@article { ISI:000329552500027, title = {HBGS (hydrate based gas separation) process for carbon dioxide capture employing an unstirred reactor with cyclopentane}, journal = {Energy}, volume = {63}, year = {2013}, month = {DEC}, pages = {252-259}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

The effect of CP (cyclopentane) as a promoter/additive, in the HBGS (hydrate based gas separation) process for pre-combustion gas mixture was investigated by employing an unstirred reactor configuration. Gas uptake measurements were performed at two different temperatures (275.7 K and 285.7 K) and at an experimental pressure of 6.0 MPa to determine the kinetics of hydrate formation. Experiments were conducted with three different volumes (7.5, 15 and 22 ml) of CP and based on induction time and the rate of hydrate growth, 15 ml of CP was determined to be the optimal volume for carbon dioxide capture at 6.0 MPa and 275.7 K. In addition, the effect of a kinetic promoter, SDS (sodium dodecyl sulfate), was investigated. Surprisingly, no improvement in kinetic performance was observed at 6.0 MPa and 275.7 K in the presence of SDS and CP. From the study, it was found that at the optimal 15 ml CP (CP layer thickness of 1.8 mm), the average composition of carbon dioxide in the hydrate phase was 90.36 mol\% with a separation factor of 17.82. Furthermore, the unstirred reactor also yielded better kinetic performance over the stirred tank reactor with the unstirred reactor having a 2.28 times higher average gas uptake. (C) 2013 Elsevier Ltd. All rights reserved.

}, keywords = {Carbon dioxide capture, Cyclopentane, Gas hydrates, Gas separation, Pre-combustion, Unstirred reactor}, issn = {0360-5442}, doi = {10.1016/j.energy.2013.10.031}, author = {Ho, Leong Chuan and Babu, Ponnivalavan and Kumar, Rajnish and Linga, Praveen} } @article { ISI:000320640500033, title = {Heat transfer calculations for decomposition of structure i methane hydrates by molecular dynamics simulation}, journal = {Journal of Physical Chemistry C}, volume = {117}, number = {23}, year = {2013}, month = {JUN}, pages = {12172-12182}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Microcanonical ensemble molecular dynamics simulations of structure I methane hydrate is presented in this work to study the endothermic decomposition process. The mechanism of decomposition of methane hydrate as a function of time was explained at the molecular level. The initial temperature and pressure of the simulation were chosen so as to depict the natural gas hydrate in conditions of oceanic sediments. A more realistic strategy was developed to perform the microcanonical ensemble simulation of solid liquid interface of hydrate and amorphous water. Two water models, SPC/E and TIP4P, were used for the simulations, and the results of the simulations were compared. Heat transfer calculations were performed on the adiabatic system, and an attempt has been made to fit the MD simulation results to the heat balance equations derived from the heat transfer calculations. Estimates of the properties at the macroscopic scale, like the equilibrium temperature of methane hydrate and rate of supply of hot water for sustained release of methane from solid hydrate phase, were determined. The equilibrium temperature obtained by the above method was found to be in agreement with the experimentally observed value. Both the SPC/E and TIP4P water models gave similar results.

}, issn = {1932-7447}, doi = {10.1021/jp4023772}, author = {Baghel, Vikesh Singh and Kumar, Rajnish and Roy, Sudip} } @article { ISI:000317352000009, title = {Hydrate phase equilibrium of ternary gas mixtures containing carbon dioxide, hydrogen and propane}, journal = {Journal of Chemical Thermodynamics}, volume = {61}, year = {2013}, month = {JUN}, pages = {58-63}, publisher = {ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD}, address = {24-28 OVAL RD, LONDON NW1 7DX, ENGLAND}, abstract = {

Hydrate phase equilibrium of the ternary guest mixtures containing carbon dioxide, hydrogen and propane at two different compositions were determined. Addition of mole composition of 2.5\% propane to the fuel gas (CO2 (40\%)/H-2 (60\%)) mixture reduces the hydrate formation conditions by 66\% at the temperature of 278.4 K. A Clausius-Clapeyron plot for the experimental results was plotted and from the slope, the enthalpy of hydrate dissociation was calculated. The enthalpy of dissociation of the mixed hydrate formed from a ternary gas mixture containing mole composition 38.1\% CO2, 59.4\% H-2 and 2.5\% C3H8 was found to be 110 kJ.mol(-1) and hence it was concluded that the mixed hydrate formed structure II (sII) hydrates. Whereas for the ternary gas mixture containing mole composition 80.0\% CO2, 18.8\% H-2, and 1.2\% C3H8, the enthalpy of dissociation of the mixed hydrate was found to be 78 kJ.mol(-1) and hence we believe the mixed hydrate formed structure I (sI) hydrate. (C) 2013 Elsevier Ltd. All rights reserved.

}, keywords = {Carbon dioxide capture, Gas hydrates, Global warming, Phase equilibrium, Pre-combustion, Thermodynamics}, issn = {0021-9614}, doi = {10.1016/j.jct.2013.02.003}, author = {Babu, Ponnivalavan and Yang, Ting and Veluswamy, Hari Prakash and Kumar, Rajnish and Linga, Praveen} } @article { ISI:000335273100012, title = {Hydrogen storage in clathrate hydrates: Current state of the art and future directions}, journal = {Applied Energy}, volume = {122}, year = {2014}, month = {JUN}, pages = {112-132}, publisher = {ELSEVIER SCI LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

Hydrogen is looked upon as the next generation clean energy carrier, search for an efficient material and method for storing hydrogen has been pursued relentlessly. Improving hydrogen storage capacity to meet DOE targets has been challenging and research efforts are continuously put forth to achieve the set targets and to make hydrogen storage a commercially realizable process. This review comprehensively summarizes the state of the art experimental work conducted on the storage of hydrogen as hydrogen clathrates both at the molecular level and macroscopic level. It identifies future directions and challenges for this exciting area of research. Hydrogen storage capacities of different clathrate structures - sI, sII, sH, sVI and semi clathrates have been compiled and presented. In addition, promising new approaches for increasing hydrogen storage capacity have been described. Future directions for achieving increased hydrogen storage and process scale up have been outlined. Despite few limitations in storing hydrogen in the form of clathrates, this domain receives prominent attention due to more environmental-friendly method of synthesis, easy recovery of molecular hydrogen with minimum energy requirement, and improved safety of the process. (C) 2014 Elsevier Ltd. All rights reserved.

}, keywords = {Clathrates, Gas hydrates, Hydrogen hydrates, Hydrogen storage, Promoters, Storage capacity}, issn = {0306-2619}, doi = {10.1016/j.apenergy.2014.01.063}, author = {Veluswamy, Hari Prakash and Kumar, Rajnish and Linga, Praveen} }