Delving into the World of Gas Delving into the World of Gas Hydrates Hydrates –– Thermodynamics, Thermodynamics, Kinetics and ApplicationsKinetics and Applications-- from from Potential Energy Source to COPotential Energy Source to CO22Sequestration and Water Sequestration and Water DesalinationDesalination

Sang-Yong Lee Ph DSang Yong Lee, Ph.D.

Chemical & Natural Gas Engineering

Texas A&M University-Kingsville

1

Texas A&M University-Kingsville

OutlineI t d ti t G H d t• Introduction to Gas Hydrate

• Thermodynamics• Applications (Current Research)pp ( )

− Gas Separation− Hydrogen Storage/ Transportation− CO2 SequestrationCO2 Sequestration

• Current Project− Flow assurance

Prediction of Gas Hydrate Equilibria Using Molecular− Prediction of Gas Hydrate Equilibria Using Molecular Dynamic Simulation

− Application of the carbon nanotube for solar cell (with Dr. Amit Verma)(with Dr. Amit Verma)

• Future Research− Desalination

CO2 Separation/Sequestration

2

− CO2 Separation/Sequestration− Natural Gas Production from Hydrate Reservoir− New Kinetic Model

What are Gas HydratesWhat are Gas Hydrates

• Nonstoichiometric crystalline compounds with water and light gases (methane, ethane, propane…)

• General formula:− Gas ·nH2O (n varies from 6 to 8)

C i d f d b h d• Comprised of gas encaged by hydrogen bonding of water moleculesSt bl t l T hi h P diti• Stable at low T high P conditions

• Structure I, Structure II, Structure H

3

Phase Behavior

Gas Hydrate Stable Region

Low T, High P

4

Plugging of Natural Gas Pipeline

• Natural gas hydrate deposits

Seafloor Stability

• Hydrate Plugging in Pipeline

Energy Resource

5

Distribution of Organic Carbon in Earth1

566.6830980

Gas Hydrate (onshore andoffshore)980

1400

offshore)

Recoverable and non-recoverable fossil fuel (coal,oil, natural gas)Soil1400

10000

Soil

Dissolved organic matter inwater

5000 Land biota

Others(Peat, Detritalorganic matter,Atmosphere, Marine biota)

6

1. Lee and Holder, Fuel Processing Technology, 71, 181 (2001)

Messoyakhi (Russia)

Start production: 1970

Composition

C1(98 7%) C2(0 03%)

Nankai (Japan)

Production: 2010 C1(98.7%) C2(0.03%)Composition

C1(94.3%), C2(2.6%)

7

Natural Gas Hydrate in the World

Pi t t k b USGS

8

Picture taken by USGS

Gas Hydrate Structure (molecular structure) Picture taken by USGS( )

G

Oxygen in water Sediment

Hydrogen bondPicture taken by USGS

Gas

Gas Hydrate

Individual Cages (cavities)

9

Holder, G. D., Zetts, S. and N. Pradhan, Review in Chemical Engineering, 5., 1.Unit Cell (Structure II)

Individual Cages (cavities)

E. Dendy Sloan, Jr., “Clathrate Hydrate of Natural Gases”, 2nd ed., Marcel Dekker (1996)

ApplicationsApplicationspppp• Energy source1 - Twice as much carbon (per unit

volume) as all other forms of fossil fuel combined

• Gas storage (Hydrogen, Natural gas)2/ Transportation

• Separation of Gas Mixtures3

• CO2 sequestration in the ocean4

• Desalination from Seawater1. Lee and Holder, Fuel Processing Technology, 71, 181 (2001)1. Lee and Holder, Fuel Processing Technology, 71, 181 (2001)2. Zhong and Rogers, Chemical Engineering Science, 55, 4175 (2000)3. Barrer and Ruzicka, Trans. Faraday Soc., 58, 2289 (1962)4. S.-Y. Lee et al., Environmental Science & Technology J., 2003

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Importance of Thermodynamicsp y• Gas Storage (methane, hydrogen) /

TransportationTransportation − Reactor Condition (T, P, concentration)− Storage Conditiong

• Gas Separation− Design (T, P, concentrations for each stage)g ( , , g )

• CO2 Sequestration− Proper location (T, P) for sequestration

• Desalination− Reactor Condition (T, P)

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Equilibrium Conditions are Needed

ThermodynamicsThermodynamics• van der Waals Model• The Distortion Model (Lee and Holder)2,3,4• The Distortion Model (Lee and Holder)

− Empirical Parameters− Molecular Dynamic Simulationy

• A Thermodynamic Model in Porous Media5

Determine the Gas Hydrate Formation Conditionsy

1. Holder, G. D., Zetts, S. and N. Pradhan, Review in Chemical Engineering, 5., 1.2 S -Y Lee and G D Holder AIChE J Vol 48 161-167 (2002)

Determine the Gas Production Conditions

2. S. Y. Lee and G. D. Holder, AIChE. J., Vol 48, 161 167 (2002).3. S.-Y. Lee and G. D. Holder, Gas Hydrates: Challenges for the Future, Ann. of the

New York Academy of Science, Vol 912, 614-622 (2000).4. S. Zele, S.-Y. Lee and G. D. Holder, J. of Phy. Chem. B, Vol 103, 10250-10257 (1999).5 S -Y Lee et al “Gas Hydrate Formation in Porous Media” AIChE Annual Meeting

12

5. S. Y. Lee et al, Gas Hydrate Formation in Porous Media , AIChE Annual Meeting, Reno, NV (2001).

Phase Equilibriaq• Two or more phases are in equilibrium

(co-existing at the same time)Temperature, Pressure and the Chemical Potentials (µi) of component i in each

h i thphase is the same

h dP

T

Water vaporNatural Gas

hydratei

wateri

vapori µµµ ==

water

Solid gas hydrateT

13

water

Minimum Cell Constant for Each Gas Hydrate(Molecular Dynamic Simulation)(Molecular Dynamic Simulation)

Minimum Energy of Cavity Structure Minimum Energy of Total Structure (Cavity+Gas)

14

Hwang, M.-J., Ph.D Dissertation, University of Pittsburgh (1984).

(Cavity+Gas)

The Distortion Model (Lee-Holder)C i i b di d di h• Cavities can be distorted according to the size of guest molecules1,2

Each single component gas hydrate has− Each single component gas hydrate has different cavity size

Ar HydrateAr Hydratei-C4H10 Hydrate

Each gas hydrate has different ∆µo and ∆ho values

15

1. S.-Y. Lee and G. D. Holder, AIChE. J., Vol 48, 161-167 (2002).2. S. Zele, S.-Y. Lee and G. D. Holder, J. of Phy. Chem. B,

Vol 103, 10250-10257 (1999).

Results (Single component Hydrate)( g p y )100000 Vapor-Ice-Hydrate Vapor-Liquid-Hydrate

10000

a)

Ar

N2ε=1.7%

ε=10.0%

1000

ress

ure

(KPa CH4

CO2

ε=7.2%ε=10.6%

ε=5 3%

100

Pr C2H6

C3H8

ε=5.3%

ε=6.0%

10240 260 280 300 320

H2S ε=7.1%

16

Temperature (K)

Sangyong Lee and Gerald D Holder, AIChE J., 2002

Molecular Dynamic Simulation

Pair potential Fr

(L-J, Kihara)

)(rFr

FFr

)(rFFrF

r

∑ = amF v∑( ) 2,

21),(),( taaayxPyxP yxoonewnew

vvr+=

17

( )2 y

Unit Cell of Empty Gas Hydrate(s-II)

Large Cavity

Water molecule

Small Cavity

18

Mamatha Sudhukar, MS Thesis, Texas A&M University-Kingsville (2006)

∆µ° For St II Gas HydrateFrom MD SimulationFrom MD Simulation

1.8002.000

um

experimental 5% Error,

1 2001.4001.600

quili

briu

J/m

ol

p

simulations

Expon. (experimental)

Isobutane

Distortion Model(empirical parameters)

0.8001.0001.200

ce in

Eq

ergy

, KJ

20% E P

(empirical parameters)

0.2000.4000.600

iffer

enc

Ene 20% Error, Propane

Hydrate

0.0003 3.5 4 4.5 5 5.5 6 6.5 7

D

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Guest Diameter, APavan Sai Kumar, MS Thesis, Texas A&M University-Kingsville (2007)

Hydrogen StorageHydrogen Storage• Hydrogen: an alternative for the fast depleting petroleum yd oge a a te at e o t e ast dep et g pet o eu

resources• Hydrogen: A clean burning fuel with security of supply

STORAGE METHOD CONCERN AREASTORAGE METHOD CONCERN AREA

Compressed form at ~250 bar Safety Li id f t 20 K Li fi ti i i t iLiquid form at 20 K Liquefication is energy intensiveAdsorption on metal alloys Low wt % ( 2-4 wt %) of HydrogenAdsorption on to carbon nano fibers Not provenp p

Gas Hydrates High pressure needed at ambient temperature, but can be stored at p ,ambient pressure at 100 K ( above liquid N2 temperature )

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Discovery of Hydrogen Gas Hydratey y g y• Mao et al. synthesized a hydrogen

clathrate hydrate (2004)clathrate hydrate (2004)− that holds 50 g/litter hydrogen by volume of

5.3wt% stable up to 145K at ambient pressure. • THF+H2 Hydrate

− 10MPa at 277K• TBAB+H2 Hydrate

− 8K higher than THF+H2 hydrate

Thermodynamic Model is needed to predict the equilibrium

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to predict the equilibrium Condition

Predicting H2 Hydrates’ Phase EquilibriumDifficulty:Difficulty:• Existing van der Waals- Platteeuw (vdW)-based

models are useful only for singly occupied hydratesy g y p y• Experimentally, very difficult to determine Cij due to

high P (200MPa) and low T (below 250K).

Hydrogen

Hydrogen

Oxygen

Hydrogen bond

Large Cavity (distorted)

Small Cavity (distorted)

Oxygen

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(distorted) (distorted)

J. Lee, P. Yedlapalli, S.-Y. Lee*, Journal of Physical Chemistry B, 110, 2332-2337, 2006

Details of Ab Initio CalculationsParameter Small cavity Large cavityy g y

Range No. Of

points

Range No. Of

pointsp p

r, Å 1.6-6.0 12 1.6-6.0 12

ξ, degrees -40 - +40 5 -40 - +40 5ξ g

φ, degrees -40 - +40 5 -40 - +40 5

α, degrees 0-180 3 0-120 3g

β, degrees 0-180 3 0-360 4

γ, degrees 0-180 3 0-120 3γ g

Number of

Configurations

8100×2

=16,200

10800×2

=21600

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J. Lee, P. Yedlapalli, S.-Y. Lee*, Journal of Physical Chemistry B, 110, 2332-2337, 2006

Calculated Dissociation Pressures for H HydratePressures for H2 Hydrate2500

Predicted Diss. Pr., barDissociation Pr bar

1500

2000

r, ba

r

Expt. Diss. Pr., bar T, K Expt. Predicted78 0.1 0.4080 1 0 54

Dissociation Pr, bar

500

1000

soci

atio

n P 80 1 0.54

150 128.35200 670.46250 2000 1999 98

0

500

0 50 100 150 200 250 300

Dis

s 250 2000 1999.98

-5000 50 100 150 200 250 300

T, K

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J. Lee, P. Yedlapalli, S.-Y. Lee*, Journal of Physical Chemistry B, 110, 2332-2337, 2006

Calculated Dissociation Pressures for H2-CH4-THF Hydrate

6

8P

a)

2 4 y

4

6ss

ure

(MP

0

2Pre

s

276 278 280 282 284 286 288 290

Temperature (K)Equilibrium prediction for the H2-CH4-THF hydrates with 6 mole% of THF in the aqueous phase. H2, and C1 in vapor phase: Filled square- 34.74 , and 65.26mol%; Filled triangle-69 71 and 30 29mol%; Filled circles: 89 13 and

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Filled triangle-69.71 and 30.29mol%; Filled circles: 89.13 and 10.87 mol%.

S.-Y. Lee, P. Yedlapalli, J. Lee*, Journal of Physical Chemistry B, 110, 26122 -26128, 2006

SummarySummary• By integrating ab-initio calculation with

statistical thermodynamics a newstatistical thermodynamics, a new calculation procedure to predict the equilibrium condition of Hydrogen gasequilibrium condition of Hydrogen gas hydrate has been developed

• A single hydrogen cluster concept has g y g pbee applied.

26

Gas Separation Using Gas Hydrate ith ti lwith nano-particles

• Advantages− Separation of close-boiling compounds

e.g.propane-propylene mixture, ethane-ethylene mixture

− Elimination of additional gas hydrate formation process in gas storage using hydratehydrate.

27

Composition of Flue Gas• Flue gas from a power plant consists of CO (15 20• Flue gas from a power plant consists of CO2 (15 – 20

mol %), O2 (5 to 9 mol %), and trace gases such as SO2, CO with the balance N2.

100000

10000e (K

Pa) N2 Hydrate

CO2 hydrate is stable hil N h d t i10000

Pres

sure

CO2 Hydrate

while N2 hydrate is stable

1000270 275 280 285 290 295

28

270 275 280 285 290 295Temperatuare (K)

Process Development(Gas Separation Using Gas Hydrate)(Gas Separation Using Gas Hydrate)

N2+CO2 gas hydrate

30000

35000

3 batch reactors•Thermodynamics

25000

30000

Pa)

GasHydrate

3 batch reactors (The Lee-Holder Model)

• Kinetic Model

15000

20000

ress

ure

(KP

(The Collision Theory)

•Process Design

5000

10000

Pr

- Number of Stages

-Optimum T P0

0 0.2 0.4 0.6 0.8 1

XNitrogen

Optimum T, P

- Residence time

29

XNitrogen

Note: values are calculated usingthe Lee-Holder model

COCO22 SequestrationSequestration22 qq• CO2 concentration in the atmosphere

increases dramatically:− 7.4 GtC in 1997− 26 GtC in 2100 (Report DOE/ER-30194, Vol 2, 1993)

G l• Goal− Sequester 1 GtC/year in 2023 and 4 GtC/year in 2050

• Gas Hydrate• Gas Hydrate− CO2 Separation from Flue Gas Using Hydrate− Geologic Sequestrationg q− Ocean Sequestration

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Concept for Producing Sinking CO2 Particles5 5005

10

500

1000A 1000m

HydrateC it

CO2 hydrate density ~10% denser than seawater.C it b d

15

20MPa

)

1500

2000 m)

Seawater

Composite(10% Conversion)

Composite can be denser than seawater at <<3000 m evenwith < 100% conversion of

25Pr

essu

re (M

2500 Dep

th (m

3000m

CO2 at 4oCt 00% co e s o o

CO2 to hydrate.

30

35

3000

3500

B3000m

400.97 0.99 1.01 1.03 1.05 1.07 1.09

4000

31

Density (g/cc)( ) ( )( ) ( ) hhcwwchw

hcwwhwcomposite xMMnx

xMMnxρρρρ

ρρρ

/)/(/)/(

++−++−

=

Experiments Using the ORNL Seafloor Process SimulatorORNL Seafloor Process Simulator

70-L Hastelloy, high pressure vesselMax = 20.6 MPa or

Temperature control(-2°C to 7°C) in an explosion-proof cold room

~2000 m H2Oproof cold room

Gas/liquid delivery and recovery systemsVessel has access ports

32

y yVessel has access ports for instrumentation and observation

Experimental Arrangementand Injector Design Details of mixing zoneand Injector Design

Water

Liquid CO2

WaterLiquid CO2

Liquid CO2

PT

Water

Borescope system

Hydrate–CO2–water composite stream

ORNL Seafloor Process Simulator(70 L hi h l)

Water

33

composite stream(70-L high pressure vessel)

1S.-Y. Lee et al., Environmental Science & Technology J., 2003

Carbon sequestrationq(Future Scenario for Ocean Sequestration)

Direct ocean CO injectionDirect ocean CO2 injection

750 m

3000 m

34

Geologic Sequestration in CO2 Hydrate Sediment

•Stable Conditions of CO22 Hydrate in the sediment can be calculated using asediment can be calculated using a thermodynamic model•Arctic permafrost region or Ocean sediments

Water

35

CO2 Gas Hydrate

Possible Scenario for Geologic S t tiSequestration

• Separation of CO2 from flue gas using gas p 2 g g ghydrate separation

• Inject CO2 hydrate slurry into the gas 2reservoir.

36

Gas Production from Hydrate DepositGas Production from Hydrate DepositGas Hydrate Equilibrium Line

1000000CO2

CH4 + CO2

100000

CO2 hydrate is more stable than

CH4 hydrate

CO2

10000ure

(KPa

)

C 4 yd ate

CH4

• Favorable ∆H for hydrate 1000

Pres

su

• Favorable ∆H for hydrate formation/dissociation

∆H = -81 KJ/gmol (7oC)( )nOHCOOHnCO 2222 →′+

1000

Data obtained from

pure gases

37

∆H = -81 KJ/gmol (7oC)

∆H = 57 KJ/gmol (7oC)( ) OnHCHOHCH n 2424 +→

100260 265 270 275 280 285 290 295 300 305

Temperature (K)

pure gases

Importance of Kineticsp• Gas Storage (methane, hydrogen) and

transportationtransportation− Faster formation of gas hydrate− Calculation of Residence time

• CO2 Sequestration− Faster formation of gas hydrateg y

• Desalination− Prediction of the conversion rate at a given T,

P condition.

Prediction and/or Control the reaction

38

rate

A New Kinetic Model• A new molecular collision model• A new molecular collision model

− Based on the molecular collision theory GasWater

2/12 8

⎞⎜⎜⎛ + BA mmkTdNNZ

Water Water

2/11 ⎞⎛ kT

2 8⎠

⎜⎜⎝

=BA

BABAAB mm

kTdNNZ π

Hydrate Formation Rate22

21

⎟⎠⎞

⎜⎝⎛=

mkTNdZ AAA

π Hydrate Formation Ratem

watergaswaterwatern

ZZ

ZZTPTPr ⎟

⎠

⎞⎜⎜⎝

⎛⎟⎠

⎞⎜⎜⎝

⎛∝ −−)()( 1|212α

totaltotal ZZ ⎠⎝⎠⎝

Net Formation rate = Formation rate –Dissociation rate

39

GasGas

Dissociation rate

Assumptions For a New ModelAssumptions For a New Model

• Hydrate formation rate is a function of:− Number of gas-water collisions in the aqueous

phase.The Maxwell energy distribution gives− The Maxwell energy distribution gives• probability of the successful hydrate formation

collisions

40

New Kinetic Model

⎤⎡ ⎞⎛⎞⎛ 11

⎥⎥⎥

⎦

⎤

⎢⎢⎢

⎣

⎡

⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛

⎟⎟⎠

⎞⎜⎜⎝

⎛−

⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛

⎟⎟⎠

⎞⎜⎜⎝

⎛= −

watergaswatergasRTE

hydrate CCkTCCkTLder21

21

2/ 88µπ

µπε

• Activation Energy

⎥⎦⎢⎣ ⎠⎝⎠⎝ mequilibriusystem

gy− Methane: 90.25 kJ/mol− Ethane: 90.3 kJ/mol

41

Comparison Proposed Model with E i t l D t (C H )

C2H6 Hydrate Formation Rate

Experimental Data (C2H6)

C2H6 Hydrate Formation RateTemp (K) Pressure (MPa) Exp (mol/s) Calculated (mol/s) error (%)

274 1.68 7.778E-06 7.441E-06 4.33276 0.83 5.833E-06 7.257E-06 24.40

1.79 7.083E-06 7.763E-06 9.60279 1.49 7.778E-06 7.901E-06 1.59282 2.19 8.889E-06 8.526E-06 4.08

1 89 8 333E-06 8 333E-06 0 001.89 8.333E-06 8.333E-06 0.00

Steric Factor : 1/14252.06

42

ConclusionConclusionConclusionConclusion• Thermodynamic model for gas hydrate

A li ti• Applications• Hydrogen Storage• CO2 Sequestration

•Separation of CO2 from flue gas•Ocean Sequestration•Geologic Sequestration•Swapping method

43

On Going ProjectsOn-Going Projects• Prediction of the Gas Hydrate EquilibriumPrediction of the Gas Hydrate Equilibrium

using Molecular Dynamic Simulation• Modeling of Hydrate Formation Rate with g y

Kinetic Inhibitors• Application of Carbon Nanotube for solar pp

Cell (with Dr. Amit Verma,PI)

44

Hydrate PreventionHydrate Preventionyd ate e e t oyd ate e e t o• Above hydrate formation condition

B i th i li− Burring the pipeline− Well head Heat addition− Insulation− Insulation

• Remove of the free water and vapor water using triethylene glycol or molecularusing triethylene glycol or molecular sieve.

• Inhibitor − Thermodynamic (typically alcohol or glycol)− Kinetic Inhibitor

45

− Anti-agglomerant

Plug Formation via Aggregation in an Oil-dominated System

Time

46

Prevention of PluggingPrevention of Plugging

• Thermodynamic Inhibitor (40 – 60 wt%)y ( )− Adding methanol

• Kinetic Inhibitor (0.2 – 2.0 wt%)( )− Poly(N-Vinylcaprolactam)− Poly(N-Vinylpyrrolidone)/(N-Vinylcaprolactam)

lcopolymer− Poly(N-Vinylpyrrolidone)

Antiagglomerant• Antiagglomerant− Shell-type AA ((1)water soluble (2) oil soluble)

47

Future Project• Gas Separation• Desalination• Control the reaction rate using surfactantg• Natural gas product from Hydrate deposit• CO2 sequestration (swapping)2 q ( pp g)

48

Gas Separation (CO2+N2)Gas Separation (CO2 N2)• Separation of CO2 from a flue gas

Equilibrium pressure

Power Plant

N2

Activated Carbon

Height

Power Plant

Height

Flue gas

Gas hydrate

Pressure

Heat ExchangerCompressor

Flue gas CO2+N2

CO2+N2

49

Compressor

DesalinationGas Hydrate(salting out) Gas

Salty Water

( g ) Gas

+Gas Potable

Water

Water with High Salt Concentration

50

Control the reaction rate using surfactant• Hydrate formation within nano particles• Hydrate formation within nano-particles.• Hydrate particle sizes are controlled by nano-particle

sizes.

Hydrate formation in a reversed micele

51

9 nano-meters

Can the New Model Also Predict the Amount of Gas Production?

Sediment

NO!!!

Ice

Gas HydrateWater

Dissociated Gas Has

52

Gas HydrateDissociated Gas Has been Trapped and can not escape

Research NeededResearch Needed• To predict the production quantity

Connectivity of Pores− Connectivity of Pores• To predict the production rate

− Kinetics of the dissociation of gas hydrates

Percolation Theory•Hosen-Kopelman Algorithmp g

Reservoir simulation

53

Reservoir simulation

Acknowledgement• Dean, Gerald D. Holder, U of Pittsburgh• Professor Jae W. Lee, The City College of New York, CUNY • Professor James C. Holste, Texas A&M

D Y i F M k T A&M• Dr. Yuri F. Makogon, Texas A&M • Dr. Olivia R. West, Oak Ridge National Laboratory• Dr. Costas Tsouris, ORNL,• Mr. Robert Warzinski, NETL• Mr. Sivacharanreddy Peddyreddy, Texas A&M U – Kingsville

M P S i K R d• Mr. Pavan Sai Kumar Redy, Texas A&M U - Kingsville• Mr. Prasad Yedlapalli, CCNY, CUNY

54