Published: September 08, 2011

r 2011 American Chemical Society 11563 dx.doi.org/10.1021/ie200825e | Ind. Eng. Chem. Res. 2011, 50, 11563–11569

ARTICLE

pubs.acs.org/IECR

Accelerated Formation of Methane Hydrate in Aluminum FoamLiang Yang, Shuanshi Fan, Yanhong Wang,* Xuemei Lang, and Donglai Xie

Key Lab of Enhanced Heat Transfer and Energy Conservation, Ministry of Education, School of Chemistry and Chemical Engineering,South China University of Technology, Guangzhou 510640, China

ABSTRACT: The effects of aluminum foam (AF, average pore size of 1000 μm) on formation and growth kinetic behaviors ofmethane hydrate with 0.03 wt % sodium dodecyl sulfate (SDS) were investigated in a 300 cm3 stainless steel vessel without stirringunder 4.2, 6.0, and 8.3 MPa and 273.15 K. AF is a porous metal medium possessing large rough surface and excellent thermalconductivity. The experimental results demonstrated that porous AF played an acceleration role in the initial formation and furthergrowth of methane hydrate by promoting hydrate nucleation and facilitating the removal of hydration heat. When AF was used, notonly was the induction time reduced but the formation and growth were also sped up significantly, compared to conditions withoutit. In addition, under the above three pressures, the maximum formation rates (Rf,max) were increased by enormous times, 52% and23%, with the help of AF, respectively. The relatively low increment of Rf,max under high pressure most likely was caused by AF’s ownlimitations (pore size). AF with smaller pore size can be selected for further study.

1. INTRODUCTION

Gas hydrates are ice-like crystalline compounds formed by thecombination of hydrogen-bonded water molecules and suitablysized gas molecules under elevated pressure and low tempera-ture. The water molecules form host cavities which encapsulatesmall gas molecules (the guest, e.g., methane, ethane, ethylene,carbon dioxide, and hydrogen).1 In recent years, gas hydrateshave drawn the attention of more and more scientists andengineers as not only a new natural energy resource2�4 but alsoa new medium for natural gas storage and transportation.5,6 Perunit volume, such hydrates can stably store 172 standard volumesof natural gas. High stability and strong storage capacity havecontributed to the development of some new applications ofhydrate, such as carbon dioxide capture and sequestration, sea-water desalination, flue gas separation, and hydrogen storage inthe form of hydrate.

However, the application of hydrate technology, especiallyindustrial natural gas storage and transportation in the form ofhydrate, has been critically challenged by slow formation rate andlow conversion ratio of gas to solid hydrate resulting in insuffi-cient storage capacity. The causes of the problems lie in theinadequate gas�water contacts and the generation of largehydration heat (438.54 ( 13.78 KJ/kg methane hydrate),7

neither of which favors hydrate formation and growth. Therefore,enhancing gas�water contacts and removing the hydration heatin a timely manner are very important for efficient hydration ofgas to solid.

The addition of surfactants to water has been proven topromote gas hydrate formation without affecting the thermo-dynamics of hydrate crystallization.8,9 Zhong and Rogers10

reported that sodium dodecyl sulfate (SDS), above its criticalmicelle concentration (CMC), increases the formation rate ofethane hydrate in a quiescent system by a factor greater than 700.Link et al.11 found that SDS may be the most appropriate sur-factant commercially available to be used for the enhancement ofmethane hydrate formation. Sun et al.12�14 carried out methane/natural gas hydrate formation experiments and confirmed the

enhancement effect of SDS on the formation rate and storagecapacity of gas hydrates. Lin et al.15 and Ganji et al.16,17 alsoreported that the presence of SDS speeds up methane uptakeduring hydrate formation. Zhang et al.18 suggested that SDSaccelerates the methane hydrate growth by increasing the totalsurface area of hydrate particles and the gas�liquid interfacialarea. Yoslim et al.19 observed that the addition of SDS to waterincreases gas�water contacts by changing the hydrate morphol-ogy and enhances the gas consumption for hydrate formation byapproximately 14 times compared to pure water. Nevertheless,fast hydrate formation is always associated with great generationof hydration heat. The hydration heat leads to system tempera-ture rise and weakens the acceleration effect of surfactants onhydrate formation. In order to enhance the process of hydrationheat removal, Carbajo20 advocated an early direct-contact chargeand discharge system for the first time, but the system requires anexpensive oil free compressor and a water separator at thereceiver. Hence the capital cost became high. Afterward, forthe purpose of reducing the cost of heat transfer system, indirect-contact charge and discharge systems with low capital cost havebeen designed by McCormack,21 Nagaaki et al.,22 Shu et al.,23

and Xie et al.24 However, the small contact area between thesystem and solid hydrate became a limitation of hydration heatremoval.

As a porous metal medium with a large rough surface, alu-minum foam (AF) can provide numerous natural microvesselswith excellent thermal conductivity walls. The thermal conduc-tivity of aluminum is about 400 times higher than that of gashydrates.25,26 There is little information available in the literatureabout the effect of AF on hydration processes. Therefore, in thepresent work, formation and growth kinetic behaviors of meth-ane hydrate in AF were investigated under various pressures and

Received: April 18, 2011Accepted: September 8, 2011Revised: September 5, 2011

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a given temperature. In order to distinctly observe the effect ofAF on hydration kinetic behaviors, SDS was used for assistingmethane hydrate to form. The experimental data can provideuseful information on kinetic behaviors of natural gas hydratesformed in metal foam.

2. EXPERIMENTAL SECTION

2.1. Apparatus and Materials. The experimental apparatusemployed in this work is shown in Figure 1. It consists of acylindrical stainless steel high-pressure vessel, a double-windowcoolant bath, a pressure control system, and a data logger. Thevessel (50 mm in diameter, 153 mm in height, and effectivevolume of 300 cm3) was designed to work safely under the pres-sure up to 20 MPa. The top detachable cover of the vessel hasthree hatches used for inserting two Pt100 resistance thermo-couple detectors (RTDs) and connecting gas inlet pipeline. TwoRTDs with a precision of (0.01 K are used for measuring thetemperatures of gas phase and liquid phase, respectively. Thetemperature of the vessel is controlled by immersing it in acirculating coolant bath (THD-3010, Ningbo Tianheng Instru-ment Factory) with a heating/cooling coil. Coolant with afreezing point lower than 243 K is prepared by an equivalentvolumemixture of water and ethylene glycol. The temperature ofthe coolant bath is controlled by the refrigeration system in therange of 258 K to ambient temperature with an accuracy of(0.01K.Additionally, a vacuumpump is used for pumping the air outof the vessel prior to the experiment; a vent is used for exhaustingthe unreacted gas or the gas in hydrates decomposing; a differ-ential pressure transducer (DPT, DG1300, Guangzhou SenexInstrument Co. Ltd.) with an accuracy of(0.02 MPa is used formeasuring the pressure in the vessel; a pressure gauge with aprecision of (0.1 MPa is used for measuring the pressure of gassupply. The temperature and pressure information is collected byan Agilent 34970A Data Logger and displayed in the computer.2.2. Procedure. The schematic structure of an AF plate

(i48mm� 6mm,ShanghaiZhonghuiFoamedAluminumProductCo., Ltd.) with open cells is shown in Figure 2a. The average poresize of AF is approximately 1000 μm, and a magnified pore with arough surface is shown in Figure 2b. Before the experimentstarted, the hydrate vessel was washed with distilled water and

loaded with four AF plates and 30 mL 0.03 wt % SDS (99%purity, Shanghai Bio Science & Technology Co., Ltd.) solution.The overlapping AF plates were immersed in the SDS solution.Each vessel-like cell of AF plates was full of SDS solution, andFigure 2c shows a schematic arrangement. Subsequently, thevacuum pump was started to remove the air from the apparatus,and then, the vessel was washed with methane (99.99% purity,Guangzhou Yinglai Gases Co., Ltd.) three times to ensure theabsence of air. Afterward, the refrigeration system was turned onto adjust the apparatus temperature to 273.15 K. Once thedesired temperature was maintained constant for several min-utes, methane was injected into the vessel until the given pressurewas satisfied, and then, gas injection was cut off. In the initialperiod of methane hydrate formation, the temperature increasedwhile the vessel pressure decreased obviously. When the pressuredrop was less than 0.01 MPa over 30 min, the hydration processwas assumed to reach its destination. In addition, a series ofexperiments of methane hydrate formation in 0.03 wt % SDSsolution without AF were also carried out by the same steps.2.3. Experimental Data Analysis. In order to study the effects

of AF on the formation and growth kinetic behaviors of gashydrates, it is necessary to calculate the formation rate of hydrate,Rf, which was defined as

Rf ¼dðV h

t, gasÞSTPV ht dt

≈ðΔVh

t, gasÞSTPV ht Δt

ð1Þ

where V h, Vgash , and ΔV gas

h are the accumulative volume of thehydrate phase, the volume of gas in the hydrate phase, and thevolume increment of gas in the hydrate phase in the period ofΔt,respectively. The subscript t, as well as 0, t +Δt and e appeared inthe following equations denote the state of time t, the initialstate, the state of time t + Δt, and the final (equilibrium) state,respectively. STP represents the standard temperature and pressure.Sloan and Koh stated that the molar volume of imaginary

empty hydrate lattice of structure I is 4.6 cm3 larger than that ofliquid water.1 This implies that the volume of water expends byabout 1.25 times during its conversion into hydrate. Therefore,Vth is determined by the following equation:

V ht ¼ 1:25αtV

l0 ð2Þ

whereV01 is the initial volume of liquid phase in the vessel andα is

the fraction of water converted into hydrate. It is evaluated withthe following equation:

αt ¼ðVh

t, gasÞSTPðV h

e, gasÞSTPð3Þ

where (Vt,gash )STP and (Ve,gas

h )STP are described by the followingformulas in units of cubic centimeters

ðV ht, gasÞSTP ¼ 22400nht, gas ð4Þ

ðV he, gasÞSTP ¼ 22400nhe, gas ð5Þ

where ngash is the molar number of gas in the hydrate phase or the

molar number of gas uptake during hydrate formation.The crystal structure of methane hydrate is structure I. Each

unit cell of structure I includes 2 small pentagonal dodecahedroncavities (512) and 6 large tetrakaidecahedron cavities (51262)formed by 46 hydrogen-bonded water molecules.1 So the idealunit cell formula of structure I is 2(512) 3 6(5

1262) 3 46H2O.When

Figure 1. Schematic diagram of experimental apparatus: DPT—differential pressure transducer, RTD—resistance thermocouple detector.

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the unit of water volume is cubic centimeters, the mass value ofwater equals its volume value. So according to the formula ofstructure I, ne,gas

h can be determined by

nhe, gas ¼V l0

18� 46ð2θ1 þ 6θ2Þ ð6Þ

where θ1 and θ2 are the occupancy of gas molecules in smallcavities and large cavities of hydrate, respectively. The twoparameters depend on temperature, pressure, and compositionof the vapor phase and can be evaluated with any one of theexisting hydrate models.27�29 In this work, the model of Chenand Guo29 is used to determine θ1 and θ2.The standard volume increment of gas in hydrate phase,

(ΔVt,gash )STP, can be calculated by the following equations with

units of cubic centimeters:

ðΔV ht, gasÞSTP ¼ 22400ðnht þ Δt, gas � nht, gasÞ ð7Þ

nht, gas ¼ ng0 � ngt ð8Þ

nht þ Δt, gas ¼ ng0 � ngt þ Δt ð9Þwhere ngas

h and ng represent the molar number of gas in thehydrate phase and the molar number of the gas phase, respec-tively. The values of n0

g, ntg, and nt+Δt

g can be determined by

ng0 ¼ P0Vg0

Z0RT0ð10Þ

ngt ¼ PtVgt

ZtRTtð11Þ

ngt þ Δt ¼PtþΔtV

gt þ Δt

ZtþΔtRTtþΔtð12Þ

where P, T, Vg, and Z are the pressure, temperature, volume ofthe gas phase, and the gas compressibility factor, respectively.The compressibility factor Z is calculated with the Benedict�Webb�Rubin�Starling equation of state.30 V0

g can be describedby

V g0 ¼ Vvessel � V l

0 � VAF ð13Þ

where Vvessel is the volume of the pressure vessel and VAF is thevolume of solid aluminum. When AF was absent from theexperiment, VAF = 0; P, T, and V0

l all can be measured directly,and VAF can be measured indirectly by pouring paraffin into thisporous metal.In view of the volume expansion of liquid water and the

constant volume of pressure vessel, the increasing volume of thecondensed phase (liquid and hydrate) will occupy the gas phasespace. It leads to decrease of the gas phase volume, correspond-ingly. So the volume of gas phase, V0

g, should be corrected by

V gt ¼ V g

0 � 0:25αtVl0 ð14Þ

V gt þ Δt ¼ V g

0 � 0:25αtþΔtVl0 ð15Þ

where α is calculated by eqs 3�5.Besides the determination of formation rate, the gas consump-

tion, C, can be obtained conveniently with the equation of C =(Vt,gas

h )STP/Vth together with the above equations.

3. RESULTS AND DISCUSSION

In order to accelerate the formation of methane hydrate,enhancement of gas�water contacts, and hydration heat removalare two crucial approaches. As reported in literature,8�19 theaddition of SDS to water increases the gas hydrate formation rateand storage capacity in quiescent systems. However, fast hydrateformation is always associated with the generation of greathydration heat that weakens the acceleration effect of SDS onhydrate formation. AF is an excellent thermal conductor posses-sing good thermal conductivity and a large rough surface. WhenAF combined with SDS is used as the additive, it can be expectedthat faster formation and growth of methane hydrate can beachieved. In that case, the achievement will serve as a guidelinefor industrial-scale storage of natural gas in the form of hydrate.

Figure 3 shows the variation of methane pressure and liquidtemperature with time in the presence of SDS and AF under theinitial pressure of 8.3 MPa and the initial temperature of273.15 K. As can be seen in Figure 3, when only AFwas presented,methane pressure and water temperature of the reaction systemrarely changed and little methane hydrate was formed. In thecases of SDS solution with and without AF, abrupt methanepressure drops were associatedwith the obvious water temperature

Figure 2. Schematic structure of AF (a), magnified pore of AF (b), and SDS solution in the pore of AF (c).

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rise in the initial 5 and 12 min, respectively, and then approachedequilibrium within 40 min. Methane hydrate was found to formfast in SDS solution, but the formation was slower than that in thesystem of SDS solution together with AF. The results indicatedthat AF played an inconspicuous role in the formation rate,because it had little contribution to the enhancement of metha-ne�water interfacial area which was more important than heattransfer. The SDS surfactant can accelerate hydrate formation byenhancing the methane�water contacts.18,19 When AF wasadded in SDS solution, the faster formation rate may be attributedto the enhancement of SDS on methane�water contacts and theenhancement of AF on hydration heat removal.

Formation rates of methane hydrate in the presence of SDS orAF under the initial pressure of 8.3 MPa and the initialtemperature of 273.15 K are shown in Figure 4. For the case ofAF added in water, the formation rate nearly approached 0 duringthe whole experimental process. The cause of little hydrationbetween water molecules and methane molecules without SDSwas the limited contacts of two kinds of molecules. For the casesof SDS solution combined with and without AF, formation rateswere both found to reach their maximum values rapidly (less than20 min). Moreover, the maximum formation rate of hydrate with

AF and SDS was reached about 5 min earlier and 2.63 m33m

�33

min�1 larger than that with only SDS. The facts showed thatincreasing the methane�water contact area was a prior enhance-ment compared with heat removal. SDS had much more con-tribution to enhancing methane�water contacts while AF mayprovide much more service to hydration heat removal.

Subsequently, in order to deeply study the effects of AF onkinetic behaviors of methane hydrate formation and growth,experiments in SDS solution attached AF were carried out at 4.2,6.0 MPa, and 273.15 K.

Figure 5 describes the effect of AF on the variation of liquidtemperature at 4.2, 6.0, and 8.3 MPa and 273.15 K. Thetemperature variation of SDS solution caused by hydration heatcan indirectly reflect the kinetic behaviors of hydrate formationand growth. As can be seen in Figure 5, when AF was used, thetemperature of SDS solution climbed up earlier and the peak oftemperature rise was higher than that without AF used undereach pressure. Under 4.2 MPa, the temperature rise of SDSsolution without AF hardly appeared, possibly because of in-sufficient hydration driving force or lack of crystal nucleus.However, obvious temperature rise (about 1 K) was foundto happen when AF was used in SDS solution. The differencemay imply that AF not only accelerated hydrate growth by fast

Figure 4. Formation rates of methane hydrate in the presence of SDSand AF under 8.3 MPa (T = 273.15 K).

Figure 5. Effect of AF on the temperature variation of SDS solutionunder various pressures (T = 273.15 K).

Figure 6. Effect of AF on formation rates of methane hydrate based onSDS solution under various pressures (T = 273.15 K).

Figure 3. Variation of methane pressure (solid) and liquid temperature(empty) in the presence of SDS and AF.

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transferring hydration heat, but also promoted hydrate formationby supplying a great rough metal surface. The faster hydrateformed and grew, the more rapidly hydration heat was released.The hydration heat was rapidly shifted to temperature measuringequipment by AF, so the higher temperature rise appeared whenAF was used.

The effect of AF on formation rates of methane hydrate basedon SDS solution at 4.2, 6.0, and 8.3MPa and 273.15 K is sketchedin Figure 6. It can be seen that except for the rate curve withnegligible variation in the condition of no AF used in SDSsolution under 4.2MPa, each other one had an obvious rate peak.The rate peaks were corresponding to the temperature rise peakin the same condition depicted in Figure 5. Under 4.2MPa, whenAF was absent from SDS solution, no hydrate was formed,possibly due to not having enough pressure driving force orfew promoters of nucleation, although SDS can increase themethane�water contacts. Besides the case of no hydrate formed,other hydration processes under 4.2, 6.0, and 8.3MPa of pressurefinished the final growth within 80, 50, and 30 min, respectively.This showed that either SDS or SDS combined with AF canincrease hydrate formation and growth rate. SDS promoted thecontacts of methane molecules and water molecules by changingthe morphology of hydrate,19 and AF removed hydration heatrapidly. For each group of experiments under the same pressure,the hydration process in the presence of AF started earlier andthe time spent on the whole hydration process was shorter,compared to the hydration in the absence of AF. This statementpossibly meant that AF and SDS jointly enable methane hydrateto form and grow faster than single SDS surfactant. AF provided alarge rough metal surface for hydrate nucleation and its excellentthermal conductivity favored taking hydration heat away.

Maximum formation rates (Rf,max), the peak values of ratecurve, are depicted in Figure 6. It is observed that Rf,max in thepresence of AF was increased by enormous times (from 0 to5.59m3

3m�3

3min�1), 52% (from6.81 to 10.32m3

3m�3

3min�1)and 23% (from 11.55 to 14.18 m3

3m�3

3min�1) under 4.2, 6.0,and 8.3 MPa, respectively. The difference of AF’s effect on Rf,max

under different pressure showed that the heat transfer effect of iton hydrate formation and growth for various pressures differed indegree. Under low pressure, hydrate produced heat slowly duringrelatively mild hydration processes due to the relatively smalldriving force based on pressure31 and AF can rapidly transfer the

hydration heat to keep the reaction temperature constant. Underhigh pressure, relatively severe hydration produced heat fast andAF only removed hydration heat partly in a limited time, mostlikely caused by its own limitations (relatively large pore size).

Figure 7 depicted the effect of AF on gas consumption duringmethane hydrate formation based on SDS solution at 4.2, 6.0,and 8.3 MPa and 273.15 K. Under 6.0 and 8.3 MPa, with the helpof AF, the gas uptake based on SDS solution started to increaseseveral minutes earlier and reached the maximum value fasterthan the case of without AF. It should be concluded that AFplayed an acceleration role in hydrate formation by quicklyevacuating hydration heat due to its large specific surface andgood thermal conductivity. Under 4.2 MPa, the reaction systemstayed in the induction period and no hydrate was formedwithout the help of AF. Hydrate started to form in 20 min, andthe final storage capacity rapidly came up to 110.49m3

3m�3 with

the help of AF. It can be claimed that a large rough metal surface ofAF not only benefited hydration heat removal but also benefitedhydrate nucleation, because the rough metal surface can providemuch metal peaklike surface for adsorbing surfactants.10

Figure 8 provides the time consumption for different methaneconversion into hydrate with SDS and AF at 4.2, 6.0, and 8.3MPaand 273.15 K. The time consumption for a certain methaneconversion into hydrate is defined as the spent time when themethane consumption reaches a certain percentage of its finalstorage capacity. It is well-known that the shorter the timeconsumed for a given conversion, the faster hydrate forms andgrows. In Figure 8, under 6.0 and 8.3 MPa, AF caused the curvesof time consumption to move down in relation to the curveswithout AF’s assistance. Typically, the time consumption of 90%conversion of gas to solid hydrate (t90) with AF was shorter thanthat without AF. In addition, it was observed that t90 with AF wasfar less than that published by Ganji.16,17 All the facts showed thatthe conversion of gas to solid hydrate with AF and SDS tookplace more rapidly than that with only SDS. The accelerationeffect of AF on methane hydrate formation and growth may havemuch to do with the properties of material itself: good thermalconductivity and large rough metal surface.

4. CONCLUSIONS

Methane consumption experiments based on PVT measure-ments were conducted to study the formation and growth kinetic

Figure 7. Effect of AF on gas consumption during methane hydrateformaiton based on SDS solution under various pressures (T = 273.15 K).

Figure 8. Effect of AF on time consumption for different methane conver-sion into hydrate with SDS solution under various pressures (T = 273.15 K).

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behaviors of methane hydrate with SDS and open-cell AF. SDSsurfactant was used as a kinetic promoter to help methanehydrate formation. The results demonstrated that porous AFplayed an acceleration role in the initial formation and furthergrowth of methane hydrate by promoting hydrate nucleation andenhancing hydration heat transfer. When AF was used, not onlywas the induction time reduced, but the formation and growthwere also sped up significantly, compared to the conditionswithout it. The peaks of temperature rise in the presence of AFwere found to becomemore prominent than those in the absenceof it. In addition, under 4.2, 6.0, and 8.3 MPa, the maximumformation rates were increased by enormous times, 52% and 23%with the help of AF, respectively. The relatively weak accelerationeffect of AF on severe hydration under high pressure most likelywas caused by AF’s own limitation. AF with smaller pore sizeshould be selected for further study. This study is expected toprovide useful information for industrial natural gas storage inthe form of hydrate in a metal foam.

’AUTHOR INFORMATION

Corresponding Author*Tel.: +86 20 2223 6581. Fax: +86 20 2223 6581. E-mail address:wyh@scut.edu.cn.

’ACKNOWLEDGMENT

This work was supported by the National High TechnologyResearch and Development Program of China (863 Program, No.2007AA03Z229), the National Basic Research Program of China(973 Program, No. 2009CB219504-03), and the FundamentalResearch Funds for the Central Universities (2009ZM0185).

’NOMENCLATURERf = formation rate of hydrate (m3

3m�3

3min�1)C = gas consumption (m3

3m�3)

Vh = accumulative volume of hydrate phase (cm3)Vgash = volume of gas in hydrate phase (cm3)

Vg = volume of gas phase (cm3)V1 = volume of liquid phase (cm3)Vvessel = volume of pressure vessel (cm3)VAF = volume of solid aluminum (cm3)ΔVgas

h = volume increment of gas in hydrate phase (cm3)Δt = time interval of two states (min)α = fraction of water converted into hydrate (%)ngash = molar number of gas in hydrate phase (mol)ng = molar number of gas phase (mol)θ1 = occupancy of gas molecules in small cavities of hydrateθ2 = occupancy of gas molecules in large cavities of hydrateP = pressure (MPa)T = temperature (K)Z = gas compressibility factort90 = time consumption when gas consumption reaches 90% of

final storage capacity (min)

Subscripts0 = initial statet = state of time tt + Δt = state of time t + Δte = final (equilibrium) stateSTP = standard temperature and pressure

’REFERENCES

(1) Sloan, E. D.; Koh, C. A. Clathrate Hydrates of Natural Gases, 3rded.; CRC Press/Taylor & Francis: Boca Raton, FL, 2008.

(2) Klerkx, J.; De Batist, M.; Granin, N.; Zemskaya, T.; Khlystov, O.Gas hydrates in a freshwater “Ocean”. Science 2004, 2, 82–91.

(3) Kerr, R. A. Energy-Gas hydrate resource: Smaller but sooner.Science 2004, 303, 946–947.

(4) Englezos, P.; Lee, J. D. Gas hydrates: a cleaner source of energyand opportunity for innovative technologies. Korean J. Chem. Eng. 2005,22, 671–681.

(5) Gudmundsson, J. S.; Brrehaug, A. A. Frozen hydrate for trans-port of natural gas. In Proceedings of the 2nd International Conference onNatural Gas Hydrates (ICGH 1996), Toulouse, France, 1996.

(6) Nogami, T.; Oya, N.; Ishida, H.;Matsumoto, H. Development ofnatural gas ocean transportation chain by means of natural gas hydrate(NGH). In: Proceedings of the 6th International Conference on GasHydrates (ICGH 2008), Vancouver, British Columbia, Canada, 2008.

(7) Gupta, A.; Lachance, J.; Sloan, E. D.; Koh, C. A.Measurements ofmethane hydrate heat of dissociation using high pressure differentialscanning calorimetry. Chem. Eng. Sci. 2008, 63, 5848–5853.

(8) Kalogerakis, N.; Jamaluddin, A. K. M.; Dholabhai, P. D.; Bishnoi,P. R. Effect of surfactants on hydrate formation kinetics. In: SPEInternational Symposium on Oilfield Chemistry, SPE25188, New Orleans,LA, 1993.

(9) Karaaslan, U.; Parlaktuna, M. Surfactants as hydrate promoter?Energy Fuels 2000, 14, 1103–1107

(10) Zhong, Y.; Rogers, R. E. Surfactant effects on gas hydrateformation. Chem. Eng. Sci. 2000, 55, 4175–4187.

(11) Link, D. D.; Ladner, E. P.; Elsen, H. A.; Taylor, C. E. Formationand dissociation studies for optimizing the uptake of methane bymethane hydrates. Fluid Phase Equilib. 2003, 211, 1–10.

(12) Sun, Z. G.; Wang, R. Z.; Ma, R. S.; Guo, K. H.; Fan, S. S.Experimental studying of additives effects on gas storage in hydrates.Energy Fuels 2003, 17, 1180–1185.

(13) Sun, Z. G.; Wang, R. Z.; Ma, R. S.; Guo, K. H.; Fan, S. S. Naturalgas storage in hydrates with the presence of promoters. Energy Convers.Manage. 2003, 44, 2733–2742.

(14) Sun, Z. G.;Wang, R. Z.;Ma, R. S.; Guo, K.H.; Fan, S. S. Effect ofsurfactants and liquid hydrocarbons on gas hydrate formation rate andstorage capacity. Int. J. Energ. Res. 2003, 27, 747–756.

(15) Lin, W.; Chen, G. J.; Sun, C. Y.; Guo, X. Q.; Wu, Z. K.; Liang,M. Y.; Chen, L. T.; Yang, L. Y. Effect of surfactant on the formation anddissociation kinetic behavior of methane hydrate. Chem. Eng. Sci. 2004,59, 4449–4455.

(16) Ganji, H.; Manteghian, M.; Rahimi Mofrad, H. Effect of mixedcompounds on methane hydrate formation and dissociation rates andstorage capacity. Fuel Process. Technol. 2007, 88, 891–895.

(17) Ganji, H.; Manteghian, M.; Sadaghiani zadeh, K.; Omidkhah,M. R.; Rahimi Mofrad, H. Effect of different surfactants on methanehydrate formation rate, stability and storage capacity. Fuel 2007, 86,434–441.

(18) Zhang, J. S.; Lee, S.; Lee, J. W. Kinetics of methane hydrateformation from SDS solution. Ind. Eng. Chem. Res. 2007, 46, 6353–6359.

(19) Yoslim, J.; Linga, P.; Englezos, P. Enhanced growth ofmethane�propane clathrate hydrate crystals with sodium dodecyl sulfate, sodiumtetradecyl sulfate, and sodium hexadecyl sulfate surfactants. J. Cryst.Growth 2010, 313, 68–80.

(20) Carbajo, J. J. A direct-contact-charged direct-contact-dischargedcool storage system using gas hydrate. Ashrae Transaction 1985, 91,258–266.

(21) McCormack, R. A. Use of clathrates for off-peak thermal energystorage. In Proceedings of the 25th Intersociety Energy Conversion Engineer-ing Conference (IECEC), 1990.

(22) Nagaaki, Y.; Kenji, W.; Noritaka, S. Actual field test of a novelcombined system of high efficiency heating and cooling heat pump andclathrate cool storage unit. In Proceedings of the 29th Intersociety EnergyConversion Engineering Conference (IECEC), 1994.

11569 dx.doi.org/10.1021/ie200825e |Ind. Eng. Chem. Res. 2011, 50, 11563–11569

Industrial & Engineering Chemistry Research ARTICLE

(23) Shu, B. F.; Guo, K. H.; Meng, Z. X.; Zhao, J. W. A new-typeclathrate hydrate cool storage system and its performance. J. Eng.Thermophys. 1999, 20, 542–544.(24) Xie, Y. M.; Guo, K. H.; Liang, D. Q.; Fan, S. S.; Gu, J. M. Steady

gas hydrate growth along vertical heat transfer tube without stirring.Chem. Eng. Sci. 2005, 60, 777–786.(25) Huang, D. Z.; Fan, S. S. Thermal Conductivity of Methane

Hydrate Formed from Sodium Dodecyl Sulfate Solution. J. Chem. Eng.Data 2004, 49, 1479–1482.(26) Gupta, A.; Kneafsey, T. J.; Moridis, G. J.; Seol, Y.; Kowalsky,

M. B.; Sloan, E. D. Composite thermal conductivity in a large hetero-geneous porous methane hydrate sample. J. Phys. Chem. B 2006, 110,16384–16392.(27) Parrish, W. R.; Prausnitz, J. M. Dissociation pressures of gas

hydrates formed by gas mixtures. Ind. Eng. Chem. Proc. Des. Dev. 1972,11, 27–35.(28) Ng, H. J.; Robinsion, D. B. The prediction of hydrate formation

in condensed systems. AIChE J. 1977, 23, 477–482.(29) Chen, G. J.; Guo, T. M. A new approach for gas hydrate

modeling. Chem. Eng. J. 1998, 71, 145–151.(30) Starling, K. E. Thermo data refined for LPG. Part 1: equation of

state and computer prediction. Hydrocarb. Process 1971, 50, 101–104.(31) Kang, S. P.; Lee, J. W. Kinetic behaviors of CO2 hydrates in

porous media and effect of kinetic promoter on the formation kinetics.Chem. Eng. Sci. 2010, 65, 1840–1845.