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Understanding Gas Hydrates and its Utility for Energy Solutions

Rajnish Kumar

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Gas hydrates are ice like crystalline material and they shares some of the unique properties of water

• Density of solid water (ice) is lower than liquid water and this

Cooper, A.I., J. Mater. Chem., 2000, 10, 207-234

y ( ) qis one reason why life exist of earth.

• Water molecules have very different boiling point compared to other molecule of similar molecular weight.

• Within the solid ice phase, 13 known phases of ice has been identified

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Molecular structure of water in different phases

Photographs are from Janda Lab

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Gas hydrates are ice like crystalline material

• Gas hydrates are crystalline non-stoichiometric compounds consisting p gof water and natural gas (CO2, CH4etc.) physically resembling ice.

• Hydrogen bonded water molecules (host) create a cage that encloses a guest molecule (typically small molecules like H2, CO2, CH4 ,neo-hexane)I h d f l• In nature gas hydrates are frequently encountered under sub sea environment (due to native high pressure and low temperature environment)

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Different guest size results in different hydrate structure

r ≈ 3.95A r ≈ 4.33A r ≈ 3.91 A r ≈ 4.06Ar ≈ 5.71A

Structure I (sI) 2S.6L.46H2O512 (S) 51262 (L)

Structure H (sH) 3S.2M.1L.34H2O512 (S) 435663 (M) 51268 (L)

r ≈ 3.91Ar ≈ 4.73A

Structure II (sII) 16S.8L.136H2O512 (S) 51264 (L)

4/25/2016 5Semi-clathrate 2S.XXX.38H2O

Importance of Natural Gas for Energy Solutions

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H2

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Clathrate Hydrates in Nature

• Natural gas is a mixture of mainly methane (90-99%), ethane (0-10%), propane (0-6%) & CO2 (0-5%) etc.

• Both pure methane and natural gas hydrates exist in the natural world (not only on earth but also on other planets)

• Large quantity of methane hydrate exist on earth either in permafrost or under the sea bed along continental margin

• Gas hydrates are a good energy resource but it can also be a potential geo y g gy p ghazard.

• Methane is 21 times more potent green house gas than CO2 and due to rise in global warming, methane in natural hydrates can decompose and create runaway effect

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Why Study Clathrate Hydrate

• Understanding the hydrate at molecular level and at what is the right temperature and pressure zone where these hydrates can exist.

Flow Assurance

right temperature and pressure zone where these hydrates can exist.

• Understanding the mechanism of hydrate formation and decomposition

• Potentially a sustainable energy source while still being a potential geo hazard and role in global warming

Gas Hydrate

As a source of methane /natural gas

As a means to develop technology

Permafrost-associatednatural gas hydrate

Deepwater marine natural gas hydrate Gas storage Gas separation Desalination Refrigeration

Hydrogen storage

Natural gas storage &

Methane separation

CO separation (CCS)

CH4 + CO2/H2S

Natural gas production

• Safety in deep oil drilling operations

• Other technological applications and energy solutions like gas separation, methane storage and transportation

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transportation CO2 separation (CCS)CH4 + O2/N2

CH4 + C2H6 + C3H8CO2 + H2

N2 + CO2

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Gas hydrates are found below permafrost or the ocean floor

A hydrate glacier sits on the sea floor, 850 m below the surface*

Methane hydrate samples

http://communications uvic ca/releases/mr020909ph htmlhttp://communications.uvic.ca/releases/mr020909ph.html

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• Total Conventional NG: 300 300 –– 370 TCM (around the world)370 TCM (around the world)

• NGH estimates worldwide: ~ 20,000 TCM 20,000 TCM (mean estimate)

• NGH estimates in India: ~2000 TCM (NGHP estimate)

– Even if 10 % is recoverable 200 TCM200 TCM

– World consumption of Natural Gas per year = 2.4 TCM2.4 TCM 9

(adapted from Collett, 2002).

Proposed GH exploitation techniques

(a) thermal injection, (b) depressurization, (c) inhibitor or other additive

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Pressure reduction, thermal stimulation or additive addition disturbs the three phase equilibria of natural gas hydrate

HydrateHydrate

PressureMethane (gas) + Water Methane (gas) + Water

HydrateHydrate

(solid)(solid)

Temperature

(g )(g )(liquid)(liquid)

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Sustainable production of methane by molecular replacement

Thermodynamic feasibility

Kinetics of replacement

Structure stability &Thermodynamic stability

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Schematic of the experimental setup

The current setup has been designed and built with a design pressure of 15 MPa, andtemperature range between -15 and 60°C. This setup can study methane hydrate dissociationin a wide range of conditions; like water depth of up to 1500 meters, and typical soiloverburdens with different methane hydrate saturations

PR PCR

GC

DAQ

Thermocouples

PC

V5 V3

V4cv

CR CrystallizerR R i

ventventV6 SPV

overburdens with different methane hydrate saturations.

CRR

ER

Gas

V1V2

R ReservoirCV Control ValvePC PC & ControllerDAQ Data Acquisition SystemPCR & PR Pressure TransmitterER External RefrigeratorGC Gas ChromatographySPV Safety Pressure Valve

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A set of mass flow meter and pressure controllers simultaneously simulates the marine environment in lab scale setup

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Temperature and pressure controlled high pressure setup for gas hydrate studies

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Bench Scale High Pressure Continuous Setup for Studying Methane Decomposition Kinetics at sub-Sea

Environment in Presence of Identified Additives

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Hydrate formation is exothermicHydrate formation is a crystallization process

0.14 275.0G s pt k

Temperature = 273.7 K, P = 10.0 MPa

Typical gas uptake curve for hydrate formation

Gas

upta

ke [m

ol]

0.04

0.06

0.08

0.10

0.12

Tem

pera

ture

[K]

273.0

273.5

274.0

274.5Gas uptakeTemperature

17

Time [min]

0 20 40 60 80 100 120

G

0.00

0.02

0.04 T

272.0

272.5(induction time = 19.0 min)

Chemical Engineering Science, 62, 4268-4276 , 2007

Hydrate formation kinetics shows multiple nucleation event

20

30

40

50

drat

e co

nver

sion

(mol

%)

100 % saturation 75 % saturation 50% saturation

T-2

0 3 6 9 12 15 180

10

Wat

er to

hyd

Time (h)

0.008

0.010

tion

er/h

r)

100 % saturation 75 % saturation 50% saturation

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Cooling / Heating Coil

T-1 T-3T 2

0 3 6 9 12 15 180.000

0.002

0.004

0.006

Rat

e of

hyd

rate

form

at (m

ol o

f gas

/mol

of w

ate

Time (hr)18

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Conclusion from lab scale measurements

Methane recovery through thermal stimulation alone is possibleKinetics of hydrate decomposition is lumped kinetics

Decomposition of methane hydrate and its recovery by depressurization alone(without any thermal stimulation) does not self sustain.

In absence of thermal stimulation partial recovery of methane is obtained at slower kinetics

CH4 recovery by CO2 replacement is technically feasible, however focus shouldnot only be on the kinetics of methane replacement but also on overallmethane recoverymethane recovery

Still the question remains, what is the mechanism for such replacement? And what drives thereplacement ?

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Understanding gas hydrate & methane recovery at molecular level

• Understanding the structure and cage dynamics of gash d t th h t t f th t l ti l t lhydrates through state of the art analytical tools

• Understanding molecular level replacement kineticsthrough molecular dynamics simulation of hydrateformation and decomposition.

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Understanding gas hydrate at molecular level through state of the art analytical tools: measurement on solid hydrate phase

Solid state NMRSolid state NMRTmin= -120oC Pmax= ~ few MPaQuantitative techniquefor Cage occupancy

Raman Spectroscopy

X-ray DiffractionTmin= -150oC Pmax~ few MPa (rare)Structure determination Raman Spectroscopy

Tmin= -190oC Pmax~ few GPaQualitative techniquefor Cage occupancy

determination

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Different guest size results in different hydrate structure

r ≈ 3.95A r ≈ 4.33A r ≈ 3.91 A r ≈ 4.06Ar ≈ 5.71A

Structure I (sI) 2S.6L.46H2O512 (S) 51262 (L)

Structure H (sH) 3S.2M.1L.34H2O512 (S) 435663 (M) 51268 (L)

r ≈ 3.91Ar ≈ 4.73A

Structure II (sII) 16S.8L.136H2O512 (S) 51264 (L)

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N2

C3H8

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2917 cm-1

2906 cm-1

Inte

nsity

(a.u

.)

Large to small cage ratio in SI is 3:1, and in SII is 1:2

Methane with a sIIformer

2940 2930 2920 2910 2900 2890 2880

Wavenumber (cm-1)

2915 cm-1

a.u.

)

Methane hydrate in sI2960 2940 2920 2900 2880 2860 2840

Inte

nsity

(a

Wavenumber (cm-1)

2904 cm-1

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Distribution of natural gas in the hydrate phase

AIChE J. 54,2132-2144, 2008.

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Calculation of cage occupancy through Raman and NMR Spectroscopy

Kumar et al. AIChE, 2008

CO2 + C3H8 mixed hydrate- SII

Long term kinetic stability of resultant hydrate

Inte

nsity

(a.u

.)

10 20 30

2Theta

CO2 hydrate - SI

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Understanding methane recovery at molecular level through MD simulation

• All atomistic molecular dynamics simulations can give– intrinsic kinetics of hydrate decompositiony p– One such simulation has identified a unique decomposition pattern

• MD will help in identifying the methane replacement mechanism inpresence of CO2 and other small gases (nitrogen is a potentialcandidate) for better methane recovery.

– CO2-N2 mixture is important because flue gas from thermal power stations alsoneeds to be sequestrated

• MD simulation can help design and speed test additives which can bescreened before carrying out an expensive experimentation in the lab.

– We have tested few additives in gas phase and few in liquid phase

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MD Simulations points toward a layer by layer decomposition

Bulk Water

100 bar

Hydrate Cages

(3 x 3 x 6 unit cells)

30

40

50

60

70

80

90

100

of

wat

er m

olec

ules

mov

ed o

ut

Row 1Row 2Row 3Row 4Row 5Row 6

30

40

50

60

70

80

90

100

SPC/E TIP4P

Z

Y

XBulk

Water

0 500 1000 1500 2000Time (ps)

-10

0

10

20

30

Perc

enta

ge o

f

0 500 1000 1500 2000Time (ps)

-10

0

10

20

30

The Journal of Physical Chemistry C, 117, 2013, 12172-121824/25/2016 28

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Evaluation of optimum gas molecule which can replace methane in natural gas hydrate: MD Simulations

ε = 0.085σ = 0.373ε = 1.23

σ = 0.353

ε = 2.3σ = 0.373

ε = 4.0σ = 0.373

.

ε = 1.23 σ = 0.6

ε in KJ/mol; σ in nm; Snap shots were taken after 2ns of run time

Physical Chemistry Chemical Physics, 2015, 17, 9509-95184/25/2016 29

Additive design and validation: MD and Experimentation

Additive + water

500 ps

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2000 ps

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Methane hydrate formation kinetics

512 62

512

512 63

270 K, 800 Bar

5 6512 64

270 K, 100 Bar

Black 512

Red 51262

Green 51263

Blue 51264

Gas hydrate formation in oil and gas pipelines: A nuisance

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Courtesy of SINTEFSINTEF, Norway, Norway

Hydrates may stick on pipeline walls…and block flow

Deadly accidentsaccidents and plant damagesdamages

from improper hydrate plug removal

in the order of millions of $$$$

Hydrate plugsHydrate plugs move with high velocity (300 km/hr)

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Cost at one oil fieldCost at one oil field: $10 million/day10 million/day

Thermodynamic inhibitors has limited applicability

34C. Koh, Chem Soc Rev 2002 31 157-167

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KHI can be more cost effective at higher water cut

•Development and test of crystal inhibitor with two key properties

•Inhibition of crystal nucleation and inhibition of crystal growth

•Control of nucleation in proteins, inhibition of urinary stone formation, inhibition of ice formation in living tissues during cryo-protection, control of crystal size in ice creams

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(courtesy STATOIL, Norway)

Hydrate formation occur not only on the interface but also in bulk water

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Hydrates formed in presence of small percent of surface modifier (in this case an hydrate inhibitor) shows zig-zag growth pattern …

There is nolink between the hydrate layer and The aqueous water

Hydrates in presenceof higher concentration

qlayer underneath

of kinetic inhibitordoes not nucleates on the water – gas interface rather it nucleates some where in the gas phase with a very strange phenomena (Bridge effect?)

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S i d T k R i h i l i d

Hydrate Formation conditions: Gas used: Pure CH4; Pressure: 5.0 MPa; Temperature: 274.15 K

Lab scale setup to experimentally identify the additives

Stirred Tank Reactor with optical window

Hydrate Based Gas Separation (HBGS) Process for separating a gas mixture

Feed gas

CO2 depleted gas phase

(CO2/ H2)

+Water

Hydrate crystallization under suitable temperature and pressure CO2 enriched

hydrate phase

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Kang, S.-P., and H. Lee, Environ. Sci. Technol., 34, 4397-4400 (2000)

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Path to commercialization

Static Mixer

Energy Intensive; not suitable for large volumesEnergy Intensive; not suitable for large volumesSolid hydrate formation in static mixerGood for P & T measurement Good for additives selection

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Two major challenges1. Improvement in kinetics of hydrate formation and water to hydrate conversion2. Effect of impurities like fly-ash, SO2, H2S on separation efficiency

Influence of additives on hydrate formation kinetics

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Gas uptake in bulk waterGas uptake in fixed bed

Kumar A, Sakpal T, Linga P , Kumar R. Fuel., 105, 664 - 671 (2013).

Bulk waterBulk water + SDS

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Influence of different contact media in presence of additives on hydrate based gas separation (HBGS) process

Kumar, A., Sakpal, T., Linga, P., Kumar, R. Chemical Engineering Science (2014)DOI: 10.1016/j.ces.2014.09.019

Kumar, A., Kumar, R. Energy and Fuel (2015) DOI: 10.1021/acs.energyfuels.5b00664

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Acknowledgements

Funding Partners

(Gas Hydrate Research)• Department of Science and Technology (DST)• CSIR 12th five year plan (Tapcoal)

Students working in the group

1. Mr. Vikesh Singh Baghel (M.E, now with Halliburton)2. Dr. Asheesh Kumar (PhD Student, Now with NUS)3 Mr Nil sh Ch dh r (PhD St d nt)• CSIR – 12th five year plan (Tapcoal)

• Gas Authority of India Limited (GAIL)(Process Development)• Department of Bio-Technology (DBT)• CSIR – 12th Five Year Plan (Indusmagic)

Scientific Partners

(Gas Hydrate Research)• Dr. Suman Chakrabarty (NCL, India)• D S di R (N ith Sh ll)

3. Mr. Nilesh Choudhary (PhD Student)4. Mr. Gaurav Bhattacharya (PhD Student)5. Mr. Subhadip Das (PhD Student)6. Mr. Vivek Bermecha (PA-II)7. Dr. Omkar Singh Kushwaha (Research Assistant)8. Mr. Amit Arora (PhD Student at IIT – Roorkee)9. Dr. Ponnivalavan Babu (PhD at NUS)10. Dr. Hari Prakash (PhD at NUS)11. Mr. Tushar Sakpal (PA-II, now at TU Delft)12. Ms. Prajakta Nakate (PA-II, Now at TU Delft )

• Dr. Sudip Roy (Now with Shell)• Dr. Praveen Linga (NUS, Singapore)(Process Development)• Dr. Sanjay Nene (NCL, India)• Dr. Prashant Barve (NCL, India)

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Thank you !http://academic.ncl.res.in/k.rajnish

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