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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
Cooper, A.I., J. Mater. Chem., 2000, 10, 207-234
• Densityy()q of solid water (ice) is lower than liquid water and this is 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
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Molecular structure of water in different phases
Photographs are from Janda Lab
4/25/2016 Dr. Rajnish Kumar, NCL ‐ Pune 3
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. • Hydrogen 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 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
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 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 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 Clathrate Hydrate
• 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 Hydrogen storage 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
4/25/2016 Dr. Rajnish Kumar, NCL ‐ Pune 8
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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. 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 gases (nitrogen 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 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
(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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