Claire ADJIMAN

© 2012 Process Systems Enterprise Limited

19th March 2012

L. Avaulléea, C.S. Adjimanb, F. Caladoc, P. Duchet‐Suchauxa, J. Fuentesc, A. Galindob, G. Jacksonb, T. Lafitteb, C.C. Pantelidesb,c*, V. Papaioannoub, T.H. Williamsc

a Total S.A.b Imperial College Londonc Process Systems Enterprise Ltd.

gSAFT: Application of the SAFT‐‐Mie EOS in the oil/gas industryFrom academic research to industrial deployment

© 2012 Process Systems Enterprise Limited2

Outline

gSAFT technology – brief overview

SAFT‐Mie, a group contribution equation of state

gSAFT for oil/gas systems – Methodology

gSAFT for oil/gas systems – Application examples

Concluding remarks


PSE’s gSAFT technologyBrief overview – I

Developed by Molecular Systems Engineering group at Imperial College acquired by PSE from Imperial College in 2009 on‐going support/technology pipeline

Objective: provide advanced thermodynamics for complex mixtures in gPROMS® a single platform that meets a wide range of modelling needs

Collaboration with Total initiated in late 2010 to test the applicability of gSAFT technology to oil and gas applications assess gSAFT’s capabilities against other technologies develop a parameter databank for oil and gas applications


PSE’s gSAFT technologyBrief overview – II

A family of Equations of State, employing different types of molecular descriptions (homonuclear vs. heteronuclear/Group

Contribution) repulsive/dispersive interactions

Interfaced to gPROMS as a Foreign Object

4

SAFT‐VR SW SAFT‐ SW SAFT‐Mie


SAFT‐Mie fundamentals

5

Lymperiadis et al., J. Chem. Phys. 127, 234903 (2007)Lymperiadis et al., Fluid Phase Equil. 274, 85 (2008)Lafitte et al., in preparation (2012)Papaioannou et al., in preparation (2012)


The SAFT‐VR equation of state

One of a generation of more advanced models specifically developed for chain and associating molecules SAFT: Chapman, Gubbins, Jackson, Radosz, Ind. Eng. Chem. Res., 29, 1709 (1990) SAFT‐VR (potentials with variable range): Gil‐Villegas, Galindo, Whitehead, Mills, Jackson,

Burgess, J. Chem. Phys., 106, 4168 (1997)

SAFT‐VR is derived from molecular theory and statistical mechanics repulsions and attractions of variable range non‐spherical molecules (e.g. polymers) association (chemical or hydrogen bonding)


Group Contribution (GC) MethodsBasic principles

Molecules are divided into functional (chemical) groups CH3, CH2, OH, NH2, …

Properties predicted as function of group parameters given number of occurrences of each group type

Parameters estimated from large database of experimental data

Can predict properties of compounds for which there are no experimental data, provided group parameters are available

GC models are an important class of predictive methods


SAFT‐molecular model

8

2‐ethyl‐5‐methylphenol

SAFThomonuclear model

SAFT ‐ heteronuclear model

C6H3CH2CH3aCCH3

aCH

Lymperiadis et al., J. Chem. Phys. 127, 234903 (2007)Lymperiadis et al., Fluid Phase Equil. 274, 85 (2008)

aCO

H


SAFT‐molecular model parameterisation

Segment‐segment dispersive interactions described via pair potential with attractive/repulsive interactions

segment diameter kk

segment dispersive energy kk segment dispersive range a,kk r,kk

cross‐interactions may be estimated from experimental data

pure component and/or mixture

computed via combining rules

Effective contribution of each segment to molecular shape shape factor Sk

Site‐site associative interactions energy hb

kkab

cut‐off range rckkab

Variable‐rangesquare‐well potential

Mie potential


gSAFT for oil/gas systemsMethodology

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gSAFT for oil/gas industry

Methodology

1. Identify key systems of interest to oil/gas industry both upstream and downstream

2. Analyse molecules in mixtures to identify complete sets of groups and group‐group interactions that are needed to characterise these systems

3. For each group, identify pure component experimental data sets that can be used to determine like and unlike group parameters typically, saturated liquid density and vapour pressure transferability of SAFT‐ parametersmolecules do not have to be those appearing in the systems of interest

4. For each group‐group interaction, identify pure component/binary mixture experimental data sets that can be used to determine group/group interaction parameters typically saturated liquid density and vapour pressure (for pure components)

and phase envelopes (for binary mixtures) group/group interaction parameters can often be estimated from pure

component data e.g. pure component data for propane parameters for CH3/CH2 interactions


gSAFT for oil/gas industry

Workflow

Defined standardised formats for experimental data sets for pure components & binary mixtures SAFT‐Mie parameter databank

Devised streamlined workflow allowing user to specify group parameters to be estimated select appropriate subset of relevant experimental data initiate parameter estimation

Implemented within MS Excel environment eliminates need for manual data transcription significantly reduces probability of errors


Systems of interest to the oil/gas industryand SAFT‐ constituent groups (partial)

System ID Description SAFT‐ groups

001 Carbon dioxide CO2002 Carbon dioxide + Water CO2; H2O 003a Methane + Carbon dioxide CH4; CO2

003b Methane + Carbon dioxide + Water (Hydrates) CH4; CO2; H2O

004 CO2‐SO2‐N2‐Ar‐O2 CO2; SO2; N2; Ar; O2005 Methane + Water CH4; H2O006 Methane + Methanol CH4; CH3OH007 Methane + Methanol + Water CH4; CH3OH; H2O008 Methanol + n‐Hexane + Water CH3OH; CH3; CH2; H2O009 Methanol + Toluene + Water CH3OH; aCCH3; aCH; H2O010 Methanol + Water (Heat of mixing) CH3OH; H2O

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . .


CH3 CH2 aCH aCCH3 aCCH2 CH4 H2O CH3OH CO2 CH2=C=CH2 C2H6

CH3

CH2

aCH

aCCH3

aCCH2

CH4

H2O

CH3OH

CO2

CH2=C=CH2

C2H6

Groups & group/group interactions

Existing group & group/group interactions in the databank (ingreen)

Most binary group/group interaction parameters were obtained from pure component data


Example of SAFT‐Mie group parameters

kl/kB [K] CH3 CH2

CH3 256.766

CH2 350.772 473.389

Group No. segments S [Å] a r

No. site types

No. sites - type e

No. sites - type H

CH3 1 0.573 4.077 6.000 15.050 0 ---- ----

CH2 1 0.229 4.880 6.000 19.871 0 ---- ----

Parameters obtained by fitting to pure VLE of n‐propane to n‐decane Other unlike parameters (kl, a,kl, r,kl ) are obtained via combining rules Resulting %AAD up to and including critical point:

1.8% in vapour pressure 0.7% in saturated liquid density


gSAFT for oil/gas systemsApplication examples

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Pure component: CO2


kl and r,kl are estimated from mixture data

Binary mixture H2O + CO2

Isotherms:

T=323.2 K (red)T=333.2 K (yellow)T=353.1 K (green)


Binary mixture H2O + CO2

Isotherms:

T=288.15 K (green)

T=293.15 K (yellow)

T=298.15 K (blue)

T=308.15 K (red)

T=313.15 K (black)

CO2 rich phase – low temperatures


Binary mixture CO2 + CH4


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Binary mixtures CO2 + n‐alkanes

kl and r,kl for CO2 + CH3 and CO2 + CH2 are estimated from mixture data

same set of parameters is used for the entire series of CO2 + n‐alkane mixtures CO2 + n‐C3H8

Predicted


Binary mixtures CO2 + n‐alkanes

CO2 + n‐C4H10

CO2 + n‐C10H22


Binary mixtures: C6H6 + n‐C6H14 to n‐C8H18


From binary to ternary mixtures: H2O + n‐C6H14 + CH3OH

n‐C6H14 + H2O at 473.15 K

Predictionat 298.15 K, 0.1 MPa


Concluding remarks

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Concluding remarks

gSAFT technology based on SAFT‐VR EOS includes recent developments such as

third‐order perturbation expansion (improved critical region) Mie potential (improved derivative properties) group contribution formalism (improved predictive capabilities)

allows reliable modelling of phase equilibria and derivative properties

Three‐way collaboration has resulted in group parameters for oil & gas application evidence of the suitability of SAFT‐Mie for modelling the

thermodynamics of many industrially‐relevant mixtures demonstration of the predictive capabilities of SAFT‐Mie

ability to derive group/group interaction parameters from pure component data transferability of group parameters


19th March 2012

L. Avaulléea, C.S. Adjimanb, F. Caladoc, P. Duchet‐Suchauxa, J. Fuentesc, A. Galindob, G. Jacksonb, T. Lafitteb, C.C. Pantelidesb,c*, V. Papaioannoub, T.H. Williamsc

a Total S.A.b Imperial College Londonc Process Systems Enterprise Ltd.

gSAFT: Application of the SAFT‐‐Mie EOS in the oil/gas industryFrom academic research to industrial deployment


Binary mixture CO2 + CH4 (including Peng‐Robinson EoS)


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CO2 + H2O mixture: CO2 rich phase (including CPA)

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Binary mixture: n‐pentane + methanol at 0.14 MPa

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Excess enthalpies for CO2 + C5H12 mixtures

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Claire ADJIMAN

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