Raising your AQ IQ. OLI Systems, Inc.

Transcription

1 Raising your AQ IQ OLI Systems, Inc.

2 Copyrights, 2004 OLI Systems, Inc. All rights reserved. The enclosed materials are provided to the lessees, selected individuals and agents of OLI Systems, Inc. The material may not be duplicated or otherwise provided to any entity with out the expressed permission of OLI Systems, Inc. 108 American Road Morris Plains, New Jersey (Fax)

3 Contents Chapter 1 Raising your AQ IQ 1 New Software Tools To Solve Chemical Process And Corrosion Problems...1 Examples of OLI Electrolyte Applications...4 OLI Real World Solutions...4 AQ IQ Example Problems...6 Chapter 2 Calculating ph for Aqueous Solutions 7 What you see is not what you get!...7 Complex Salt Solutions...8 Using the OLI/StreamAnalyzer...8 What s the bottom line?...19 Advanced Problems...19 Chapter 3 Neutralized an Acid 21 How to avoid accidental hazardous waste generation!...21 Hydrofluoric Acid Stream...21 Neutralizing Stream...22 Using the StreamAnalyzer...22 Mixing the HF Acid with the CaCl 2 stream...28 Analysis of the Chemistry...31 Conclusion...34 Advanced Problems...35 Chapter 4 Water Treatment 37 You can t get there from here!...37 Let s get started What is the ph?...39 Now, What About the Contaminated Waste?...48 Conclusion...52 Advanced Problems...53 Chapter 5 Sour Gas Treatment 55 A little bit of water can go a long way (in creating a Big Process Problem)...55 Scope...55 Purpose...56 Objectives...56 Start the tour...57 Let s get started The Corrosion Rate at the Dew Point...63 Adding the rates calculation Mitigation...68 Adjusting the solution chemistry...69

4 Alloys...74 Save...74 Advanced Problems...76 Chapter 6 Chlorine Scrubbing 77 If 10 percent is good, 20 has to be better?...77 Let s get started Stream Review...80 Adding a Mixed Stream...81 Why does adding base remove Chlorine?...89 What happens if you use more concentrated solutions?...91 Conclusion...93 Advanced Problems...96 Chapter 7 Gypsum Solubility 97 Getting an edge on the competition Let s get started What is a precipitation point calculation? Back to the application Adding sodium chloride Save your work Conclusion Advanced Problems Chapter 8 H 2 S-CO 2 Injection 125 Out of Sight Out of Mind? Let s get started Reconciling Electroneutrality Back to the reconciliation Converting an Analysis into a stream Simulations at reservoir conditions Adding the waste gas Reviewing the results What does this all mean? Save your file Conclusion Advanced Problems Chapter 9 Organic Acid Removal 153 When Henry s Law Constants don t really help you Let s get started Solution ph Washing the acids out of the aqueous phase Removing the organic acids from the 2 nd liquid phase Save, save, and save again Conclusion Advanced Problems Appendix A OLI Company Profile 167 OLI Software Simulation Tools... Providing Real World Answers ii Raising your AQ IQ

5 Appendix B References 171 Appendix C Product Description Sheets 173 Overview Environmental Simulation Program (ESP) FEATURES APPLICATIONS CAPABILITIES RELATED PRODUCTS Corrosion Analyzer FEATURES APPLICATIONS CAPABILITIES RELATED PRODUCTS Stream Analyzer and Lab Analyzer FEATURES APPLICATIONS CAPABILITIES ScaleChem FEATURES CAPABILITIES SCALECHEM V HYSYS Electrolytes OLI (HEO) FEATURES APPLICATIONS CAPABILITIES Aspen OLI FEATURES CONTACT US...186

6 iv Raising your AQ IQ

7 Chapter 1 Raising your AQ IQ New Software Tools To Solve Chemical Process And Corrosion Problems What is Your AQ IQ? By that we mean: How well do you understand aqueous chemistry and apply it routinely to solving real-world problems in your operations? How do you manage process upsets, water treatment, scale, corrosion, and other aqueous electrolyte related operating problems today? This seminar will provide you with insights and methods to address these and many other common industry applications. Aqueous electrolytes are everywhere and ignoring electrolytes doesn t make your problems go away. You can spend a lot of time and money doing laboratory and plant testing, or conventional process simulation, and still be plagued by persistent scale, corrosion, ph control, conversion efficiency, process upsets, environmental contamination, water and offgas treatment, and countless other problems All because you haven t properly accounted for electrolytes. And what s more, predicting the behavior of chemicals in water for realistic industrial conditions has never been easy or intuitive. What are electrolytes? Simply put, electrolytes are chemicals that break down, recombine, and react in water or other solvents. When this happens in the real world, the result is a complex mixture that is very difficult to predict and control. The result in your operations is ph control problems, unwanted scale and solids formation, corrosion, water and gas effluent emissions and permit violations, process upsets, and a host of other problems. Raising your AQ IQ Chapter 1 Raising your AQ IQ 1

8 Prediction of phase equilibria for electrolyte systems is complicated by virtue of the fact that chemical reaction equilibrium and phase equilibrium must be considered simultaneously. The phase equilibrium methods commonly taught as part of a university chemical thermodynamics curriculum are applicable for hydrocarbons and other nonaqueous systems, but not aqueous electrolyte systems. Furthermore, to predict the behavior of real-world aqueous systems, all of the species that can form, including aqueous complexes and solids, and their non-ideal behavior in real solutions, must be accounted for. OLI refers to real solutions as those containing multiple components at ionic strengths where the common simplified methods and ideal solution assumptions are invalid. Electrolyte Technology And Applications A great many industrial processes cannot be designed and operated effectively without comprehensively and accurately addressing electrolyte chemistry and phenomena. The same statement can be made with regard to many oil and gas production and environmental problems as well. Electrolyte chemistry plays an important role in many chemical operations, including: Aqueous chemical and separations processes ph neutralization, Ion exchange, Desalination Chemical conversion and reactors Corrosion and scaling of equipment in chemical plants, refineries, gas plants, pipelines, oil and gas wells, tanks Reactive separations including acid gas treatment Water treatment including heavy metals removal Environmental behavior of wastes, discharges, and accidental releases Pharmaceutical and specialty chemical manufacturing Solution crystallization Electrochemical processes Real-World Risk. Electrolyte chemistry is particularly complex and challenging to understand and predict, especially for real industrial systems containing many components and operating over broad ranges of temperature, pressure, and concentration. Simplified aqueous modeling and computational approaches using approximation methods are usually useless, or worse yet, dangerously misleading, when applied to real-world electrolyte applications. Aqueous electrolyte systems often behave in complex and counter-intuitive ways, introducing great risk into plant design and operation if not properly understood and accounted for. For example, when solids form at the wrong place at the wrong time, the results can be catastrophic. On the other hand, reliable electrolyte models make possible tremendous insight, process alternatives, and efficiencies in plant design, troubleshooting, and optimization. Modeling Electrolyte Chemistry. The first key to predicting the behavior of aqueous electrolyte systems is to account for all of the species that can form in the system. For example, sodium chloride in water forms 5 species: H 2 O, H +, OH -, Na +, and Cl -. But ferric chloride in water can form over 15 species because of the tendency of iron to complex with hydroxide and chloride in the aqueous phase, and because of the possibility of solids to form and precipitate under some conditions. A solution such as a brine with only 5 cations and 5 2 Chapter 1 Raising your AQ IQ Raising your AQ IQ

9 anions can have well over 200 species. All of these must be properly accounted for in order to accurately predict ph, reaction and phase equilibria, and solids formation. The next key is to have a proper framework to model the standard state properties over a broad range of conditions. Next, a robust activity coefficient model must be used in order to account for species-species interactions and non-ideal behavior of real systems. These must all be supported by a complete database of regressed and estimated parameters based on high quality experimental data. Finally, the complete system of equilibrium and mass balance equations must be rigorously and efficiently solved. The OLI electrolyte approach is based on and distinguished by the following unique elements: Complete speciation. The OLI model predicts and considers all of the true species in solution, and accounts for these in the computations. Robust standard state framework. Based on the Helgeson equation of state and parameter regression and proprietary estimation techniques, the OLI model provides accurate equilibrium constants and other standard state properties over the broadest possible aqueous range of conditions. Activity coefficients for complex, high ionic strength systems. Based on the combined work of Bromley, Zemaitis, Meissner, Pitzer, and OLI technologists, OLI models can predict behavior under real world conditions. Comprehensive databank. The OLI Databank covers over 80 inorganic elements and their associated compounds and complexes, and over 3000 organic chemicals. OLI Data Service provides customized coverage of clients chemistry in the form of private databanks. Thermo-physical properties. OLI has developed unique chemical-physical based models to compute thermodynamic and transport properties for complex aqueous mixtures. All of this know-how, methods, and data taken together make up the OLI Engine. The OLI Engine is at the heart of every OLI software product. It is applicable over the range of conditions of -50 to 300 C, 0 to 1500 bar, and up to 30 molal ionic strength. OLI Engine provides all the required facilities out of the box. This enables a user to avoid all of the complexities associated with aqueous electrolyte systems. This means that the user never has to: Write an equilibrium reaction Define true species in the aqueous phase (the user only provides the customary molecular chemical components) Deal with any complexities associated with solving for the occurrence of other physical phases in addition to the aqueous phase Carry out any data regressions to develop model coefficients (these are all provided by the in-place OLI databank) The OLI Engine provides comprehensive and accurate simulation and prediction of the behavior of complex electrolyte systems. OLI clients have used this unique and powerful electrolyte capability to provide hundreds of millions of dollars benefit through a host of applications in the oil and gas, chemicals, government research, paper, metals and mining, pharmaceutical, petroleum, and energy industries. This seminar covers some of the basics of aqueous electrolyte chemistry and applications. For further information, the reader is referred to OLI s Resource Center on the OLI website ( which contains many technical papers and articles on these and related topics. Raising your AQ IQ Chapter 1 Raising your AQ IQ 3

10 Examples of OLI Electrolyte Applications Emergency Chlorine Scrubber Caustic Wash Tower Acid Stream Neutralization Manufacture of KF Dynamic ph Control Removal of Fluoride Ions from Waste Water Scrubbing Refinery Process Streams with DEA Chlor-Alkali Brine Treatment Ahlstron NSSC Stora Process Tower Scale Control Foul Feed Stripper Multi-Effect Evaporator Cooling Tower Coke Oven Gas Ammonia Still Organic Acid Removal in Brines BTEX Stripper MSF Desalination Plant Removal of Chlorobenzene with Biological Treatment Dregs Washer and Clarifier CO2 Corrosion Corrosion Rates in Acids Inhibitor Squeeze in Oil/Gas Reservoirs Corrosion in LiBr Refrigeration Brines Thermodynamic Analysis of Corrosion Inhibitors Electrostatic Precipitator Separation H2S/CO2 Corrosion Products under Gas Pipeline Conditions Hazardous Waste Deep well Disposal Contaminated Groundwater Management OLI Real World Solutions In the Plant: o Optimized the design of a ph-control neutralization system saving more than $3MM o Identified the cause (elemental sulfur corrosion) and modified process conditions for the absorber and regenerator of a desulfurization process. Identified the cause (ammonium bisulfide precipitation and corrosion) and appropriate materials for an ammonia separation process o Identified the conditions for de-alloying of a copper/nickel alloy, defined the precise conditions for nickel dissolution in the process, and defined process modifications to eliminate the corrosion problem. o Predicted scaling indices in process streams and, therefore, their effects on process equipment, minimizing costly upsets and downtime o Evaluated process changes to minimize corrosion in units, reducing downtime and equipment replacement o Predicted the onset and effects of CaCO3 scaling so stream conditions could be altered to avoid a problem. In the Laboratory: o Evaluated and selected inorganic corrosion inhibitors for Lithium Bromide chiller systems, reducing costly laboratory evaluations o Minimized lab time and expense to find operating conditions for producing ceramic materials of the highest purity o Identified laboratory analysis errors, preventing costly errors in the diagnosis and correction of a plant problem. 4 Chapter 1 Raising your AQ IQ Raising your AQ IQ

11 In the Environment: o Optimized conditions for the removal of trace metals from wastewaters, allowing regulatory permit limits to be met. o Developed a sound scientific basis for a successful technical defense in a law suit involving more than $100MM. o Saved more than $20MM by devising a more effective remedy to protect groundwater from heavy metals, which was then accepted by the US EPA.Identified the cause and effective corrective action for the buildup of materials in a biotreatment unit, avoiding a costly unit shutdown and clean-out. In the Oilfield: o Predicted the severity of halite scale formation at the early design stage of a deep well project, and then used the results to design a water treatment plant, chokes, subsea production template. o Determined the prospective costs for an oilfield lease purchase where the redevelopment plan calls for completing deeper zones and water flooding other zones with co-mingling of brines. o Diagnosed the cause of calcium fluoride and lead (Pb) sulfide scale formation in a deep sour well, and used the results to design a scale management strategy. o Determined the relative likelihood of halite formation problems (rather than calcite or iron sulfide) in an old oilfield redevelopment to support the choice of remedy (fresh water injection versus inhibitor squeeze) that saved money and increased production time. Raising your AQ IQ Chapter 1 Raising your AQ IQ 5

12 AQ IQ Example Problems Basic electrolytes What you see is NOT what you get Study of different salts in water, ph, speciation, solids and hydrates Effluent discharge Discharge limits Sour gas Chlorine scrubbing Gypsum solubility Sulfur removal Organic acid removal How to avoid accidental hazardous waste generation Study of mixing waste streams with hydrofluoric acid (HF) stream and CaCl2 You can't get there from here Study of reagents and techniques for reducing the soluble nickel to 0.1 mg/l in a discharge stream A little bit of water can go a long way (in creating process problems) Study of an alkanolamine gas sweetening plant with scale and corrosion in the condensed overhead gas If 10% is good, is 20% better? Problems with emergency release of chlorine gas from a process Getting an edge on the competition Modern gypsum (CaSO4.2H2O) production involving recovery of sulfur waste products. Study to find the optimum conditions to recover a pollutant and use it for commercial purposes Out of sight - out of mind? Study of ratios of H2S mixed with produced water re-injecting into the formation a possible H2S disposal method. The issue is the possibility of plugging the reservoir with unexpected solids. When Henry's Law Constants don't really help you Study of organic acids in produced waters from oil and gas production, with methods for analysis and removal from the oil - and from the produced water. 6 Chapter 1 Raising your AQ IQ Raising your AQ IQ

13 Chapter 2 Calculating ph for Aqueous Solutions What you see is not what you get! The behavior of aqueous electrolytes solutions is more complicated that most people would like to admit. Even simple single salt systems may yield many new complexes in aqueous solution. Accurate calculation of ph depends on accounting for all of the molecules, ions, complexes, and other species that can exist in the system (i.e., complete speciation ) Let s look at a simple salt solution; sodium chloride in water. How many species are there in this solution? NaCl + H 2 O Na + + Cl - + H + + OH - + H 2 O Water appears on both sides of the reaction since it does not fully dissociate. This gives us five aqueous species. What would the ph be of a 1 molal 1 solution of sodium chloride at 25 o C and 1 atmosphere? Sodium chloride essentially dissociates in water to give us equal moles of sodium ion and chloride ion. Because of its tendency to completely dissociate in water, sodium chloride is referred to as a strong electrolyte. The water dissociates according to the dissociation constant for water. At 25 the dissociation constant for water is approximately: K w = [H + ][OH - ] = The unit molal is moles of solute per kilogram of solvent. In aqueous systems is moles/kg H 2 O. Raising your AQ IQ Chapter 2 Calculating ph for Aqueous Solutions 7

14 Complex Salt Solutions This results in an aqueous concentration for hydrogen of 10-7 moles/kg H 2 O. So the final concentrations are: [Na + ] = 1.0 moles/kg H 2 O [Cl - ] = 1.0 moles/kg H 2 O [H + ] = 10-7 moles/kg H 2 O [OH - ] = 10-7 moles/kg H 2 O H 2 O = 1.0 Kg/H 2 O The definition of ph is: ph = - Log [H + ] Thus the ph of this solution is: ph = - Log (10-7 ) = -(-7) = 7 Is it possible to accurately predict ph for chemicals that react and form complexes in water? What are the keys to getting the right answer? Now let s look at a more complicated solution. What is the ph of a 1.0 molal Iron (III) Chloride solution at 25 o C and 1 atmosphere? Let s use the simple salt approach first. FeCl 3 + H 2 O Fe Cl - + H + + OH - + H 2 O The final concentrations would be: [Fe 3+ ] = 1.0 mole/kgh 2 O [Cl - ] = 3.0 mole/kgh 2 O [H + ] = 10-7 moles/kg H 2 O [OH - ] = 10-7 moles/kg H 2 O H 2 O = 1.0 Kg/H 2 O Using the OLI/StreamAnalyzer The ph would then be: ph = - Log [H + ] = - Log (10-7 ) = -(-7) = 7 The experimentally measured ph is approximately 2.2. The simple salt approach does not seem to work for this salt. We will now use the OLI/StreamAnalyzer to look at the chemistry of the iron chloride system. We will first start the StreamAnalyzer. Locate the StreamAnalyzer icon on your desktop or find it via the start button. Figure 2-1 The OLI StreamAnalyzer Icon for version Chapter 2 Calculating ph for Aqueous Solutions Raising your AQ IQ

15 This will display the main StreamAnalyzer Window. Figure 2-2 The StreamAnalyzer Splash Screen. This splash window shows what version and build number is being used (in this case it is version 1.3 build 23). The window will disappear in a few moments. The main StreamAnalyzer window will then appear. Figure 2-3 The StreamAnalyzer main window Raising your AQ IQ Chapter 2 Calculating ph for Aqueous Solutions 9

16 This window is the tree view. A list of currently defined objects is displayed here. This window is the explorer view. Normally we start by clicking on Add New Stream Figure 2-4 The main Stream Analyzer Window Click on the Add New Stream icon. The program will automatically create a new stream with a default name. We will then be positioned on a data entry dialog named Definition. 10 Chapter 2 Calculating ph for Aqueous Solutions Raising your AQ IQ

17 A new object, a Stream, has appeared in the treeview. Figure 2-5 Adding a single point calculation Raising your AQ IQ Chapter 2 Calculating ph for Aqueous Solutions 11

18 The yellow areas are required. We enter the data in the white spaces in the grid. The component iron (III) Chloride is entered here as FeCL3 Click on the Add Single Point button to start a calculation. Figure 2-6 Entering Stream Information The shaded areas of the stream definition are required by the program. By default, we will start at 25 degrees centigrade, 1 atmosphere and moles of water. This amount of water is 1 kilogram of water. This effectively makes any component concentration a molal concentration. We enter the chemical formula of FeCl 3 in the inflow grid and then enter a value of 1.0. You may use the mouse or tabs keys to move around the grid. The concept employed here is that the user will define a stream (or import it from another program or process) whose values will propagate throughout all subsequent calculations. If a red X appears next to the name you entered, then the program does not recognize the name. Please check to see if the spelling is correct. More about entering user data later in this course. Enter the chemical formula FeCl3 and then enter a value of 1.0 in mole units. Click on the Add Single Point button when finished. 12 Chapter 2 Calculating ph for Aqueous Solutions Raising your AQ IQ

19 The tree view expands to show the new calculation. Figure 2-7 Starting the calculation. We are now ready to start the calculations but let us review some options on this screen. Raising your AQ IQ Chapter 2 Calculating ph for Aqueous Solutions 13

20 What to do next? Click this button to find out! We can select from several types of calculations. The summary box indicates the current status of the calculation. Green means GO! Click here to start Figure 2-8 Entering the conditions of the calculation. The data in the Definition grid has been propagated from the stream that we just previously entered. You may change the values or add to the list of species. This does not affect the original stream definition. Please note: The names that you enter in the grid may be different from what is displayed depending on settings in the Tools menu. This will be discussed later. We will leave the values as is, click the Type of Calculation button. Figure 2-9 Single Point Calculation Types There are several types of calculations that can be performed. We will use the default calculation type of Isothermal for this demonstrations. Each type of calculation is defined as: 14 Chapter 2 Calculating ph for Aqueous Solutions Raising your AQ IQ

21 Isothermal Isenthalpic Bubble Point Dew Point Vapor Amount Vapor Fraction Set ph Precipitation Point Composition Point Custom A constant temperature and pressure calculation. A constant heat loss/gain is applied to the calculation and a temperature or pressure can be adjusted to meet this new heat content. The temperature or pressure is adjusted to reach a condition where a small amount of vapor begins to appear. The temperature or pressure is adjusted to reach a condition where a small amount of aqueous liquid appears. The temperature or pressure is adjusted to produce a specified amount of vapor. The temperature or pressure is adjusted to produce a specified amount of vapor as a fraction of the total quantity. The ph of the solution can be specified by adjusting the flowrate of a species. The amount of a solid (solubility point) may be specified by adjusting the flowrate of a species. The aqueous concentration of a species may specified by adjusting the flowrate of a species Combinations of the above calculations can be created. Select Isothermal calculations. Raising your AQ IQ Chapter 2 Calculating ph for Aqueous Solutions 15

22 We re already to go, click the green calculate button! Figure 2-10 Let's GO! Click the Calculate button! Click the green calculate button The program will now start the calculation. After a moment, an Orbit will appear illustrating that the calculation is proceeding. For long-time users of the OLI Software message will appear that might seem familiar. Cancel will end the calculation. Close removes the Orbit The current operation is displayed as well as the current calculation point. Figure 2-11 The OLI Orbit The calculation will continue for several moments. When it is done, you will be returned to the same Definition screen. 16 Chapter 2 Calculating ph for Aqueous Solutions Raising your AQ IQ

23 Click on the Report tab. Scroll down to find the Stream Parameters section. Here is our Answer, the ph is We also report some additional information. We can scroll down to see more information or use the Customize button to tailor our report. We can use the Windows Print commands to print this information. Figure 2-12 The Stream Parameter The answer to our question is that the ph of the solution is approximately 2.2. This is fairly acidic and a good question to ask is why is it so acidic? Scroll down the report to see the list of species. Scroll up or down to see the list of species Simple salts in solution can create many species which were not deemed important. The concentration of many of the iron hydroxide species appear to be small but have a great effect on the ph. For example, the concentration of [FeOH + ] = 5.2x10-3 moles/kg H 2 O which is sufficient to remove the equivalent amount of hydroxide ions. The water equilibrium must shift to replace these ions and produces some additional hydrogen ion. Figure 2-13 Species in solution. Why is the ph so low? The aqueous iron species complex the hydroxide ion which shifts the water dissociation in the direction to replenish the hydroxide ions 2. This also produces hydrogen ions which do not have a corresponding place to go and therefore remain free, lowering the ph. This equilibrium is always present: H 2 O = H + + OH - 2 Le Châtelier s principle. P.W.Atkins. Physical Chemistry. W.H.Freeman and Company, San Francisco (1982) p 269. Raising your AQ IQ Chapter 2 Calculating ph for Aqueous Solutions 17

24 Getting the Chemistry Right To control and troubleshoot your process, you must start by getting the chemistry right. For aqueous systems, that means two essential considerations: Comprehensively taking into account the presence of all of the species that can form in the system ( complete speciation ) Rigorously taking into account the non-ideal behavior resulting from the interactions of charged species (ions) and molecules in solution. This is especially important as concentrations get above very dilute levels as typically is the case for most real world systems. (Discussed in a later chapter) Regarding speciation, OLI software automatically accounts for all of the species that can form from the inflows that you specify. Furthermore, the OLI Databank contains all of the physical properties data and parameters needed to complete the calculations. The user does not need to supply data or regress parameters. The OLI software is ready to use out-of-the-box. The curve above is taken from a StreamAnalyzer survey. You will learn to generate these curves in a later chapter. The curves above plot the predominant species in the ferric chloride water system. You can see that along with the Fe +3 and Cl -1 ions that might be suspected, the predominant iron species is actually the iron hydroxide complex FeOH +2. As explained in the text, the formation of this complex is the reason that the H + ion concentration is elevated above neutral (between and 0.01 on the plot compared to 10-7 for a neutral solution), yielding a ph of Chapter 2 Calculating ph for Aqueous Solutions Raising your AQ IQ

25 What s the bottom line? Simple approaches to even simple salts solutions can lead to serious errors in ph and concentration. The rigorous calculation of solution concentrations are necessary to make good engineering decisions. Advanced Problems 1. How many kilograms of sodium chloride (NaCl) will dissolve into 1 kilogram of water at 50 o C and 1 atmosphere pressure? 2. How many kilograms NaCl will dissolve into 0.9 kilograms of water with Kg of methanol at 50 o C and 1 Atmosphere? Raising your AQ IQ Chapter 2 Calculating ph for Aqueous Solutions 19

26 20 Chapter 2 Calculating ph for Aqueous Solutions Raising your AQ IQ

27 Chapter 3 Neutralized an Acid How to avoid accidental hazardous waste generation! Effluent discharge costs and regulations encourage consideration of novel recycle options. Blending plant streams can often lead to unwanted, and perhaps costly results. The formation of solids and aqueous complexes greatly influences the ph of a mixture. Acid or base neutralization can be readily calculated, but only when all species are accounted for. A waste stream containing small amounts of HF had a ph that was low enough to be borderline RCRA 1 hazardous (acidity). An attempt to neutralize the stream using another plant stream of neutral ph gave an unexpected and potentially costly result. Hydrofluoric Acid Stream The hydrofluoric acid (HF) stream was to be at 25 centigrade, 1 atmosphere and a concentration of 0.1 moles HF/Kg H2O. This is often referred to as the molal concentration scale. What would the ph be of this stream? We can estimate the ph from the know dissociation constant for the acid. The pka for HF at the stated conditions is This is an equilibrium constant of Ka = x To estimate the ph we use the following simple assumptions. HF AQ ( ) + = H + F 1 RCRA is the Resource Conservation and Recovery Act. 42 U.S.C. s/s 6901 et seq. (1976). RCRA (pronounced "rickrah") gave EPA the authority to control hazardous waste from the "cradle-to-grave." This includes the generation, transportation, treatment, storage, and disposal of hazardous waste. RCRA also set forth a framework for the management of non-hazardous wastes. Raising your AQ IQ Chapter 3 Neutralized an Acid 21

28 If we start with 0.1 molal HF, at equilibrium we have the following condition HF (aq) = H + + F - (0.1 X) (X) (X) 2 X K = = x10 (0.1 X ) 4 Assuming that X is much less than 0.1, the value for X = 7.85x10-3. Since this is a value for H +, the concentration of the hydrogen ion is 7.85x10-3 molal. Since + [ ] ph = Log H The ph = 2.10 This is fairly acid by RCRA standards. Neutralizing Stream We will use calcium chloride (CaCl 2 ) to neutralize the HF stream. We will use the same concentration of 0.1 molal and the same temperature and pressure. CaCl 2 dissociates in water according to: 2 CaCl Ca Cl The corresponding acid for this reaction is HCl which also strongly dissociates. The corresponding base is Ca(OH) 2 which also strongly dissociates. The expectant ph of a solution which is the product of a strong acid and a strong base is approximately 7.0. Using the StreamAnalyzer We will now start the StreamAnalyzer to see how close are estimates are to the actual rigorous calculations. Start the StreamAnalyzer and use the File/Open menu item to locate a pre-loaded file. This file should be located in the following folder: \My Documents\My OLI Cases\Analyzer 1.3\Samples and has the name: Hazardous Waste.sta 2 The file contains two stream that have been previous defined. 2 The file extension may not be displayed depending on your folder option settings. 22 Chapter 3 Neutralized an Acid Raising your AQ IQ

29 Figure 3-1 Preloaded file Just how good was our prediction for the ph of the hydrofluoric acid stream? To find out, we will need to perform some calculations. Double-click on the HF Acid icon either in the tree view on the left or in the Explorer view on the right. Raising your AQ IQ Chapter 3 Neutralized an Acid 23

30 Figure 3-2 Stream Definition for the HF stream We have defined the HF stream to be at 25 o C, 1 Atmosphere pressure, moles of water 3, and 0.1 moles of HF. Click the Add Single Point button in the upper right-hand corner moles of H 2 O is exactly equal to 1000 grams of water, or 1 Kg. This makes any concentration in this stream effectively a molal concentration value. 24 Chapter 3 Neutralized an Acid Raising your AQ IQ

31 Figure 3-3 Adding an isothermal single point calculation. As you can see, we have added a dependant object to the HF Acid object in the tree view. This indicates that much of the information in this calculation was derived from the parent Stream. Click the Calculate button to find the ph. When the program finishes, look in the Summary box. Raising your AQ IQ Chapter 3 Neutralized an Acid 25

32 Figure 3-4 ph = 2.12 The calculated ph is The estimated ph is This is very good agreement. It would tend to imply that the acid HF did not dissociate to a large degree. Now what about the ph of the calcium chloride stream? Double-Click the CaCl2 stream object in the tree-view. Double-click this object Figure 3-5 Click the CaCl2 object 4 This value may be different that what you actually observed due to small improvements in the data base. 26 Chapter 3 Neutralized an Acid Raising your AQ IQ

33 Figure 3-6 Entering the CaCl2 stream The conditions for the calcium chloride stream are similar except that we are using a 0.1 molal solution of CaCl 2. Double-click the Add Single Point button. As before, we now have an input grid for the calculation. Figure 3-7 Click on Calculate Click on the Calculate button to find the ph As before, the calculated ph can be found in the Summary box. Raising your AQ IQ Chapter 3 Neutralized an Acid 27

34 Figure 3-8 the ph is 6.91 Mixing the HF Acid with the CaCl 2 stream. The calculated ph is 6.9 which is somewhat lower than the predicted ph of 7.0. This probably due to some complexing of calcium and hydroxide ions in solution. Our estimate is still not too bad a number. What would happen if we mixed the two stream. After all, that is the purpose of the experiment. The HF stream is nearly too acidic to discharge to the environment. Neutralization could be obtained by the more basic CaCl 2 stream. Since the volumes of the two streams are nearly the same, we could average the ph s to see the neutralized ph. Average ph = ( )/2 = 4.5 This would be an allowable discharge ph according to RCRA. What is the actual calculated ph? Figure 3-9 Selecting Streams from the menu Select Streams from the menu items. Figure 3-10 Selecting mixed streams Select Add Mixed Stream from the menu 28 Chapter 3 Neutralized an Acid Raising your AQ IQ

35 This will display the Mix Stream Calculation. Many streams may be mixed at isothermal conditions, or at other varying conditions. We will mix the stream isothermally. Figure 3-11 Available streams for the mix calculation. Select each Stream and click the right-double-arrow (>>) to select it. Figure 3-12 Both streams selected. The two streams have been selected. You can see a new object has appeared in the tree-view. This is the mixed stream object. Raising your AQ IQ Chapter 3 Neutralized an Acid 29

36 Figure 3-13 A new object appears The name of the object is automatically created. The number is automatically updated (in this case MixedStream6). You will probably have a different number. Click the Calculate button. After a few moments, the ph will be returned in the Summary box. Figure 3-14 The ph is 1.4 The calculated ph is 1.44!!! Can this be correct? We have taken an acid and neutralized it with a more basic solution. The ph decreased. Something else besides acid and base chemistry must be taking place. 30 Chapter 3 Neutralized an Acid Raising your AQ IQ

37 Analysis of the Chemistry Figure 3-15 The input grid Click on the Report tab and scroll down to the species section. Figure 3-16 Scrolled down to find the True Species output. Focused on CaF2 The circle above is focused on a solid species, CaF 2. This solid is formed when the calcium ion Sees two fluoride ions according to this equation: 2 CaF Ca + 2 ( s ) + 2 F The solid is very insoluble and forms rather easily. There was an initial amount of 0.1 moles of HF that we entered. Almost moles of CaF 2 were formed. Since Raising your AQ IQ Chapter 3 Neutralized an Acid 31

38 there are 2 moles of fluoride ion per mole of calcium fluoride, this accounts for moles of fluoride ion. Only moles of fluoride ion remain in solution. This means that we have taken the equilibrium: HF AQ ( ) + = H + F and placed it under stress. In the mixing operation we have removed fluoride ions from aqueous solution. Le Chatlier s principle states that if we disturb an equilibrium, the equilibrium will shift to restore itself. In this case, the undissociated HF will dissociate to produce more fluoride ions. This also produces additional hydrogen ions. Double-click the original HF Stream and then the Single Point Calculation beneath it. Click the Report tab and scroll down to the Species report. Locate the H+1 row. Figure 3-17 The H+1 amount for the HF Stream In the initial HF stream, the ph was equal to This corresponds to x 10-3 moles of H + ion per Kilogram of water 5. Now double-click the Mixed Stream object and go back to the Species report. Figure 3-18 Back to the Mixed Stream Species Report 5 The relationship of the hydrogen ion to ph is actually ph = -log(a H ) where a H is the activity of the hydrogen ion (a = γ[h + ]). You need the activity coefficient of the hydrogen ion (which is reported lower in the report) to make an exact conversion) 32 Chapter 3 Neutralized an Acid Raising your AQ IQ

39 We have produced a total of mole of hydrogen ion, an additional moles of H + from further dissociation of HF. But this is in approximately 2 Kg of water. The real concentration is.047 moles of hydrogen ion per Kg H2O with a ph of approximately 1.4 Generating Titration Curves The graph above illustrates an interesting titration curve resulting from the neutralization of HF using calcium phosphate. Once again, solids are formed during the process. This results in several inflection points in the titration curve. The neutralization of the HF waste stream with a calcium chloride waste stream was performed using the Mixed Stream Single Point calculation feature. Titration curves like the one above can be readily performed using the Mixed Stream, ratio, volume or proportion features in StreamAnalyzer. Raising your AQ IQ Chapter 3 Neutralized an Acid 33

40 Calculated Partial Pressures of Gases (VLE only) CO2 (60 C) H2S (60 C) 100 NH3 (60 C) 10 CO2 (20 C) 1 H2S (20 C) 0.1 NH3 (20 C) Diagonal Experimental Calculated Partial Pressure of Gases (Full OLI Model) CO2 (60 C) H2S (60 C) NH3 (60 C) CO2 (20 C) H2S (20 C) NH3 (20 C) 0.1 Diagonal Experimental Vapor Liquid Equilibrium (VLE) Accurate vapor liquid equilibrium for multi-component aqueous electrolytes systems also requires accounting for all possible species ( complete speciation ). In this case, solids may or may not form. Either way, it is impossible to accurately determine the phase equilibria and the aqueous phase ph unless all of the reactions in the aqueous phase are considered. An important industry application is sour gas scrubbing. The graph on the left illustrates the results of calculating the phase equilibrium considering VLE only, and ignoring the aqueous phase reactions. An example of this approach would be using Henry s Law constants from a Table, or using an equation of state such as SRK or Peng-Robinson. Such approaches may provide an approximate solution for just binary systems (e.g. CO 2 H 2 O, H 2 S H 2 O, or NH 3 H 2 O). But when more than one compound is present with water, reactions in the aqueous phase lead to aqueous complexes that significantly reduce the partitioning of the acid gases to the vapor phase. The graph on the right shows that the OLI models, which take into account the aqueous phase complexes, accurately predict the chemistry and phase partitioning for acid gas systems. Conclusion The ph s of the individual streams were based on simple chemistry and therefore the ph s were easily estimated. The mixed stream involved more complicated chemistry and our simple estimate was not even close. A statement can be made that we can not reliably predict mixed ph s knowing the ph s of the individual stream. As an aside, it seems that the following is also true The resultant ph of a mixed stream of a weak acid and a strong base will have a ph lower than that of the acid providing that a component leaves the solution via a phase change The weak acid in this case is HF and the strong base is Ca(OH) 2 with the fluoride ion leaving solution as CaF Chapter 3 Neutralized an Acid Raising your AQ IQ

41 Advanced Problems 1. How many moles of ammonia (NH 3 ) will it take to dissolve 0.1 moles of copper hydroxide (Cu(OH) 2 ) in moles of water at 25 o C and 1 atmosphere pressure? Raising your AQ IQ Chapter 3 Neutralized an Acid 35

42 36 Chapter 3 Neutralized an Acid Raising your AQ IQ

43 Chapter 4 Water Treatment You can t get there from here! Metals are often removed from water by precipitation processes. Careful control of the ph of the precipitation process is necessary in order to achieve the best possible metal removal. The presence of other species in a waste stream can significantly affect the removal levels that can be achieved. A thorough understanding of the chemistry is needed to design effective water treatment polishing processes such as ion exchange. The Application... The city of Clearwater, Florida has a discharge limit for nickel of 0.1 mg/l 1. In this application, a user is discharging a wastewater that contains nickel ion at a concentration of moles/kg H 2 O. The existing treatment strategy is to precipitate the nickel ion as Nickel Hydroxide - Ni(OH) 2 prior to discharge into the municipal sewage system. The soluble nickel remaining after precipitation is less than 0.1 mg/l which is a design specification. During the course the plant operation, some cyanide ion is inadvertently added to the waste stream. The soluble nickel is now many times in excess of 0.1ppm. Let s get started... We begin by starting the OLI/StreamAnalyzer Program. This may be accomplished by clicking the StreamAnalyzer icon or by using the Start button and finding the StreamAnalyzer under Program. Once started, the OLI Splash screen will display. 1 See Raising your AQ IQ Chapter 4 Water Treatment 37

44 Figure 4-1 The OLI Splash Screen After a few moments, the main OLI/StreamAnalyzer welcome screen will display. Figure 4-2 The StreamAnalyzer Welcome Screen Use File/Open menu item to locate a pre-loaded file. This file should be located in the following folder: \My Documents\My OLI Cases\Analyzer 1.3\Samples and has the name: 38 Chapter 4 Water Treatment Raising your AQ IQ

45 Nickel Removal.sta 2 Figure 4-3 The pre-loaded file The pre-loaded file has a stream that contains only the mole/kg H2O Nickel concentration and the a stream contaminated with cyanide. What is the ph? Let s review the stream definition. Double-click the stream Nickel Stream. Double-click this object Figure 4-4 The tree view This will display the Definition window. 2 The file extension may not be displayed depending on your folder option settings. Raising your AQ IQ Chapter 4 Water Treatment 39

46 Figure 4-5 the definition grid You can see that we have already added moles of Ni(OH) 2 to the sample. Water is also entered at moles. The amount of water is one kilogram of water which makes the nickel hydroxide concentration effectively a molal concentration unit. Normally we would either add a single point calculation or a survey at this time. These have already been done for you. We would like to see the natural ph of the solution. Click on the ph object. Double-click this object Figure 4-6 Click on ph There are several calculation types from which we could select. We use the default type of Isothermal. Click the Calculate button. When the program is completed (the wave is gone) we are ready to review the results. This may be done in several ways. This tour will examine several of the methods. Click on the Advanced button. Figure 4-7 the advanced button 40 Chapter 4 Water Treatment Raising your AQ IQ

47 We want to display the calculated state and additional stream parameters. The Update button can be used to update new values found in the stream to this calculation. Select the Calculated State radio button. Click Additional Stream Parameters. Click OK The grid will now change to blue to indicate that these are calculated values. The ph can be found in the grid. The results are displayed in blue. The resultant ph is approximately This number may be different from your value because the database is constantly updated. Figure 4-8 the results, the ph is 8.4 Our primary interest in this application is finding the optimum ph for nickel removal. To create a plot of the data, we will need to make a survey. Adding a ph Survey There are many ways to move around in the StreamAnalyzer. We will constantly highlight them as we move around in the tours. Remember that there are frequently more than one method to achieve a desired result. Click on the ph Survey icon in the tree view on the left-hand side of the window. Raising your AQ IQ Chapter 4 Water Treatment 41

48 Double-click this object Figure 4-9 click on ph Survey Figure 4-10 The ph Survey Definition Tab. The calculate button light is grayed out which indicates that the calculation is not yet ready to proceed. The Summary box indicates that we require additional information. 42 Chapter 4 Water Treatment Raising your AQ IQ

49 Figure 4-11 The summary box, an acid and a base need to be selected The acid titrant and the base titrant need to be defined. For this tour, these will be hydrochloric acid (HCl) and sodium hydroxide (NaOH). Add the component inflows HCl and NaOH to the grid. Do not add any values for them. Figure 4-12 Added new component inflows. Click the Specs button Raising your AQ IQ Chapter 4 Water Treatment 43

50 Figure 4-13 ph Survey Options Click this X to close the box Select HCl from the Acid column and NaOH from the Base column. Click on OK. We are now ready to begin the calculations. Click the Calculate button. The program will run for a short time. When the orbit disappears, check the summary box to see if the calculation is complete. In the tree-view, you can expand the survey to see if all the points converged. A small calculation result window may appear. If it does, simply close it. Figure 4-14 Calculation result windows. Click the X to close it. Obtaining results We can now obtain some graphical results. Click on the Plot tab. 44 Chapter 4 Water Treatment Raising your AQ IQ

51 Figure 4-15 the default plot For many calculations, the values on the plot extend over a very large range of numbers. The default linear axis may not capture all the details we require. Right-Click anywhere in the plot window and select Toggle Y-axis Log Figure 4-16 the plot right-click The display will now change. Raising your AQ IQ Chapter 4 Water Treatment 45

52 You can select and drag the legend to comfortable positions. Figure 4-17 log axis plot Although this plot tells us a great deal, we require more specific information about nickel species. Remember, there is a limit to the amount of soluble nickel that can be discharged. We need to clean this diagram up. Click the Customize button. Scroll down this list to find more variables Figure 4-18 The customize plot dialog The Dominant Aqueous variable in the Y-Axis box should be displayed. Select it and then click the left double-arrow (<<) button which will remove it from the plot. Scroll down the left-hand window to find MBG Aqueous Totals. 46 Chapter 4 Water Treatment Raising your AQ IQ

53 Figure 4-19 Selecting more variables MGB is an abbreviation for Material Balance Groups The grid updates to show the material balance totals available to display. In this case we desire the Nickel (+2) species. The variable displayed will be the sum of all nickel containing species in the aqueous phase. Double-Click the NI(+2) item or select it and use the >> button. Click the OK button This is the 0.1mg/L limit for Nickel. Figure 4-20 The results of the ph survey. The material balance group variable is a sum of all the species for that material in the phase requested. For example, in this case all the NI(+2) Aq variable is a sum of all nickel containing ions in solution. Any solids are excluded. Raising your AQ IQ Chapter 4 Water Treatment 47

54 You can see that a minimum in aqueous solubility seems to occur in the ph=10 range. This is the result of nickel solids forming and leaving the aqueous phase. The limit of 0.1 ppm for Ni +2 is approximately 2 x 10-6 moles. At a ph=10, we are several orders of magnitude below this limit. What else is important in this solution. Click the Customize button and add the following species to the plot (you may need to scroll up or down to find all the species). Aqueous: Ni(OH)2 NiOH+1 Ni+2 Ni(OH)3-1 Solids: Ni(OH)2 Figure 4-21 Important nickel species You can see that the soluble nickel (Ni(+2)-Aq) is a summation of the other species. The large drop in the value is because most of the nickel leaves the aqueous solution as Ni(OH)2-Solid at ph s greater than 7.0 with a maximum near ph=10. Now, What About the Contaminated Waste? The real importance of aqueous speciation modeling of this treatment is only really appreciated if we introduce the cyanides which brings us to the real waste treatment problem. 48 Chapter 4 Water Treatment Raising your AQ IQ

55 Please follow these steps for this next scenario. Please note: we will only show the screens that are substantially different from those that you have scene. What is the ph of the Cyanide contaminated stream? Click the Contaminated Stream in the tree view in the left-hand window. Double-click this object Figure 4-22Click on the Contaminated object This will display the stream view in the right-hand window. Figure 4-23 The input grid As you can see, 0.01 moles of hydrogen cyanide have been added to the solution. As before, we have already partially added a single point calculation and a survey. Click the ph object under the Contaminated object. Double-click this object Figure 4-24Click the ph object The grid should now look like this: Raising your AQ IQ Chapter 4 Water Treatment 49

56 Figure 4-25 Adding HCN Getting results of the Single Point Calculation. When the Calculate Button light turns green, click the button. There are several method for reviewing the results of a calculation. Scenario 1 showed how the advanced button can reveal additional information. In this scenario we will use a different technique. Right-Click anywhere in the grid The following pop-up menu will appear. Figure 4-26 Right-clicking on the grid Select Show Calculated Right-Click again and select Additional Stream Parameters The resultant ph should be approximately 4.04 Run the ph survey. Click the ph Survey Object stream in the tree view in the left-hand window. 50 Chapter 4 Water Treatment Raising your AQ IQ

57 Double-click this object This will display the grid view in the right-hand window. We have already added the HCl and NaOH to the grid since we already know that they will be the ph titrants. The titrants have already been selected. All we have to do is: Click the Calculate Button. Reviewing results. When the program has finished calculating: Click on the Plot tab. 0.1mg/L limit Figure 4-27 Nickel Waste Stream with HCN added We have provided you with a partial list of species to plot. We now want you to add two additional variables: Raising your AQ IQ Chapter 4 Water Treatment 51

58 Click on the Customize button and add: NI(+2) MBG Aqueous Totals NiNi(CN)4 Solid The results have changed very dramatically. The new optimum ph for Ni removal is around 4.0, rather than The lowest total Ni remaining in solution is now on the order of 10-5 which is actually well over 0.1 mg/l. The culprit is the Ni(CN) -2 complex of nickel and cyanide. Basically, the plot of the total Ni in solution and the Ni(CN) -2 complex overlap over the interval ph=5 to 12. This means that virtually all nickel in solution is in the form of this complex. This complex thus holds the Ni in solution and does not allow the nickel hydroxide to even form. Instead, a much weaker precipitate, the NiNi(CN) 4 salt forms over a narrow range of ph with 4.0 being the optimum. The nickel can no longer be discharged into the municipal sewage system. Alternative forms of removal must now be considered The StreamAnalyzer survey feature makes it easy for you to perform sensitivity studies to determine how the key variables in your process affect the outcome. For example, the surveys you performed could be repeated at different temperatures to see if there is a significant effect. The plot on the left shows that as the temperature is varied and there is no cyanide ion present, the total nickel concentration remaining in the aqueous phase is about the same, but the ph at which the minimum occurs varies over a range from about 9 to 11. The right plot shows that when the cyanide ion is present, the chemistry is relatively insensitive to temperature over a range of 15 to 45 C. The survey feature can help guide and save you lab time and cost. One option to remove the nickel when cyanide is present could be ion exchange. Although is might be assumed that a cationic resin would be needed to remove the nickel, the OLI software shows that the important species to remove is actually the nickel cyanide complex which is a negatively (-2) charged species. The correct alternative would be an anionic exchange resin.. Conclusion Water treatment processes can be optimized and effectively managed when the chemistry is thoroughly understood. Trace species can have a significant effect on the performance and compliance of these processes. 52 Chapter 4 Water Treatment Raising your AQ IQ

59 Advanced Problems 1. Could 0.01 moles/kg H 2 O sodium sulfide be used to react with the cyanide contaminated stream to remove the nickel? 2. Would lowering the operating ph to 2 improve the nickel removal? Raising your AQ IQ Chapter 4 Water Treatment 53

60 54 Chapter 4 Water Treatment Raising your AQ IQ

61 Chapter 5 Sour Gas Treatment A little bit of water can go a long way (in creating a Big Process Problem) Whenever water is present in a process, there is the possibility of condensation of a liquid phase that can lead to solids deposition and/or corrosion. Real world systems are often complicated by the presence of a second liquid phase, making phase equilibrium prediction challenging. Conventional process simulation cannot readily address these kinds of situations. They can be addressed by importing streams into the OLI Analyzers. Scope An alkanolamine gas sweetening plant has scaling and corrosion problems in the condensed overhead gas. Raising your AQ IQ Chapter 5 Sour Gas Treatment 55

62 Figure 5-1 An Alkanolamine gas sweetening plant (diagram from HYSYS 3.1) Purpose Diethanolamine is used to neutralize an acid gas containing carbon dioxide and hydrogen sulfide. The Diethanolamine is regenerated and the acid gases are driven off in a stripper. The off gas from this stripper is saturated with water vapor. As these gases cool, they will condense. This condensate can be very corrosive. The service life of the plant can be shortened considerably due to these condensed acid gases. Objectives 1. Determine the dew point temperature of the acid gas 2. To remove the condensed aqueous phase and perform corrosion rate calculations. 3. To consider mitigation strategies for the pipes. 56 Chapter 5 Sour Gas Treatment Raising your AQ IQ

63 Start the tour Let s get started... We begin by starting the OLI/StreamAnalyzer Program. This may be accomplished by clicking the StreamAnalyzer icon or by using the Start button and finding the StreamAnalyzer under Program. Once started, the OLI Splash screen will display. Figure 5-2 The OLI Splash Screen After a few moments, the main OLI/StreamAnalyzer welcome screen will display. Raising your AQ IQ Chapter 5 Sour Gas Treatment 57

64 Figure 5-3 The StreamAnalyzer Welcome Screen Use File/Open menu item to locate a pre-loaded file. This file should be located in the following folder: \My Documents\My OLI Cases\Analyzer 1.3\Samples and has the name: Sour Gas.sta 1 This file was saved with the CorrosionAnalyzer Plug-In enabled. A warning message will appear. 1 The file extension may not be displayed depending on your folder option settings. 58 Chapter 5 Sour Gas Treatment Raising your AQ IQ

65 Figure 5-4 Corrosion Analyzer Plug-In warning. Clicking on the OK button will launch the program but any CorrosionAnalyzer related objects will be disabled. Figure 5-5 StreamAnalyzer with disabled rates calculation The Analyzers allow you to Plug-In other analyzers into each other. For example, we can plug-in the CorrosionAnalyzer into the StreamAnalyzer. The files created are still StreamAnalyzer files. Select Tools from the menu item. Raising your AQ IQ Chapter 5 Sour Gas Treatment 59

66 Figure 5-6 Selecting Tools This will display a menu. Figure 5-7 The tools menu Select Options from the list. Figure 5-8 the Options Dialog. There are many things that can be modified with this dialog. The look and feel for the software as well as default locations can be specified. Click on the Plug-Ins line in the Category Tree-view. 60 Chapter 5 Sour Gas Treatment Raising your AQ IQ

67 Figure 5-9 The plug-ins dialog Several OLI programs are available here. Check the CorrosionAnalyzer box. Figure 5-10 Selecting the corrosion Analyzer. Click on the OK button. You will now be required to close and restart the program. Close the program without saving the file. Restart the program opening the same file Sour Gas.STA Raising your AQ IQ Chapter 5 Sour Gas Treatment 61

68 The stream has the following composition. We have already added the stream for you in this example. Table 1 Gas Concentration Species Concentration (mole %) H2O 5.42 CO N H2S 16.6 CH C2H C3H Temperature 38 o C Pressure 1.2 Atmospheres Stream Amount 100 moles You will notice that the value for water is in yellow. This value will be automatically calculated from the sum of the other inflow components. Error message may occur if you have concentrations that require the mole percentages of water to be negative. 62 Chapter 5 Sour Gas Treatment Raising your AQ IQ

69 The Corrosion Rate at the Dew Point What s all this about corrosion rates? OLI Systems, Inc. is also a world leader in providing simulation tools for corrosion scientists and engineers. OLI holds a separate course called the Corrosion Teach-In. It is held at several locations world wide each year. We now want to determine the corrosion rate at the dew point temperature for this gas. The dew point is the temperature where the first amount of aqueous liquid will condense. We have already added a corrosion rates calculation to the stream. Contact OLI for more information. Figure 5-11 Adding the rates calculation. This will display a default view of the rates of corrosion. We have already filled out the grid for you. If you are working from scratch we did the following: We will now change the Types of Rates Calculation and the Flow Conditions. Figure 5-12 Default conditions. Change the type of calculation to Single Point Rate and the flow conditions to Pipe Flow and use the default values. Figure 5-13 The contact surface should be set to Carbon steel G10100 (generic) Raising your AQ IQ Chapter 5 Sour Gas Treatment 63

70 Figure 5-14 We now will add the dew point calculation on top of the corrosion rates calculation. Click the Specs button. Figure 5-15 The specs button. Now select the Calculation Type line. Figure 5-16 The calculation type dialog Click the Type of Calculation button and select Dew Point. 64 Chapter 5 Sour Gas Treatment Raising your AQ IQ

71 Figure 5-17 Selecting dew point Figure 5-18 Temperature selected. We want to calculate the corrosion rate at the dew point temperature. Click the Temperature radio button and then click OK We now have a screen that should look like this: Raising your AQ IQ Chapter 5 Sour Gas Treatment 65

72 Figure 5-19 The completely filled out grid. Click the Calculate button. When the program finishes, we would like to see the rate of corrosion of the steel. Click the Point 1 of 1 mini-tab at the bottom of the grid. 66 Chapter 5 Sour Gas Treatment Raising your AQ IQ

73 Figure 5-20 The output grid Right-click anywhere on the grid to display a pop-up menu. Figure 5-21 The pop-up grid menu Raising your AQ IQ Chapter 5 Sour Gas Treatment 67

74 Select Corrosion Values from the menu Figure 5-22 Selecting Corrosion Values. This will display the overall corrosion information for this stream. What are all those other tabs? It is beyond the scope of this course to explain those tabs. OLI s Corrosion Teach-In course explains these diagrams in great detail. Figure 5-23 The corrosion information The corrosion rate is approximately 0.7 mm/yr. The dew point is approximately a temperature of 37.6 o C. The value is in green to note that it was a secondary calculation. Click on the Report Tab and scroll down to the Stream Parameters. Figure 5-24 The stream parameters The ph is nearly 3.9 of the condensed vapor. Mitigation There are several solutions for mitigating the corrosion problem. A simple solution is to add insulation to prevent temperature drops. The dew point is very close to the overhead gas temperature so this may not be a suitable option. Adding heat to keep the temperature above the dew point is usually considered along with insulation. Changing the chemistry to change the partial oxidation and reduction processes is also an option. Finally, changing alloys could mitigate the corrosion problem. 68 Chapter 5 Sour Gas Treatment Raising your AQ IQ

75 Adjusting the solution chemistry. In this section, we will add sodium hydroxide to raise the ph to 8.0 Click on the original stream in the tree view. The original stream should be the first stream in the list. Figure 5-25 Selecting the first stream. This stream contains the original input information. Click the Add Single Point button. Select Set ph. When setting the ph, you must specify a titrant. There are several methods of selecting titrants. Click the Specs button. Figure 5-26 Figure 5-27 The desired titrant, sodium hydroxide (NaOH), is not on the list. We can add it by entering a new inflow species. Click the New Inflow button. Raising your AQ IQ Chapter 5 Sour Gas Treatment 69

76 Figure 5-28 You can search for any component in an OLI database. If the species has stored synonyms and / or structures, they will be displayed. Enter the species name NAOH in the Component box. Figure Chapter 5 Sour Gas Treatment Raising your AQ IQ

77 As you can see, synonyms are filled out as well as the internal OLI name (OLI Tag), molecular weights and the chemical abstract service number. Click the Add to Stream button. Click the Close button. The Select titrant window will be updated with a new species. Figure 5-30 Select NaOH and then click OK. The input window will now be updated with a grid entry for NaOH and a target ph value initially set to 0.0. Raising your AQ IQ Chapter 5 Sour Gas Treatment 71

78 Initial target ph is 0.0, it must be changed to 8.0 New species, NaOH with zero concentration Figure 5-31 Enter a target ph of 8.0 The program is now set up to adjust the amount of NaOH to match a target value of ph = 8.0. Figure 5-32 Click the Calculate button. Look at the summary box when the calculation is complete. 72 Chapter 5 Sour Gas Treatment Raising your AQ IQ

79 Figure 5-33 The ph is indeed set to 8.0 and the concentration of NaOH is approximately 42 mole percent in the aqueous phase. Also notice that in the Phase Amount section, there is some solid material. Click on the Report tab. Scroll down to the Species Output (True Species) section. Figure 5-34 This section of the report shows the detailed speciation for this point. At a ph of 8.0, this gas stream will form 72.4 moles of sodium bicarbonate (NaHCO 3 ) for every 100 moles of gas (the initial amount). Using sodium hydroxide is probably a bad choice for mitigating the corrosion since a scale of NaHCO 3 would likely form and plug the process equipment. Metal hydroxides are very good at scrubbing carbon dioxide from gas streams. Raising your AQ IQ Chapter 5 Sour Gas Treatment 73

80 Alloys Since treating the acid gas with a base is probably not a good idea for metal hydroxides, perhaps we can change the alloy. We will go back to the condensate stream (the second stream on the tree view) and add a new corrosion rates calculation. Figure 5-35 Click on the Sour Gas stream. Click on the Add Corrosion Rates button. Change the Contact Surface to 13%Cr stainless steel We will now change the Types of Rates Calculation and the Flow Conditions. Change the type of calculation to Single Point Rate and the flow conditions to Pipe Flow and use the default values. Click the Specs button and select Calculation Type and then Select Dew Point Temperature. Click the Calculate button. Click on the Report Tab and scroll down to the Calculated Rates section. Figure 5-36 The calculated corrosion rate is 0.06 mm/yr. A little more than one order of magnitude decrease over carbon steel Save This would be a good time to save your work. 74 Chapter 5 Sour Gas Treatment Raising your AQ IQ

81 This example showed how the addition of a reagent used to raise the ph led to the formation of potentially problematic solids. In real world applications such as upstream oil and gas, it is possible to have situations where gas, aqueous liquid (brine), second liquid (oil), and solids co-exist. For example in this case CO 2 may partition between the gas, oil, brine, and solids (as a solid carbonate for example). Accurate simulation of this situation requires accounting for the equilibrium in all four phases at once, the so called four phase flash. This can be a difficult situation for conventional simulators to handle. The OLI software is designed to make it easy to perform four phase flash calculations, and then plot the results as a function of variables that you select. The OLI software can even import streams from a conventional simulator so that corrosion, solids scaling, and other process conditions or options can be evaluated. Below is an excerpt from a StreamAnalyzer report illustrating the calculated results for a four phase flash calculation. Note that the true species composition, in this case reported as moles, is reported by phase. Note also that CO2 does in fact partition to all four phases (to the solid phase in the form of calcium carbonate). Species Output (True Species) Total Aqueous Vapor Solid 2nd Liquid mol mol mol mol mol Water e-3 Carbon dioxide Hydrogen sulfide Ammonia e e-4 Dodecane e e Calcium chloride e e Calcium carbonate (calcite) e e e Hydrogen chloride e e e Ammonium ion(+1) Bicarbonate ion(-1) Calcium bicarbonate ion(+1) e e Calcium hydroxide ion(+1) e e Calcium ion(+2) e e Calcium monochloride ion(+1) e e Carbamate ion(-1) Carbonate ion(-2) e e Chloride ion(-1) Hydrogen ion(+1) e e Hydrogen sulfide ion (-1) Hydroxide ion(-1) e e Sulfide ion(-2) e e Total (by phase) e Conclusion. Whenever water is present in a process, there is the possibility of condensation of a liquid phase that can lead to solids deposition and/or corrosion. Real world systems are often complicated by the presence of a second liquid phase, making phase equilibrium prediction challenging. Conventional process simulation cannot readily address these kinds of situations. They can be addressed by importing streams into the OLI Analyzers. The Analyzers can perform ph adjustment, dew point and bubble point, precipitation point, and corrosion rate calculations for streams that you define or import from a conventional simulator. Raising your AQ IQ Chapter 5 Sour Gas Treatment 75

82 Advanced Problems 1. As we saw in the example, using sodium hydroxide to adjust the ph caused unwanted solids to form. Using ammonia (NH 3 ), recalculate the ph calculation to see if solids form. 2. Are there any other titrants that would raise the ph but not cause solids to form? 76 Chapter 5 Sour Gas Treatment Raising your AQ IQ

83 Chapter 6 Chlorine Scrubbing If 10 percent is good, 20 has to be better? An emergency scrubber is to be designed to handle the emergency release of chlorine gas from a process. The gas stream contains chlorine, carbon dioxide and nitrogen. Caustic (NaOH) is to be the scrubbing liquid. The design specification is to remove 90 % of the total chlorine. There is a concern that due to the presence of CO 2 that carbonate solids may form and plug the scrubber. Emergency Chlorine Scrubber Caustic 25 o C 1 Atm 1000g/hr total 10 wt% NaOH FC 3 Stages 25 o C 1 Atm Overhead Waste Gas 25 o C 1 Atm Cl mol/hr CO 2 52 mol/hr N 2 58 mol/hr Figure 6-1 Schematic of the scrubber Bottoms The scrubber (also referred to as an absorber) contains a feed back controller to control the amount of caustic used to neutralize the chlorine. The flow rate of the Raising your AQ IQ Chapter 6 Chlorine Scrubbing 77

84 caustic stream is an initial guess and may be larger or smaller when the program finishes. It is sometimes useful to perform a simple one stage calculation prior to performing a multistage calculation. In this case a simple one stage equilibrium calculation was performed using survey feature of the OLI/StreamAnalyzer. Although this is not a true scrubber, in that only one stage will be simulated, it does provide some insight into the chemistry taking place inside. Let s get started... We begin by starting the OLI/StreamAnalyzer Program. This may be accomplished by clicking the StreamAnalyzer icon or by using the Start button and finding the StreamAnalyzer under Program. Once started, the OLI Splash screen will display. Figure 6-2 The OLI Splash Screen After a few moments, the main OLI/StreamAnalyzer welcome screen will display. 78 Chapter 6 Chlorine Scrubbing Raising your AQ IQ

85 Figure 6-3 The StreamAnalyzer Welcome Screen Use File/Open menu item to locate a pre-loaded file. This file should be located in the following folder: \My Documents\My OLI Cases\Analyzer 1.3\Samples and has the name: Chlorine Removal.sta 1 1 The file extension may not be displayed depending on your folder option settings. Raising your AQ IQ Chapter 6 Chlorine Scrubbing 79

86 Figure 6-4 the partially filled out file We have provided you with a chlorine stream (Cl2) and two sodium hydroxide streams. One at ten weight percent (10 % NaOH) and the other at twenty weight percent (20 % NaOH). We will use both of these streams to remove chlorine. Stream Review We should take a brief look at each of the streams to determine if they are correct. The following figures display the Stream Description tab for each stream. Figure 6-5 Chlorine Stream 80 Chapter 6 Chlorine Scrubbing Raising your AQ IQ

87 Figure weight percent NaOH Stream Adding a Mixed Stream Figure weight percent Stream Now that we have reviewed our streams. Let us mix the streams together. The StreamAnalyzer has the ability to perform a titration. To start this will need to add a new type of stream, the Mixed Stream. Locate the Streams menu item. Figure 6-8 The streams menu item. Select Add Mixed Stream from the pull down menu. Figure 6-9 The pull down menu. This will display the mixed stream dialog. Raising your AQ IQ Chapter 6 Chlorine Scrubbing 81

88 Figure 6-10 Adding Mixed Streams The Available Streams window displays what streams are ready to use for mixing calculations. Figure 6-11 Available streams. We can highlight the stream (or streams) that we need and then double-click the right arrow button. Figure 6-12 Multiple selections are allowed. Click this button after making your selection. 82 Chapter 6 Chlorine Scrubbing Raising your AQ IQ

89 Figure 6-13 Selected streams If you want to remove a stream (or streams) you can highlight them in the Selected window and use the left double-arrow. Once we have selected the streams we now need to set up the calculation. We have two streams with which can be varied in proportion to each other. We want to keep the flow of the chlorine gas constant and vary the flow of the 10 % NaOH stream. Click this button to make your selection. Figure 6-14 The action items for the calculation. We need to change the Type of survey button to a ratio calculation. The menu will display as follows: Figure 6-15 Survey menu options. Single Point Mix Volume Ratio The streams are mixed according to the proportions specified in the grid. The volume of the target stream is mixed according to the specs button. The reported volume is for the total system The amount of one stream is adjusted while the other is held constant. The report is in terms of the adjusted stream only Proportion The flow of one stream is increased while the flow of the remaining streams are decreased to maintain a constant proportion. For our purposes, select the Ratio menu item. We want to calculate each point at isothermal conditions (as not to add another degree of freedom to our calculations, we can study heating effects later if we wish). We now need to tell the program to vary a stream and by how much Click on the Specs button. Raising your AQ IQ Chapter 6 Chlorine Scrubbing 83

90 Figure 6-16 The specs... dialog The variable which is highlighted is the ratio variable. We will adjust one stream from a flow rate of zero to a flow that is 10 times the initial flow of the stream. In this case, we are adjusting the 10 % NaOH stream which has a mass flow rate of approximately 1 Kg/hr. The flow will be adjusted from 0 to 10 Kg/hr. We do need to specify which stream is to be adjusted. Highlight the General item in the tree-view: Figure 6-17 Highlight the General item. The streams to be considered are displayed next to the tree view. 84 Chapter 6 Chlorine Scrubbing Raising your AQ IQ

91 If chlorine is highlighted, change the focus to 10 % NaOH Figure 6-18 Chlorine is selected. If the chlorine stream is highlighted, we will have to change it to the 10 % NaOH stream. Click on the 10 % NaOH stream. Figure 6-19 Selecting the correct stream. Click back on the Variable-Ratio item in the tree view. Raising your AQ IQ Chapter 6 Chlorine Scrubbing 85

92 Figure 6-20 back to the ranges Change the increment value from 1.0 to Figure 6-21 Change the increment. This provides for a smoother looking curve. Click the OK button. You are now ready to calculate. Click the Calculate button. When the calculation has completed, click on the Plot tab. 86 Chapter 6 Chlorine Scrubbing Raising your AQ IQ

93 Figure 6-22 The default plot We will need to change the plot to see how much chlorine was removed. Click the Customize button. Figure 6-23 The customize plot button. We need to find the amount of chlorine vapor that is remaining in the gas phase. Double-click the Dominant Aqueous item in the Y-Axis window. Raising your AQ IQ Chapter 6 Chlorine Scrubbing 87

94 Scroll up or down to find the Vapor section and select Cl2 by double-clicking it in the left window. Figure 6-24 Selecting chlorine vapor Click on the OK button. This is approximately 0.58 moles of Cl2(VAP). Figure 6-25 Chlorine in the vapor phase. We initially had 5.8 moles of chlorine. Thus at 0.58 moles of chlorine in the vapor corresponds to 10 % remaining or 90% removed. You can mouse-over the points to find a value near 0.58 moles of chlorine. 88 Chapter 6 Chlorine Scrubbing Raising your AQ IQ

95 Why does adding base remove Chlorine? This corresponds to a ratio of the 10 % NaOH stream of 3.5. That implies that we need about 3.5 Kg/hr of the base stream to remove the desired chlorine. The chlorine stream is approximately 4.3 Kg/hr so the ratio we want is 4.3/3.5 or 1.23 The absorption of chlorine gas follows these equilibria: Cl 2(vap) = Cl 2(aq) Cl 2(aq) + H2O = H + + Cl - + HClO o (aq) HClO o (aq) = H + + ClO - Adding a base, such as sodium hydroxide, increases the ph. ph is defined by ph = - Log 10 [H + ] Thus if the ph increases, the concentration of hydrogen ion must decrease. As the hydrogen ion decreases, the equilibria above have to shift to restore the equilibrium. Let s look at each equilibrium individually: HClO o (aq) = H + + ClO - As the hydrogen ion concentration decreases, this equilibrium will dissociate more to replace the hydrogen ion. We can say that they hypochlorous acid concentration will also decrease as the hydrogen ion decreases. Cl 2(aq) + H2O = H + + Cl - + HClO o (aq) This equilibrium is more complicated. It too will shift to the right (decreasing the chlorine concentration and the water concentration) as the hydrogen ion concentration decreases. A double effect occurs because the hypochlorous acid is also decreasing. Cl 2(vap) = Cl 2(aq) As the aqueous chlorine concentration decreases, the amount of vapor chlorine must also decrease. This is why basic scrubbing of an acid gas works. For this case, a mole of sodium hydroxide should remove two moles of chlorine gas. The slope of the line should be straight. This brings up the question, why did the curve for the chlorine remove level off at a non-zero value? To review, look a the plot once again: Raising your AQ IQ Chapter 6 Chlorine Scrubbing 89

96 Figure 6-26 Reviewing chlorine removal Something else must be occurring. Perhaps solids are appearing. Click the Customize button. Scroll down to find the Solids section and select Dominant Solids. Click OK when done. Figure 6-27 Same figure with solids added 90 Chapter 6 Chlorine Scrubbing Raising your AQ IQ

97 The dominant solid on the plot is sodium bicarbonate (NaHCO 3 ). It seems to appear above a ratio of 4.8. Why does the formation of the sodium bicarbonate solid prevent any more chlorine from being absorbed? Let s start with some basic equilibria: When the solid sodium bicarbonate is forming, this equilibrium exists: NaHCO 3(s) = Na HCO 3 As long as the solid sodium bicarbonate is forming, the amounts of the sodium ion and bicarbonate ion remain constant. The bicarbonate ion dissociates: HCO - 3 = H CO 3 Since the bicarbonate ion is constant, so is the hydrogen ion and the carbonate ion. Since the hydrogen ion concentration is essentially fixed by the formation of the sodium bicarbonate, the chlorine hydrolysis (the second reaction) is fixed. This fixes the VLE equilibrium in the first equation. The hypochlorous acid species can not dissociate further since it is also fixed by the constant hydrogen ion. All this is acceptable since our design specification was to remove 90 % of the vapor chlorine using 10 weight percent sodium hydroxide. What happens if you use more concentrated solutions? In actual practice, a user used twenty weight percent instead of ten weight percent. The ratio of the flows (1.23 chlorine/base) was still maintained. We are going to repeat the steps above except we will use the 20 % NaOH stream instead. Please follow these steps. Locate the Streams menu item. Select Add Mixed Stream from the pull down menu. The Available Streams window displays what streams are ready to use for mixing calculations. Select the Cl2 and the 20% NaOH streams Change the Type of survey button to a ratio calculation. The menu will display as follows: Select the Ratio menu item. Click on the Specs button. Highlight the General item in the tree-view: Click on the 10 % NaOH stream. Click back on the Variable-Ratio item in the tree view. Change the increment value from 1.0 to Click the OK button. Click the Calculate button. When the calculation has completed, click on the Plot tab. Raising your AQ IQ Chapter 6 Chlorine Scrubbing 91

98 Figure 6-28 The default plot Click the Customize button. Double-click the Dominant Aqueous item in the Y-Axis window. Scroll up or down to find the Vapor section and select Cl2 by double-clicking it in the left window. Scroll up or down to fine the Solid section and select Dominant Solids 92 Chapter 6 Chlorine Scrubbing Raising your AQ IQ

99 This is approximately 0.58 moles of Cl2(VAP). The original set point Figure % NaOH We initially had 5.8 moles of chlorine. Thus at 0.58 moles of chlorine in the vapor corresponds to 10 % remaining or 90% removed. You can mouse-over the points to find a value near 0.58 moles of chlorine. This corresponds to a ratio of the 20 % NaOH stream of 3.5. That implies that we need about 3.5 Kg/hr of the base stream to remove the desired chlorine. The chlorine stream is approximately 4.3 Kg/hr so the ratio we want is 4.3/3.5 or 1.23 So what is different here? In this case you will notice that the line corresponding the solid NaHCO 3 is non-zero at our operating point. This means that solids will form if we want to get to our desired set point. Solid formation in a scrubber can be bad news. Solids plug process equipment, trays and packing. Pressure drops and unexpected heat profiles may occur. Shortened equipment life is expected and frequent maintenance is required. Conclusion Good results were obtained with only 10 % NaOH. Using the more concentrated solution under the idea that more is better was certainly a bad idea. Raising your AQ IQ Chapter 6 Chlorine Scrubbing 93

100 Reliable prediction of solids precipitation from aqueous solutions can be challenging. Recall from a previous discussion, the two essential considerations for modeling aqueous systems: Comprehensively taking into account the presence of all of the species that can form in the system ( complete speciation ) Rigorously taking into account the non-ideal behavior resulting from the interactions of charged species (ions) and molecules in solution. This is especially important as concentrations get above very dilute levels as typically is the case for most real world systems. (Discussed in a later chapter) Often at higher concentrations, there is a significant departure from ideal solution behavior. OLI captures this behavior through a combination of robust standard states thermodynamic model and activity coefficients models. The solid-liquid equilibrium behavior is also modeled as a function of temperature. The result is unsurpassed solid prediction capability for aqueous solutions. The solubility of a salt in water varies with temperature, usually increasing with increasing temperature. However some salts exhibit inverse solubility behavior over a given temperature range. An example of this is sodium sulfate shown on the right. This type of behavior can lead to unexpected plugging of pipes, heat exchangers, and towers as the fluid temperature changes through the system. OLI software can predict this kind of behavior for real solutions to help you avoid these problems. 94 Chapter 6 Chlorine Scrubbing Raising your AQ IQ

101 Tower separations are a common industrial unit operation. OLI has developed an aqueous flowsheet simulator called ESP that is designed specifically to simulate aqueous electrolytes processes. One of the unique features of this product is the ability to include heat and mass transfer as well as chemical reactions and reaction rate constants in the tower separations simulations. This feature provides the most realistic simulation possible for electrolyte separations. Contact OLI for more details on the ESP product. Raising your AQ IQ Chapter 6 Chlorine Scrubbing 95

102 Advanced Problems Using sodium hydroxide (caustic) can be expensive. Cheaper bases such as lime or quick lime (Ca(OH) 2 ) are frequently used. 1. How much calcium hydroxide is required to remove 90 % of the chlorine from the vapor? 2. Are there any additional solids that are produced. 3. Can you determine another reagent that may be cheaper and better than sodium hydroxide? 96 Chapter 6 Chlorine Scrubbing Raising your AQ IQ

103 Chapter 7 Gypsum Solubility Getting an edge on the competition. Reliable simulation of complex processes can provide insights for process optimization and reduced operating costs. The solubility of salts is significantly effected by the presence of other salts. Modern gypsum (CaSO 4 2H 2 O) production frequently involves recovering sulfur waste products from the off gas of power plants. This gas is scrubbed with a lime (CaO) solution which can form gypsum. This impure solid is re-dissolved and purified to make commercial wallboard. There are many advantages to this process, notably the ability to recover a pollutant and use it for commercial purposes (reducing the cost of scrubbing) and reducing the need to mine a mineral. In this application we will see that there is a region where we can optimize the solubility of gypsum in the re-dissolving process. Let s get started... We begin by starting the OLI/StreamAnalyzer Program. This may be accomplished by clicking the StreamAnalyzer icon or by using the Start button and finding the StreamAnalyzer under Program. Once started, the OLI Splash screen will display. Raising your AQ IQ Chapter 7 Gypsum Solubility 97

104 Figure 7-1 The OLI Splash Screen After a few moments, the main OLI/StreamAnalyzer welcome screen will display. Figure 7-2 The StreamAnalyzer Welcome Screen We will build this file from scratch. Click the Add New Stream Icon. Figure 7-3 Add a new stream Our first goal is to determine the solubility of calcium sulfate (CaSO 4 ) as a function of temperature. The input grid should look like the following: 98 Chapter 7 Gypsum Solubility Raising your AQ IQ

105 Figure 7-4 Standard input grid Enter CaSO4 into the Inflow section. Figure 7-5 Entering CaSO4 If the display is not in formula view, use the menu item Tools and Select Names Manager. Select Formula from the list. If formulas are displayed, skip down to Resuming the application Selecting Formula View Figure 7-6 Select Tools Raising your AQ IQ Chapter 7 Gypsum Solubility 99

106 Figure 7-7 Select Names Manager Figure 7-8 Select Formula and then click OK Resuming the application Click the Add Survey button. Figure 7-9 Click Add Survey Our input screen should look like the following: 100 Chapter 7 Gypsum Solubility Raising your AQ IQ

107 Figure 7-10 Survey Input grid We would like to work in weight fraction units. Select Tools from the menu line. Figure 7-11 Select Tools Select Units Manager from the menu. Figure 7-12 Select Units Manager Raising your AQ IQ Chapter 7 Gypsum Solubility 101

108 Click the Custom Radio Button Figure 7-13 The Units Manager Dialog Click the Custom radio button. Figure 7-14 Use the drop down arrow to find Mass Fraction. Click the OK button. We have now set up our units for mass fraction. As you can see the input grid is now set to 100 mass% water. The default survey is temperature, which we want. However we only want to go to 30 o C while saturating the solution with CaSO 4. The solid phase that should appear is CaSO 4 2H 2 O (gypsum). By default, a temperature survey will only vary the temperature in the range specified. We will need to instruct the simulation to adjust our inflow to maintain saturation as well. Click the Specs button. 102 Chapter 7 Gypsum Solubility Raising your AQ IQ

109 Figure 7-15 the specs... button. Change the Start and End values to 0 and 30 o C. The Increment will be 2. After changing the start, end and increment boxes. Click the Calculation Type object Figure 7-16 the changed start, end and increment values. We now need to change the calculation type. Click on the Calculation Type object in the tree view. Raising your AQ IQ Chapter 7 Gypsum Solubility 103

110 Click this button Figure 7-17 the calculation type The default calculation type is isothermal. We need to perform a precipitation point calculation. Click the Type of Calculation button. Figure 7-18 Selecting precipitation point. The dialog will change. Figure 7-19 New items for selection. 104 Chapter 7 Gypsum Solubility Raising your AQ IQ

111 We need to select an inflow to adjust and also select a solid to precipitate. Select CaSO 4 2H 2 O from the left window, and then select CaSO 4 from the right. Figure 7-20 Selecting variables. Click OK and we are ready to start the calculation. What is a precipitation point calculation? Before we start the calculation, we should discuss what is involved in a precipitation point calculation. To do this we first need to discuss the chemistry model. When we added the inflow species for water and calcium sulfate, we created a model with many species; Inflow Species We entered two Inflow species. These species are the same as what we entered on the inflow grid. H 2 O IN CaSO 4IN The IN indicates to the program (internally) that these are inflow entered in the grid. We also find additional inflow species in our database that have common elements as our species. These are: CaSO 4.2H 2 O IN SO 3IN Ca(OH) 2IN H 2 SO 4IN Ca(HSO 4 ) 2IN These species are normally masked from the user but can be displayed if required. Raising your AQ IQ Chapter 7 Gypsum Solubility 105

112 Aqueous Species Many aqueous species are retrieved from our database. These species are: H 2 O SO 3 o CaSO 4 o H 2 SO 4 o H + OH - Ca 2+ CaOH + HSO4 - SO 4 2- H 2 O VAP SO 3VAP H 2 SO 4VAP CaSO 4.2H 2 O (s) CaSO 4(s) Ca(OH) 2(s) There are 16 species on this list. These, in terms of mathematical equations, are unknowns. We need to generate 16 mathematical equations. Equilibrium Equations We automatically create in the software the mass action relationships. H 2 O=H + + OH - SO3 o +H 2 O=H 2 SO 4 o CaSO 4 o =Ca 2+ + SO 4 2- H 2 SO 4 o =H + + HSO 4 - CaOH + =Ca 2+ + OH - HSO4 - =H + + SO 4 2- H 2 O VAP =H 2 O SO 3VAP =SO 3 o H 2 SO 4VAP =H 2 SO 4 o CaSO 4.2H 2 O=Ca 2+ + SO H 2 O CaSO 4(s) =Ca 2+ +SO 4 2- Ca(OH) 2(s) =Ca 2+ +2OH - These are then converted into the traditional equilibrium relationships. K K K H 2O SO3 CaSO4 γ = γ = γ H + SO3aq + [ H ] γ a H 2SO4 [ H [ SO OH H 2O 2 3aq γ Ca+ 2[ Ca = γ CaSO4aq [ OH SO4 ] ] a 2+ H 2O ] ] γ SO4 2[ SO [ CaSO ] 4aq 2 4 ] 106 Chapter 7 Gypsum Solubility Raising your AQ IQ

113 K K K γ H + [ H = γ ] γ [ HSO4 ] SO ] + HSO4 H 2SO4 o H 2SO4aq[ H 2 4 CaOH + = γ γ Ca+ 2 γ [ Ca 2+ CaOH + [ H γ ] γ OH [ CaOH [ OH + ] γ SO4 2[ SO [ HSO ] + H + HSO4 = HSO4 4 ] 2 4 ] ] K SO3vap γ = φy SO3aq SO3 [ SO ] P o 3 Total K K K H 2SO4vap H 2Ovap γ = a = φy H 2SO4aq φy H 2O H 2O [ H H 2SO4 P Total 2 P SO Total CaSO4.2H 2O( s) = γ Ca+ 2[ Ca ] γ SO4 2[ SO4 ] ah 2O o 4 ] K CaSO4( s) 2+ = γ [ Ca ] γ [ SO Ca+ 2 SO ] K Ca( OH )2( s) = γ Ca+ 2[ Ca ] γ OH [ OH ] This gives us 12 equations but we have 16 unknowns. This required 4 more equations. Electroneutrality We now write an equation were we sum up the cations and anions. [H + ] + 2[Ca 2+ ] + [CaOH + ] = [OH - ] + [HSO 4 - ] + 2[SO 4 2- ] This gives us one more equation for a total of 13, we still need thee more equations: Raising your AQ IQ Chapter 7 Gypsum Solubility 107

114 Hydrogen Balance We will sum up all the hydrogen in the equations. What comes in must go out. In reality, we have a choice of writing either a hydrogen balance or an oxygen balance. Either is acceptable but you should not write both. 2H 2 O IN + 4CaSO 4.2H 2 O IN + 2Ca(OH) 2IN + 2H 2 SO 4IN + 2Ca(HSO 4 ) 2IN = 2H 2 O + 2H 2 SO 4 o + H + + OH - + CaOH + + HSO H 2 O VAP + 2H 2 SO 4VAP + 4CaSO 4.2H 2 O (s) + 2Ca(OH) 2(s) This gives us one more equation for a total of 14. We need a total of 16, 2 more equations are required. Calcium Balance We only have two other atoms left (besides oxygen). These are calcium and sulfur. First we will balance the total calcium. CaSO 4IN + CaSO 4.2H 2 O IN + Ca(OH) 2IN + Ca(HSO 4 ) 2IN = CaSO 4 o + Ca 2+ + CaOH + + CaSO 4.2H 2 O (s) +CaSO 4(s) + Ca(OH) 2(s) This is one more equation for a total of 15. The sulfur equation is the final equation. Sulfur Balance CaSO 4IN + CaSO 4.2H 2 O IN + SO 3IN + H 2 SO 4IN + Ca(HSO 4 ) 2IN = SO 3 o + CaSO 4 o + H 2 SO 4 o + HSO4 - + SO SO 3VAP + H 2 SO 4VAP + CaSO 4.2H 2 O (s) + CaSO 4(s) This gives a total of 16 equations which match the total number of unknowns. The solution to these equations can now be computed. Back to the precipitation point To discuss the precipitation point calculation, we had to discuss the chemical model first. In a normal Isothermal calculation, the user provides the temperature, pressure and inflow amounts of the species. These equations above are then evaluated. The precipitation point calculation is a bit different. In this, we hold the amount of a particular solid, in our case CaSO 4 2H 2 O, at a specified amount. We then Back Solve our equations for an inflow amount that satisfies our specified amount. Scaling Tendency To perform this back solving, we need to define a new concept, Scaling Tendency. Essentially, this is the ratio of ions in solution to the thermodynamic solubility product for a particular solid. 108 Chapter 7 Gypsum Solubility Raising your AQ IQ

115 In our case, we are concerned about CaSO 4 2H 2 O. The Scaling tendency for this solid is defined as: ST CaSO4.2H 2O γ = Ca [ Ca ] γ K SO4 2 [ SO CaSO4.2H 2O( s) 2 4 ] a 2 H 2O When this value is less than 1.0, we can say that the solid is under-saturated. This means that there are insufficient ions in solution to form the solid. If the value is greater than 1.0, then the solid is super-saturated and there more than enough ions to form the solid. In a standard Isothermal calculation, the program will adjust the ions such that any excess ions are combined into the solid and removed from solution. The scaling tendency becomes exactly equal to 1.0 at saturation. In the precipitation point calculation, we force the scaling tendency for the indicated solid (CaSO 4 2H 2 O) to be exactly equal to 1.0. To do this, we must adjust some variable. The easiest variable to adjust is an inflow variable that contains some or all of our solid. There are two mass balance equations of interest here: CaSO 4IN + CaSO 4.2H 2 O IN + Ca(OH) 2IN + Ca(HSO 4 ) 2IN = CaSO 4 o + Ca 2+ + CaOH + + CaSO 4.2H 2 O (s) +CaSO 4(s) + Ca(OH) 2(s) CaSO 4IN + CaSO 4.2H 2 O IN + SO 3IN + H 2 SO 4IN + Ca(HSO 4 ) 2IN = SO 3 o + CaSO 4 o + H 2 SO 4 o + HSO4 - + SO SO 3VAP + H 2 SO 4VAP + CaSO 4.2H 2 O (s) + CaSO 4(s) These equations are very similar. In the program, we selected the inflow species CaSO4 which has been bold-faced above. The other inflow values remain constant. We now allow the program to vary the inflow amount to match the scaling tendency of 1.0. As this occurs, the relative amounts of the other species are also calculated. In a precipitation point calculation it is important to make sure you select the proper precipitating solid (it must be able to form under the conditions you specify) and the proper adjusting species. Back to the application The application window should now look like this: Raising your AQ IQ Chapter 7 Gypsum Solubility 109

116 Figure 7-21 Read to go! Click the Calculate button. We would now like to see the solubility of CaSO 4 2H 2 O as a function of temperature. When the program stops spinning the Electron Click on the Plot tab. 110 Chapter 7 Gypsum Solubility Raising your AQ IQ

117 Figure 7-22 Default plot This is the default plot for this simulation. We would like to see a different plot showing the amount of calcium sulfate (CaSO 4 ) that had to be adjusted to form the first tiny amount of solid. This to be displayed versus temperature. Click the Customize button. Double-click this item Figure 7-23 the customize dialog Raising your AQ IQ Chapter 7 Gypsum Solubility 111

118 We do not wish to see the Dominant Aqueous Species. Double-Click the Dominant Aqueous Species in the right hand window to remove the entry. Click the + to expand the tree Figure 7-24 Expanding the Inflows Tree Click the + next to the Inflows item in the tree to expand the list. Double-Click CaSO4 from the list. Figure 7-25 CaSO4 Selected Click OK 112 Chapter 7 Gypsum Solubility Raising your AQ IQ

119 Adding sodium chloride Figure 7-26 The solubility of CaSO4 in water v. Temperature. We now have a plot of the solubility of calcium sulfate in water as a function of temperature. We forced the program to consider the solid phase of gypsum (CaSO 4 2H 2 O). What would happen if we added a new compound such as sodium chloride. It is been long suspected that adding sodium chloride increased the solubility of calcium sulfate in water but why? To simulate this we are going to look at a single temperature (25 o C) and vary the concentration of sodium chloride. As we did with the temperature survey, we will allow the program to calculate the precipitation point for gypsum as we vary the amount of sodium chloride. Figure 7-27 Clicking on the stream object Click on the Stream1 object. Raising your AQ IQ Chapter 7 Gypsum Solubility 113

120 Figure 7-28 Selecting a new survey Click on the Add Survey button. The program updates the tree and grids for the new calculation. Figure 7-29 Updated grid The default calculation is for temperature. We will need to change the survey type. Click the Survey By button. Figure 7-30 Click the button that currently says "Temperature" 114 Chapter 7 Gypsum Solubility Raising your AQ IQ

121 Figure 7-31 Select Composition Select Composition. As before, we need to change the specifications of this calculation. First we need to add a new component to the inflow grid. Add NaCl to the inflow grid. Add NaCl to the grid Figure 7-32 Adding NaCl We also need to change the units. Select Tools from the menu line. Figure 7-33 Select Tools Select Units Manager from the menu. Figure 7-34 Select Units Manager Raising your AQ IQ Chapter 7 Gypsum Solubility 115

122 Click the Custom Radio Button Figure 7-35 The Units Manager Dialog Click the Custom radio button. Figure 7-36 Use the drop down arrow to find Mass Fraction. Click the OK button. The units are now in mass fraction. We now need to change the specifications for the calculation. We need to define the component we are going to vary (NaCl) and to specify the precipitation point calculation. Click the Specs button. Figure 7-37 Select the specs... button 116 Chapter 7 Gypsum Solubility Raising your AQ IQ

123 Click on NaCl Figure 7-38 Changing specs... Since we are adding sodium chloride Click on the NaCl object. We now need to change the range of the survey. Click on the Survey Range tab. Figure 7-39 Composition survey range We want the survey to start at 0 weight percent NaCl and finish at 15 weight percent. Change the Start value to 0, the End value to 15 and the Increment to 1.0 Raising your AQ IQ Chapter 7 Gypsum Solubility 117

124 Figure 7-40 The filled out start, end and increments. We now need to specify a precipitation point calculation as we did before. Figure 7-41Click on Calculation type Click on Calculation Type in the tree-view. This will bring up a dialog that is similar to the previous dialogs. Figure 7-42 Default calculation type. Click on the Type of Calculation button (it currently displays Isothermal). Figure 7-43 Select Precipitation Point. Select Precipitation Point. 118 Chapter 7 Gypsum Solubility Raising your AQ IQ

125 Figure 7-44 Selecting inflows and solids. This dialog is similar to the previous dialog of this type. The addition of sodium chloride had added additional options. We will continue with the same options as before. Select CaSO4.2H2O from the left-hand window (Solid Precipitate) and CaSO4 from the right-hand window (Adjusted Inflow). Figure 7-45 Selected options. Click OK to continue. Click the Calculate button to start. When the calculation finishes, Click the Plot tab. Raising your AQ IQ Chapter 7 Gypsum Solubility 119

126 Figure 7-46 The default plot As before, we are going to change the plot to view the amount of CaSO 4 added. This time the amount of NaCl has been varied. Click the Customize button. We do not wish to see the Dominant Aqueous Species. Double-Click the Dominant Aqueous Species in the right hand window to remove the entry. Click the + next to the Inflows item in the tree to expand the list (You may have to scroll up or down to find Inflows). Double-Click CaSO4 from the list. Click OK 120 Chapter 7 Gypsum Solubility Raising your AQ IQ

127 Figure 7-47 Solubility of CaSO4 v. NaCl As you can see from the figure, the solubility of calcium sulfate (with CaSO 4 2H 2 O as the precipitating solid) increases. Compare the solubility maximum of approximately 0.66 weight percent CaSO4 (at approximately 11 percent NaCl) to the value at 25 o C in the solubility v. Temperature plot in Figure 26 (approximately 0.21 weight percent). Adding sodium chloride increases the solubility about approximately three times. The question remains, why does adding sodium chloride increase the solubility? Let s plot the various forms of aqueous sulfates versus NaCl. Click on the Customize Button. Remove CaSO4 from the Y-Axis window. Scroll up or down in the Variables window to find the Aqueous item. Expand the tree if necessary. Select the following variables. CaSO4 H2SO4 HSO4-1 NaSO4-1 SO4-2 Click OK. Raising your AQ IQ Chapter 7 Gypsum Solubility 121

128 Figure 7-48 Sulfate Species The aqueous sulfate species are displayed. The faint blue line is the concentration of NaSO -1 4 ion. It seems to follow the solubility curve for CaSO We can see that a great deal of sulfate ion is complexed as NaSO 4. What does this imply? We have two equilibrium equations that are affected: CaSO 4 2H 2 O = Ca 2+ + SO H 2 O NaSO -1 4 = Na SO 4 As NaSO -1 4 forms, sulfate ions are effectively removed from solution. That is to say the second equilibrium is shifted to the left. Since equilibrium must be maintained, the CaSO 4 2H 2 O solid must increase its dissolution to replace the sulfate ion. This has the effect of increasing the solubility of the CaSO 4 2H 2 O solid. Save your work Now would be a good time to save your work. 122 Chapter 7 Gypsum Solubility Raising your AQ IQ

129 Conclusion The solubility of one salt in a complex aqueous mixture can be significantly affected by the presence of other salts. Accurate modeling of these types of systems requires a robust activity coefficient model that includes the interactions of all species. When done properly, reliable simulation of complex processes provide a powerful tool for process optimization and reducing operating costs. Figures 7-47 and 7-48 illustrate the significant effect that one salt has on the solubility of other salts in a complex aqueous mixture. Accurate modeling of these types of systems requires a robust activity coefficient model that includes the interactions of all species. The OLI software predictions are based on parameters that are regressed from reliable experimental data. In most cases, binary data is sufficient to accurately represent a systems (e.g., NaCl and H 2 O, or CaCl 2 and H 2 O). In some cases, the regressions are performed on ternary systems (e.g., NaCl, CaCl 2, and H 2 O). The OLI Databank contains the thermodynamic data and regressed parameters needed to reliably model aqueous systems over the range of 50 to 300 C, 0 to 1500 bar, and ionic strength 0 to 30 molal. Raising your AQ IQ Chapter 7 Gypsum Solubility 123

130 Advanced Problems 1. Given a gypsum concentration of 5 weight percent and a sodium chloride concentration of 10 weight percent at 1 atmosphere, what temperature would be required to evaporate 95 % of the solution? 2. What is the normal boiling point of the solution? 124 Chapter 7 Gypsum Solubility Raising your AQ IQ

131 Chapter 8 H 2 S-CO 2 Injection Out of Sight Out of Mind? The behavior in subsurface environments (ph, mineral dissolution, scale formation, and corrosion) can be reliably simulated based on surface samples. Water laboratory analyses need to be adjusted to account for normal laboratory error and down hole or process environments. Production of natural gas frequently occurs from gas and oil fields that are particularly sour. This means that a large percentage of the gas that is produced contains hydrogen sulfide. There are some issues with hydrogen sulfide: H 2 S is a noxious compound and should be removed from natural gas. H 2 S causes corrosion and scaling problems in process equipment What to do with the removed H 2 S? No commercial market for H 2 S Cheap Disposal A typical disposal method for hydrogen sulfide is to re-inject the gas back into a depleted reservoir. There could be some problems in re-injecting the gas. The produced water may have been altered such that re-injecting the brine back into the formation causes plugging of the reservoir. Other problems may involve increased corrosion behavior. We will investigate the potential for increased plugging. In this application, we will take a water sample, measured at surface conditions, and reconcile it for changes in ph and electroneutrality. We will then simulate the sample at reservoir conditions. We will then add the gas containing hydrogen sulfide to the reservoir at various ratios to see if new solids (plugging) will occur. Let s get started... We will be using a different OLI/Analyzer program. This program is the Lab Analyzer program. We begin by starting the OLI/LabAnalyzer Program. This may be accomplished by clicking the LabAnalyzer icon or by using the Start button and finding the LabAnalyzer under Programs/OLI Systems. Raising your AQ IQ Chapter 8 H2S-CO2 Injection 125

132 We will first start the LabAnalyzer. Locate the LabAnalyzer icon on your desktop or find it via the start button. Figure 8-1 The OLI LabAnalyzer Icon for version 1.3 Once started, the OLI Splash screen will display. Figure 8-2 The OLI Splash Screen After a few moments, the main OLI/LabAnalyzer welcome screen will display. 126 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

133 Figure 8-3 The StreamAnalyzer Welcome Screen This window is similar to the StreamAnalyzer window. We will not discuss the features here. Use File/Open menu item to locate a pre-loaded file. This file should be located in the following folder: \My Documents\My OLI Cases\Analyzer 1.3\Samples and has the name: H2S-CO2 Injection.laa 1 The following window should be displayed: 1 The file extension may not be displayed depending on your folder option settings. Raising your AQ IQ Chapter 8 H2S-CO2 Injection 127

134 Figure 8-4 The loaded file We have pre-loaded a water analysis and a stream for you. Many of the icons on the window are the same as in the StreamAnalyzer. However, there are two new icons. Figure 8-5 Add a Water Analysis This icon allows us to add a water analysis to the program. We will look at the analysis already loaded. Figure 8-6 Adding a Composite analysis This icon allows us to Blend analysis to make a single analysis. An analysis needs to exist before we can use this icon. 128 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

135 The produced water was measured at the surface. The conditions and concentrations are: Temperature 25 o C Pressure 1 Atmosphere ph 6.4 density g/ml TDS 2 223,000 ppm Ca 2+ 17,589 ppm - HCO ppm Na + 46,631ppm Cl - 110,442 ppm K + 2,700 ppm 2- SO 4 1,470 ppm Sr 2+ Mg 2+ Fe 2+ C 12 H ppm 2,045 ppm 11.5 ppm 283 ppm Click on the WaterAnalysis1 icon in the explorer view: Figure 8-7Clicking on WaterAnalysis1 Click on this icon This will display the current input state for the water analysis. We have purposely left out two cations in the analysis. Magnesium ion and ferrous ion. We will have to add these ions before continuing. 2 Total dissolved solids Raising your AQ IQ Chapter 8 H2S-CO2 Injection 129

136 Figure 8-8 Incomplete input grid Add the following concentrations to the Cations section of the grid Mg ppm(mass) Fe ppm(mass) Add the missing ions Figure 8-9 Add ions Figure 8-10 The ions have been added 130 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

137 Once the ions have been added, we now need to reconcile the sample for ph and electroneutrality. Click the Add Reconciliation button. Figure 8-11 Add a reconciliation This will add a reconciliation to our sample. Figure 8-12 The reconciliation window You can see that the tree-view on the left has added a new object. This was automatically created when we clicked the Add Reconciliation button. The program will automatically reconcile our same for electroneutrality. This enforces our rule that the sum of positive charges must equal the sum of negative charges. We can also calculate the solution ph and determine if it matches our measured ph. Before we go any further, we need to examine the different methods of reconciling the electroneutrality of the solution. Raising your AQ IQ Chapter 8 H2S-CO2 Injection 131

138 Reconciling Electroneutrality Why Electroneutrality? Almost all water samples that are measured have small experimental errors associated with each ion. This is the nature of the experiment. For example, the concentration of the sodium ion may only be accurate to ± 5 % while the bicarbonate ion may only be accurate to ± 10 %. These uncertainties will usually result in the cation concentration not equaling the anion concentration. Figure 8-13 The reconciliation box. Click the Specs button. Clicking the Specs button allows us to change how the sample is reconciled. There are many options. The OLI software requires that this equality be enforced. As an aside, any sample that balances perfectly is to be treated with suspicion. It just does not a happen in nature. Figure 8-14 Default reconciliation This is the default electroneutrality balance. This method is known as Dominant Ion. In this case, the difference in cation and anion charges are determined. It is found that there is more positive charge than negative. The imbalance, on an equivalent basis, is equivalents/kg. To balance this, we need to add a negative species in the amount of eq/kg. The Dominant Ion method takes the counter ion with the largest concentration and then adds the amount. In this case, ppm of chloride ion is to be added. 132 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

139 The determination of the amount of counter ion is as follows: eq 1moleCl gcl mgcl Kg eq molecl gcl We can now toggle trough the other reconciliation methods: mgcl = Kg Figure 8-15 The type of balance button. Click the Type of balance button. Figure 8-16 Types of balance Select each option to see how the reconciliation changes. Prorate An equal percentage of all deficient species is added. In this case we are keeping the relative amounts of the anions constant (since we have too much positive charge). All the anions are then added. Figure 8-17 Adding all anions Prorate Cations Equal percentages of the cations are either added or subtracted to reconcile the sample. Figure 8-18 Removing cations. In this case, since there is too much positive charge, we are removing the cations. Raising your AQ IQ Chapter 8 H2S-CO2 Injection 133

140 Prorate Anions Equal percentages of the anions are either added or subtracted to reconcile the sample. Figure 8-19 Adding anions In this example, the Prorate Anions option is the same and Prorate. Na +, Cl - Sodium is added when there is an excess of negative charge, chloride is added when there is an excess of positive charge. Figure 8-20 Adding chloride In this case, since there is too much positive charge, chloride is added. For this example, this is the same as the Dominant Ion method. Make Up Ion The specified ion is either added or subtracted to balance the charge. 134 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

141 Figure 8-21 Selecting make-up ion for sodium With the make-up ion option, either a cation or anion can be used to adjust the Electroneutrality. Since in this example, there is an excess of positive charge, selecting a cation will result in ions being removed. In this example, the sodium ion has been selected and 32.9 ppm has to be removed. User Specification The user specifies the cation or anion required to balance the sample. Raising your AQ IQ Chapter 8 H2S-CO2 Injection 135

142 Figure 8-22 Selecting user choice Since there is an excess of positive charge, only the anions are available for selection with this option ppm of SO 4 2- is needed to balance the sample. Make sure the Type of Balance button is set to Dominant Ion and the click the OK button. 136 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

143 The summary box updates with the electroneutrality Figure 8-23 Updated electroneutrality Back to the reconciliation We are now ready to reconcile our sample. The electroneutrality has already been done so now we need to adjust the ph. It is generally a good idea to see how close are prediction is to the measured ph. Click the Calculate button. After the calculation finishes, the summary box will update with new values. Figure 8-24 Updated values Raising your AQ IQ Chapter 8 H2S-CO2 Injection 137

144 The ph of the sample is calculated to be 5.9 which is somewhat lower than the measured ph of 6.4. We will now add the ph reconciliation. Figure 8-25 Selecting ph reconciliation Check the Auto NaOH/HCl radio button in the Reconciliation box. This will automatically use NaOH to raise the calculated ph or HCl to lower the calculated ph. The input grid is now updated with a new section. Add a recorded ph of 6.4 and a target ph of 6.4 Figure 8-26 Calc Parameters now appears We need to tell the program about the ph. Figure 8-27 ph's entered Click the Calculate button 138 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

145 The summary window updates with the amount of acid or base added. Figure 8-28 Updated information Converting an Analysis into a stream Approximately ppm mg/l of NaOH was added to raise the ph from 5.9 to the measured ph of 6.4 We are now ready to take our analysis and convert it into a stream. All streams in the OLI/Analyzers have inputs that are molecular. This means we can not support ions in a stream input grid. Only the LabAnalyzer supports ions as input. Fortunately we have an automatic method of converting the ions in our reconciliation into a molecular stream. Figure 8-29 Locating Add as Stream Locate the Add as Stream button at the bottom of the reconciliation input grid. Click this button. Raising your AQ IQ Chapter 8 H2S-CO2 Injection 139

146 Figure 8-30 The converted Analysis The reconciled water analysis has been converted into a molecular stream. In our example, this has been created as Stream3. You can rename this stream to a more desirable name. Figure 8-31 The new stream Right-click the new stream Stream3 and select Rename Figure 8-32 the right-click menu 140 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

147 Figure 8-33 Highlighting the stream The stream name will be highlighted which indicates that we can rename this tream. Rename the stream to Produced Water. Figure 8-34 The renamed stream Simulations at reservoir conditions We now will simulate injecting just this produced water into the formation. The formation is at 160 o F and 2500 PSIA. Select the Add Single Point button. The input grid will be displayed. We have seen this type of grid many times before. The stream parameters are still the same as for the water analysis. Figure 8-35 The stream parameters We need to change the temperature and pressure. Figure 8-36 Selecting units Click in the Unit field for temperature and select o F. Click in the Unit field for Pressure and select PSIA. Raising your AQ IQ Chapter 8 H2S-CO2 Injection 141

148 Figure 8-37 Correct units! Enter a temperature of 160 o F and a pressure of 2500 PSIA Figure 8-38 New temperature and pressures Click the calculate button. As with the Water Analysis, we can save the results of a calculation as a stream. Figure 8-39 Locating Add as Stream Locate the Add as Stream button at the bottom of the input grid. Click this button. Figure 8-40 Removing phases As we save this calculation as a new stream, we will be given the option to remove phases. This could simulate a filtering operation. The filtered material could also be saved as a new stream. We will not do any of these options at this time. Click the OK button. 142 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

149 A new object has appeared in the Tree-View. It usually has the name of the parent object that created it (in this case a SinglePoint case) and a number to update the object so it does not overwrite another object. This can be confusing. As before, rename the new object as Aquifer Figure 8-41 The renamed object Adding the waste gas We are now ready to inject the waste sour gas into the brine in the aquifer. To do this, we will you a mix calculation. Figure 8-42 Select Streams Select Streams from the menu items. Figure 8-43 Select Add Mixed Stream Select Add Mixed Stream Raising your AQ IQ Chapter 8 H2S-CO2 Injection 143

150 Figure 8-44 The mix stream input From this window we can select several streams to mix. We wish to mix the Aquifer stream with the H2S/CO2 Gas stream. Select the H2S/CO2 Gas steam and then click the >> button. Select the Aquifer stream and then click the >> button. 144 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

151 Remember that we are simulating at reservoir conditions. Change the temperature and pressure to 160 o F and 2500 PSIA Figure 8-45 The selected Stream As you can see, the grid has updated with a considerable amount of information. What we now need to determine is the ratios of the gas to the aquifer in which solids may form. The Mixed Streams calculation has this type of calculation. Click the Type of Survey button. Select Ratio Figure 8-46 Ratio selected We need tell the program which stream to adjust in the ratio. We also need to specify the ranges for the calculation. Click the Specs button. Raising your AQ IQ Chapter 8 H2S-CO2 Injection 145

152 Figure 8-47 The default range dialog We want the H2S/CO2 Gas stream to vary over a wide range of flows. Change the range from Linear to Log. Change the Start value to 1.0E-06 Change the End value to 1.0 Change the Number of Steps to 10. Figure 8-48 The completed ranges We now need to tell the program what stream to vary. Figure 8-49 Select General 146 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

153 Select the General object in the Category view. Reviewing the results Figure 8-50 Select the correct stream Select the H2S/CO2 Gas stream. Click OK. Click the Calculate button. When the calculation has completed Click the Plot tab. Raising your AQ IQ Chapter 8 H2S-CO2 Injection 147

154 Figure 8-51 Default plotthis default plot is not very usable Right-click on the plot and select Toggle X-axis Log. Figure 8-52 X axis in log 148 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

155 We still need to see the solids. Click the customize button. Remove Dominant Aqueous by selecting it in the Y axis window and then clicking the << button. Locate Dominant Solids under the Solids object in the Variables list. Select it and click the >> button. Click OK. Figure 8-53 Dominant solids A faint line is present for FeS. This may be hard to see. Click the Customize button. Select Variable Settings. Raising your AQ IQ Chapter 8 H2S-CO2 Injection 149

156 Figure 8-54 Variable Settings. Select FeS Sol Select a more a color with more contrast. Change the line style or line width if you desire. Figure 8-55 FeS now shows up more clearly. 150 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

157 What does this all mean? The ratio at the left-hand side of the diagram represent conditions where the gas has not been injected into the reservoir. You can see that CaCO 3, SrSO 4 and CaSO 4 2H 2 O are initially present in the reservoir. Adding the gas, which is represented by higher ratio values, shows that we have a dissolution of CaCO 3 which indicates that we may actually have an increase in porosity in the formation. There is a slight increase in the amount of CaSO 4 2H 2 O which may be due the increased presence of calcium ions as the CaCO 3 solid dissolves. There appears to be little effect on SrSO 4 A new solid appears as we add the gas. FeS begins to form in larger amounts. This material may plug the formation or remain suspended in the aquifer. This material may re-enter the production well and cause corrosion problems. Save your file. Now would be a good time to save your work. Conclusion The behavior in subsurface and other oilfield environments (ph, mineral dissolution, scale formation, and corrosion) can be reliably simulated based on surface samples. Water laboratory analyses need to be adjusted to account for normal laboratory error and down hole or process environments. The Analyzers perform like a desktop laboratory, readily performing simulations that may be difficult or impossible to perform in the field or laboratory. The OLI calculations assume thermodynamic equilibrium. For some systems, kinetics may be important. For example, some solids, although thermodynamically predicted to form, are formed so slowly that the solid does not exist in the real world. The mineral dolomite is an example of a solid that may form slowly in the H2S injection Case. OLI software allows you to easily omit such solids form the calculation. OLI s ESP aqueous flowsheet simulator can be used for cases where a process is to be modeled including the effects of kinetics, Raising your AQ IQ Chapter 8 H2S-CO2 Injection 151

158 Advanced Problems 1. Given a solution of 1 weight percent MgCl 2 and 1 weight percent CaCl 2 and 200 ppm CO 2 determine the solubility of calcium carbonate. 2. Repeat the calculation with the GEOCHEM database. 3. Was the solubility in both cases the same? If not, why? 152 Chapter 8 H2S-CO2 Injection Raising your AQ IQ

159 Chapter 9 Organic Acid Removal When Henry s Law Constants don t really help you The partitioning behavior of many chemicals is very dependent on ph. Simple methods such as the use of Henry s law coefficients or other distribution factor approximation approaches do not work for real aqueous solutions. Effective separations for these systems can only be achieved when taking into account the complete speciation of the system. Produced waters from oil and gas production frequently contain organic acids. These acids, which are undesirable in oils must be washed. Of course, these acids are also undesirable in the produced water that is to be discharged. In this application we will take an oil/water mixture that has organic acids. The ph of the water indicates that the acids are in the water phase. This is a problem. We will adjust the solution ph to force the organic acids out of the water phase into the hydrocarbon phase. Finally we need to remove the organic acids from the hydrocarbon phase. We will take the hydrocarbon and wash it with a high ph solution to remove the acids. Let s get started... We begin by starting the OLI/StreamAnalyzer Program. This may be accomplished by clicking the StreamAnalyzer icon or by using the Start button and finding the StreamAnalyzer under Program. Once started, the OLI Splash screen will display. Raising your AQ IQ Chapter 9 Organic Acid Removal 153

160 Figure 9-1 The OLI Splash Screen After a few moments, the main OLI/StreamAnalyzer welcome screen will display. Figure 9-2 The StreamAnalyzer Welcome Screen Use File/Open menu item to locate a pre-loaded file. This file should be located in the following folder: \My Documents\My OLI Cases\Analyzer 1.3\Samples and has the name: 154 Chapter 9 Organic Acid Removal Raising your AQ IQ

161 Organic Acid Removal.sta 1 In this example we have preloaded several streams and calculations. Figure 9-3 The Organic Acid removal example Our example uses a stream named Produced Oil. This stream has the following composition: Temperature 25 Pressure 1.0 Atmospheres H 2 O mole C 12 H 26 (Dodecane) 5000 mole HCOOH (Formic Acid) 0.1 mole CH 3 COOH (Acetic Acid) 0.1 mole CH 3 CH 2 COOH (Propanoic Acid) 0.1 mole NaCl 0.5 mole 1 The file extension may not be displayed depending on your folder option settings. O C Raising your AQ IQ Chapter 9 Organic Acid Removal 155

162 CaCO mole Mg(OH) mole HCl 0 mole NaOH 0 mole The large quantity of organic (dodecane) simulates an Oil phase. This means we need to ensure that we are allowing the 2 nd Liquid Phase to form. Click on the Produced Oil object in the tree-view. Click on Produced Oil Figure 9-4 The loaded tree-view This will display the input grid. We have already filled this out for you. Figure 9-5 Input conditions 156 Chapter 9 Organic Acid Removal Raising your AQ IQ

163 Figure 9-6 Chemistry menu item Click on Chemistry Raising your AQ IQ Chapter 9 Organic Acid Removal 157

164 This will display the Chemistry model options. Figure 9-7 Chemistry Menu Select Model Options This will display the chemistry model options. Figure 9-8 Chemistry Model Options There are several tabs on this dialog. We can add databases and redox if necessary. We will not do that at this time. Click on the Phases tab. 158 Chapter 9 Organic Acid Removal Raising your AQ IQ

165 Why Select Phases? We can select and unselect entire phases in the chemistry model. Why would you want to do that? If you know you did not have an Second Liquid phase, you can exclude it from the calculations. This speeds up the calculations. By default, this option is unchecked. Also, you can remove specific solid phases. You may know that a particular solid can not form in the time frame of the simulation. Excluding the solid speeds the calculation. Figure 9-9 The phases tab Click the OK button. Make sure the Second Liquid check box is selected. Solution ph Let s find the solution ph. We have already added a single point calculation for you. Select SinglePoint1 Figure 9-10 the tree-view Select the SinglePoint1 calculation below the Produced Oil. Click the Calculate button after selection. After the calculation finishes, review the Summary box. Raising your AQ IQ Chapter 9 Organic Acid Removal 159

166 Figure 9-11 Summary box The ph is approximately 6.4. This is fairly Neutral ph. How much of the organic acids are present in the aqueous phase at this ph? Click on the Report tab. Scroll down to the Molecular Output (Apparent Species) section. Figure 9-12 Molecular Output The Molecular Output section represents the species on a total molecular basis. You will notice that there are no ions present in this section of the report. This section has taken the true species and converted them to neutral species. The conversion is some what arbitrary but for each phase it is a quick view of the species. In the aqueous phase, you can see that the organic acids and their ions are mostly tied up as complexes. Remember, there is approximately 0.1 moles of each acid. You can see that roughly ½ of the acids are still in the aqueous phase at this ph. 160 Chapter 9 Organic Acid Removal Raising your AQ IQ

167 Washing the acids out of the aqueous phase. There are some rules for a species to enter the second liquid phase. These are: 1. The species must be neutral 2. The species must have a possible vapor species in the model This means that if we can shift the form of the organic acid away from it s ions towards the neutral form, it can dissolve into the second liquid. Select Survey2 Figure 9-13 Selecting the survey Click Survey2 Figure 9-14 the survey This survey has been set up for you. It is a ph survey from a ph=0 to a ph=14 range with 0.5 ph increments. The survey first determines the natural ph of the solution and then adds the acid titrant (in this case hydrochloric acid) and performs Raising your AQ IQ Chapter 9 Organic Acid Removal 161

168 the first ph set point. This continues up to the natural ph. Above the natural ph the base titrant is added to the end of the range. Click Calculate. There should be 29 calculated point. Click on the Plot tab. We have predefined the plot for you. Figure 9-15 Plotting material balance groups v. ph In this figure we are plotting the material balance groups (MBG) for the various acid forms as a function of ph. For example, the variable MBG Aqueous ACETATEION is actually the sum of all acetate containing species in the aqueous phase. For example: MBG Aqueous ACETATEION = C 2 H 3 O C 4 H 8 O 4 + Ca[C 2 H 3 O 2 ] +1 + Ca[C 2 H 3 O 2 ] 2 + Mg[C 2 H 3 O 2 ] +1 + Mg[C 2 H 3 O 2 ] 2 +Na[C 2 H 3 O 2 ] This is true for the other material balance groups as well. We can see that at high ph s, greater than the natural ph of 6.4, that the dominant form of the acids are the aqueous ions. At lower ph s, the dominant form are the acids dissolved into the organic liquid. 162 Chapter 9 Organic Acid Removal Raising your AQ IQ

169 In this region, the dominant form of the acids are the acids dissolved in to the organic liquid. In this region, the dominant form of the acids are the aqueous ions. Most of the acid is in the water phase. Figure 9-16 The same plot again. It appears that if we lower the ph to 2.0, most of the organic acids will have been washed out of the aqueous liquid and are soluble in the organic liquid. We can save a point from the survey as a single point. We have already done this for you. We have taken the 5 th point and saved it as a stream. This can be seen in the treeview. We have also separated out the aqueous portion and the organic portion of the streams. Figure 9-17 Saved streams Both of these streams were saved from the 5 th data point. the first stream is the aqueous stream with any solids or vapors. The second stream is the 2 nd liquid stream with only organic liquid. The aqueous brine can now be treated and disposed of an in appropriate manner. Removing the organic acids from the 2 nd liquid phase We can now wash the organic stream with a high ph solution to remove the acids from the hydrocarbon. A 1 molal sodium hydroxide solution has been created for you in this file. We will mix this stream with the organic stream containing the acids. How much base do we need to remove the acids? Raising your AQ IQ Chapter 9 Organic Acid Removal 163

170 Figure 9-18 Using the mixed stream Click on the MixedStream5 object. Figure 9-19 The input for the mix calculation. We have a mix calculation that has selected the saved organic liquid point from the previous survey. This is indicated by the stream Point 5 of 29, ph = nd Liquid,3. The base stream has also been selected and is represented by the stream 1 m NaOH. This case will add increasing amounts of the sodium hydroxide stream to the organic stream. We can then plot the various acids in each of the phases. Click the Calculate button. 164 Chapter 9 Organic Acid Removal Raising your AQ IQ

171 Figure 9-20 Washing with NaOH It would appear from this plot, that most of the organic acids have been removed from the organic phases and are in the aqueous phase at a ratio of 0.3. This is a 0.3:1 ratio of the NaOH stream to the organic stream. There is approximately 1140 L of the organic stream and a total of 1.0 L of the sodium hydroxide stream. The ratio value of 0.3 indicates that only 0.3 L (300 ml) of the base solution was required to remove the acids from the organic liquid. Save, save, and save again. Now it would be a good time to save your work. Conclusion The partitioning behavior of many chemicals is very dependent on ph. Simple methods such as the use of Henry s law coefficients or other distribution factor approximation approaches do not work for real aqueous solutions. Effective separations for these systems can only be achieved when taking into account the complete speciation of the system. OLI software is useful for designing and evaluating separations systems involving aqueous electrolytes along with a second liquid phase such as oil or organic solvents. As such, OLI electrolytes technology is a useful complement to conventional simulation products that often do not accurately handle electrolytes. The Analyzer ratio Mix feature allows many simple processes to be simulated on your desktop. You can test an almost endless set of innovative options to deal with challenging process problems. Raising your AQ IQ Chapter 9 Organic Acid Removal 165

172 Advanced Problems Given a stream with the following conditions: Temperature 75 o C Pressure 200 Atmosphere H 2 O mole CO 2 1 mole 1. What would the temperature be if the pressure was reduced to 1 atmosphere? 166 Chapter 9 Organic Acid Removal Raising your AQ IQ

173 Appendix A OLI Company Profile OLI Software Simulation Tools... Providing Real World Answers Do you have these problems? ph control Corrosion in process operations Scaling and fouling of towers, heat exchangers Oil and gas wells production slowdown Effluent discharge limits Regulatory and liability issues Water and offgas treatment The wrong answer is worse than no answer at all OLI offers unsurpassed rigor in simulation for reactive phase equilibrium for aqueous electrolytes OLI Clients have an edge on their competition Corrosion Solutions Understanding the effect of the corrosion environment on rates of general and localized corrosion Oil Field Solutions Understanding the behavior of scaling and brine chemistry in production Process Chemistry Solutions Understanding the behavior of complex aqueous systems Predict the behavior of complex mixtures of chemicals in water Anticipate and diagnose problems and develop solutions for costly problems Optimize plant and lab operations and oilfield production Simulate and predict complex chemical and electrochemical phenomena in aqueous and mixed solvent environments Meet OLI OLI is a cutting edge chemical process technology and computer software company whose products and services save the worldwide Chemical Process Industry (CPI) and related industries millions of dollars every year. OLI's unique, powerful, and valuable software provides process, corrosion, and environmental chemistry solutions in the plant, in the lab, in the oilfield, and in the environment. Our software makes it easy for users to: Anticipate, diagnose, avoid and fix costly problems in chemical and petroleum operations while minimizing the time, cost, inaccuracy and risk of the lab, pilot or plant / field tests. Raising your AQ IQ Appendix A OLI Company Profile 167

174 Accurately predict the behavior of any mixture of chemicals in water and mixed solvents and simulate aqueous or mixed solvent processes and corrosion Develop unique solutions and great cost savings for problems involving corrosion, oil and gas well plugging, and wastewater contamination and chemical processing plant operation and optimization The result for you is: o o o o o Saved engineering, lab and pilot plant time Lower cost engineered solutions Improved process operations Increased production Avoided problems Reduced risk o OLI software and technology is the standard for simulation of aqueous electrolyte systems. OLI has established an extensive CPI client base and reputation for excellence based upon our products and our technical support. We have served the CPI and related industry for 30 years, specializing in complex aqueous electrolyte systems. OLI products are now used by hundreds of process engineers, industrial chemists, chemical process technologists, researchers, corrosion specialists, and process design engineers within chemical manufacturing and engineering service companies, and public and private research organizations in over 35 countries on 6 continents worldwide, including nearly all of the world s 30 largest chemical and petroleum companies. In about 1990, OLI cracked the code when it comes to rigorous prediction of the chemical reaction and phase behavior of complex mixtures of chemicals in water under modest to extreme conditions of temperature, pressure, and ionic strength. The combination of thermophysical properties models, solvers, and databank that enable this unique capability is known as the OLI Engine. Since 1990, OLI has built on this technology base a family of simulation technology and software products, with applications covering Chemical Processes, Rates of Corrosion, Oilfield Scale Prediction, Water Treatment, and Environmental Simulation. The OLI Engine is also available through all of the major process flowsheet simulators currently in use worldwide, including Aspen Plus, HYSYS, PROII, gproms, and IDEAS. What Makes OLI Different? OLI has four passions that drive everything we do: o The right chemistry o Advanced technology o Easy to learn and use interfaces o Expert service OLI is proud to be a different kind of simulation company, dedicated to technology development and committed to customer service, tech support, and training. We believe that no matter what your process problem is, you start by getting the chemistry right. This relentless pursuit of accurate chemical simulation has allowed OLI to address problems that no one else can even attempt let alone succeed in solving. A case in point is the new Mixed Solvent Electrolyte (MSE) chemistry model that enables chemical process simulations that heretofore were not possible to accomplish. And we never stop looking for new applications and simulation technology to leverage this powerful chemistry capability. Chemical Process Technology OLI software can help you address a single stream, a single unit operation, a complete process flowsheet, or an environmental process. On the stream level, OLI s StreamAnalyzer provides a virtual chemistry lab on your PC. With StreamAnalyzer you can predict reaction products, phase splits, and complete speciation of all phases for a complex mixture of chemicals in water. You can predict bubble and dew point, ph and ph adjustments, precipitation point, acid/base/chelant titrations curves, and temperature, pressure, and composition dependence of thermo-physical properties. With the LabAnalyzer, you can define a process stream on an ionic basis, evaluate the quality of and reconcile Providing the CPI Value Through Technology for the Plant the Laboratory the Oilfield the Environment Innovative Chemical Process Solutions Advanced Technology Simulations Powerful User-Friendly Software Expert Service 168 Appendix A OLI Company Profile Raising your AQ IQ

175 laboratory analyses, and then use these results in StreamAnalyzer or a process simulator such as ESP. At the process level, OLI s ESP (steady state) and DynaChem (dynamic) are the only rigorous aqueous process simulators. ESP includes unit operations such as mixing, precipitator, ph adjustment, reactive separations towers (including mass transfer), bioreactor, solvent extraction, ion exchange, and membrane separations. The crystallization model under development will include prediction of crystal size distribution and include particle kinetics such as growth, nucleation, agglomeration, and attrition. OLI s electrolyte technology is also available through all of the major process flowsheet simulators currently in use worldwide, including Aspen Plus, HYSYS, PROII, gproms, and IDEAS. Corrosion Technology OLI has developed the world s first predictive rates of general corrosion and localized models. OLI s corrosion technology allows corrosion engineers and specialists to understand the effect of the corrosion environment on the likelihood and extent of corrosion. Using this unique capability, users can: o o o o o o o o Anticipate the occurrence and extent of corrosion Locate corrosion hot spots for monitoring Interpret the results of plant coupon and monitoring data Reduce corrosion laboratory time and expense Conduct virtual experiments without risking the lab and plant Rapidly identify corrosion causes and corrective actions Simulate and predict the effects of process and material changes Optimize process conditions to minimize corrosion damage The mechanistically-based model is made possible by refinements to the OLI Engine to include rigorous redox chemistry and predictive models for transport properties such as electrical conductivity, viscosity, and diffusivity. The corrosion rate prediction model is based first on an accurate thermodynamic view of corrosion, precisely defining the conditions of activation and passivation at the surface. Then by taking into account all of the partial electrochemical and transport processes in the bulk aqueous phase and in the boundary layer at the metal/fluid interface, as well as the presence or absence of passive films, the model calculates the ion transport and hence the corrosion rate at the surface. conditions. The software tool also provides real solution stability (Pourbaix) diagrams and theoretical polarization curves to aid the engineer and corrosion specialist in understanding the mechanism, causes, and possible fixes for the corrosion situation being studied. CorrosionAnalyzer is available now for a broad array of common chemical systems and for carbon and stainless steels, and nickel-based alloys. Under a research award from the US Department of Energy, OLI is expanding the applicable metallurgy and chemistry to include essentially all of the alloys and environments of industrial interest. Oilfield Technology OLI s dedicated oilfield product is ScaleChem, the world s premier mineral scale prediction tool. Designed by and for production chemists and engineers, ScaleChem uses OLI s rigorous aqueous chemistry model to predict the formation of scale in the reservoir, well, and surface facilities. ScaleChem provides both the most accurate as well as the most versatile tool for scaling scenario analysis. Recent enhancements include adding in the oil phase and providing a facilities Wizard to determine downhole conditions based on surface samples. OLI Engine - Aqueous Electrolytes and MORE OLI Engine, the world s first and only rigorous predictive aqueous model is based on the combined work of Helgeson, Pitzer, Zemaitis, Bromley, Meisner, and OLI scientists, and a comprehensive databank that has taken over 25 years to develop. The OLI Engine has now been expanded to include Mixed Solvent Electrolyte systems. This proprietary model, the first and only one of its kind, will allow a whole new dimension of chemical process simulation for industry. The new model, by combining the best aqueous and non-aqueous (i.e., UNIQUAC) models, provides for the comprehensive thermo-physical properties engine for systems that exist beyond the limits of the aqueous models. Most notably, these include very high ionic strength solutions, and solutions containing 2 electrolyte solvents (e.g., water and ethanol). CorrosionAnalyzer allows the prediction of rates of general and localized corrosion as a function of pressure, temperature, composition, and flow Raising your AQ IQ Appendix A OLI Company Profile 169

176 170 Appendix A OLI Company Profile Raising your AQ IQ

177 Appendix B References 1. Anderko, A. and M.M. Lencka Computation of electrical conductivity of multicomponent aqueous systems in wide concentration and temperature ranges. Ind. Eng. Chem. Res., v36 p Anderko, A. and M.M. Lencka Modeling self-diffusion in multicomponent aqueous solutions in wide concentrations. Ind. Eng. Chem. Res., in press. 3. Anderko, A., S.J. Sanders, and R.D.Young Real solution stability diagrams: A thermodynamic tool for corrosion modeling. Corrosion v53, p Bromley, L.A Thermodynamic properties of strong electrolytes in aqueous solutions. AIChE J., v19 p Lencka, M.M., A.Anderko, S.J. Sanders, and R.D. Young. Modeling viscosity of multicomponent electrolyte solutions. Int. J. Thermophysics, In press. 6. Meissner, H.P. and C.L. Kusik Aqueous solutions of two or more strong electrolytesvapor pressures and solubilities. IEC Proc. Des. Dev., v12, p Meissner, H.P. and N.A. Peppas Activity coefficients - aqueous solutions of polybasic acids and their salts. AIChE J., v19, p Rafal, M, J.W. Berthold, N.C. Scrivner, and S.L. Grise Models for Electrolyte solutions. in Models for thermodynamic and phase equilibria calculations, S.I. Sandler, ed. Marcel Dekker, Inc. New York. 9. Shock, E.L. and H.C. Helgeson Calculation of the thermodynamic and transport properties of aqueous species at high pressure and temperatures: Correlation algorithms for ionic species and equation of state predictions to 5 kb and 1000 deg. C. Geo. et Cosmo. Acta, v52, p2009. Raising your AQ IQ Appendix B References 171

178 10. Shock, E.L. and H.C. Helgeson Calculation of the thermodynamic and transport properties of aqueous species at high pressure and temperatures: Standard partial molal properties of organic species. Geo. et Cosmo. Acta, v54, p Shock, E.L. H.C. Helgeson, and D.A. Sverjensky Calculation of the thermodynamic and transport properties of aqueous species at high pressure and temperatures: Standard partial molal properties of inorganic neutral species. Geo. et Cosmo. Acta, v53, p Sverjensky, D.A Calculation of the thermodynamic properties of aqueous species and the solubilities of minerals in supercritical electrolyte solutions. In: Reviews in Mineralogy v117, I.S.E. Carmichael and H.P. Eugster, Eds. Mineralogical Society of America, Washington, DC. 13. Sverjensky, D.A. and P.A. Molling A linear free energy relationship for crystalline solids and aqueous ions. Nature, v356(19), p Tanger, J.C. IV Calculation of the standard partial molal thermodynamic properties of aqueous ions and electrolytes at high pressure and temperature. Ph.D. Dissertation, Univ. California at Berkeley. 15. Zemaitis, J.F, Jr., D.M. Clark, M. Rafal, and N.C. Scrivner Handbook of aqueous electrolyte thermodynamics. AIChE. Washington, DC. 851 pages 172 Appendix B References Raising your AQ IQ

179 Appendix C Product Description Sheets Overview This appendix contains product description sheet for the following products: ESP (Environmental Simulation Program ) CorrosionAnalyzer StreamAnalyzer and LabAnalyzer ScaleChem Aspen OLI Raising your AQ IQ Appendix C Product Description Sheets 173

180 174 Appendix C Product Description Sheets Raising your AQ IQ

181 Environmental Simulation Program (ESP) Emergency Chlorine Scrubber FC Caustic Overhead 25 o C 1 Atm 1000g/hr total 10 wt% NaOH 3 Stages 25 o C 1 Atm The Environmental Simulation Program (ESP) is a steady-state aqueous process simulator with a proven record in enhancing the productivity of engineers and scientists. With applications industry-wide, the software is not only applied to the environmental applications but to any aqueous chemical processes. Waste Gas 25 o C 1 Atm Cl mol/hr CO 2 52 mol/hr N 2 58 mol/hr Bottoms FEATURES Chemistry Model Where the chemistry for the system is defined Process Build Units are selected and streams are defined. Unit connections are made by naming the output stream of one operation as input to the next. Process Analysis Process is run Reports Stream and unit reports and export to MS Excel The conventional and environmental unit operations, and controllers, that are available include: Mix Precipitator Manipulate Electrodialysis Split Reactor Controller Saturator Separate Exchanger Feedfoward Dehydrator Neutralizer Extractor Crystallizer Membrane (UF,RO) Absorber Component Split Clarifier Bioreactor Stripper Incinerator Sensitivity Compressor APPLICATIONS Design, debottlenecking, retrofitting, troubleshooting, and optimizing either existing or new processes Waste water treatment Upstream waste minimization Regulatory limits Simulation of Chlor-alkali plants, Claus plants Separations with mass transfer and kinetics, including absorbers, strippers, and extractors, scrubbers Gas treatment, Sour gas sweetening, amines Reaction kinetics Rigorous biotreatment, including heterotrophic and autotrophic biological degradation, multiple substrates Biotreatment processes, including sequential batch reactors and clarifiers with multiple recycle Raising your AQ IQ Appendix C Product Description Sheets 175

182 CAPABILITIES Flowsheet simulation with speciation Comprehensive data bank Sensitivity Analysis Controllers Mixed Solvent Applications thousands of organics. Data service provides customized coverage of client chemistry in the form of private databanks. Facility to allow the user to determine easily the sensitivity of output results to changes in the unit parameters and physical constants. Process flowsheet with multiple recycles and control loops are allowed. Feedfoward and feedback Controllers and Manipulate blocks help to achieve process specifications. Process flowsheet with multiple recycles and control loops are allowed. Feedfoward and feedback Controllers and Manipulate blocks help to achieve process specifications. On an individual application for OLI consortium members, ESP is available for process using OLI s mixed solvent electrolyte framework. RELATED PRODUCTS With an ESP lease, these software packages are also included: DynaChem: The dynamic response of a process can be studied using the dynamic simulation program, DynaChem, to examine control strategy, potential upsets, scheduled waste, controller tuning, and startup/shutdown studies. Discrete dynamic simulation of processes with control can be accomplished. Studies of ph and compositional control, batch treatments interactions, multistage startup and shutdown, controller tuning, multicascade and adaptive control are all possible. Stream Analyzer/Lab Analyzer: The OLI Stream Analyzer and Lab Analyzer provide flexible stream definition and easy single-case (e.g. bubble points) and parametric-case (e.g., ph sweep) calculations. These tools allow the user to investigate and understand the stream chemistry, as well as develop treatment ideas before embarking on process flowsheet simulation. The Analyzers also allow direct transfer of stream information to other simulation tools for parallel studies. 176 Appendix C Product Description Sheets Raising your AQ IQ

183 Corrosion Analyzer OLI's Corrosion Analyzer TM addresses the cause of corrosion by understanding the corrosion environment. This is in contrast to most corrosion treatments that address the symptoms by measuring corrosion rates, determining life expectancy and periodically replacing corroded material and equipment. Now with the Corrosion Analyzer TM, you can investigate and determine the causes of corrosion before they happen, allowing preventive actions to be evaluated and implemented. This includes choosing correct operating conditions and corrosion resistant materials. OLI Clients save material, equipment, and time, in corrosion related costs. FEATURES Pourbaix Diagrams Graphical depiction of EH vs. ph for any mixture of chemicals in water is available to evaluate stable and meta-stable corrosion and redox products. Real-solution chemistry is used, accounting for all activities, and assessing the effect of passivating species without any simplifying assumptions. Stablity Diagrams Flexible selection of independent variables and graphical depiction of local and global equilibria in various projections are available. Depictions include EH vs. composition and composition vs. ph for any chemical mixture, including trace components, to assess stable and metastable species in real solutions. Yield Diagrams A graphical tool is provided for designing the synthesis of compounds (e.g., ceramics) with desired yield for virtually any chemical mixture, including trace components. Rates of Corrosion Titrations, plotting, and mix/separate phases for further calculations. Polarization Curves Calculations and display of polarization curves to support the rates calculations. The polarization curves show the rate at which the reactions at the metal surface are proceeding. The sum of all the reactions results in the net current, or polarization curve. Potential for Pitting The corrosion potential is calculated and plotted against the repassivation potential. In regions where the corrosion potential is larger than the pitting repassivation potential, localized corrosion will occur. APPLICATIONS Screening to focus lab and plan test Materials selection Hot spots for sensor locations Useful remaining life Process changes and corrections actions testing Outage planning Lab and plant screening sensitivity studies Raising your AQ IQ Appendix C Product Description Sheets 177

184 ph, composition, and temperature effects Failure diagnosis and avoidance CAPABILITIES Automatic inclusion of Corrosion and Redox chemistry Kinetic Parameters of Corrosion Electrical Conductivity and Oxidation- Reduction Potential (ORP) Real-Solution Calculations Elemental and alloy metal oxidation and the reduction reactions for 79 inorganic elements and thousands of species are available in the OLI Databank. The Corrosion Analyzer automatically generates the redox reactions and the resulting species and solves for equilibrium conditions using its predictive thermodynamic model. Calibrated on literature and field data Rigorous prediction of electrical conductivity and ORP for multicomponent systems is computed for aqueous solutions Non-ideal behavior modeled with activity coefficients for complex, high Based on the combined work of Bromley, Zemaitis, Meissner, Pitzer and OLI technologists. RELATED PRODUCTS With a Corrosion Analyzer lease, these software packages are also included. Stream Analyzer provides a virtual desktop chemistry Stream Analyzer laboratory on your PC. Real systems are complex and concentrated. Stream Analyzer predicts the significant, non-intuitive departure from ideal solution behavior. Capabilities include complete phase equilibrium and speciation, along with accurate thermophysical properties (e.g. ph). Single point calculations, survey, and mix and separate operations are included. Lab Analyzer Lab Analyzer is companion software to the OLI Analyzers that enable you to evaluate the quality of laboratory data and then use the laboratory data (ionic composition) directly in your simulations. Used in conjunction with all of the other OLI software, the Lab Analyzer provides the translator from real laboratory analyses to molecular input. 178 Appendix C Product Description Sheets Raising your AQ IQ

185 Stream Analyzer and Lab Analyzer Stream Analyzer TM is simulation software which provides a virtual desktop chemistry laboratory on your PC. Real systems are complex and concentrated the Stream Analyzer TM can predict the significant, non-intuitive departure from ideal solution behavior. The software produces complete phase equilibrium and speciation, along with accurate thermophysical properties (e.g., ph). The software calculates single point, multiple point, mix and separate operations, and accepts further calculations on the mixed stream. Lab Analyzer TM is companion software to the OLI Analyzers that enables you to evaluate the quality of laboratory data, and then use the laboratory data (ionic composition) directly in your simulations. Used in conjunction with all of the other OLI software, the Lab Analyzer TM provides the translator from real laboratory analyses and all other simulation. FEATURES Flexible Stream Definition Single Point Calculations Survey Calculations Mix and separate Import/Export OLI s public databank, ready to support searches for a component via formula and common synonyms, organics structure to help locate organics, Names Dictionary to custom tailor the names of components you display. Isothermal, adiabatic, bubble and dew points, set ph, precipitation point, composition targets, vapor fraction or amount equilibrium calculations Temperature, pressure, composition, and ph surveys on any stream. Both a primary (one variable adjustment) and a covariant (two variable adjustment) are supported. Graphical reporting of the results. Titrations, plotting, and mix/separate phases for further calculations Analyze a stream s electrolyte behavior while still modeling a process in your flowsheet simulator of choice. Raising your AQ IQ Appendix C Product Description Sheets 179

186 APPLICATIONS Four-phase flash ph adjustment Solids deposition Waste water treatment Upstream waste minimization Meeting regulatory limits Laboratory water analysis, including reconciliations Process chemistry sensitivity studies Titration curves Reagent screening and selection Partitioning into second-liquid phase Trace metal removal CAPABILITIES Complete speciation The OLI model predicts and considers all of the true species in solution in the range of 50 to C to 1500 bar, and 0 to 30 molal ionic strength. Robust standard state framework Activity coefficients for complex, high ionic strength systems Based on the Helgeson Equation-of-state, parameter regression and proprietary estimation techniques Based on the combined work of Bromley, Zeimaitis, Meisnner, Pitzer, and OLI technologists Comprehensive databanks The Complete OLI Databank with 79 inorganic associated compounds and complexes, and thousands of organics. Data service provides customized coverage of client chemistry in the form of private databanks. Thermo physical properties OLI has developed unique chemical/physical based models to compute thermodynamic and transport properties for complex aqueous mixtures. 180 Appendix C Product Description Sheets Raising your AQ IQ

187 ScaleChem ScaleChem is simulation software for the assessment of scaling problems in oil and gas production. ScaleChem is synonymous with accurate olifield scaling prediction. OLI System s expertise is in aqueous chemistry. ScaleChem calculates the phase separation and scaling tendencies of brines at the extreme, high T, P conditions characteristic of today s well conditions. The standard solids chemistry covered by ScaleChem includes analysis for these solids. Scaling tendencies for these solids are reported for every calculation request. anhydrite CaSO 4 iron sulfide FeS barite BaSO 4 halite NaCl calcite CaCO 3 celestite SrSO 4 gypsum CaSO 4.2H2O dolomite CaMg(CO 3 ) 2 siderite FeCO 3 EXPANDED SOLIDS With ScaleChem is expanded chemistry, the solids analysis has been expanded to include all solids which are covered by the extensive OLI databanks. This allows solids analysis from the new cations and anions which have been added. Over 275 solids are available in the ScaleChem databank. Scaling tendencies for every solid with a scaling index > 1.0E-05 will be reported for a calculation request which uses expanded solids. FEATURES Well Profiles ScaleChem can be used to calculate scaling tendencies at user specified temperatures and pressures. Detailed phase reports and solids formation is given at each point. Mixing Compatible Waters Saturation at Reservoir Conditions Facilities Calculations Downhole Wizard Check the compatibility of different waters at user specified ratios, in order to find safe ratios (no solids formation) for injection and disposal operations. Saturate a water with respect to one or more solids to simulate reservoir conditions. Simulate the filtering, mixing and separating of waters in post-processing operations. Determine downhole conditions by analyzing the surface sample Raising your AQ IQ Appendix C Product Description Sheets 181