A modelling study of h2s absorption in pure water and in rainwater

A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER ER SHOW LIN NATIONAL UNIVERSITY OF SINGAPORE 2004 A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER ER SHOW LIN (B. ENG (Hons), UOA) A THESIS SUBMITTED FOR THE DEGREE OF MASTER OF ENGINEERING DEPARTMENT OF CHEMICAL AND BIOMOLECULAR ENGINEERING NATIONAL UNIVERSITY OF SINGAORE 2004 In memory of my beloved sister ACKNOWLEDGEMENTS ACKNOWLEDGEMENTS I would like to express my greatest appreciation to the following people who make this research completed. To my supervisors Dr. Balasubramanian and Assoc. Prof. Rangaiah for their patience, guidance and advices not only in the research work, but also how to be a good engineer and researcher. To Yang Tzuo Sern and Ellis, See Siao Wei. The invaluable friendship, encouragement and assistance from them continue supporting me. They have made my two years work here enjoyable and unforgettable. To Dr. Rath for his kindness in helping my research. To lab officer Ms. Li Feng Mei for teaching me the operations of many laboratory equipments. A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER i TABLE OF CONTENTS TABLE OF CONTENTS ACKNOWLEDGEMENTS i TABLE OF CONTENTS . ii SUMMARY . vi NOMENCLATURE viii LIST OF FIGURES xiii LIST OF TABLES xix CHAPTER : INTRODUCTION 1.1 Background . 1.2 Process Specifications . 1.3 Objectives CHAPTER : LITERATURE REVIEW . 2.1 Phase equilibrium . 2.2 Henry’s law approach 10 2.3 Equations of state (EOS) 12 2.3.1 Van der Waals equation of state 13 2.3.2 Redlich-Kwong equation of state (RK EOS) . 14 2.3.3 Soave-Redlich-Kwong equation of state (SRK EOS) 15 2.3.4 Peng-Robinson equation of state (PR EOS) . 16 2.3.5 Peng-Robinson-Stryjek-Vera equation of state (PRSV EOS) . 16 2.3.6 Modified Peng-Robinson equation of state (MPR EOS) 19 A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER ii TABLE OF CONTENTS 2.4 Activity functions 21 2.4.1 Extended Debye-Hückel approximation 22 2.4.2 Pitzer equation for the excess Gibbs energy 23 2.4.3 Chen and Evans Model . 26 2.5 Previous models for the prediction of the solubility of H2S in aqueous solutions 28 CHAPTER 3.1 : MODELLING DEVELOPMENT 33 Chemistry background and equations . 34 3.1.1 H2S-pure water system 38 3.1.2 H2S-single electrolyte system 38 3.1.3 H2S-rainwater system 41 3.2 Parameters and constants 43 3.2.1 Debye Hückel parameter, Aφ . 43 3.2.2 Equilibrium (KR) and Henry’s constants (Hij) 44 3.2.3 Saturated pressure of water, P satw 45 3.2.4 Partial molar volume of H2S in infinity dilution of water, v H S . 46 3.2.5 Interaction coefficients of EOS . 47 3.2.6 Interaction parameters for Pitzer equation of excesss Gibbs energy . 47 3.3 Computational procedures and block diagram . 49 CHAPTER 4.1 ∞ : RESULTS AND DISCUSSION 52 Comparisons of models 53 4.1.1 Low pressures system (P < 10 bar) 53 4.1.2 High pressures system (P > 10 bar) . 56 A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER iii TABLE OF CONTENTS 4.2 Effects of pressure and temperature on H2S solubility . 62 4.3 Effect of pH on H2S solubility in aqueous phase . 65 4.4 Effects of single electrolyte on H2S solubility 68 4.4.1 H2S in NaNO3 solution of different concentrations 69 4.4.2 H2S in NaCl solution of different concentrations . 71 4.4.3 H2S in Na2SO4 solution of different concentrations . 73 4.4.4 H2S in NH4NO3 solution of different concentrations . 76 4.4.5 H2S in NH4Cl solution of different concentrations 78 4.4.6 H2S in (NH4)2SO4 solution of different concentrations 78 4.5 Solubility of H2S in rainwater System . 81 4.5.1 Application of the model on H2S – rainwater system . 81 4.5.2 Advantages of H2S removal by rainwater 84 CHAPTER : CONCLUSIONS . 87 CHAPTER : REFERENCES . 90 APPENDIX A : EQUATIONS OF STATE 98 A.1 Redlich-Kwong Equation of State (RK EOS) 98 A.2 Soave-Redlich-Kwong Equation of State (SRK EOS) . 99 A.3 Peng-Robinson Equation of State (PR EOS) . 100 A.4 Peng-Robinson-Stryjek-Vera Equation of State (PRSV EOS) . 101 A.5 Modified Peng-Robinson Equation of State 102 APPENDIX B : THE PITZER’S INTERACTION PARAMETERS FOR THE CALCULATIONS OF THE ACTIVITY OF WATER (aW) 103 A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER iv TABLE OF CONTENTS APPENDIX C : RAINWATER ANALYSIS 105 A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER v SUMMARY SUMMARY The removal of H2S from industrial flue gas by absorption process is an important pollution control operation in many industries such as petroleum, natural gas and chemical industries. Although this absorption process is widely used in many countries, it requires enormous amount of pure water. For countries with water scarcity like Singapore, this absorption process appears to be less economically viable. The use of rainwater in place of pure water is an attractive option since it is freely available. However, the effectiveness of using rainwater for the removal of H2S through absorption has not been investigated yet. Many investigations have been carried out to study the phase behaviour of H2S in various aqueous media such as pure water, electrolyte solutions and alkanolamine solutions. However, no data are currently available in the literature on the solubility of H2S in rainwater. Such data are needed to evaluate the efficiency of removal of H2S by rainwater and to design an absorber for the desired industrial applications. Moreover, the reported investigations on the phase behaviour of H2S in pure water were conducted over moderate pressure and temperature ranges. Therefore, a robust vapour-liquid equilibrium (VLE) model, which is applicable over broader temperature and pressure ranges, is necessary for gaining a better understanding of the solubility of H2S not only in pure water bur also in rainwater. In this study, the Gamma/Phi formulation for VLE based on the use of the equation of state (EOS) for vapour phase and the activity function for liquid phase were employed in the modelling work. Four models with four different EOS and activity function A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER vi SUMMARY derived from the Pitzer equation of excess Gibbs energy were developed. The developed models were verified by comparing predicted values with experimental H2S solubility data on pure water and on single electrolyte systems at pressures up to 150 bar and temperatures up to 171 oC. The effects of different pH values and electrolytes on the H2S solubility were also investigated. Among the four models developed in this work, the model based on modified PengRobinson equation of state (MPR EOS) was found to be the best model by way of comparison of the predicted values with the experimental data. Therefore, this model was applied for the investigation of H2S solubility in the rainwater system. Since it is impossible to estimate the thermodynamic properties of individual ions directly (Pitzer, 1991), rainwater is treated in this research as a multi-salt solution instead of multi-ion solution. The H2S solubility in pure water in relation to temperature, pressure, pH and electrolytes is modelled and discussed in this thesis. The H2S solubility in rainwater was also investigated, and was found to be similar to that in pure water due to very dilute concentration of electrolytes in the solution and the pH value which is smaller than its first dissociation constant, pKR1. This intercomparison suggests that the use of rainwater as an absorption medium for the removal of H2S is highly desirable in the view of growing interest in water conservation and preservation. . A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER vii CHAPTER REFERENCES Carroll, J. J. and A. E. Mather. Phase Equilibrim in the System Water-Hydrogen Sulphide: Modelling the Phase Behavior with an Equation of State. Can. J. Chem. Eng., 67, pp. 999-1003. 1989. Carroll, J. J. Phase Behaviour in the System Water-Hydrogen Sulphide. Ph.D Thesis, University of Alberta, 1990a. Carroll, J. J. Reliably Prediction the Solubility of H2S in Water. Chem. Eng., 97, pp. 227-229. 1990b. Carroll, J. J. Use Henry’s Law for Multicomponent Mixtures. Chem. Eng. Prog., 88, pp. 53-58, 1992. Carroll, J. J. What is Henry’s Law?. Chem. Eng. Prog., 87, pp. 48-52. 1991. Chen, C. C., Britt, H. I., Boston, J. F. and L. B. Evans. Local Composition Model for Excess Gibbs Energy of Electrolyte Systems. 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A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER 97 APPENDIX A EQUATIONS OF STATE APPENDIX A : EQUATIONS OF STATE A.1 Redlich-Kwong Equation of State (RK EOS) Standard form: P= RT a − V −b T V (V + b) (A.1.1) Polynomials: z − z + ( A − B − B ) z − AB = RT a ab − bRT − Pb )V − =0 V + ( P P T p T V3 − (A.1.2) (A.1.3) Parameters: = 0.42748 R 2TCi2.5 PCi (A.1.4) bi = 0.08664 RTCi PCi (A.1.5) Ai = P RT 2.5 (A.1.6) Bi = bi P RT (A.1.7) For mixtures: a = ∑∑ yi y j aij i aii = (A.1.8) j aij = a j (Redlich Kwong’s original rule) (A.1.9) b = ∑ yibi (A.1.10) aP RT 2.5 (A.1.11) B = ∑ yi Bi (A.1.12) i A= i The partial fugacity coefficients of species i ∧ ln φ j =   Bi ( z − 1) − ln (z − B ) + A  Bi − Ai  ln 1 + B  B B B A  z (A.1.13) A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER 98 APPENDIX A A.2 EQUATIONS OF STATE Soave-Redlich-Kwong Equation of State (SRK EOS) Standard form: P= RT aα − V − b V (V + b ) (A.2.1) Polynomials: Z − Z + ( A − B − B ) Z − AB = (A.2.2) RT (aα )b V + (aα − Pb )V − =0 P P p (A.2.3) V3 − Parameters: R 2TCi2 PCi = 0.42747 (A.2.4) α i = [1 + κ i (1 − TR0.5 )] (A.2.5) κ i = 0.480 + 1.574ω i − 0.176ω i2 (A.2.6) i bi = 0.08664 Ai = (aα ) i P ; ( RT ) RTCi PCi (A.2.7) (A.2.8) (aα ) i = a i α i bi P RT Bi = (A.2.9) For mixtures: a = ∑∑ yi y j aij i (A.2.10) aii = j (aα ) ij = (1 − k ij ) ( aα ) i ( aα ) j k ii = (A.2.11) b = ∑ yibi (A.2.12) ( aα ) P ( RT ) (A.2.13) i A= B = ∑yB i i (A.2.14) i The partial fugacity coefficients of species i ∧ ln φ j =   2∑ y j aij Bi B   B A (Z −1) − ln(Z − B) −  j =1 − i  ln1 +  B B a B   Z   (A.2.15) A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER 99 APPENDIX A A.3 EQUATIONS OF STATE Peng-Robinson Equation of State (PR EOS) Standard form: P= RT aα − V − b V + 2bV − b (A.3.1) Polynomials: Z − (1 − B) Z + ( A − 2B − 3B2 ) Z − ( AB − B2 − B3 ) = V − (b − RT aα − 2bRT RTb2 − aαb )V + ( − 3b )V + (b + )=0 P P P (A.3.2) (A.3.3) Parameters: = 0.45724 R 2TCi2 PCi (A.3.4) α i = [1 + κ i (1 − TR0.5 )] (A.3.5) κ i = 0.37464 + 1.54226ω i − 0.26992ω i2 (A.3.6) i bi = 0.07780 Ai = RTCi PCi ( aα ) i P ; ( RT ) (A.3.7) (A.3.8) ( aα ) i = a i α i bi P RT Bi = (A.3.9) For mixtures: a = ∑∑ yi y j aij i aii = (aα ) ij = (1 − k ij ) (aα ) i ( aα ) j b= (A.3.10) j k ii = (A.3.11) ∑yb (A.3.12) ( aα ) P ( RT ) (A.3.13) i i i A= B = ∑yB i i (A.3.14) i The partial fugacity coefficients of species i  2∑ y j aij  Bi A  j =1 Bi   Z + 2.414B  ln φi = (Z − 1) − ln(Z − B ) − −  ln   B B   Z − 0.414B  2B  aα   ∧ (A.3.14) A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER 100 APPENDIX A A.4 EQUATIONS OF STATE Peng-Robinson-Stryjek-Vera Equation of State (PRSV EOS) Standard form: P= RT aα − V − b V + 2bV − b2 (A.4.1) Polynomials: Z − (1 − B)Z + ( A − 2B − 3B2 )Z − ( AB − B2 − B3 ) = V − (b − RT aα − 2bRT RTb2 − aαb )V + ( − 3b )V + (b3 + )=0 P P P (A.4.2) (A.4.3) Parameters: = 0.45724 R 2TCi2 PCi (A.4.4) α i = [1 + κ i (1 − TR0.5 )] (A.4.5) κ i = κ 0i + κ 1i (1 + T Ri0.5 )( 0.7 − T Ri ) (A.4.6) i κ 0i = 0.378893 + 1.4897153ω i − 0.1713848ω + 0.0196554ω κ1i = 0; for TR < 0.7 bi = 0.07780 Ai = (aα ) i P ( RT ) RTCi PCi ; (A.4.8) (A.4.9) (aα ) i = aiα i bi P RT Bi = (A.4.7) (A.4.10) For mixtures: a = ∑∑ yi y j aij i (A.4.11) aii = j ( aα )ij = (aα )i ( aα ) j (1 − k ij k ji yi kij + y j k ji ) ; kii = (A.4.12) ∑ yb (A.4.13) A= ( aα ) P ( RT ) (A.4.14) B = ∑yB b= i i i i (A.4.15) i i Partial fugacity coefficients of species i, ∧ ln φi =   bi (Z − 1) − ln(Z − B) − A  a + − bi  ln Z + 2.414B  b b   Z − 0.414B  2B  a = 2∑ y j j − a + 2∑ yi y j aiia jj kijk ji j j ≠1 i yi kij + y j k ji − kij ( yikij + y j k ji )2 (A.4.16) (A.4.17) A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER 101 APPENDIX A A.5 EQUATIONS OF STATE Modified Peng-Robinson Equation of State Standard form: P= RT aα − V − b V + 2bV − b (A.5.1) Polynomials: Z − (1 − B)Z + ( A − 2B − 3B )Z − ( AB − B − B3 ) = V − (b − RT aα − 2bRT RTb2 − aαb )V + ( − 3b )V + (b + )=0 P P P (A.5.2) (A.5.3) Parameters: = 0.45724 R 2TCi2 PCi (A.5.4) α i = [1 + κ i (1 − TR0.5 )] (A.5.5) i [ αW = 1.008568 + 0.8215(1 − TR ,W [ { 1/ αW = + 0.4530 − TR ,W (1 − 0.0103csw1.1 ) ] ) , TR ,W < 0.72 ]} for brine system. κ i = 0.37464 + 1.54226ω i − 0.26992ω i2 bi = 0.07780 RTCi Bi = (A.5.7) (A.5.8) PCi ( aα ) i P ; ( RT ) Ai = (A.5.6) (A.5.9) ( aα ) i = a iα i bi P RT (A.5.10) For mixtures: a = ∑∑ yi y j aij i aii = (A.5.11) j (aα ) ij = (1 − k ij ) (aα ) i (aα ) j k ii = b = ∑ yibi (A.5.12) (A.5.13) i A= (a α ) P ( RT ) B = (A.5.14) ∑yB i i (A.5.15) i The partial fugacity coefficients of species i ∧ ln φ i =   2∑ y j aij  Bi B   Z + .414 B  (Z − 1) − ln (Z − B ) − A  j =1 − i  ln   B aα B   Z − 0.414 B  2B    (A.5.16) A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER 102 APPENDIX B THE PITZER’S INTERACTION PARAMETERS FOR THE CALCULATIONS OF THE ACTIVITY OF WATER APPENDIX B : THE PITZER’S INTERACTION PARAMETERS FOR THE CALCULATIONS OF THE ACTIVITY OF WATER (aW) Table B-1 Ion interaction parameters for aqueous phase of NaNO3 and NH4NO3  T  f (T / K ) = q1 + q 1 − R  T   (B.1) Salts Parameters q1 Q2 Reference NaNO3 β(0) 0.0038 0.04938 Sing et al. (1999) 0.21151 8.6493 C (φ ) -0.00006 -0.0003 β(0) -0.01476 (1) 0.13826 (1) β NH4NO3 β C (φ ) Table B-2 Kim and Frederick (1988) 0.00029 Ion interaction parameters for aqueous phase of Na2SO4 and NaCl 1 f (T / K ) = q1 − q2  −  T TR  − 680 q7  680 ( T )T −   T    1  + q3 T − TR2 + q4 (T − TR ) + q5 ln  + 263q6   − 263 263 − − T T T T T ( ) ( ) R R    R    − (TR − 680)TR  Salts Q1 Na2SO4 NaCl Parameters ( ) q2 β(0) 0.01869 2317.941 β(1) 1.0994 23268.081 C (φ ) 0.005549 -22.618687 β(0) 0.0765 777.03 β(1) 0.2664 C (φ ) 0.00127 -33.317 q3 q4 q5 q6 -1.03611 3.0029 -1.43441 -6.66894 Roger and x 10-5 10-2 x 101 x 10-1 Pitzer (1981) -3.23550 5.76552 -1.88769 -2.05974 1.46744 x 10-4 x 10-1 x 102 x 10-1 x 103 -3.3158 5.14316 3.45791 x 10-5 x 10-1 0.008946 q7 (B.2) -4.4706 x 10-6 Reference Silvester and Pitzer (1977) 1.0715 6.1608 x 10-6 x 10-5 -4.655 0.09421 x 10-5 A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER 103 APPENDIX B THE PITZER’S INTERACTION PARAMETERS FOR THE CALCULATIONS OF THE ACTIVITY OF WATER Table B-3 f (T / K ) = q1 + Salts Ion interaction parameters for aqueous phase of (NH4)2SO4 q2 + q3 ln T + q4T T (B.3) Parameters (NH4)2SO4 Table B-4 q1 q2 β(0) 17.7912 -589.017 β(1) 766.00 -23129.6 C (φ ) -0.18855182 14.4081 q3 q4 -2.979609 4.005157 x 10 -130.631 Reference Weyrich -3 (1997) 0.189579 2.45392 X 10-2 Ion interaction parameters for aqueous phase of NH4Cl f (T / K ) = q1 + q2 ln T + q3T + q4T + q5 q6 q11   + + (P − ) q7 + q8 ln T + q9T + q10T + T − 227 647 − T 647 − T   Parameters β(0) β(1) C (φ ) Q1 -929.689 x 10-3 673.399 x 10-3 -2.79772 x 10-3 Q2 2.20237 x 10-1 -1.42555 x 10-1 0.0 q3 -1033.06 x 10-6 1093.95 x 10-6 -7.41476 x 10-6 q4 5.49192 x 10-7 0.0 0.0 q5 -91.5057 x 10-2 0.0 9.09242 x 10-2 q6 0.0 0.0 2.12227 x 10-1 q7 4.88766 x 10-2 0.0 0.0 q8 -1.09552 x 10-2 0.0 0.0 q9 5.61713 x 10-5 0.0 0.0 q10 -3.62817 x 10-8 0.0 0.0 q11 1.93572 x 10-2 0.0 0.0 A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER (B.4) 104 2000 (Jan-Dec) 1984(Apr)-1988(Mar) 1990-1992 1996(Dec)-1998(Apr) 1990 1989(Jun-Nov) 1983-1994 1986(Jul)- 1988(Dec) 1987-1993 1988(Oct)-1990 (Jun) 1992(Feb)-1995(Feb) Singapore Hiroshima, Japan Hong Kong Irbid, Jordon Carmel, Israel South-east England Northeastern Spain Albany, New York Mexico Central Amazon,Brazil La Selva, Costa Rica 5.27 4.77 4.63 4.54 4.84 4.43 4.74 5.03 4.29 5.01 4.11 pH 5.4 17.0 23.5 29.0 14.5 37.0 18.3 9.3 51.0 9.8 78.1 H+ 2.3 0.8 3.1 4.0 3.7 9.5 7.2 1.2 9.5 K+ A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER Period(samples) 7.1 2.4 70.5 8.7 56.6 59.0 44.7 131.3 22.1 10.0 13.4 Ca2+ 38.9 2.4 4.4 22.3 232.0 166.0 83.9 57.0 17.7 29.5 Na+ 10.1 0.9 9.7 3.7 9.7 40.0 28.0 39.8 14.2 5.7 5.9 Mg2+ 8.7 3.0 93.5 9.9 22.8 24.3 36.9 25.7 29.9 17.2 NH4+ 47.6 4.6 4.7 28.5 69.0 176.3 94.0 68.2 29.7 28.9 Cl- 17.7 2.0 131.3 25.0 46.0 63.0 150.3 100.2 66.3 40.2 78.8 SO42- 105 5.3 4.2 41.5 25.0 20.6 38.0 28.0 25.9 13.2 15.5 20.3 NO3- RAINWATER ANALYSIS Comparison of measured ion concentrations (meq/l) and other ratios in rainwater at various sites (Begum (1998)) RAINWATER ANALYSIS Site Table C-1 APPENDIX C : APPENDIX C Concentration (mmol/L) 0.083 0.008 0.008 0.005 0.093 0.033 0.007 0.0316 Ions Na+ Mg2+ Ca2+ K+ Cl- SO42- HCO3- H+ The major ion compositions of rainwater with ionic strengths < 0.1 mol/L (Pitzer, 1991). A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER Ionic strength, I = 0.21 mmol/L pH = 4.5 Table C-2 APPENDIX C RAINWATER ANALYSIS 106 [...]... not a desired option in Singapore Fortunately, Singapore receives abundant of rainfall every year, (about 2400 A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER 1 CHAPTER 1 INTRODUCTION mm rainfall yearly) Thus, rainwater has become an attractive source of water for many domestic and industrial processes, which require the production of deionised water and ultra pure water According... experimental data available in the literature After establishing the reliability of the model, it will be used for the examination of the phase A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER 2 CHAPTER 1 INTRODUCTION behaviour of H2S in rainwater The modelling work will be done by applying the fundamental phase equilibrium equation namely, “Gamma/Phi formulation” for the study of the vapour... steam generated by reboiling the lean solution In practice, the hot rich solution is usually allowed to flash into the top of regenerator and no separate flash drum is provided A typical absorber unit is also attached in igure 1-2 A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER 4 Treated Gas Out HF Idealised solvent absorption acid gas removal process A W A MODELLING STUDY OF H2S ABSORPTION. .. research on rainwater analysis conducted by Begum (1998) (cf APPENDIX C), the rainwater in Singapore is of high quality despite the fact that it is relatively acidic if compared to other cities/countries such as Hiroshima, Japan and Albany, New York, USA Therefore, this study investigates the use of rainwater as a potential replacement of pure water for the absorption of H2S in industrial flue gas Note... ABSORPTION IN PURE WATER AND IN RAINWATER xvii LIST OF FIGURES Figure 4-29 The MPR EOS predicted H2S solubility in RW ( ) and PW (solid lines) as compared to experimental results of Selleck et al (1952) ( ) at T = 171.1 oC 84 A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER xviii LIST OF TABLES LIST OF TABLES Table 3-1 Values of the constants for the dielectric constant, D, of water. .. .77 Table 4-9 The compositions of artificial rainwater expressed in terms of component neutral salts 82 A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER xix LIST OF TABLES Table 4-10 The solubility product of metal sulphides in water at 25 oC (Millero (1986)) 86 Table B-1 Ion interaction parameters for aqueous phase of NaNO3 and NH4NO3 103 Table B-2 Ion interaction... than 70 bar is to be examined In view of the non-availability of experimental data on the solubility of H2S in rainwater, modelling work is needed to investigate the phase behaviour of H2S in rainwater system A robust and reliable model applicable over a wide range of operating conditions is required Thus, the objectives of the research are: 1 To determine a reliable model which is applicable in pure. .. (solid lines) mole fraction of H2S in liquid phase at different temperatures and pressures (experimental data of Selleck et al (1952)) 61 A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER xiv LIST OF FIGURES Figure 4-9 The approximate solubility of H2S as a function of pH at P = 1bar and T = 25 oC and 93.3 oC respectively 67 Figure 4-10 The approximate solubility of H2S as a function... Waals, 1873) was the first practical cubic equation of state that reasonably represented both the gas and liquid phases This equation plays a very important part since it inspired the development of a large family of other equations of state These equations include, the Redlich-Kwong equation of A MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER 12 CHAPTER 2 LITERATURE REVIEW state (RK EOS)... bar) Hence at the pressure range, it is normally assumed to be one Eqs (2.8) and (2.9), known as Gamma ( γ )/Phi ( ϕ ) formulation has been widely used in the modelling of many industrial processes (Carroll, 199 0a and 1990b; HajiA MODELLING STUDY OF H2S ABSORPTION IN PURE WATER AND IN RAINWATER 11 CHAPTER 2 LITERATURE REVIEW Sulaiman et al., 1998; Li and Chang, 1994, etc.) By applying this equation, the . THE ACTIVITY OF WATER (a W ) 103 TABLE OF CONTENTS A MODELLING STUDY OF H 2 S ABSORPTION IN PURE WATER AND IN RAINWATER v APPENDIX C : RAINWATER ANALYSIS 105 SUMMARY A MODELLING STUDY. conservation and preservation. . NOMEMCLATURE A MODELLING STUDY OF H 2 S ABSORPTION IN PURE WATER AND IN RAINWATER viii NOMENCLATURE Abbreviations A absorber AMP 2-amino-2-methyl-1-propanol. a ij parameters of EOS NOMEMCLATURE A MODELLING STUDY OF H 2 S ABSORPTION IN PURE WATER AND IN RAINWATER ix A φ Debye Hückel parameter a i activity of species i a parameter in PRSV