CURRENT STATUS OF THE UCR-EPA ENVIRONMENTAL CHAMBER PROJECT

Transcription

1 CURRENT STATUS OF THE UCR-EPA ENVIRONMENTAL CHAMBER PROJECT By William P. L. Carter College of Engineering Center for Environmental Research and Technology (CE-CERT), University of California, Riverside, CA, Outline July 10, 2003 Background, Description and Timeline Characterization Results Current Projects Summary of Experiments and Results to Date New and Upcoming Programs and Funding Potential future research directions

2 BACKGROUND Chemical mechanisms used to predict VOC reactivity have many uncertain estimates and approximations Environmental chambers are essential evaluating the predictive capabilities of mechanisms The existing chambers had limitations affecting utility and range of conditions for mechanism evaluation The UCR EPA Chamber was developed to address these limitations. Major design features include: Indoor chamber for best control, & characterization Large volume to minimize background and for best sampling capability (two ~100,000-L reactors) Arc light used simulates sunlight intensity and spectrum. (Blacklights also installed) Replaceable Teflon reactors in a clean room to further minimize background effects Temperature control range is ~5 o to ~50 o C (±1 o C) Array of analytical instrumentation for gas-phase species and PM Chamber conditions characterized to reduce uncertainties for mechanism evaluation

3 DIAGRAM OF CHAMBER AND ENCLOSURE 2 Banks of Blacklights Temperature controlled room flushed with purified air and with reflective material on all inner surfaces 200 KW Arc Light Movable top frame allows reactors to collapse under pressure control 20 ft. This volume kept clear to maintain light uniformity Dual Teflon Reactors 20 ft. 20 ft. Two air Handlers are located in the corners on each side of the light (not shown). Access Door SEMS (PM) Instrument Floor Frame Gas sample lines to laboratory below

4 DIAGRAM OF REACTOR AND FRAMEWORK (One of Two) Ceiling Cable Takeup Drum Pulleys Shaft Supports Approximately 90,000 Liters Maximum Volume Motor Shaft Upper Frame Ports for Mixing, Low Volatility Injection and Exchange System Lower Frame Teflon Film Access Hatch and Sampling Port Holder Enclosure Floor Supports

5 PICTURE OF SINGLE REACTOR Location of 2 nd Reactor (Added later) Movable top frame holds and seals sheets and allows reactor to collapse Firmness sensor controls top frame movement to maintain pressure ~6 M Deep ~5 M 2 Mil FEP Teflon Ports for injection, mixing, exchange, and emptying Reflective Floor covered with Teflon film Rigid frame holds and seals sheets ~2.5 M

6 ARC LIGHT SOURCE AND SPECTRUM 0.6 M Solar Blacklights New Chamber 3 Normalized Power (arbitrary units) Wavelength (nm)

7 Time Activity TIMELINE 1999 Project Started. International chamber workshop held in Riverside 2000 Design work and small reactor evaluation experiments Construction 2002 Component, chamber, instrument testing, problem resolution, general debugging, initial evaluation experiments Jan 03 Jan-Mar 03 Feb 03 - present Mar 03 Mar-Jun 03 Jun 03 - present First experiment in current configuration Characterization runs and low NO x runs on simple chemical systems PM Instrumentation on line. Begin blacklight experiments for PM evaluation Initial characterization for dry, single temperature conditions complete Surrogate evaluation runs for low NO x and to support reactivity studies. Coatings component reactivity experiments underway

8 CHARACTERIZATION RESULTS Contamination or dilution of reactors by enclosure air is negligible when run on positive pressure control Light intensity with lamp at 80% recommended maximum gives NO 2 photolysis rate of 0.25 min -1 Characterization results indicate chamber effects are probably as low as can be obtained in Teflon film chambers O 3 wall loss rate is 0.8%/hour, comparable to that in other Teflon film reactors Apparent HCHO offgasing rate is ~160 ppt/hour. (This is not measured in most other chambers because of inadequate sensitivity for HCHO) Apparent NO x offgasing rate, determined by modeling in CO - air runs, is ~40-80 ppt/hour Apparent chamber radical source and minimum NO x offgasing rates are ~40-80 ppt/hour Good side equivalency obtained when the same experiment is simultaneously run in the two reactors (except for some NO x offgasing-sensitive runs)

9 COMPARISON OF RADICAL SOURCE AND NO x OFFGASING RATES IN VARIOUS CHAMBERS Old CE-CERT 5000-Liter Teflon Chamber (RS) Small Pillowbag (in clean enclosure) (RS) TVA Chamber NOx Offgasing New 1 Large UCR Chamber (RS) New UCR Chamber NOx Offgasing 3-5 ppt Apparent minimum range Radical and / or NO x Input Rate / NO 2 Photolysis Rate Ratio (ppb) Approximate Average NO 2 (ppb)

10 CURRENT PROGRAMS AND TYPES OF CHAMBER WORK COVERED Current EPA Chamber Program Construction and evaluation of chamber performance Experiments with simple chemical systems for testing Begin surrogate evaluation for reactivity studies Begin evaluating utility for PM studies Funds now exhausted. CARB LOW NO x Mechanism Evaluation Primarily surrogate - NO x experiments at NO x Levels Funding limited to relatively few experiments CARB Coatings Reactivity Reactivity experiments with Texanol and selected petroleum distillates Petroleum distillate experiments now underway NSF Grant and Startup Funds (D. Cocker, PI) Limited support to blacklight runs for PM studies Experiments for comparison with previous PM yield studies with aromatics now underway (when chamber not needed for CARB projects)

11 CHAMBER EXPERIMENTS CONDUCTED 6/16/03 (Excluding Characterization) Type of Experiment No. Simple Chemical Systems Formaldehyde NO x (with & w/o added CO) 4 Acetaldehyde NO x (with & w/o added CO) 2 Ethene and Propene NO x 4 Toluene NO x or Toluene NO x + CO 8 m-xylene NO x + or m-xylene NO x + CO 2 Surrogate Evaluation Experiments Surrogate - NO x (Various ROG and NO x ) 12 n-octane reactivity 5 m-xylene reactivity 7 Coatings Reactivity Petroleum Distillate Reactivity MIR Conditions 1 Petroleum Distillate Reactivity Low NO x 2 Blacklight Aerosol Yield Experiments Toluene - NO x 9 m-xylene - NO x 12

12 SUMMARY OF NEW MECHANISM EVALUATION RESULTS TO DATE Low NO x Mechanism Evaluation No apparent low NO x mechanism performance problems for following systems: Formaldehyde - CO - NO x (NO x down to ~15 ppb) Toluene and m-xylene - NO x (NO x down to ~5 ppb) Ethene - NO x (NO x down to ~10 ppb) Ambient Surrogate Runs (NO x down to ~2 ppb) Aromatic Mechanism Evaluation Satisfactory simulations of single aromatic - NO x and aromatic reactivity experiments (as with previous data) BUT new data indicate aromatic mechanism problems: Probable compensating errors. Model underestimates effect of adding CO to aromatic - NO x runs. (Sensitive to radical initiation) Direct reactivity measurement overpredicted Surrogate Evaluation Good simulations with MOIR or higher ROG/NO x levels Model underpredicts O 3 formation rates with MIR or lower ROG/NO x levels n-octane reactivity data reasonably well simulated in runs where base case well simulated.

13 TOLUENE & TOLUENE CO - NO x RUNS Ozone (ppm) 25 ppb NOx, 150 ppb Toluene, 45 ppm CO Toluene Expt Toluene - CO Expt Model Model Time (minutes) Ozone (ppm) 5 ppb NOx, 60 ppb Toluene, 25 ppm CO Toluene Expt Toluene - CO Expt Model Model Time (minutes)

14 MODEL PERFORMANCE IN SIMULATING DIRECT REACTICITY DATA (HONO +VOC FLOW TUBE EXPERIMENTS) Average Direct Reactivity Model Bias (Calculated) - (Experimental) / (Calculated) CO Ethane Propane (avg) n-hexane n-octane (avg.) n-decane n-c12 n-c13 n-c14 n-c16 Iso-Octane Ethyl Acetate MEK Propene Benzene Toluene 1,3,5-TMB Overprediction of direct reactivity for aromatics

15 MATRIX OF SURROGATE EXPERIMENTS 100 Surrogate - NOx \Runs Conducted n-octane Reactivity Experiment m-xylene Reactivity Experiment MIR Conditions Maximum O3 (MOIR) Conditions NOx 1/2 Maximum O3 Levels 80 Initial NOx (ppb) A B Initial Base Case ROG (ppmc) Base case conditions chosen for initial reactivity assessment experiments A...MIR Conditions (Higher NO x / VOC) B...Lower NO x / VOC; NO x 1/2 MOIR Level

16 BASE CASE SURROGATE EXAMPLES MIR Conditions (NOx=30,ROG=0.5) 0.16 Ozone (ppm) Model EPA110B EPA114A EPA127B Time (minutes) ½ MOIR NOx Conditions (NOx=25,ROG=1) 0.16 Ozone (ppm) Model EPA095B EPA123A EPA124B EPA126A Time (minutes)

17 MODEL PERFORMANCE SIMULATING O 3 AT DIFFERENT ROG AND NO x LEVELS Run 1 Run 2 Model MIR MOIR 1/2 MOIR NOx NOx (ppb) ROG (ppmc) Experimental and Calculated O 3 in Selected Surrogate - NO x Experiments

18 PM REPRODUCIBILITY Number (cm -3 ) vs.time Volume (µg/cm -3 ) vs. time Surrogate - NO x Runs 82A vs. 83A EPA082A EPA083A EPA082A EPA083A Number / cm Irradiation Time (min) Volume (um 3 /cm 3 ) Irradiation Time (min) Number / cm 3 Surrogate - NO x Runs 85A vs. 86A EPA086A EPA085A EPA086A EPA085A Irradiation Time (min) Volume (um 3 /cm 3 ) Irradiation Time (min) m-xylene - NO x Runs 104A vs. 29A (Blacklight) EPA104A EPA129A EPA104A EPA129A Number / cm Volume (um 3 /cm 3 ) Irradiation Time (min) Irradiation Time (min)

19 EFFECT OF ADDING m-xylene ON PM Particle Number (uncorrected for wall losses) 50 ppb NOx, 1 ppmc ROG Surrogate Surrogate + m-xylene Number / cm Irradiation Time (min) Particle Volume (Uncorrected for wall losses) Surrogate (EPA083A) Surrogate + m-xylene (EPA084A) 5 Volume (um 3 /cm 3 ) Irradiation Time (min)

20 COMPARISON OF UCR AND CALTECH CHAMBER RESULTS ON AEROSOL YIELDS FOR M-XYLENE Aerosol Yield from m-xylene (ug/ug) UCR EPA Data (Blacklight Irradiation) Caltech Indoor Chamber Data Fit to Caltech Data Aerosol Formed in Experiment (ug/m3)

21 NEW AND UPCOMING PROGRAMS AND FUNDING SCAQMD PROGRAM (~$200K) Support for overall VOC reactivity research of interest to SCAQMD. Includes: Base Case Surrogate evaluation Experiments with additional coatings VOCs Support for PM measurements with CARB and SCAQMD reactivity experiments Investigation of utility for availability research Contract being prepared EPA OBM PROJECT (~$175K for UCR) Obtain data to evaluate model predictions of indicator ratios for predicting O 3 sensitivities to emissions. Subcontract to Bill Brune of Penn State to make radical measurements in UCR chamber for a ~3 month period Experiments consist of: Selected with simple chemical systems to test model and measurements Surrogate - NO x runs at various ROG and NO x levels (may be in conjunction with reactivity runs) Most of funding in place, remainder due soon. Radical instruments scheduled to come to UCR in September

22 NEW AND UPCOMING PROGRAMS AND FUNDING FY EPA EARMARK (~$200K) Provides needed support for Improvements and maintenance of facility and instrumentation Mechanism evaluation and reactivity assessment at full range of temperature and RH conditions Studies of PM formation and gas and aerosol interactions Other experiments to advance agenda of original EPA chamber proposal and work plan To be funded through EPA Ann Arbor as part of a larger earmark for CE-CERT projects. Funding not yet in place

23 POTENTIAL FUTURE RESEARCH DIRECTIONS Evaluation of Temperature Effects Temperature expected to affect O 3 and PM formation, but existing data highly limited. Research on Gas and Aerosol Phase Interactions Chamber well suited to study effects of PM on gasphase processes and vise-versa Research on PM Formation Potentials of Organics Organics differ widely in effects on secondary PM. Chamber can provide data under more controlled, and atmospherically realistic conditions than previously possible Development and Evaluation of Models for Secondary PM Chamber can provide the well-characterized data most needed for model evaluation. Chamber well suited to test models for temperature and humidity effects