditioning the filter box prior to a sample run had no appreciable effect on the performance of the method. The five minute pre-run purge through the borosilicate glass stopcock is sufficient conditioning for Method 26. It is unknown if Method 26A would benefit from a pre-conditioning step; it does not currently require such a step. Evaluation of Best Practices for Methods 26 and 26A The following best practices were identified as a result of the laboratory study: The probe material should be made of borosilicate glass and not Teflon. The filter holder and support should be made of borosilicate glass or quartz. The Teflon filter holders specified in the method are confirmed to not be compatible with the temperature of the filter box in which the holder should be placed, both by experience and by the manufacturer. The temperature of the probe should always be well above the acid dew point of the flue gas. The method currently specifies a probe temperature in the range of C ( F) in order to prevent condensation. A typical source today can very well be the outlet of a wet scrubber, where the flue gas is relatively cool and condensing. In this case, the probe acts as a heater to vaporize the flue gas prior to passing through the filter and into the impinger train. In this study, the simulated probe in the system was set to be constantly above 200 C (392 F). This insures that the simulated flue gas temperature (which is decidedly different than probe temperature) will never drop below the acid dew point. Potential sampling biases resulting from improper or inadequate sampling train cleaning practices were investigated. Specific guidelines for cleaning the sampling train impingers prior to the start of test program, and between test runs were developed as a result of the laboratory study. The cleaning procedures are intended to mitigate contamination from previous tests, from the cleaning materials, or from interactions of analytes with cleaning material residue. Recommended procedures for equipment cleaning are provided in Appendix E. 5-3

80 The QA/QC requirements for the analytical portion of Methods 26/26A may require further scrutiny. In order to minimize possible breakthrough of chlorides deposited on the filter media, minimize the run time, especially at high temperature sources. The sample volume should be sufficiently large to have acceptable detection; however, shorter run times at high temperatures is recommended. In Method 26, a majority of total chloride content is recovered in the knockout impinger prior to the first acidic impinger. Therefore an enhanced rinsing procedure is necessary to ensure high chloride recovery. In Method 26A, the knockout impinger is not dry and so chloride recovery in that impinger is lower. While it is important to adequately rinse every piece of glassware, the knockout impinger rinse and recovery of Method 26A will more closely follow the rinse and recovery of other impingers. Recommendations for Future Research Further investigation should be conducted into method modifications that could potential address the lack of speciation of halogens in high SO2 sources. In the case of an unscrubbed source, there is potential to preferentially scrub SO2 and inhibit the SO2-Cl2 reaction. In the case of a source with a wet FGD, there are data from the 2010 ICR tests that suggest SO2 may be preferentially scrubbed compared to halogens and hydrogen halides. In either case, there is also the possibility of spiking the acidic impingers with a hydrogen halide (or halide ion) that would drive the SO2-Cl2 reaction towards Cl2. If the amount of halide spiking is known, that amount can be subtracted from the final concentration. This helps in terms of equilibrium but may have a negative effect on the method detection limit. Further research on the subject of optimum probe temperature in coal combustion source testing would be beneficial. If probe temperature is too cold, hydrogen halides may condense prior to the first impinger. If probe temperature is too hot, filter breakthrough of volatile components is possible. The objective would be to optimize probe temperature for maximum recovery. In addition to probe temperature, gas stream temperature is important. Reactions between gas stream components occur before reaching the sampling train and the stack exit. It is possible that the temperature of the gas stream affects these reactions. Laboratory testing may simulate identical initial gas streams with varying temperatures. In order to isolate possible ammonia effects, additional testing is necessary with varying ammonia concentrations. Further evaluation of the effects of fly ash on the filter should be conducted. If fly ash contains high alkalinity, then it follows that there is a greater chance of halide dropout on the filter. However, alkalinity of the different types of fly ash were assumed and not determined in this study. Better characterization of fly ash used in future studies will provide greater insight as to how fly ash presence and type might have an effect on HCl measurement. Bromine addition to facilitate Hg removal is a growing trend in the power generation industry; thus, the conversion between Br2 and HBr and its effect on both the method performance and control technology performance should be studied further. A study of varying Br2 and HBr concentrations, along with varying temperatures and flow rates could help characterize typical kinetic behaviors of bromine in a flue gas stream. 5-4

81 6 REFERENCES ASTM Standard Test Method for Measurement of Gaseous Chlorides and Fluorides from Mineral Calcining Exhaust Sources-Impinger Method. Central Pollution Control Board (Delhi), Chapter 3 Determination of Hydrogen Halides (Hx) and Halogens from Source Emission and Chapter 4 Standard Operating Procedure for the Sampling of Hydrogen Halides and Halogens from Source Emission, September CFR, National Emission Standards for Hazardous Air Pollutants From Coal and Oil-Fired Electric Utility Steam Generating Units and Standards of Performance for Fossil-Fuel-Fired Electric Utility, Industrial-Commercial- Institutional, and Small Industrial-Commercial- Institutional Steam Generating Units. Vol. 77, No. 32. February 16, Cheney, J.L. and Fortune, C.R Evaluation of A Method for Measuring Hydrochloric Acid in Combustion Source Emissions, The Science of the Total Environment, 13, pp Cheney, J.L. and Fortune, C.R Improvements in the Methodology for Measuring Hydrochloric Acid in Combustion Source Emissions, Journal of Environmental Science & Health, A19(3), pp DeWees, W.G., Steinsberger, S.C., Margeson, J.H., Knoll, J.E. and Midgett, M.R Laboratory and Field Evaluation of A Methodology for Measuring HCl Emissions from Stationary Sources, in Proceedings of the 1989 EPA/AWMA International Symposium: Measurement of Toxic and Related Air Pollutants, Document VIP-13, Air and Waste Management Association, Pittsburgh, PA. EPA Method 5, 40 CFR Part 60, Determination Of Particulate Matter Emissions From Stationary Sources. EPA. 1994a. United States EPA Method 26A- Determination of Hydrogen Halide and Halogen Emissions from Stationary Sources Isokinetic Method. EPA. 1994b. United States EPA Method 26, 40 CFR Part 60, Determination of Hydrogen Halide and Halogen Emissions from Stationary Sources Non-Isokinetic Method. EPA. 2007a. SW-846 Method 0050, Isokinetic HCl/Cl2 Emission Sampling Train. EPA. 2007b. SW-846 Method 0051, Midget Impinger HCl/Cl2 Emission Sampling Train. EPA Supporting Statement for OMB Review of EPA ICR No (OMB Control Number ): Information Collection Effort for New and Existing Coal- and Oil-Fired Electric Utility Steam Generating Units, December 24, EPA EPA Fact Sheet: Mercury and Air Toxics Standards for Power Plants, December 21,

82 EPRI Data Quality Evaluation of Hazardous Air Pollutants Measurements for the U.S. Environmental Protection Agency s Electric Utility Steam Generating Units Information Collection Request. EPRI, Palo Alto, CA: EPRI Emission Factors Handbook: Guidelines for Estimating Trace Substance Emissions from Fossil- Fuel-Fired Steam Electric Power Plants. EPRI, Palo Alto, CA: Institute of Clean Air Companies White Paper: Monitoring of HCl, Washington, DC, January Johnson, L.D. Stack Sampling Methods for Halogens and Halogen Acids. In Proceedings of the EPA/A&WMA International Symposium, Measurement of Toxic and Related Air Pollutants; A&WMA: Pittsburgh, PA, May 1996; Publication VIP-64, pp Lanier, W. S., and Hendrix, C. D., Reference Method Accuracy and Precision (ReMAP): Phase I, Precision of Manual Stack Emission Measurements, ASME, February State of California Air Resources Board. Method 421 Determination of Hydrochloric Acid Emissions from Stationary Sources. March 18, Steger, J.L., Wagoner, D.E., Bursey, J.T., Merrill, R.G., Fuerst, R.G. and Johnson, L.D., Steinsberger, S.C. and Margeson, J.H Laboratory and Field Evaluation of a Methodology for Determination of Hydrogen Chloride Emissions from Municipal and Hazardous Waste Incinerators, EPA/600/3-89/064, NTIS PB /AS, U.S. Environmental Protection Agency, Research Triangle Park, NC. Steger et al Laboratory Evaluation of Method 0050 for Hydrogen Chloride, in Proceedings of the 13th Annual International Incineration Conference, Houston, TX, University of California, Irvine, CA, May, Stern, D.A., Myatt, B.A., Lachowski, J.F. and McGregor, K.T Speciation of Halogen and Halide Compounds in Gaseous Emissions, in Incineration and Treatment of Hazardous Waste: Proceedings of the Ninth Annual Research Symposium, EPA-600/ , NTIS PB Sun, J.Q., et al The Effect of Coal Combustion Flue Gas Components on Low-Level Chlorine Speciation Using EPA Method 26A, Journal of the Air and Waster Management Association, 50(6), pp , June. Von Seebach, M., Gossman, D Cement Kilns Sources of Chlorides Not HCl Emissions, presented at the AWMA International Specialty Conference on Waste Combustion in Boilers and Industrial Furnaces, April, 1990, Kansas City, Mo. 6-2

83 A LITERATURE REVIEW Table A-1 Literature Reviewed for this Study Name of Study/Paper Author(s) Organization Date Published Speciation of Halogen and Hydrogen Halide Compounds in Gaseous Emissions Improvements in the Methodology for Measuring Hydrochloric Acid in Combustion Source Emissions Laboratory and Field Evaluation of a Methodology for Determination of Hydrogen Chloride Emissions from Municpial and Hazardous Waste Incinerators Cement Kilns Sources of Chlorides not HCl Emissions EMTIC Workshop Background Paper for Method 26 and 26A Stack Sampling Methods for Halogens and Halogen Acids The Effect of Coal Combustion Flue Gas Components on Low- Level Chlroine Speciation Using EPA Method 26A ReMAP: Phase 1- Precision of Manual Stack Emission Measurements Methods and Standard Operating Procedures (SOPs) of Emission Testing in Hazardous Waste Incinerator Stern, Myatt, Lachowski, McGregor United States Environmental Protection Agency (USEPA) May 1983 J.L. Cheney, C.R. Fortune USEPA July 1984 S.C. Steinsberger, J. H. Margeson USEPA August 1989 Dr. Michael von Seebach Gossman Consulting, Inc. April 1990 Prepared by Emission Measurement Center Emission Measurement Technical Information Center (EMTIC), USEPA September 1994 Larry D. Johnson USEPA January 1996 Sun, Crocker, Lillemoen W. Steven Lanier Ansari, Gouda, Thirumurthly, et. Al. Energy and Environmental Research Center (EERC) American Society of Mechanical Engineers (ASME) Central Pollution Control Board (CPCB) June 2000 February 2001 September 2007 A-1

84 Speciation of Halogen and Hydrogen Halide Compounds in Gaseous Emissions, Stern (1983). This is the first study that evaluated speciation between the halides and halogens using an impinger method. Several possible biases in the method were evaluated. The author proposed the current 4 impinger (without the optional short-stemmed impinger at the front) setup with two acidic impingers followed by two alkaline impingers based on a modified version of Method 6. A flue gas matrix was used in the study, and HBr was also present when evaluating the speciation of chlorine and HCl. The study found that it was possible to effectively speciate HCl and Cl2 provided the conditions are set properly. The study also found that purging the train with dry, clean air for up to 30 minutes after a run will not increase the amount chlorine collected in the two alkaline impingers. In other words, bubbling through the impingers will not push the chlorine that remained in the acidic impingers after the run through to the alkaline impingers. Finally, ion chromatography was concluded to be the preferred analytical method for measuring analytes. This was one of the first studies that employed ion chromatography in the analysis of chloride. It was determined that NOx and SOx in the flue gas during sampling did not interfere in the ion chromatographic analysis of chlorides, providing that a slow anion separator column was used. Previous analytical methods used an o-tolidine colorimetric method and a mercuric nitrate titration method. Improvements in the Methodology for Measuring Hydrochloric Acid in Combustion Source Emissions, Cheney (1984). This study looked at the preferred materials and operating conditions for the particulate filters when sampling for HCl in combustion sources. The overall conclusions of the study are as follows: A quartz filter is preferred over a glass filter or glass plug A high-velocity sample flow reduces chloride percent retention A minimum sample volume minimizes ash medium build-up on the filter A minimum filter temperature minimizes the chloride retention on the filter Comparing a glass wool plug, a glass fiber filter, and a quartz glass filter, it was determined that the quartz glass filter will absorb the least amount of equivalent chloride concentration in a sample stream, whereas a glass fiber filter will actually absorb more chloride than a glass wool plug. However, in a field situation operating at isokinetic flow rates (typically higher flow rates) the quartz filter is still preferred for minimum absorption and the glass plug retains the most chloride content. Another result from the study was that ash content from coal-fired sources and from cement plant sources accumulating on the filter had different affinities for gaseous HCl. Cement plant ash had much greater retention of chloride than coal-fired ash; however, high velocity sampling through a quartz filter at lower temperatures minimized chloride retention with any ash type. A-2

85 Laboratory and Field Evaluation of a Methodology for Determination of Hydrogen Chloride Emissions from Municipal and Hazardous Waste Incinerators, Steinsberger (1989). Steinsberger (1989) evaluated and refine the protocol for measuring HCl and performed a ruggedness field evaluation. The original modified Method 6 train (now used for M26) was used in sampling, along with a modified Method 5 train (now used for M26A). The author found that it is possible to reduce a high bias in the HCl measurement from Cl2 presence to less than 5% of the actual concentration. Also, increases in Cl2 concentrations (up to as high as 50 ppmv) do not appear to effect the speciation; rather, the flow rate appears to be the main influence in speciation efficiency. It is suggested that maximum speciation occurs around 2 liters per minute. The study also found that at concentrations below 5 ppmv, regular-sized impingers were significantly biased low compared to midget impingers. This effect was hypothesized to be due absorption of HCl by lime that built on the glass-fiber. In an effort to reduce the reaction of HCl with alkaline particulate, the study proposed a probe nozzle that is oriented counter to stack flow. A TECO HCl continuous emission monitor (CEMS) and a Bran and Luebbe HCl CEMS were compared to the trains in the field test. It was found that the TECO was in comparatively good agreement with the impinger train results, and that at high (~200 ppmv) concentrations of HCl, both CEMS and both trains were in relative agreement. The Bran and Luebbe HCl CEMS were consistently biased low but tracked changes in the HCl the same as the other CEMS and the trains. Cement Kilns Sources of Chlorides Not HCl Emissions, von Seebach (1990). This study looked at a broader analysis of the impinger catches in cement kilns. The objective was to show that HCl emissions need not be monitored in cement kilns because chlorides measured by Method 26 and 26A originated from salts. It has been proposed that HCl emissions from cement kilns are not possible; rather, in cement kilns other cations should be analyzed in ion chromatography. This is because some chloride content originates from chloride salts instead of HCl. If these cations are found in the impingers, this would indicate penetration of the filter by volatile or pseudoparticulate solids (salts). This study showed that 24 of 27 tested impingers had sufficient ammonium to account for all of the chloride content caught in the same impinger as ammonium chloride. The other three contained enough potassium, sodium, and other common cations to account for the remaining chlorides caught in the individual impingers. Temperature and velocity of the gas stream may play a role in this issue. EMTIC Workshop Background Paper for Method 26 and 26A (1994). The EPA produced this general summary of the two methods, available on their web site at The paper discusses the potential biases associated with temperature differences in the probe and filter, as well as the presence of chloride salts. It also suggests that when Cl2 and HBr are simultaneously present, both concentrations will be under-reported while the corresponding HCl and Br2 concentrations will be over-reported. Stack Sampling Methods for Halogens and Halogen Acids, Johnson (1996). A-3

86 This paper provides a detailed background on some of the scientific research that went into developing Methods 26 and 26A. Key strengths and limitations of both methods are discussed, and are compared and contrasted to the SW-846 methods (EPA, 2007a; b) comparable to Method 26 and 26A (0051 and 0050, respectively). One of the main topics discussed in this paper is filter penetration. Assuming that the filter is properly placed and is not wet or damaged to start sampling, there is still concern that ammonium chloride could penetrate the filter as a vapor and positively bias the HCl measurement. Hypochlorous acid could also penetrate the filter; however, Johnson reports that it is yet unknown if hypochlorous acid will come out in the acidic impingers or the alkaline impingers. The author also asserts that other solid halide salts such as NaCl, CaCl2, or KCl will not penetrate a properly chosen and placed filter and will therefore not be a source of bias to the trains. Johnson concluded that alkaline particulate caught on filters is another source of possible bias in the methods, and needs to be addressed somehow. Steinsberger s suggestion of a probe nozzle oriented counter to stack flow has the most promise; however, when isokinetic sampling is necessary, such an arrangement will not be possible. Also, CEMS monitoring will encounter the same problems on their individual filters and can probably be discounted as part of a permanent solution. Finally, Johnson says that there has been some evidence in several unpublished studies to the EPA that adding sodium thiosulfate to the alkaline impingers in gross excess will affect the halogen measurements, including a positive bias and a higher detection limit. As such, the methods state 25 mg of sodium thiosulfate as the amount to add to the alkaline impingers and advises that this amount already is in excess by up to five times. Adding more sodium thiosulfate would be detrimental to the analysis of halogens collected in the trains. The Effect of Coal Combustion Flue Gas Components on Low-Level Chlorine Speciation Using EPA Method 26A, Sun et al. (2000). One of the most recent studies of Methods 26A, and one that is particularly relevant to this project, is the Energy and Environment Research Center s (EERC) study on low-level chlorine speciation using Method 26A. This research evaluated the method s ability to speciate chlorine and HCl in a synthetic flue gas representative of a coal combustion source. The study concluded that chlorine and HCl cannot be speciated in a coal combustion source with the method as currently written, because SO2 reacts with and traps chlorine in the acidic impinger. Chemical reactions in the impinger result in the chlorine being converted to HCl. The study found that if the SO2/HCl ratio in the flue gas is sufficiently low, then speciation of HCl and chlorine is feasible; however, a coal combustion source is not likely to have a ratio low enough for speciation. Figure A-1, below, shows the percent recovery of a chlorine spike in the alkaline impinger, for ratios of SO2 to HCl ranging from 1:1 to 8:1. Before simulating a complete flue gas matrix, tests were performed to demonstrate that the method can speciate chlorine when only chlorine (balance nitrogen) is present. Subsequent testing introduced different species of the flue gas. A-4

87 Figure A-1 Effect of SO2/HCl Ratio on Cl2 Speciation (from Sun et al., 2000) ReMAP: Phase 1-Precision of Manual Stack Emission Measurements, Lanier (2001). The ReMAP compiled and performed statistical analysis on results from three different HCl Method 26 studies. These three studies were: tests done by Rigo and Chandler (1977) at an MWC facility in Pittsfield, MA; data collected by Entropy Corp, as part of the EPA/OAQPS validation of Method 26 (Steinberger and Margeson, 1989); and low HCl data collected by EER that were part of an EPA/OSW effort (EER, 1997). The ReMAP study examined multiple train data (duplicate and quadruplicate trains) and the deviations of the train data for each run. A correlation between relative standard deviation (RSD) and HCl concentration was developed from the data that can be used to estimate the precision of replicate trains. The ReMAP correlation is shown in Figure A-2. Where, S=Standard Deviation between duplicate or quadruplicate trains C=True sample concentration When: (1<C<100 mg/dscm) A-5

88 Figure A-2 ReMAP %RSD Correlation with HCl Concentration Extrapolating the ReMAP plot to the lower concentrations in the current EPRI project, about 17% and 21% relative standard deviation is to be expected at the project spike levels of 0.5 and 0.2 mg/dscm, respectively. These extrapolated relative standard deviations are on par with observed RSD during the ReMAP study for this range of concentrations. EPRI test results in this range of concentrations had consistently lower RSDs. One interesting data point is at 1 mg/dscm, where for a triplicate measurement, the correlation suggests that the measured concentration can be expected to vary from 0.8 to 1.2 mg/dscm. This means that duplicate trains on any given run can vary by as much as 0.4 mg/dscm and still be within the anticipated range of HCl concentration collected. Methods and Standard Operating Procedures (SOPs) of Emission Testing in Hazardous Waste Incinerator, Chapters 3 and 4, Ansari (2007). This publication from the Indian government closely follows Method 26A. Chapter 4 is meant to provide details of the method as performed in the field. It includes some steps that are not explicitly stated as obligatory in the methods, including pre-washing procedures of the glassware and maximum rinse volume restrictions. It is suggested to prewash glassware in this manner: Rinse all sampling train glassware with hot tap water and then wash in hot soapy water. Rinse glassware three times with tap water, followed by three additional rinses with distilled water. Soak all glassware in a 10 percent (V/V) nitric acid solution for a minimum of 4 hours, later rinse three times with distilled water, rinse finally with acetone, and allow to air dry. Cover all glassware opening where contamination can occur until the sampling train is assembled for sampling. A-6

89 In addition to a prewash procedure, the quantity of all rinses to the acidic and knockout impingers should not exceed 25 ml, and the quantity of all rinses to the alkaline impingers should not exceed 25 ml. The total volume added should then not exceed 50 ml. This guideline is not found in U.S. literature. A-7

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91 B DELIVERY SYSTEM AND FTIR TEST PROTOCOL 1 Pre-Testing Checks 1.1 Prior to phase condition testing, the system must pass the following checks: 1.1A Leak Check - A total system leak check must pass at temperature. Pull a vacuum, sealing all vents and exit streams. The leak rate according to a meter box must not exceed 0.02 LPM. If it does, then push nitrogen into the system at 2 psig and find all leaks with snoop. Throughout serial dilutions and testing, there will be an O2 analyzer at the end of the instrument side to detect the presence of oxygen at all times. When not running air or NO2 (the cylinder is 10% O2), the oxygen levels should be approximately zero. When running the full flue gas matrix, calculate the total expected oxygen delivery and check with the analyzer. If they are not approximately in agreement, then there is an inward leak in the system that needs to be addressed immediately. 1.1B All thermocouples in the system should give an acceptable temperature. All temperatures should be at least 180 C (~360 F). If not, there may be a cold spot. Also, there should be no exposed glass outside of the oven. 1.1C The FTIR must be at temperature (191 C) for at least 24 hours and with a N2 purge stream running through the interferometer and detector optics (can be <0.1 LPM each) before taking sample measurements. Also, the FTIR must pass a software diagnostic check on all levels. The liquid nitrogen level at all times should be such that the detector is sufficiently cooled. After filling the detector with liquid nitrogen, wait no less than 10 minutes before collecting sample data, and wait no more than 10 hours before refilling the detector with liquid nitrogen. The diagnostics software also gives a quality rating to each measurement, and whenever indicated by the software, liquid nitrogen should be added in order to maintain quality sample data. * Note that all other analyzers (oxygen, LGD, etc.) should have the proper start-up and diagnostics run before running any gases. All instruments should be periodically monitored for functionality by a person competent in that technology. 1.1D Confirm the calibration of or re-calibrate each Hovacal port (gas and liquid). If a recalibration is needed, use the calibration curve system in the Hovacal software. 1.2 Before starting any conditions with flue gas, a bare-bones serial dilution must take place. 1.2A First, set the nitrogen mass flow controller to deliver 3 LPM into the system and set the instrument pump to pull 2.5 LPM. Run for no less than 30 minutes, until there is a stable HCl reading. If after 30 minutes there remains a significant amount of HCl being measured by the FTIR (>0.2 ppmv), flush the system with a zero gas and 20% water content for at least 5 minutes. Reset the system to only deliver the dry nitrogen as stated above and allow the water reading to go to zero. Any HCl concentration should have been flushed; however, if any significant amounts remain, refer to diagnostics to ensure FTIR quality. Take the background and check the next 5 scans to ensure that the average HCl and water measurements are approximately zero. If they are not, repeat background. B-1

92 *Note: The FTIR method will be continuously scanning for a variety of compounds, and it is important to confirm that for any compound not being actively delivered into the system, the average of all data points for that compound should be reasonably close to zero. 1.2B Next, set the Hovacal HCl and water concentrations to 5 ppmv and 10%, respectively, with a flow rate no less than 4 LPM. Place the HCl/water solution on a scale and record the mass and the exact time. Throughout subsequent steps, record the mass and exact time no less than three times. Take care not to turn off the flow once the solution is being weighed. Set the ADI pump to about 3 LPM to ensure proper flow through the instruments. Allow the HCl concentration to stabilize, and collect 10 continuous minutes (10 scans) of stable data. If during the 10 minutes it is observed that the concentration is not steady, then extend the run to 20 minutes. After the 10 minutes (or 20 minutes) have passed, turn the bypass valve to flow directly to the back of the FTIR. Allow 5 minutes of stabilization and then begin collecting 10 continuous minutes of stable data. 1.2C After the run is completed, turn the bypass valve back toward the system side and repeat step 1.2B but set the HCl concentration to 2 ppmv. *Note: Regardless of the target HCl concentration, the target water concentration should remain the same. 1.2D After the run is completed, turn the bypass valve back toward the system side and repeat step 1.2B but set the HCl concentration to 1 ppmv. 1.2E After the run is completed, turn the bypass valve back toward the system side and repeat step 1.2B but set the HCl concentration to 0.5 ppmv. 1.2F After the run is completed, turn the bypass valve back toward the system side and repeat step 1.2B but set the HCl concentration to 0.2 ppmv. 1.2G After the run is completed, turn the bypass valve back toward the system side and repeat step 1.2B but set the HCl concentration to 0 ppmv. 1.3A Turn the bypass valve back toward the system side and turn off all Hovacal flows. Run dry nitrogen at 3 LPM through the system (using the N2 MFC) and pull 2.5 LPM through the instrument side with the ADI pump. Run until the HCl and water readings are stable. They should both be at zero; however, if they are not, redo the background and serial dilution as stated above. 1.3B Once zero is achieved, turn off the nitrogen flow and run 3 LPM of the dry HCl cylinder gas through the Hovacal and into the system (ADI pump at 2.5 LPM). Allow the SF6 concentration to stabilize, and collect 5 continuous minutes (5 scans) of data. Switch the bypass valve to flow through the heated sample line directly to the back of the FTIR. Allow the SF6 concentration to stabilize again and collect 5 continuous minutes of data. Turn off all Hovacal settings and run nitrogen once again at 3 LPM through the system, keeping the ADI pump at 2.5 LPM. B-2

93 *Note: An SF6 check must be performed once per day. Each check must be within 1% of the value of the previous SF6 check. If it is not, then check for leaks and take a second SF6 check. The ratio of the concentrations of HCl and SF6 during these checks should remain the same at all times. 2. Pre-Conditioning Procedure 2.1 Prior to testing on any condition, a serial dilution must be performed using the flue gas matrix established for that condition. At the start of every day, and before conduction a condition-specific serial dilution, a documented background and zero must be achieved as stated above in 1.2A. During pre-condition procedures, the wet train port valves will be turned to vent. In addition, all three sampling ports must be compared at the same stable matrix condition and proven that there is no preferential sample loss among the three ports. This will involve plumbing the vents from the two wet train ports into the instrument leg. 2.1A After performing the required background and zero, set the Hovacal concentrations of all flue gas components as specified by the condition to be run, with the exception of HCl. 2.1B Next, set the Hovacal HCl and water concentrations to 5 ppmv with a flow rate no less than 4 LPM. Place the HCl/water solution on a scale and record the mass and the exact time. Throughout subsequent steps, record the mass and exact time no less than three times. Take care not to turn off the flow once the solution is being weighed. Set the ADI pump to about 3 LPM to ensure proper flow through the instruments. Allow the HCl concentration to stabilize, and collect 10 continuous minutes of stable data. If during the 10 minutes it is observed that the concentration is not steady, then extend the run to 20 minutes. After the 10 minutes (or 20 minutes) have passed, turn the bypass valve to flow through the heated sample line directly to the back of the FTIR. Allow 5 minutes of stabilization and then begin collecting 10 continuous minutes of stable data. 2.1B-1 After the run is complete, turn the heated valve at the back of the FTIR after connecting one of the wet train ports to the other valve inlet and establish stability. Collect at least 10 minutes of data, and repeat on the other wet train port. Switch the valve back to the instrument sampling port to the instrument leg and continue the serial dilution. 2.1C After the run is completed, turn the bypass valve back toward the system side and repeat step 2.1B but set the HCl concentration to 2 ppmv. 2.1D After the run is completed, turn the bypass valve back toward the system side and repeat step 2.1B but set the HCl concentration to 1 ppmv. 2.1E After the run is completed, turn the bypass valve back toward the system side and repeat step 2.1B but set the HCl concentration to 0.5 ppmv. 2.1F After the run is completed, turn the bypass valve back toward the system side and repeat step 2.1B but set the HCl concentration to 0.2 ppmv. 2.1G After the run is completed, turn the bypass valve back toward the system side and repeat step 2.1B but set the HCl concentration to 0 ppmv. B-3

94 2.2A Turn the bypass valve back toward the system side and turn off all Hovacal flows. Run dry nitrogen at 3 LPM through the system (using the N2 MFC) and pull 2.5 LPM through the instrument side with the ADI pump. Run until the HCl and water readings are stable. They should both be at zero; however, if they are not, redo the background and serial dilution as stated above. 2.2B Once zero is achieved, turn off the nitrogen flow and run 3 LPM of the dry HCl cylinder through the Hovacal and into the system (ADI pump at 2.5 LPM). Allow the SF6 concentration to stabilize, and collect 5 continuous minutes of data. Switch the bypass valve to flow directly to the back of the FTIR. Allow the SF6 concentration to stabilize again and collect 5 continuous minutes of data. Turn off all Hovacal settings and run nitrogen once again at 3 LPM through the system, keeping the ADI pump at 2.5 LPM. 3. Pre-Run Procedure 3.1 Before any run, ensure that the wet train port valves are turned to vent and set the Hovacal concentrations to the full flue gas matrix specified by the condition to be run, except for HCl (set initially to zero). Set the nitrogen MFC according to the specified condition as well. 3.1A Once zero has been achieved, set the Hovacal HCl concentration as specified by the condition to be run. Allow all flue gas concentrations to stabilize (no less than 5 minutes). Set the HCl/water solution on a scale to measure mass loss. *Note: During each condition, one blank run must occur. This means that the full flue gas and water will be delivered to the system with the exception of HCl. The impingers will be analyzed normally and will give an idea of any interferences or residual HCl in the system that is not picked up on the instrument side. 3.2A Ensure that the wet trains have been loaded and leak checked according to the method (including weighing each impinger for the moisture content calculation and a filter assembly), and are securely connected to the wet train port outlets. All meter boxes, hardware, glassware, and method-specific pre-run procedures have been verified by competent personnel. [1, 2] 3.2B Ensure basic functionality of every instrument. This must be done with a person that is competent in that instrument. 3.3A Before testing, check that there is a sufficient amount of gas in each cylinder and enough liquid in the solution bottles to last the entire run. 3.3B Ensure that every installed thermocouple is reading at least 190 C, the Hovacal evaporators are at 200 C, the oven is above 200 C, and all heater controllers are working correctly. 3.3C Ensure that both Hovacal peristaltic pumps are operating within the 20-90%RPM capacity range. Set the Hovacal parameters to be recorded into a unique file for each run. 3.3D Ensure that the pressure transducer on the vent is functioning and that the vent back pressure is less than 10 inches H2O. B-4

95 3.3E Ensure that the knockout jar between the instrument side and the ADI pump has enough capacity such that any liquid knocked out during the run will not fill up the jar. 3.4F Ensure that all computers in use have their times synced. 4. Run Procedures 4.1 To start a run, turn both wet train port valves to the sampling side at the same time and open the meter box pumps. Record the time that this occurs. 4.2A At the start of the run, record all parameters necessary to satisfy the wet method. [1,2] 4.2B Also at the start of the run, record the mass of the solution bottle and its contents. Also record the oxygen reading from the analyzer, as well as the measured concentrations of each flue gas component as given by the Hovacal software (including the liquid flow rate observed). Visually confirm that every heater controller is up to the appropriate temperature. 4.3A Every five minutes during the run, record all parameters necessary to satisfy the wet method. Also, ensure that for both Method 26 and Method 26A, there is a visual ice bath at all times during the run, and that the exit temperature of the Method 26A trains is ALWAYS below 68 F. [1, 2] 4.3B At about the halfway point during the run, record the mass of the solution bottle and its contents. Also record the oxygen reading from the analyzer, as well as the measured concentrations of each flue gas component as given by the Hovacal software (including the liquid flow rate observed). Visually confirm that every heater controller is up to the appropriate temperature. 4.3C Observe the FTIR measurements (as well as any other supplemental analytical instruments) every five minutes for excessive variation. If in a 10 minute period there are more than 5 scans that deviate more than 10% from the average concentration in the run, then abandon the run and run diagnostics on the flow rates, pressures, temperature, cylinder/solution levels, etc. to resolve the issue and restart the run. 4.4A Each Method 26 and 26A run will last 30 continuous minutes (30 scans) and must satisfy all applicable method requirements to be a validated run. [1, 2] This includes the 5 minute purge through the filter box prior to sampling. [1] 5. Post-Run Procedures 5.1A At the end of the run, the wet train port valves will be turned to vent and the meter pumps turned off. Leak check the trains and disconnect from the outlet port. 5.1B Each impinger is weighed and recovered according to the method. The impinger or tube that contains silica gel should also be weighed for the moisture content calculation. The filter holders must be rinsed in order to prevent any contamination from the preceding run to the proceeding run. *Note: For the Method 26A trains, rinse and recovery of the first impinger will include the small jumper used to connect the trains to the wet train port. B-5

96 5.1C After recovering the samples, the entire train will be rinsed once more to ensure no contamination between runs, and turned over for subsequent runs. This proof blank will be saved for possible analysis later. 5.2A When the run is completed, set the HCl concentration in the system to zero. Set all other flue gas components and flow rates to the next run s set points. Allow the HCl to go to zero and for all other flows and components to stabilize at the set point. If the HCl will not stabilize at zero (or is stable at a non-zero concentration) then follow 1.2A to take a new background. 5.2B Begin the next pre-run procedures. 6. Post-Test Procedures 6.1 When all testing is done, another bare-bones serial dilution must be done, following all subsets of 1.2 (this includes the SF6) check. 6.2 A system leak check must be performed and all leaks recorded. 6.3 All Hovacal ports (gas and liquid) must have calibrations confirmed. The MFC for nitrogen should be confirmed as well. B-6

97 C FLY ASH SIZING AND SEEDING This section describes the procedures used to prepare fly ash samples for the study and to place the fly ash on the Method 26 filter. A flow chart of the procudures used is shown in Figure C-1. Sample Preparation An aliquot of each sample was sieved through an 80 Mesh (177 μm) sieve tray prior to analysis. This is performed in order to remove any possible foreign objects and to break up any agglomerated particles which can clog the instrument feeder tube. Particle Density Particle density was measured using an AccuPyc 1330 helium pycnometer manufactured by Micromeritics. The AccuPyc works by measuring the amount of displaced gas in a test cell. The pressures observed upon filling the sample chamber and then discharging it into a second empty chamber allow computation of the sample solid phase volume. Gas molecules rapidly fill the tiniest pores of the sample; only the truly solid phase of the sample displaces the gas. The instrument uses a 10 cm 3 sample chamber and is operated in Run-Precision mode. The Run-precision mode allows high repeatability. The instrument automatically purges water and volatiles from the sample and then repeats the analysis until successive measurements converge upon a consistent result. Six matching measurements are completed during a given sample analysis. Size Distribution Analysis The samples were analyzed in accordance with ASME Power Test Code 28 using a Bahco Centrifugal Classifier. This instrument is a combination air centrifuge- elutriator consisting of a rotor assembly driven by a totally enclosed electrical motor. The rotor is enclosed in a housing which also supports the sample feed mechanism. The motor operates at 3600 rpm creating precisely controlled air velocities within the air spiral and sifting chamber of the centrifuge. The sample is then introduced into a spiral shaped air current flowing toward the center. The spiral current of air has suitable values of tangential and radial velocities so that a certain part of the sample is accelerated by the centrifugal force toward the periphery of the whirl, the other part of the sample is being carried by the air current toward the center of the whirl by aerodynamic means. The size, shape, and weight of the particles determine which direction they will take in the air current. By varying the air flow, it is possible to change the terminal velocity limit of division and thus the material can be divided into a number of fractions with limited terminal velocity ranges. C-1

98 EPA Method 26A Start with ~10 g of flyash sample EPA Method 26 Start with ~10 g of flyash sample Measure Particle Density Measure Particle Density Save each fraction separately Perform Bahco Centrifugal Classification Perform Bahco Centrifugal Classification Save each fraction separately Combine All Fractions Combine Fractions From First Three Throttle Spacers (<4 mm) Mix Well Mix Well Pull a 25 mg Aliquot Using Weighing Paper Pull a 5 mg Aliquot Using Weighing Paper Seed a Tared 82.6 mm Filter Using Vacuum Action Seed a Tared 47 mm Filter Using Vacuum Action Weigh Filter to a Constant Weight Record Photographic Description of Filter/PM Weigh Filter to a Constant Weight Record Photographic Description of Filter/PM Use Seeded Weighed Filter in Sampling Use Seeded Weighed Filter in Sampling Weigh Filter to a Constant Weight Record Photographic Description of Filter/PM Weigh Filter to a Constant Weight Record Photographic Description of Filter/PM Record Filter Weight Change and Save for Possible Future Analyses Record Filter Weight Change and Save for Possible Future Analyses Figure C-1 Flowchart for Seeding Fly Ash on the Filter C-2

99 D QA/QC GRAPHS AND FIGURES Figure D-1 Mass Flow Controller Calibration Curve D-1

100 Figure D-2 Water Concentration Port Confirmations \ Figure D-3 Sampling System Confirmation with SF6, Performed on Different Days D-2

101 Figure D-4 A Cracked Filter Holder Made of Teflon and Tefzel Figure D-5 An Attempt to Leak Check an Individual Filter Holder D-3