thermodynamic model for prediction of phase equilibria of clathrate hydrates in the presence of...

This article was downloaded by: [York University Libraries]On: 11 August 2014, At: 09:25Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House,37-41 Mortimer Street, London W1T 3JH, UK

Chemical Engineering CommunicationsPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/gcec20

Thermodynamic Model for Prediction of PhaseEquilibria of Gas Hydrates in the Presence of Water-Insoluble Organic CompoundsArash Kamran-Pirzaman a b , Amir H. Mohammadi c d & Hassan Pahlavanzadeh aa Chemical Engineering Department , Faculty of Engineering, Tarbiat Modarres University ,Tehran , Iranb Chemical Engineering Department , Mazandaran University of Science and Technology ,Behshahr , Iranc Institut de Recherche en Génie Chimique et Pétrolier (IRGCP) , Paris Cedex , Franced Thermodynamics Research Unit, School of Chemical Engineering, University of KwaZulu-Natal , Durban , South AfricaAccepted author version posted online: 07 Aug 2014.

To cite this article: Arash Kamran-Pirzaman , Amir H. Mohammadi & Hassan Pahlavanzadeh (2014): Thermodynamic Model forPrediction of Phase Equilibria of Gas Hydrates in the Presence of Water-Insoluble Organic Compounds, Chemical EngineeringCommunications, DOI: 10.1080/00986445.2013.878876

To link to this article: http://dx.doi.org/10.1080/00986445.2013.878876

Disclaimer: This is a version of an unedited manuscript that has been accepted for publication. As a serviceto authors and researchers we are providing this version of the accepted manuscript (AM). Copyediting,typesetting, and review of the resulting proof will be undertaken on this manuscript before final publication ofthe Version of Record (VoR). During production and pre-press, errors may be discovered which could affect thecontent, and all legal disclaimers that apply to the journal relate to this version also.

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) containedin the publications on our platform. However, Taylor & Francis, our agents, and our licensors make norepresentations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of theContent. Any opinions and views expressed in this publication are the opinions and views of the authors, andare not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon andshould be independently verified with primary sources of information. Taylor and Francis shall not be liable forany losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoeveror howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use ofthe Content.

This article may be used for research, teaching, and private study purposes. Any substantial or systematicreproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in anyform to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/terms-and-conditions

http://www.tandfonline.com/loi/gcec20

http://www.tandfonline.com/action/showCitFormats?doi=10.1080/00986445.2013.878876

http://dx.doi.org/10.1080/00986445.2013.878876

http://www.tandfonline.com/page/terms-and-conditions

http://www.tandfonline.com/page/terms-and-conditions

ACCEPTED MANUSCRIPT

ACCEPTED MANUSCRIPT 1

Thermodynamic Model for Prediction of Phase Equilibria of Gas Hydrates in the Presence of Water-Insoluble Organic Compounds

Arash Kamran-Pirzaman1,2, Amir H. Mohammadi3,4, Hassan Pahlavanzadeh1

1Chemical Engineering Department, Faculty of Engineering, Tarbiat Modarres

University, Tehran, Iran 2Chemical Engineering Department, Mazandaran University of Science and Technology, Behshahr, Iran 3Institut de Recherche en Génie Chimique et Pétrolier (IRGCP), Paris Cedex, France 4Thermodynamics Research Unit, School of

Chemical Engineering, University of KwaZulu-Natal, Durban, South Africa

Corresponding authors E-mail: [email protected]; [email protected].

Abstract

A thermodynamic model for the prediction of pressure – temperature phase diagrams of

structures II and H clathrate hydrates of methane, carbon dioxide, or hydrogen sulfide in

the presence of "water-insoluble" organic componds is presented. The model is based on

the equality of water fugacity in the aqueous and hydrate phases. The solid solution

theory of van der Waals – Platteeuw (vdW-P) is used for calculation of the fugacity of

water in the hydrate phase. Peng-Robinson (PR) equation of state (EoS) is employed to

calculate the fugacity of the components in the gas phase. It is assumed that the gas phase

is water and promoter free and the organic compounds do not have considerable effects

on water activity in liquid phase. The results of this model are compared to existing

experimental data from the literature. Acceptable agreement is found between the model

predictions and the investigated experimental data.

KEYWORDS: Gas hydrate, Thermodynamic model, van der Waals – Platteeuw theory,

Water-Insoluble Organic Compounds, Phase equilibria

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


1. INTRODUCTION

Gas hydrates (Clathrate hydrates) are inclusion compounds, which are composed of water

and guest species (Sloan and Koh, 2008). Gas hydrates are stabilized by the guest

molecules enclathrated in the hydrogen-bonded water cages. At relatively high pressures

and low temperatures, water molecules form various crystalline structures generally

depending on the size and shape of the guest molecule(s) (Sloan and Koh, 2008).Three

common structures, I (sI), II (sII), and H (sH) are known to form, as a function of the

size and shape of the guest molecules (Sloan and Koh, 2008).sI and sII contain two types

of cavities (small and large) while sH contains three types of cavities (small, medium,

and large) (Sloan and Koh, 2008).

Recently, novel technologies (Sloan and Koh, 2008) utilizing gas hydrates have been

proposed. These clathrate structures may be used as media for the storage and

transportation of natural gas and hydrogen (Sloan and Koh, 2008; Eslamimanesh et al.

2012; Kamran-Pirzaman et al. 2012). Therefore, various experimental and theoretical

studies have been carried out determine the phase equilibrium of corresponding systems

and the capacity of gas storage in hydrate structures.

Mooijer-van den Heuvel et al. (Mooijer-van den Heuvel et al. 2000) studied the

formation of sII gas hydrates of cyclic organic compounds like tetrahydropyran (THP)

and cyclobutanone (CB). Østergaard et al. (Østergaard et al. 2001) investigated the

effects of cyclopentane, cyclohexane, neopentane, isopentane, methylcyclopentane, and

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


methylcyclohexane at various concentrations on the phase behavior of methane clathrate

hydrates. Østergaard et al. (Østergaard et al. 2001) was found that sII clathrate hydrate is

more stable structure for the aforementioned systems. Østergaard et al. (Østergaard et al.

2001) also found that these heavy hydrocarbons can have significant effects on the gas

hydrate phase boundary of petroleum systems at high concentrations. Sun and coworkers

(Sun et al. 2002) reported four-phase liquid water (L) + hydrate (H) + liquid hydrocarbon

(LH) + vapor (V) equilibrium data for sII hydrates of methane + cyclohexane or

cyclopentane systems. It was concluded that the hydrate dissociation pressure of the

methane + cyclohexane or cyclopentane systems are lower than that of the system

containing clathrate hydrate of pure methane at a given temperature.

Three sets of experimental data for the methane + cyclohexane, nitrogen +

cyclohexane, and methane + nitrogen + cyclohexane over wide ranges of temperatures

have been reported by Tohidi et al. (Tohidi et al. 2002) .The solid solution theory of van

der waals and Platteeuw (van der waals and Platteeuw et al.1959), as implemented by

Parrrish and Prausnitz (Parrish and Prausnitz, 1972), was applied by Tohidi et al. (Tohidi

et al. 2002) for thermodynamic modeling of the aforementioned systems. Tohidi and

coworkers (Tohidi et al.1997) reported the hydrate dissociation data for the nitrogen

and/or methane + cyclopentane/neopentane systmes. The subsequent results showed that

both of the mentioned heavy hydrocarbons are strong hydrate promoters. Mohammadi

and Richon (Mohammadi and Richon, 2009) reported experimental dissociation data for

clathrate hydrates of the carbon dioxide + methyl cyclopentane, methyl cyclohexane,

cyclopentane, or cyclohexane.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


The effective of addaitives on the phase behaviors of sH clathrate hydrate of 1,1-

dimethylcyclohexane and 2,2-dimethylpentane stabilized by methane molecules have

been studied by Hara et al. (Hara et al. 2005)and Kozaki et al. (Kozaki et al. 2008) for

natural gas transportation technology. Kang et al. (Kang et al.1999) measured the four

phase (sH hydrate + water-rich liquid + hydrocarbon-rich liquid + vapor) equilibrium.

They also provided a thermodynamic model for representation/prediction of the obtained

data.

However, the model proposed by Mehta and Sloan (Mehta and Sloan, 1994,1996)

is among the most widely-used thermodynamic models for calculation/estimation of the

phase equilibrium of the aforementioned systems. Recently, Eslamimanesh et al

(Eslamimanesh et al. 2011) have presented two different approaches on the basis of the

group contribution model and Quantitative Structure Property Relationship (QSPR) to

determine the phase behavior of the systems containing water-insoluble hydrocarbon

promoters clathrate hydrates.

A concise literature survey indicates that almost all of the literature available models for

calculation/estimation of the hydrate dissociation conditions of the systems including

water-insoluble heavy hydrocarbons (except the two latter ones (Eslamimanesh et al.

2011)) have been developed using the Holder model (Holder et al. 1980) as a basis of

their theory. Therefore, the reference parameters for sII or sH clathrate hydrates are

required for this purpose. Moreover, they have been generally developed for the systems

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


containing methane as the help gas. In the present work, we develop a thermodynamic

model, based on our previous study (Kamran-Pirzaman et al. 2012), for

representation/prediction of clathrate hydrate (sII or sH) dissociation pressure for the

methane, carbon dioxide, or hydrogen sulfide + water-insoluble heavy hydrocarbon

systems.

2. THERMODYNAMIC MODEL

2.1. Developing The Equations

The equality of fugacity of water in liquid phase to that in hydrate phase at

equilibrium has been used as equilibrium criteria for phase equilibrium calculations as

follows (Kamran-Pirzaman et al. 2012):

L HW Wf f= (1)

where f is fugacity, subscript W refers to water and superscripts L and H refer to liquid

water phase and hydrate phase, respectively. The fugacity of water in the hydrate phase is

related to the chemical potential difference of water in the filled and empty hydrate lattice

( )MT LWµ

−∆ using the following expression (Kamran-Pirzaman et al. 2012; Klauda and

Sandler,2000; Anderson and Prausnitz,1986; Mohammadi and Richon,2008;

Eslamimanesh et al.2011):

expMT H

H MT WW Wf f

RTµ − −∆

=

(2)

In Eq. 2, the superscript MT represents the empty hydrate, R and T are universal

gas constant and temperature, respectively. The fugacity of the hypothetical empty

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


hydrate lattice, MTWf , is given by the following equation (Kamran-Pirzaman et al. 2012;

Klauda and Sandler, 2000; Anderson and Prausnitz, 1986; Mohammadi and Richon,

2008; Eslamimanesh et al. 2011):

expMT

W

P MTMT MT MT W

W W WP

dPf PRT

υϕ −

=

∫ (3)

where P stands for pressure, φ and v are fugacity coefficient and molar volume,

respectively, MTWP is the vapor pressure of water in empty hydrate lattice. The fugacity

coefficient of water in empty hydrate, MTWϕ , is taken as unity due to low vapor pressure

of water. The partial molar volume of water in the empty hydrate lattice, MTWv in the

Poynting correction term of the preceding equation is assumed to be pressure

independent. Therefore, Eq. 3 can be re-written in the following from (Kamran-Pirzaman

et al. 2012; Klauda and Sandler, 2000; Anderson and Prausnitz,1986; Mohammadi and

Richon,2008; Eslamimanesh et al.2011):

( )expMT MT

MT MT W WW W

v P Pf PRT

−=

(4)

In Eq. 2, MT LWµ

−∆ is calculated using the van der Waals and Platteeuw model (Sloan and

Koh,2008 ; van der Waals and Platteeuw, 1959; Holder et al.1980; Klauda and. Sandler,

2000; Anderson and Prausnitz, 1986; Mohammadi and Richon, 2008):

ln (1 )H MT

W Wi ki

i k

v YRT

µ µ− = − ∑ ∑ (5)

where νi is the number of cages of type i per water molecules in a unit hydrate cell. Yki

(the fractional occupancy of the hydrate cavity i by guest molecule of type k) is expressed

using the following equation (Sloan and Koh, 2008; van der Waals and Platteeuw, 1959;

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Holder et al. 1980; Klauda and. Sandler, 2000; Anderson and Prausnitz,1986;

Mohammadi and Richon, 2008):

1ki k

kik ki k

C fYC f

=+∑

(6)

where fk is the fugacity of the hydrate former and Cki stands for Langmuir constant.

Substituting Eq. 6 in Eq. 5 results in (Sloan and Koh,2008 ; van der Waals and

Platteeuw, 1959 ; Holder et al.1980 ; Klauda and. Sandler, 2000 ; . Anderson and

Prausnitz,1986 ; Mohammadi and Richon, 2008 ; Eslamimanesh et al.2011):

ln (1 ) ln (1 )H MT

viW Wi ki k ki i

i k j

v C f C fRT

µ µ −− =− + = + ∑ ∑ ∑ (7)

It is assumed that, small and medium cavities are occupied by gases and large cavities are

occupied by the heavy hydrocarbon hydrate formers .Consequently, Eq. 7 can be re-

written as follows for sII clathrate hydrate:

argargln[(1 ) (1 ) ]l esmall

H MTvvV LW W

small g l e ocC f C fRT

µ µ −−−= + + (8)

and for sH clathrate hydrate:

argargln[(1 ) (1 ) (1 ) ]l esmall medium

H MTvv vv V LW W

small HC medium HC l e ocC f C f C fT

µ µ −− −−= + + + (9)

where the superscripts V and L represent gas and liquid phases, g and oc stand for gas and

organic components (heavy hydrocarbon hydrate former), respectively.

In eq.1, the fugacity of water in the aqueous phase ( )LWf can be calculated using

the following equation:

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


,, (exp ( )

L sat LL L sat L W W

W W W Wv P Pf x P

RTγ −

= (10)

where LWx , Wγ , sat

WP and LWv represent mole fraction of water in the aqueous phase,

activity coefficient of water, water vapor pressure, and molar volume of liquid water,

respectively. Activity coefficient of water is assumed to be unity because of the slight

solubility of promoters and help gas in water. Furthermore, LWx can be obtained using the

following equation:

1L LW gx x= − (11)

To calculate solubility of methane in the aqueous phase ( Lgx ), the Krichevsky-

Kasarnovsky equation can be applied (Krichevsky and Kasarnovsky, 1935):

exp ( ( ))

VgL

gg sat

g W W

fx

vH P P

RT

∞

−

=−

(12)

where g WH − is Henry’s constant of gases in water, and the superscript ∞ represents

infinite dilution condition. By substituting the above equations in Eq.1, the following

expression is finally obtained:

For clathrate hydrate sII:

argarg

( )expln[(1 ) (1 ) ] 1 0

( )exp ( )

l esmall

MT MTMT W W

WvvV L

small g l e ocL satL sat W WW W

v P PPRT

C f C fv P Px P

RT

−−

− × + + − =

− (13)

For clathrate hydrate sH:

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


argarg

( )expln[(1 ) (1 ) ] 1 0

( )exp ( )

l esmall

MT MTMT W W

WvvV L

small g l e ocL satL sat W WW W

v P PPRT

C f C fv P Px P

RT

−−

− × + + − =

− (14)

The hydrate dissociation pressure (P) at a given temperature (T) is obtained by solving

the latter equations.

2.2. Model Parameters

The values of the Langmuir constants are calculated using the following expression

(Munck et al.1988):

exp ( )ij ijij

a bC

T T= (15)

The parameters (aij and bij) are reported in Table 1.

Because of the orders of magnitude of small and medium cavities sizes, their Langmuir

constants parameter values in Eq. 15 have been assumed to be equal. In addition, the

optimal values of the corresponding parameters for large cavities of sII clathrate hydrate

and those of the small and medium cavities of sH have been obtained using tuning the

existing phase equilibrium experimental data. The following equation is applied for

calculation of the Langmuir constants for large cavities in sH clathrate hydrate (Madsen

et al.2000):

1 1exp ( ( ))273.15

ijij ij

aC b

T T= − (16)

where the optimized parameters a and b have been reported in Table 2.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


The saturated vapor pressure of water in empty hydrate ( MTWP ) is calculated using the

method of Dharmawardhana et al. (Dharmawardhana et al.1980) for structures I and II as

following:

[ ] 0.1exp (17.44 6003.9 / )MTWP sI T= − (17)

[ ] 0.1exp (17.332 6017.6 / )MTWP sII T= − (18)

Additionally, the following equation is obtained for calculation of MT

WP of structure H

clathrate hydrate through adjusting of the parameters against the corresponding phase

equilibrium data:

[ ] 0.1exp (18.401 6284.32 / )MTWP sH T= − (19)

Where the units of MTWP and T are, respectively, MPa and K. MT

Wv for structures I and II

are obtained using the following expressions (Klauda and Sandler,2000) :

25 6 2

9 12 2

10[ ] (11.835 2.217 10 2.242 10 )

8.006 10 5.448 10

MT AW MT

W

NsI T TN

P P

υ−

− −

− −

= + × + ×

− × + ×

(20)

4 6 2 9 3

309 12 2

[ ] (17.13 2.249 10 2.0.13 10 1.009 10 )

10 8.006 10 5.448 10

MTW

AMT

W

sII T T T

N P PN

υ − − −

−− −

= + × + × + ×

× − × + × (21)

and it is calculated using the following equation for structure H (Ballard and Sloan,2002):

4

7 2 7

[ ] (24.2126exp (3.5749 10 ( 273.15)

6.29439 10 ( 273.15) 3 10 ( 0))

MTWv sH T

T P

−

− −

= × −

+ × − − × − (22)

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


where NA is Avogadro's number and MTWN stands for the number of water molecules per

hydrate cell. In the proceeding equations, the units of the pressure and temperature are

MPa and K respectively. The following equations are applied to evaluate the molar

volume of the help gas at infinite dilution (Saul and Wagner, 1987) :

, ,

, ,

0.095 2.35c i c i

c i c i

P v TPRt CT

∞ = +

(23)

ww wsat

w

UC U H RTυ∆

= ∆ =∆ − (24)

2/7(0.2905 0.08775 )1 (1 )sat cW r

c

RTv TP

ω= − + − (25)

Moreover, the quantities that are applied to evaluate the number of cages of type i

per water molecule in a unit hydrate cell have been reported in Table 3 (Sloan and

Koh,2008) :

Fugacity of gases in the gas phase is calculated using the Peng-Robinson equation of state

(PR-EoS) (Peng and Robinson,1976). Due to the low concentrations of water and hydrate

promoters in the gas phase, it is assumed that the it consists of pure gases (help gases)

(Jager et al. 1999; Deugd et al.2001). Table 4 summarizes the parameters required in this

model.

3. RESULTS AND DISCUSSION

The representations/predictions of the hydrate dissociation conditions of methane + heavy

hydrocarbon hydrate former systems including cyclohexane (CH), cyclopentane (CP),

cyclobutane (CB), or tetrahydropyran (THP) are shown in Figures 1 to 4 respectively.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Acceptable agreement between the model results and existing experimental phase

equilibrium data is observed. It can be seen that the aforementioned heavy hydrate

formers contribute to the promotion effects that can change hydrate dissociation pressure

values to the lower pressures and the temperature values to the higher temperatures. In

other words, these promoters shift the phase boundary of the investigated systems to the

right. For a comparison purpose between the promotion effects of the studied heavy

hydrocarbon hydrate formers, the corresponding phase behavior calculations along with

the experimental data have been shown in Figure 5. It is found out that the promotion

effects can be expressed in the following order: CP > THP > CB > CH.

The determined hydrate dissociation conditions for the carbon dioxide + (CH, CP,

CB, or THP) systems are shown in Figure 6 along with the selected experimental data

from the literature. Reasonable deviations between results of the model and the

experimental data are observed. In addition, it is interpreted that these hydrate promoters

show the same promotion effects priority with respect to the related phase equilibria of

methane hydrates (Figure 5). However, cyclohexane exhibits negligible effects on

clathrate hydrate phase behavior of the systems containing CO2 compared to the other

hydrate promoters. It is also assumed that the later systems form clathrate hydrates of

structure II. Moreover, there is an intercross the CO2 between hydrate dissociation

conditions curve and CO2+CH hydrate dissociation conditions curve indicating that CH

shows inhibition effect rather than promotion effect after the intersection point (Mooijer-

van den Heuvel et al.2000).

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Figure 7 reports the capability of the proposed model to calculate/estimate hydrate

dissociation conditions for methane + methylcyclohexane (MCH), methylcyclopentane

(MCP), cycloheptane (CHP), dimethylcyclohexane (DMCH), neohexane (NH) or

cuclooctane (CO) systems. The highest promotions effects are detected for DMCH, NH,

MCH, CHP, CO and MCP, respectively. Negligible promotion effects of MCH, CHP, or

CO on the hydrate dissociation conditions of carbon dioxide are shown in Figure 8. These

low effects can also be identified using the developed thermodynamic model. The

calculated/estimated hydrate dissociation conditions for H2S + MCH or NH systems are

shown in Figure 9 and compared to the existing experimental values. As can be seen, the

model results coincide well with the investigated experimental phase equilibrium data.

Beside the acceptable accuracy of the presented thermodynamic model to

represent/predict the phase behaviors of the studied systems, it should be mentioned that

there is no need to use the clathrate hydrates reference parameters as it has been applied

in the previous models (Mehta and Sloan,1996 ; Chen et al.2003).In addition, the

calculation procedure of the developed model is generally easy and straight-forward.

4. CONCLUSION

In this work, we proposed a thermodynamic model for representing/predicting hydrate

phase boundaries of methane, carbon dioxide, or hydrogen sulfide systems in the

presence of heavy hydrocarbon hydrate formers. The effects of CH, CB, CP, THP, MCH,

MCP, CHP, DMCH, NH or CO on the corresponding phase behaviors were investigated

to present a comprehensive study. The solid solution theory of vdW-P (van der Waals

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


and Platteeuw, 1959) was applied for modeling of the hydrate phase while the PR-EoS

(Peng and Robinson,1976) was used to determine the fugacity of hydrate formers in the

gas and liquid phase.

Acceptable agreement between results of the model and the existing experimental

hydrate dissociation data from the literature demonstrates the reliability and accuracy of

the model. It was also found that CH (which form stucture II) and all of structure H

hydrate formers show slight effects on the phase behavior of clathrate hydrate of CO2.

The advantages of the model compared to the available models in the literature can be

stated as: no requirement of the clathrate hydrates reference parameters; straightforward

calculation algorithm; extension to CO2 and H2S containing systems.

REFERENCES

Anderson, F. E., Prausnitz, J. M. (1986). Inhibition of Gas Hydrates by Methanol, AIChE

J., 32, 1321.

Ballard, A. L., Sloan, E. D. (2002).The next generation of hydrate prediction I. Hydrate

standard states and incorporation of spectroscopy .Fluid Phase Equilib. 194–197, 371

(Also: Adam L. Ballard “A non-ideal hydrate solid solution model for a multi-phase

equilibria program”. PhD thesis, Colorado School of Mines, USA, 2002).

BASF Corporation Chemicals Division 3000 Continental Drive–North Mount Olive, NJ

07828-1234 www.basf.com.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Chapoy, A., Mohammadi, A. H., Valtz, A., Coquelet, C., Richon, D. (2008). Water and

Inhibitor Distribution in Gas Production Systems. GPA Research Project 987, RR-198;

Tulsa, OK.

Chase, M. W., NIST-JANAF Thermochemical Tables, 4th ed. J. Phys. Chem. Ref. Data

Monograph No. 9, 1998.

Chen, G. J., Sun, C.Y., Guo, T.M.(2003).Modelling of The Formation Conditions of

Structure-H Hydrates . Fluid Phase Equilib. 204, 107.

Chen, Z.-Y., Li, Q.-P., Yan, Z.-Y., Yan, K.-F., Zeng, Z.-Y., Li, X.-S. (2010).Phase

equilibrium and dissociation enthalpies for cyclopentane + methane hydrates in NaCl

aqueous solutions .J. Chem. Eng. Data.55, 4444.

de Deugd, R. M., Jager, M. D., de Swaan Arons, J. (2001). Mixed hydrates of methane

and water-soluble hydrocarbons modeling of empirical results . AIChE J. 47,693.

Dharmawardhana, P. B., Parrish, W.R., Sloan, E.D. (1980).Experimental thermodynamic

parameters for the prediction of natural gas hydrate dissociation conditions. Ind. Eng.

Chem. Fundam. 19 ,410.

Eslamimanesh, A., Mohammadi, A. H., Richon, D., Naidoo, P., D. Ramjugernath, D.

(2012) .Application of gas hydrate formation in separation processes: A review of

experimental studies . J. Chem. Thermodyn.46, 62.

Eslamimanesh, A., Gharagheizi, F., Mohammadi, A.H., Richon, D.(2011). Phase

equilibria of semiclathrate hydrates of CO2, N2, CH4, or H2 +Tetra-n-butylammonium

Bromide Aqueous Solution. J. Chem. Eng. Data .56, 3775.

Eslamimanesh, A., F. Gharagheizi, F., Mohammadi, A.H., Richon, D., Illbeigi, M.,

Fazlali, A., Forghani, A. A., Yazdizadeh, M.(2011). Phase equilibrium modeling of

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


structure H clathrate hydrates of methane + water "insoluble" hydrocarbon promoter

using group contribution-support vector machine technique., Ind. Eng. Chem. Res. 50,

12807.

Eslamimanesh, A., Mohammadi, A. H., Richon, D.(2011). Thermodynamic consistency

test for experimental data of water content of methane . AIChE J. 57, 2566.

Hara, T., Hashimoto, S., Sugahara, T., Ohgaki, K.(2005).Large Pressure Depression of

Methane Hydrate by Adding 1,1-Dimethylcyclohexane. Chem. Eng. Sci. 60, 3117.

Holder, G. D., Corbin, G., Papadopoulos, K. D.(1980). Hydrate dissociation pressures of

(methane+ethane+water). Existence of a locus of minimum pressures. Ind. Eng. Chem.

Fundam. 19, 282.

Jager, M.D., de Deugd, R.M., Peters, C. J., de Swaan Arons, J., Sloan, E.D. (1999).

Experimental determination and modeling of structure II hydrates in mixtures of

methane+water+1,4-dioxane . Fluid Phase Equilib. 165, 209.

Kamran-Pirzaman, A., Pahlavanzadeh, H., Mohammadi, A.H., (2012) . Thermodynamic

modeling of pressure–temperature phase diagrams of binary clathrate hydrates of

methane, carbon dioxide or nitrogen + tetrahydrofuran, 1,4-dioxane or acetone Fluid

Phase Equilib. 320 ,32.

Kang, S.P., Seo, T., Lee, H.(1999). SH hydrate equilibria of (methane + water +2-

methylbutane + magnesium chloride), (methane+ water + 2,2-dimethylbutane +

magnesium chloride), and (methane + water +methylcyclohexane + magnesium chloride)

. J. Chem. Thermodyn. 31, 763.

Klauda, J.B., Sandler, S.I. (2000). A fugacity model for gas hydrate phase equilibria. Ind.

Eng. Chem. Res. 39, 3377.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Kozaki, T., Takeya, S., Ohmura, R. (2008). Phase Equilibrium and Crystallographic

Structures of Clathrate Hydrates Formed in Methane + 2,2-Dimethylpentane + Water

System . J. Chem. Eng. Data. 53, 2820.

Krichevsky, I. R., Kasarnovsky, J. S.(1935). Thermodynamical calculations of

solubilities of nitrogen and hydrogen in water at high pressures. J. Am. Chem. Soc. 57,

2168.

Madsen, J., Pedersen, K. S., Michelsen, M. L. (2000).Modeling of structure H hydrates

using a Langmuir adsorption model. Ind. Eng. Chem. Res. 39, 1111.

Mao, W. L., Mao, H. ( 2004 ). Hydrogen storage in molecular compounds. Proc. Natl.

Acad. Sci. U.S.A. 101, 708.

Makino, T., Nakamura, T., Sugahara, T., Ohgaki, K.(2004).Thermodynamic stability of

structure-H hydrates of methylcyclopentane and cyclooctane helped by methane. Fluid

Phase Equilib. 218, 235.

Mehta, A. P., Sloan, E. D. (1994).A Thermodynamic Model for Structure – H Hydrates.

AIChE J. 40, 312.

Mehta, A. P., Sloan, E.D. (1996). Improved thermodynamic parameters for prediction of

structure H hydrate equilibria . AIChE J. 42, 2036.

Mehta, A. P., Sloan, E. D.(1994). Structure H hydrate phase equilibria of

paraffins,naphthene, olefins with methane. J. Chem. Eng. Data. 39,887.

Mohammadi, A. H., Richon, D.(2010).Clathrate hydrate dissociation conditions for the

methane + cycloheptane/ cyclooctane + water and carbon dioxide +

cycloheptane/cyclooctane + water systems . Chem. Eng. Sci. 65,3356.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Mohammadi, A. H., Richon, D.(2011). Equilibrium Data of Neohexane + Hydrogen

Sulfide and Neohexane + Methane Clathrate Hydrates. J. Chem. Eng. Data.56, 5094.

Mohammadi, A. H., Richon, D.(2011).Phase equilibria of binary clathrate hydrates of

nitrogen + cyclopentane/cyclohexane/methylcyclohexane and ethane +

cyclopentane/cyclohexane/ methyl cyclohexane. Chem. Eng. Sci. 66, 4936.

Mohammadi, A. H., Richon, D.(2011).Equilibrium data of (tetrahydropyran +hydrogen

sulphide) and (tetrahydropyran + methane) clathrate hydrates .J. Chem. Thermodyn.

2012, Article in press, DOI: 10.1016/j.jct.2011.12.038.

Mohammadi, A. H., Richon, D.(2009).Phase equilibria of hydrates of methyl

cyclopentane, methyl cyclohexane, cyclopentane or cyclohexane+carbon dioxide ",

Chem. Eng. Sci. 64, 5319.

Mohammadi, A.H., Richon, D.(2008).Thermodynamic model for predicting liquid water-

hydrate equilibrium of the water-hydrocarbon system. Ind. Eng. Chem. Res. 47, 1346.

Mohammadi, A. H., Anderson, R., Tohidi, B.(2005).Carbon monoxide clathrate hydrates:

equilibrium data and thermodynamic modeling . AIChE J. 51, 2825.

Mooijer-van den Heuvel, M. M., R. Witteman, R., Peters, C. J. (2001). Phase behaviour

of gas hydrates of carbon dioxide in the presence of tetrahydropyran, cyclobutanone,

cyclohexane and methylcyclohexane .Fluid Phase Equilib. 182, 97.

Mooijer-van den Heuvel, M.M., Peters, C.J., de Swaan Arons, J. (2000). Influence of

water-insoluble organic components on the gas hydrate equilibrium conditions of

methane. Fluid Phase Equilib.172, 73.

Munck, J., Skjold-Jørgensen, S., Rasmussen, P. (1988).Computations of the Formation of

Gas Hydrates. Chem. Eng. Sci. 43, 2661.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Østergaard, K. K., Tohidi, B., Burgass, R. W., Danesh, A., Todd, A.C. (2001).Hydrate

Equilibrium Data of Multicomponent Systems in the Presence of Structure-II and

Structure-H Heavy Hydrate Formers. J. Chem. Eng. Data.46, 703.

Parrish, W. R., Prausnitz, J. M. (1972). Pressures of gas hydrates formed by gas

mixtures. Ind. Eng. Chem. Process Des. Develop.11, 26.

Peng, D.Y., Robinson, D.B. (1976).A New Two-Constant Equation of State. Ind. Eng.

Chem. Fundam. 15 ,59.

Saul, A., Wagner, W.(1987).International equation for the saturation properties of

ordinary water substance . Phys. Chem. Ref. Data. 4, 893.

Sun, Z.G., Fan, S.S., Guo, K.H., Shi, L., Guo, Y.K., Wang, R.Z. (2002). Hydrate Phase

Equilibrium Data of Cyclohexane and Cyclopentane .,J. Chem. Eng. Data. 47 ,313.

Sloan, E.D., Koh, C.A. ( 2008). Clathrate Hydrates of Natural Gases, Third Edition,

CRC Press, Taylor & Francis Group, Boca Raton.

Tohidi, B., Danesh, A., Burgass, R. W., Todd, A. C. (1996). Equilibrium Data and

Thermodynamic Modeling of Cyclohexane Gas Hydrates. Chem. Eng. Sci. 51, 159.

Tohidi, B., Danesh, A., Todd, A.C., Burgass, R.W., Østergaard, K. K. (1997).Equilibrium

data and thermodynamic modelling of cyclopentane and neopentane hydrates . Fluid

Phase Equilib. 138, 241.

Tohidi, B., Danesh, A., Burgass, R. W., Todd, A. C. (1996). Hydrate Equilibrium Data

and Thermodynamic Modelling of Methylcyclopentane and Methylcyclohexane.

Presented at 2nd Int. Conf. on Gas Hydrates, 2-6 June, Toulouse, France, 109-115.

van der Waals, J. H., Platteeuw, J.C. (1959).Clathrate solutions .Adv. Chem. Phys.2, 1.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Table 1. The values of aij and bij parameters in Eq. 15 for gases and organic compounds,

which form clathrate hydrate structure II (Munck, 1998).

Hydrate former Small cavity Large cavity

aij (×103 K.bar-1) bij(K) aij (×103K.bar-1) bij (K)

CH4 0.2207 3453 0 0

CO2 0.0845 3615 0 0

CH* 0 0 0.3403 6045

CB* 0 0 1.2397 6440

CP* 0 0 2.1559 5950

THP* 0 0 1.9073 6200

* Adjusted values.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Table 2. The values of aij and bij parameters in Eq. 15 and 16 for gases and organic

compounds, which form clathrate hydrate structure H (Madsen et al., 2000).

Hydrate former Small and medium cavities Large cavity

aij (K.bar-1) bij(K) aij (K.bar-1) bij (K)

CH4 * 0.1619 1568.6076 0 0

CO2* 0.09565 1730.34 0 0

H2S* 0.01505 3128.8239 0 0

MCH 0 0 9681 3604

2,3-DMB 0 0 940 3608

MCP 0 0 1584 4024

CHP 0 0 41840 5050

1,1-DMCH 0 0 74330 4089

NH 0 0 1794 3175

CO 0 0 61010 4135

* Adjusted values.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Table 3. The quantities that are applied to evaluate the number of cages of type i per

water molecule in a unit hydrate cell

Hydrate Crystal Structure

Cavity

І II H

Small Large Small Large Small Medium Large

Number of cavities/unit cell 2 6 16 8 2 3 1

Coordination number 20 24 20 28 20 20 36

Number of waters/Unit cell 46 136 34

number of cages of type i per

water molecule in a unit cell

1/23 3/23 2/17 1/17 2/34 3/34 1/34

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Table 4. The required parameters of the developed model.

Para

mete

r

Expression Unit

s

Ref.*

LWv )15.273(105.29241.10 4 −×+− − T

74 101325.0(10559.1)101325.0(10532.3 −×+−×− −− PP

cm3

/mo

l

and

MP

a, K

NIST-

JANAF

,1998

Chapoy

et al.

2008

satWP )0161277.0)ln(1539.49332.55006537.7exp(10 6 TT

T×−+−− MP

a, K

Kluda

,sandler

, 2000

www.b

asf.com

WH∆

RT ×−×+ )1277.161539.49332.5500( K Saul,

Wagner

, 1987

WCHH −4

10(1.0 018616.0log2952.52/3.5768788.147 TT ++−×

MP

a, K

Chapoy

et al.

2008

WCOH −2

0011.0)ln(6712.21426.8742868.159exp( T

T×−×−−

MP

a, K

Kluda

,sandler

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


, 2000

WSHH −2

00129.0)ln(2327.20328.82275510.149exp( T

T−×−−

MP

a,K

Kluda

,sandler

, 2000

* References of the equations.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Figure 1. Experimental and represented/predicted dissociation conditions of the CH4

clathrate hydrates in the absence/presence of CH heavy hydrocarbon hydrate former.

Symbols represent experimental data: ∆,pure CH4 clathrate hydrate, Sloan and Koh

(2008) AAD%=1.94; ○, pure CH4 clathrate hydrate, Sloan and Koh (2008) AAD%=2.83;

■, pure CH4 clathrate hydrate, Mohammadi and Richon et al.(2005) AAD%=3.82; ▲,

CH4+CH clathrate hydrate ,sun et al. (2002) AAD%=5.38; ♦, CH4+CH clathrate hydrate

,Mohammadi and Richon (2009) AAD%=6.43; ●, CH4+CH clathrate hydrate, Mooijer-

van den Heuvel (2000) AAD%=7.02; solid lines,_______ model predictions; AAD% is

average absolute deviation between experimental data and our model prediction

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Figure 2. Experimental and represented/predicted dissociation conditions of CH4 clathrate

hydrates in the absence/presence of CP heavy hydrocarbon hydrate former. Symbols

represent experimental data: ∆,pure CH4 clathrate hydrate, Sloan and Koh (2008)

AAD%=1.94; ○, pure CH4 clathrate hydrate, Sloan and Koh (2008) AAD%=2.83; ■, pure

CH4 clathrate hydrate, Mohammadi and Richon et al.(2005) AAD%=3.82;▲, CH4+CP

clathrate hydrate ,Chen et al. (2010) AAD%=8.06; □, CH4+CP clathrate hydrate,

Mohammadi and Richon (2009) AAD%=2.42; ●,CH4+CP clathrate hydrate ,Sun et al.

(2010) AAD%=4.35;solid lines,______ model predictions. AAD% is average absolute

deviation between experimental data and our model prediction

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT



hydrates in the absence/presence of CB heavy hydrocarbon hydrate former. Symbols



CH4 clathrate hydrate, Mohammadi and Richon et al.(2005) AAD%=3.82; ●, CH4+CB

clathrate hydrate, Mooijer-van den Heuvel (2000) AAD%=5.82;solid lines,_____ model

predictions. AAD% is average absolute deviation between experimental data and our

model prediction

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT



hydrates in the absence/presence of THP heavy hydrocarbon hydrate former. Symbols



CH4 clathrate hydrate, Mohammadi and Richon et al.(2005) AAD%=3.82;♦ CH4+THP

clathrate hydrate, Mooijer-van den Heuvel (2000) AAD%=5.01; +,CH4+THP clathrate

hydrate, Mohammadi and Richon et al.(2012) AAD%=4.30;solid lines, _____model


model prediction

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT



hydrates in the absence/presence of CH, CB, CP or THP heavy hydrocarbon hydrate

formers. Symbols represent experimental data: ∆,pure CH4 clathrate hydrate, Sloan and

Koh (2008) AAD%=1.94; ○, pure CH4 clathrate hydrate, Sloan and Koh (2008)

AAD%=2.83; ■, pure CH4 clathrate hydrate, Mohammadi and Richon et al.(2005)

AAD%=3.82;▲, CH4+CH clathrate hydrate ,sun et al. (2002); ♦, CH4+CH clathrate

hydrate ,Mohammadi and Richon (2009); ●, CH4+CH clathrate hydrate, Mooijer-van den

Heuvel (2000); ◊, CH4+CP clathrate hydrate, Mohammadi and Richon (2009); +,CH4+CP

clathrate hydrate ,Chen et al. (2010); х,CH4+THP clathrate hydrate, Mooijer-van den

Heuvel (2000); □,CH4+THP clathrate hydrate, Mohammadi and Richon (2012); solid

lines,_____ model predictions. AAD% is average absolute deviation between

experimental data and our model prediction. all of AAD reported in last figures.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Figure 6. Experimental and represented/predicted dissociation conditions of CO2 clathrate

hydrates in the absence/presence of CH, CB, CP or THP heavy hydrocarbon hydrate

formers. Symbols represent experimental data ; ∆,pure CO2 clathrate hydrate, Sloan

and Koh (2008) AAD%=6.3; ○, pure CO2 clathrate hydrate, Sloan and Koh (2008)

AAD%=4.1; ■, pure CO2 clathrate hydrate, Sloan and Koh (2008) AAD%=5.8;

♦,CO2+CH clathrate hydrate, Mohammadi and Richon (2009) AAD%=14.8;●, CO2+CH

clathrate hydrate, Mooijer-van den Heuvel (2001) AAD%=11.7; ▲, CO2+CB clathrate

hydrate, Mooijer-van den Heuvel (2000) AAD%=5.55; □, CO2+CP clathrate hydrate,

Mohammadi and Richon (2009) AAD%=5.93;◊, CO2+THP, clathrate hydrate, Mooijer-

van den Heuvel (2001) AAD%=1.06;solid lines, model predictions. AAD% is average

absolute deviation between experimental data and our model prediction.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT



hydrates in the absence/presence of MCH, MCP, CHP, DMCH, NH or CO heavy

hydrocarbon hydrate formers. There exists an inflexion and the curve become flat for

methane + MCP and methane + DMCH systems at high pressure and temperature. This is

likely a numerical problem. Symbols represent experimental data Symbols represent

experimental data: ∆,pure CH4 clathrate hydrate, Sloan and Koh (2008) AAD%=1.94; ○,

pure CH4 clathrate hydrate, Sloan and Koh (2008) AAD%=2.83; ■, pure CH4 clathrate

hydrate, Mohammadi and Richon et al.(2005) AAD%=3.82; ▲,CH4+MCH clathrate

hydrate, Mooijer-van den Heuvel (2000) AAD%=12.7; ♦, CH4+MCH clathrate

hydrate,Tohidi et al.(1996) AAD%=20.9;●, CH4+MCH clathrate hydrate, Mehta and

Sloan(1994) AAD%=20.8 ; ◊, CH4+MCP clathrate hydrate, Mehta and Sloan(1994)

AAD%=13.07 ; , CH4+MCP clathrate hydrate, Makino et al.(2004) AAD%=7.8;

□,CH4+CHP clathrate hydrate, Mohammadi and Richon (2010) AAD%=13.6 ;+,

CH4+DMCH clathrate hydrate,Hara et al.(2005) AAD%=4.7;ж, CH4+NH clathrate

hydrate, Mohammadi and Richon (2011) AAD%=5.86 ;×, CH4+CO clathrate hydrate,

Mohammadi and Richon (2010) AAD%=10.20 ; solid lines,_____ model predictions.

AAD%=1.06;solid lines, model predictions. AAD% is average absolute deviation

between experimental data and our model prediction.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Figure 8. Experimental and represented/predicted dissociation conditions of CO2 clathrate

hydrates in the absence/presence of MCH, CHP or CO heavy hydrocarbon hydrate

formers. . Symbols represent experimental data ; ∆,pure CO2 clathrate hydrate, Sloan

and Koh (2008) AAD%=6.3; ○, pure CO2 clathrate hydrate, Sloan and Koh (2008)

AAD%=4.1; ■, pure CO2 clathrate hydrate, Sloan and Koh (2008)

AAD%=5.8;▲,CO2+CHP clathrate hydrate, Mohammadi and Richon(2010)

AAD%=7.47 ;ж,CO2+CO clathrate hydrate, Mohammadi and Richon(2010)

AAD%=18.5 ; solid lines,_____ model predictions. AAD% is average absolute deviation

between experimental data and our model prediction.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

ACCEPTED MANUSCRIPT


Figure 9. Experimental and represented/predicted dissociation conditions of H2S clathrate

hydrates in the absence/presence of MCH or NH heavy hydrocarbon hydrate formers.

Symbols represent experimental data ;□ ,pure H2S clathrate hydrate, Sloan and Koh

(2008) AAD%=9.37; ♦, pure H2S clathrate hydrate, Sloan and Koh (2008) AAD%=5.96;

●, H2S+MCH clathrate hydrate, Mohammadi Richon (2011) AAD%=8.82; ∆, H2S+NH

clathrate hydrate,Mohammadi and Richon(2011) AAD%=13.09 ; solid lines, _____model


model prediction.

Dow

nloa

ded

by [

Yor

k U

nive

rsity

Lib

rari

es]

at 0

9:25

11

Aug

ust 2

014

thermodynamic model for prediction of phase equilibria of clathrate hydrates in the presence of...

Documents