02058nas a2200241 4500008004100000022001400041245009300055210006900148260009900217300001200316490000800328520118700336653002701523653002201550653001301572653001501585653001601600100001901616700001901635700001901654700001901673856012401692 2013 eng d a0016-236100aInfluence of contact medium and surfactants on carbon dioxide clathrate hydrate kinetics0 aInfluence of contact medium and surfactants on carbon dioxide cl aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLANDbELSEVIER SCI LTDcMAR a664-6710 v1053 a

Carbon dioxide (CO2) hydrate formation kinetic was investigated in a fixed bed crystallizer at constant pressure (3.55 MPa) and temperature (274 K). Porous media of three different silica gels were used, with a mesh size of 60-120, 100-200 and 230-400 having different surface area. The observed trends indicate that silica gel with larger surface area leads to higher gas consumption as well as reduces the induction time. The effect of pore diameter and particle size distribution has already been reported in a previous study [1]. In this study the effect of additives on hydrate formation kinetics were also investigated. The additives studied were nonionic surfactant Tween-80 (T-80), cationic dodecyltrimethylammonium chloride (DTACl) and anionic Sodium Dodecyl Sulphate (SDS). Out of the three surfactants used in this study, SDS was found to be most effective in enhancing the rate of hydrate formation as well as reducing the induction time. The current result shows significant improvement in water to hydrate conversion in silica gel media compared to quiescent water or surfactant-water system under similar conditions. (C) 2012 Elsevier Ltd. All rights reserved.

10aCarbon dioxide capture10aClathrate hydrate10akinetics10aSilica gel10aSurfactants1 aKumar, Asheesh1 aSakpal, Tushar1 aLinga, Praveen1 aKumar, Rajnish uhttps://library.ncl.res.in/content/influence-contact-medium-and-surfactants-carbon-dioxide-clathrate-hydrate-kinetics-001845nas a2200229 4500008004100000022001400041245011200055210006900167260007700236300001200313490000600325520102600331653001501357653001301372653001501385653001301400653002401413100001901437700001901456700001901475856012101494 2015 eng d a2194-428800aInfluence of low-dosage hydrate inhibitors on methane clathrate hydrate formation and dissociation kinetics0 aInfluence of lowdosage hydrate inhibitors on methane clathrate h aBOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcJUL a717-7250 v33 a

This work investigates the effect of low-dosage hydrate inhibitors (LDHIs) on methane hydrate formation and dissociation. The hydrate inhibitors used in this study were the sodium salt of polyacrylic acid, a polysaccharide chitosan, and the linear sulfated polysaccharide i-carrageenan; the inhibiting behavior of these additives were compared with that of the commonly used hydrate inhibitor polyvinylpyrrolidone for methane hydrate formation. A LDHI concentration of 1wt% was found to increase the induction time relative to that at a LDHI concentration of 0.1wt%. Chitosan was found to be better than the others in reducing nucleation and the growth rate of the hydrate at a concentration of 1wt%. At a lower concentration of 0.1wt%, nucleation inhibition was minimal, however, growth inhibition was significant. The effect of these inhibitors on the decomposition rate of the hydrate was also studied, and the decomposition kinetics at a constant driving force in excess of three-phase equilibrium is reported.

10agas uptake10ahydrates10ainhibitors10akinetics10athermal stimulation1 aKumar, Asheesh1 aSakpal, Tushar1 aKumar, Rajnish uhttps://library.ncl.res.in/content/influence-low-dosage-hydrate-inhibitors-methane-clathrate-hydrate-formation-and-001468nas a2200241 4500008004100000022001400041245009800055210006900153260010500222300001400327490000700341520058000348653002000928653003200948653001400980653001700994653001301011100001901024700002001043700001801063700001901081856012601100 2016 eng d a0256-111500aCrystallization kinetics for carbon dioxide gas hydrate in fixed bed and stirred tank reactor0 aCrystallization kinetics for carbon dioxide gas hydrate in fixed aF.5, 119, ANAM-RO, SEONGBUK-GU, SEOUL 136-075, SOUTH KOREAbKOREAN INSTITUTE CHEMICAL ENGINEERScJUN a1922-19300 v333 a

The phase change from germ nuclei to growth nuclei and subsequent volume transformation in a crystallization process was modeled by Avrami equations. The phase change during the hydrate formation was fitted with the classical Avrami model by utilizing gas uptake data. The idea is to understand the difference in growth behavior of hydrate crystals when in small pores compared to a stirred tank reactor which does not pose any physical restrictions to hydrate growth. The parameters n and k of the Avrami equation were determined explicitly for CO2 hydrate formation.

10aAvrami Equation10aCO2 Capture & Sequestration10aFixed Bed10aGas hydrates10akinetics1 aKumar, Asheesh1 aKhatri, Dishant1 aLee, Ju, Dong1 aKumar, Rajnish uhttps://library.ncl.res.in/content/crystallization-kinetics-carbon-dioxide-gas-hydrate-fixed-bed-and-stirred-tank-reactor02099nas a2200253 4500008004100000022001400041245007600055210006900131260000800200300001400208490000700222520131000229653001501539653001901554653001601573653001301589653003301602100002601635700002201661700001901683700002301702700001901725856010101744 2016 eng d a1875-510000aEffect of the amino acid L-histidine on methane hydrate growth kinetics0 aEffect of the amino acid Lhistidine on methane hydrate growth ki cSEP a1453-14620 v353 a

In the present study, the effect of a polar amino acid, L-histidine on methane hydrate growth kinetics has been investigated. Methane hydrate formation experiments were carried out in a stirred tank reactor setup at pressure and temperature conditions of 274.15 K and 5.0 MPa respectively. Two different concentrations (0.1 and 1 wt %) of L-histidine were studied. Hydrate growth through molecular dynamic (MD) simulation was also studied; pressure and temperature conditions for the simulations were set at 10.0 MPa and 270.0 K, while the concentration of L-histidine was kept fixed at 0.94 wt %. Hydrate formation runs using MD simulation were carried out with optimal concentration of methane in water. The presence of L-histidine in the system was found to significantly enhance methane hydrate growth kinetics as compared to pure water for both experimental and MD simulation runs. Final gas consumption with 1 wt % L-histidine was found to be comparable to that with 1 wt % SDS, the most commonly used additive for hydrate promotion studies. L-histidine is a benign additive which offers considerable enhancement in methane hydrate formation kinetics and can be utilized for various hydrate based technologies such as methane storage and transport. (C) 2016 Elsevier B.V. All rights reserved.

10aAmino acid10aCrystal growth10aGas hydrate10akinetics10aMolecular dynamic simulation1 aBhattacharjee, Gaurav1 aChoudhary, Nilesh1 aKumar, Asheesh1 aChakrabarty, Suman1 aKumar, Rajnish uhttps://library.ncl.res.in/content/effect-amino-acid-l-histidine-methane-hydrate-growth-kinetics02056nas a2200253 4500008004100000022001400041245017300055210006900228260000800297300001200305490000800317520116300325653001301488653001601501653001301517653002001530653001301550653002401563100002601587700002001613700002401633700001901657856012601676 2018 eng d a0021-961400aKinetic promotion of methane hydrate formation by combining anionic and silicone surfactants: scalability promise of methane storage due to prevention of foam formation0 aKinetic promotion of methane hydrate formation by combining anio cFEB a248-2550 v1173 a

Methane storage in its solid hydrate form has recently come up as a rather attractive and low risk option for large scale storage of the gas owing to its mild storage conditions, high gas retention capacity and benign (non-explosive) character. However, it has its fair share of limitations with the slow rate of hydrate formation being one of the most prominent. The addition of surfactants like Sodium dodecyl sulfate (SDS) to the hydrate forming system significantly speeds up the process of methane hydrate formation but the large amount of foam generated by these surfactants during the process of hydrate formation and dissociation stands as a major roadblock towards the scaling up of the technology. In the current work, a small amount of a silicon based surfactant has been proposed to be used as antifoam in conjunction with an anionic surfactant SDS to eliminate the foam generation while at the same time promote the kinetics of methane hydrate formation. The idea is simple, cost effective and can be a potential game-changer in the quest to develop a commercially scalable hydrate based methane storage technology. (C) 2017 Elsevier Ltd.

10aAntifoam10aGas hydrate10akinetics10aMethane storage10ascale-up10aSilicone surfactant1 aBhattacharjee, Gaurav1 aBarmecha, Vivek1 aKushwaha, Omkar, S.1 aKumar, Rajnish uhttps://library.ncl.res.in/content/kinetic-promotion-methane-hydrate-formation-combining-anionic-and-silicone-surfactants02708nas a2200313 4500008004100000022001400041245011000055210006900165260000900234300001100243490000800254520170900262653001601971653001301987653001902000653002002019653002102039653002402060653001202084100002602096700002202122700002002144700002402164700002102188700002002209700001502229700001902244856013102263 2019 eng d a0306-261900aMethane recovery from marine gas hydrates: a bench scale study in presence of low dosage benign additives0 aMethane recovery from marine gas hydrates a bench scale study in cNOV  a1135660 v2533 a

De-pressurization is one approach which has been found to be economically feasible for methane recovery from marine hydrates. Hydrate dissociation being an endothermic process suggests that de-pressurization alone would not be sufficient and some additional stimulation would be required for sustained production from one such reservoir. Thermal stimulation may overcome the challenge posed by the endothermic dissociation process; however, economically it may not be ideal. A possible way out is to use thermal stimulation, but at relatively low temperatures as compared to conventional practice. This would be economical and can be accomplished in the presence of small doses of additives mixed in with the water stream used for thermal stimulation. In the present study, a number of benign additives were identified which when used in low concentrations enhance the kinetics of methane hydrate dissociation compared to pure water. Additives were first shortlisted from a wide potential pool using quantum mechanical calculations. These additives were later tested for their efficacy in stirred tank reactor to quickly identify the best additives for the job and few selected additives were then studied in a larger bench scale setup (fixed bed configuration) where they were injected in the form of an additive-water stream to dissociate already formed hydrates. Factors such as toxicity of the additive, fluidity of additive-water stream, foam formation on mixing of additive with water, etc. were also taken into account. An energy and efficiency analysis revealed that reported additives enhance the energy ratio and thermal efficiency of the process as compared to pure water stimulation.

10aBench scale10akinetics10aMarine hydrate10amethane hydrate10aMethane recovery10aNatural gas hydrate10aProcess1 aBhattacharjee, Gaurav1 aChoudhary, Nilesh1 aBarmecha, Vivek1 aKushwaha, Omkar, S.1 aPande, Nawal, K.1 aChugh, Parivesh1 aRoy, Sudip1 aKumar, Rajnish uhttps://library.ncl.res.in/content/methane-recovery-marine-gas-hydrates-bench-scale-study-presence-low-dosage-benign-additives02526nas a2200277 4500008004100000022001400041245009700055210006900152260000800221300001400229490000700243520165200250653001801902653001701920653002201937653002401959653001301983653002401996653001902020100002102039700001702060700001802077700001502095700001902110856011902129 2019 eng d a1004-954100aMolecular dynamics study on growth of carbon dioxide and methane hydrate from a seed crystal0 aMolecular dynamics study on growth of carbon dioxide and methane cSEP a2074-20800 v273 a

In the current work, molecular dynamics simulation is employed to understand the intrinsic growth of carbon dioxide and methane hydrate starting from a seed crystal of methane and carbon dioxide respectively. This comparison was carried out because it has relevance to the recovery of methane gas from natural gas hydrate reservoirs by simultaneously sequestering a greenhouse gas like CO2. The seed crystal of carbon dioxide and methane hydrate was allowed to grow from a super-saturated mixture of carbon dioxide or methane molecules in water respectively. Two different concentrations (1:6 and 1:8.5) of CO2/CH4 molecules per water molecule were chosen based on gas-water composition in hydrate phase. The molecular level growth as a function of time was investigated by all atomistic molecular dynamics simulation under suitable temperature and pressure range which was well above the hydrate stability zone to ensure significantly faster growth kinetics. The concentration of CO2 molecules in water played a significant role in growth kinetics, and it was observed that maximizing the CO2 concentration in the aqueous phase may not result in faster growth of CO2 hydrate. On the contrary, methane hydrate growth was independent of methane molecule concentration in the aqueous phase. We have validated our results by performing experimental work on carbon dioxide hydrate where it was seen that under conditions appropriate for liquid CO2, the growth for carbon dioxide hydrate was very slow in the beginning. (C) 2019 The Chemical Industry and Engineering Society of China, and Chemical Industry Press Co., Ltd. All rights reserved.

10aCage dynamics10aCH4 recovery10aCO2 sequestration10aF-4 order parameter10akinetics10aNatural gas hydrate10aThermodynamics1 aNakate, Prajakta1 aGhosh, Bappa1 aDas, Subhadip1 aRoy, Sudip1 aKumar, Rajnish uhttps://library.ncl.res.in/content/molecular-dynamics-study-growth-carbon-dioxide-and-methane-hydrate-seed-crystal