Aspen Physical Property System - Physical Property Models

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This section provides theoretical background for the model. All model equations and parameter requirements are included. The Pitzer model is commonly used in the calculation of activity coefficients for aqueous electrolytes up to 6 molal ionic strength. Do not use this model if a non-aqueous solvent exists. Henry's law parameters are required for all other components in the aqueous solution. The model development and working equations are provided in the following sections. Parameter conversion between the Pitzer notation and our notation is also provided. The Pitzer model in the Aspen Physical Property System involves usersupplied parameters that are used in the calculation of binary and ternary parameters for the electrolyte system. Five elements (P1 through P5) account for the temperature dependencies of parameters � (0) , � (1) , � (2) , � (3) , C � , �, and �. These parameters follow the temperature dependency relation: Where: T ref The user must: = 298.15 K � Supply these elements for the binary parameters using a Properties | Parameters | Binary | T-Dependent form. � Supply these elements for � on the Properties | Parameters | Electrolyte Ternary form. � Specify Comp ID i and Comp ID j (and Comp ID k for �) on these forms, using the same order that appears on the Components Specifications Selection sheet. The parameters are summarized in the following table. There is a Pitzer parameter databank in the Aspen Physical Property System (see Physical Property Data). Parameter Name Provides P1 - P5 for Cation-Anion Parameters 136 2 Thermodynamic Property Models No. of Elements Default MDS Units GMPTB0 � (0) 5 0 x — GMPTB1 � (1) 5 0 x — GMPTB2 � (2) 5 0 x — GMPTB3 � (3) 5 0 x — GMPTC C � 5 0 x — Cation-Cation Parameters GMPTTH � cc' Anion-Anion Parameters GMPTTH � aa' Ternary Parameters 5 0 x — 5 0 x —
Parameter Name GMPTPS, GMPTP1, GMPTP2, GMPTP3, GMPTP4 Provides P1 - P5 for � ijk 2 Thermodynamic Property Models 137 No. of Elements Default MDS Units 1 (in each parameter) 0 x — Molecule-Ion and Molecule-Molecule Parameters GMPTB0 � (0) 5 0 x — GMPTB1 � (1) 5 0 x — GMPTC C � 5 0 x — Model Development The Pitzer model analyzes "hard-core" effects in the Debye-Hückel theory. It uses the following expansion as a radial distribution function: Where: gij = Distribution function r = Radius qij With: = zi = Charge of ion i Qe = Electron charge (pair potential of mean force) �j(r) = Average electric potential for ion j k = Boltzmann's constant T = Temperature This radial distribution function is used in the so-called pressure equation that relates this function and the intermolecular potential to thermodynamic properties. From this relation you can obtain an expression for the osmotic coefficient. Pitzer proposes a general equation for the excess Gibbs energy. The basic equation is: Where: G E = Excess Gibbs energy (1) (2)
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Aspen Physical Property System Phys
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Contents Contents..................
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General Pure Component Solid Molar
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1 Introduction This manual describe
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Pure Component Temperature- Depende
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the Properties Parameters Pure-Comp
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2 Thermodynamic Property Models Thi
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Property Model Model Name Phase(s)P
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Property Model Model Name 2 Thermod
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Where: Parameter Name/Element 2 The
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critical temperature, the critical
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Where the ideal-gas contribution
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, where � For polar, associating
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Parameter Name/ Element 2 Thermodyn
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The denominator of equation 8 is gi
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V. V. De Leeuw and S. Watanasiri, "
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References M. Benedict, G. B. Webb,
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References L. Haar, J.S. Gallagher,
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Parameter Name/Element NTHDDH 0 †
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Gibbs free energy departure: The fo
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For a block copolymer, there is onl
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Copolymer PC-SAFT Dispersion Term T
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The association-site number of the
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Then I2(�) and I3(�) are comput
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A databank called PC-SAFT contains
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Parameter Name/Element PRKBV/1 k ij
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Predictive SRK (PSRK) This model us
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ka,ij kb,ij = = For best results, b
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J. Schwartzentruber and H. Renon, "
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Redlich-Kwong-Soave-MHV2 This equat
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‡ RKUC0, RKUC1, and RKUC2 are tre
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Parameter Name/ Element SRKLIJ/3 l
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Parameter Name/ Element Symbol Defa
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Association Equilibria Every associ
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and respectively. For the reactions
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R. W. Long, J. H. Hildebrand, and W
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Where the L, M, and N are parameter
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Alpha function Model name First Opt
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mi = Computed by equation 6 Equatio
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Parameter Name/Element 2 Thermodyna
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standard RKS alpha function, except
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These mixing rules are discussed se
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Where both Ai* and Am are calculate
Page 87 and 88: Like Huron and Vidal, the limiting
Page 89 and 90: Model Type Wilson Local composition
Page 91 and 92: Therefore, the simplified Pitzer eq
Page 93 and 94: Parameter Name/Element Symbol Defau
Page 95 and 96: Where: �i 2 Thermodynamic Propert
Page 97 and 98: The electrolyte NRTL model uses the
Page 99 and 100: Parameter Symbol No. of Name Elemen
Page 101 and 102: with Where: xi = Mole fraction of c
Page 103 and 104: It should be understood that equati
Page 105 and 106: The reference Gibbs energy is deter
Page 107 and 108: Where: j and k can be any species (
Page 109 and 110: The pure component dielectric const
Page 111 and 112: 2 Thermodynamic Property Models 109
Page 113 and 114: �I *PDH = Pitzer-Debye-Hückel te
Page 115 and 116: Where: �i Vi = Activity coefficie
Page 117 and 118: Recommended cij Values for Differen
Page 119 and 120: Parameter Name/ Element 2 Thermodyn
Page 121 and 122: NRTL-SAC Reference States The NRTL-
Page 125 and 126: For an anionic component, we have M
Page 127 and 128: For a molecular segment, the activi
Page 129 and 130: Specifically, The long range intera
Page 131 and 132: where and are activity coefficients
Page 133 and 134: and Y+, are used to reflect the wid
Page 135 and 136: Parameter Name/ Element Symbol Defa
Page 137: Reference C.-C. Chen and Y. Song, "
Page 141 and 142: zi = Charge of ion i Subscripts c,
Page 143 and 144: For option code = 0 (default), the
Page 145 and 146: and for n-m electrolytes: 2 Thermod
Page 147 and 148: = 0.00979 Perform the necessary con
Page 149 and 150: Pitzer, K.S., J.R. Peterson, and L.
Page 151 and 152: A4,ij = gij / T + hij A5,ij = mij /
Page 153 and 154: Symmetric and Unsymmetric Electroly
Page 155 and 156: Parameter Symbol No. of Name Elemen
Page 157 and 158: Reference state for ionic component
Page 159 and 160: with 2 Thermodynamic Property Model
Page 161 and 162: G for these pairs is calculated the
Page 163 and 164: with 2 Thermodynamic Property Model
Page 167 and 168: Activity Coefficient Basis for Henr
Page 169 and 170: Where is the liquid Gibbs free ener
Page 171 and 172: Ionic components 2 Thermodynamic Pr
Page 173 and 174: the pure fused salts. Applying Eq.
Page 175 and 176: �k is the activity coefficient of
Page 177 and 178: References U. Weidlich and J. Gmehl
Page 179 and 180: ti' = �ij 2 Thermodynamic Propert
Page 181 and 182: Wagner Interaction Parameter The Wa
Page 183 and 184: References G.M. Wilson, J. Am. Chem
Page 185 and 186: Extended Antoine Equation Parameter
Page 187 and 188: IK-CAPE Vapor Pressure Equation The
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Harlacher and Braun, "A Four-Parame
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General Pure Component Heat of Vapo
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IK-CAPE Heat of Vaporization Equati
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Where: xp = Mole fraction of pseudo
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Parameter Name/Element VLBROC/1 V i
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Where: Vm l,t = Liquid volume per n
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Debye-Hückel Volume The Debye-Hüc
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DIPPR DIPPR equation 105 is the def
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Rackett The Rackett equation is: Wh
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Rackett/Campbell-Thodos Mixture Liq
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Zm RA Zi *,RA Vcm 2 Thermodynamic P
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General Pure Component Solid Molar
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Liquid Volume Quadratic Mixing Rule
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If THRSWT/6 is This equation is use
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Parameter Symbol Default MDS Lower
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General Pure Component Ideal Gas He
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(Other DIPPR equations may sometime
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General Pure Component Solid Heat C
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The expression for the liquid mole
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� Entropy: � Heat capacity: �
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Parameter Name † /Element CPIXPn/
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Option Codes for Electrolyte NRTL E
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Parameter Name Applicable Component
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For subcritical components: Hm l -H
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The vapor enthalpy is calculated fr
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Where: 2 Thermodynamic Property Mod
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Correlation algorithms for ionic sp
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Model Model name Phase(s) Pure Mixt
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Model Type Aspen Liquid Mixture Vis
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(Other DIPPR equations may sometime
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�i = Viscosity of component i (N-
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Parameter Name/Element 3 Transport
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Where: The Stockmayer or Lennard-Jo
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Where: Vcij = �ij = 0 (in almost
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Where: Vcij = �ij = 0 (in almost
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Jones-Dole Electrolyte Correction T
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Letsou-Stiel The Letsou-Stiel model
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Where: The parameter is the mole fr
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Reference C.H. Twu, "Internally Con
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Vcij 3 Transport Property Models 27
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You must provide parameters for the
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Linear extrapolation of � *,l ver
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If TRNSWT/4 is This equation is use
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References R.C. Reid, J.M. Prausnit
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The mixture surface tension is then
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Where: �solv = Dielectric constan
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4 Nonconventional Solid Property Mo
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wij = Mass fraction of the jth cons
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The oxygen and organic sulfur conte
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Parameter Name/Element Symbol Defau
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The complete oxidation of carbon is
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Parameter Name/Element Symbol Defau
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The equation for �i dm is good fo
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5 Property Model Option Codes The f
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Model Name Option Code 5 Property M
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Model Name Option Code 5 Property M
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Soave-Redlich-Kwong Option Codes Th
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Model Name Option Code HLRELNRT and
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Model Name Option Code GLRELNRT, GL
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Index A activity coefficient models
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ideal gas/DIPPR heat capacity model
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S Sato-Riedel/DIPPR thermal conduct
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Aspen Physical Property System - Physical Property Models

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