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Understanding and its Utility for Energy Solutions

Rajnish Kumar

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

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

• Densityy()q of water (ice) is lower than liquid water and this is one reason why life exist of . • Water have very different boiling point compared to other of similar molecular weight. • Within the solid ice phase, 13 known phases of ice has been

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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 comppgounds consisting

of water and natural gas (CO2, CH4 etc.) physically resembling ice. • bonded water molecules (host) create a cage that encloses a guest molecule (typically small molecules like

H2, CO2, CH4 ,neo-hexane) • IhdflIn 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 structure r ≈ 5.71A r ≈ 4.33A r ≈ 3.95A r ≈ 3.91 A r ≈ 4.06A

12 12 2 5 (S) 5 6 (L) 512 (S) 435663 (M) 51268 (L) Structure I (sI) Æ 2S.6L.46H O 2 Structure H (sH) Æ 3S.2M.1L.34H2O

r ≈ 4.73A r ≈ 3.91A

512 (S) 51264 (L)

Structure II (sII) Æ 16S.8L.136H2O 4/25/2016 5 Semi-clathrate Æ 2S.XXX.38H2O

Importance of Natural Gas for Energy Solutions

Coal 27 kg of C ed n

21 kg of C Oil

per GJ of energy obtai Natural 14 kg of C gas Wood, muscles H2 power 0* 1800 1960 2005 20xx (Post industrial revolution) 4/25/2016 Dr. Rajnish Kumar, NCL ‐ Pune 6

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Clathrate Hydrates in Nature

• Natural gas is a mixture of mainly (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 )

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

• Gas hyyggydrates are a good energy resource but it can also be a p pgotential geo hazard.

• 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

4/25/2016 Dr. Rajnish Kumar, NCL ‐ Pune 7

Why Study

• Understanding the hydrate at molecular level andFlow at Assurance what is the

right temperature and pressureGas Hydrate zone where these hydrates can exist.

• UnderstandingAs athe source ofmechanism methane of hydrateAs a means to developformation and /natural gas technology

Permafrost-associateddecompositionDeepwater marine natural Gas storage Gas separation Desalination Refrigeration natural gas hydrate gas hydrate • Potentially a sustainable energy source while still being a potential Natural gas production Methane separation

geo hazard and role in global warming CH4 + CO2/H2S Natural gas storage & CO separation (CCS) transportation 2 CH + O /N • Safety in deep oil drilling operations 4 2 2 CO2 + H2 CH4 + C2H6 + C3H8

• Other technological applications and energy solutionsN2 + CO2 like gas separation, methane storage and transportation

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Gas hydrates are found below permafrost or the ocean floor A hydrate sits on the sea floor, 850 m below the surface*

Methane hydrate samples

http://communications. uvic. ca/releases/mr020909ph. html • Total Conventional NG: 300 – 370 TCM (around the world)

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

• NGH estimates in India: ~2000 TCM (NGHP estimate) – Even if 10 % is recoverable Î 200 TCM

– World consumption of Natural Gas per year = 2.4 TCM 4/25/2016 9

Proposed GH exploitation techniques (adapted from Collett, 2002).

(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

Hydrate (solid)

Pressure

Methane (gas) + Water (liquid)

Temperature

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Sustainable production of methane by molecular replacement

¾ Thermodynamic feasibility

¾ Kinetics of replacement

¾ 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, and temperature range between -15 and 60°C. This setup can study methane hydrate dissociation in a wide range of conditions; like water depth of up to 1500 meters, and typical soil overburdens with different methane hydrate saturations.

Thermocouples

PC DAQ GC

PR PCR

V4 vent cv V6 SPV vent V5 V3

CR Crystallizer R RiReservoir V1 CV Control Valve V2 PC PC & Controller DAQ Data Acquisition System PCR & PR Pressure Transmitter ER External Refrigerator ER GC Gas Chromatography SPV Safety Pressure Valve R CR G a s

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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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HydrateTypicalHydrate gasformation uptake formation curveis a crystallization for is exothermichydrate formation process

Temperature = 273.7 K, P = 10.0 MPa 0.14 275.0 GsGas uptptkake 0.12 Temperature 274.5 0.10 274.0 0.08 273.5 0.06 273.0 as uptake [mol] 0.04 [K] emperature G T 272.5 0.02 (induction time = 19.0 min) 0.00 272.0 0 20406080100120 Time [min]

Chemical Engineering Science, 62, 4268-4276 , 2007 17

Hydrate formation kinetics shows multiple nucleation event 50 100 % saturation 75 % saturation 50% saturation 40

30

20 rate conversion (mol%) conversion rate d

10

Water to hy Water 0 0369121518 Time (h) 0.010 100 % saturation 75 % saturation 0.008 50% saturation r/hr) ion t T-2 e T-1 T-3 0.006

0.004

Cooling / Heating Coil 0.002 Rate of hydrate forma hydrate of Rate (mol of gas/mol of wat 0.000 4/25/2016 0 3 6 9 12 1518 18 Time (hr)

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Conclusion from lab scale measurements

¾ Methane recovery through thermal stimulation alone is possible ¾ Kinetics of hydrate decomposition is lumped kinetics

¾ Decomposition of methane hydrate and its recovery by depressurization alone (without any thermal stimulation) does not self sustain. ¾ In absence of thermal stimulation partial recovery of methane is obtained at slower kinetics

¾ CH4 recovery by CO2 replacement is technically feasible, however focus should not only be on the kinetics of methane replacement but also on overall methane recovery ¾ Still the question remains, what is the mechanism for such replacement? And what drives the replacement ?

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Understanding gas hydrate & methane recovery at molecular level

• Understanding the structure and cage dynamics of gas hdhydra tes through stttateof theart analtillytical tltools

• Understanding molecular level replacement kinetics through molecular dynamics simulation of hydrate formation 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 NMR o Tmin= -120 C Pmax= ~ few MPa Quantitative technique for Cage occupancy X-ray Diffraction o Tmin= -150 C Pmax~ few MPa (rare) Structure determination Raman Spectroscopy o Tmin= -190 C Pmax~ few GPa Qualitative technique for Cage occupancy

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Different guest size results in different hydrate structure r ≈ 5.71A r ≈ 4.33A r ≈ 3.95A r ≈ 3.91 A r ≈ 4.06A

12 12 2 5 (S) 5 6 (L) 512 (S) 435663 (M) 51268 (L) Structure I (sI) Æ 2S.6L.46H O 2 Structure H (sH) Æ 3S.2M.1L.34H2O

r ≈ 4.73A r ≈ 3.91A

N2

C3H8 512 (S) 51264 (L)

Structure II (sII) Æ 16S.8L.136H2O 4/25/2016 22

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Large to small cage ratio in SI is 3:1, and in SII is 1:2 2906 cm-1

Methane with a sII 2917 cm-1

former (a.u.) Intensity

2940 2930 2920 2910 2900 2890 2880

Wavenumber (cm-1)

2915 cm-1 .u.) a

-1 2904 cm Intensity (

2960 2940 2920 2900 2880 2860 2840 4/25/2016 23 Methane hydrate in sI Wavenumber (cm-1)

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

Long term kinetic stability of resultant hydrate

CO2 + C3H8 mixed hydrate- SII

Intensity (a.u.)

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 decomposition – One such simulation has identified a unique decomposition pattern

• MD will help in identifying the methane replacement mechanism in

presence of CO2 and other small ( is a potential candidate) for better methane recovery.

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

• MD simulation can help design and speed test additives which can be screened 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 100 bar Water

Row 1 SPC/E TIP4P Row 2 100 Row 3 100 Row 4 90 Row 5 90 Row 6 80 80

70 70 Hydrate 60 60 Cages 50 50 (3 x 3 x 6 unit 40 40 cells) 30 30 of water molecules moved out Z 20 20

Percentage of 10 10 Y 0 0 -10 -10 0 500 1000 1500 2000 0 500 1000 1500 2000 X Time (ps) Time (ps) Bulk The Journal of Physical Chemistry C, 117, 2013, 12172-12182 4/25/2016Water 28

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

ε = 0.085 ε = 1.23 σ = 0.373 σ = 0.353

ε = 2.3 σ = 0.373 ε = 1.23 σ = 0.6

ε = 4.0 σ = 0.373

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

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Additive design and validation: MD and Experimentation

Additive + water

500 ps

2000 ps

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Methane hydrate formation kinetics

270 K, 800 Bar

512 62 512 512 63 512 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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Hydrates may stick on pipeline walls… and block flow

Courtesy of SINTEF, Norway Deadly accidents and plantdamages from improper hydrate plug removal in the order of millions of $$

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

Cost at one oil field: $1010 million/day 33

Thermodynamic inhibitors has limited applicability

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

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KHI can be more cost effective at higher water cut •Development and test of 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

(courtesy STATOIL, Norway)

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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 no link between the hydrate layer and The aqueous water layer underneath

Hydrates in presence of higher concentration of kinetic inhibitor does 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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Lab scale setup to experimentally identify the additives Hydrate Formation conditions:

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

SSitirred dT Tank kR Reactor wi ihth opti cal wi nd ow

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

CO2 depleted gas phase

Feed gas

(CO2/ H2) + Water

Hydrate crystallization under suitable temperature and pressure CO2 enriched hydrate phase

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 volumes Solid hydrate formation in static mixer Good for P & T measurement Good for additives selection

Two major challenges 1. Improvement in kinetics of hydrate formation and water to hydrate conversion

2. Effect of impurities like fly-ash, SO2, H2S on separation efficiency

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Gas uptake in bulk water Gas uptake in fixed bed Influence of additives on hydrate formation kinetics

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

Bulk water Bulk 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 Students working in the group (Gas Hydrate Research) 1. Mr. Vikesh Singh Baghel (M.E, now with Halliburton) • Department of Science and Technology (DST) 2. Dr. Asheesh Kumar (PhD Student, Now with NUS) • CSIR – 12th five year plan (Tapcoal) 3. Mr. Nile sh Chou dha ry (PhD Stu de nt) • Gas Authority of India Limited (GAIL) 4. Mr. Gaurav Bhattacharya (PhD Student) (Process Development) 5. Mr. Subhadip Das (PhD Student) 6. Mr. Vivek Bermecha (PA-II) • Department of Bio-Technology (DBT) 7. Dr. Omkar Singh Kushwaha (Research Assistant) th • CSIR – 12 Five Year Plan (Indusmagic) 8. Mr. Amit Arora (PhD Student at IIT – Roorkee) 9. Dr. Ponnivalavan Babu (PhD at NUS) Scientific Partners 10. Dr. Hari Prakash (PhD at NUS) (Gas Hydrate Research) 11. Mr. Tushar Sakpal (PA-II, now at TU Delft) 12. Ms. Prajakta Nakate (PA-II, Now at TU Delft ) • Dr. Suman Chakrabarty (NCL, India) • Dr. S udi p Roy (Now w ith Sh ell) • 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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