@article { ISI:000236715600020, title = {Modeling of rotary cement kilns: applications to reduction in energy consumption}, journal = {Industrial \& Engineering Chemistry Research}, volume = {45}, number = {7}, year = {2006}, month = {MAR}, pages = {2315-2330}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Rotary cement kilns are used for converting calcineous raw meal into cement clinkers. In this paper, we discuss and evaluate possible ways of reducing energy consumption in rotary cement kilns. A comprehensive one-dimensional model was developed to simulate complex processes occurring in rotary cement Kilns. A modeling strategy comprising three submodels. viz. a model for simulating the variation of bed height in the kiln, a model for simulating reactions and heat transfer in the bed region, and a model for simulating coal combustion and heat transfer in the freeboard region, was developed. Melting and formation of coating within the kiln were accounted for. Combustion of coal in the freeboard region was modeled by accounting for devolatilization, finite-rate gas-phase combustion, and char reaction. The simulated results were validated with the available data from three industrial kilns. The model was then used to understand the influence of various design and operating parameters on kiln performance. Several ways of reducing energy consumption in kilns were then computationally investigated. The model was also used to propose and to evaluate a practical solution of using a secondary shell to reduce energy consumption in rotary cement kilns. Simulation results indicate that varying kiln operating variables, viz. solid flow rate or RPM, can result only in small changes in kiln energetics. Use of a secondary shell over the kiln and energy recovery by passing air through the annular gap between the two appears to be a promising way to achieve significant energy savings. The developed model and the presented results will be useful for enhancing the performance of rotary cement kilns.

}, issn = {0888-5885}, doi = {10.1021/ie050617v}, author = {Mujumdar, Kaustubh S. and Arora, Amit and Ranade, V. V.} } @article { ISI:000263732700047, title = {Effects for the incorporation of five-atom thioacetamido nucleic acid (TANA) backbone on hybridization thermodynamics and kinetics of DNA duplexes}, journal = {Journal of Physical Chemistry B}, volume = {113}, number = {9}, year = {2009}, month = {MAR}, pages = {2944-2951}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Thermodynamic studies of nucleic acids serve not only to widen our understanding on the nature and strength of forces that stabilize nucleic acids in a myriad of structural states they assume but also to facilitate the development of databases that could be used to predict the stability and selectivity of probe/primer-sets required in a broad range of nucleic acid-based diagnostic and therapeutic protocols. In the current study, we investigated the effect of a novel, backbone-modified {\textquoteleft}{\textquoteleft}thioacetamido linkage{\textquoteright}{\textquoteright} (TANA) on thermodynamics of hybridization, binding kinetics, and conformation of a DNA duplex. The modification comprises of an extended five-atom amide (N3{\textquoteright}-CO-CH(2)-S-CH(2)) linker, as opposed to four-atom phosphodiester linker backbone present in DNA. One to three TANA-substitutions have been introduced in the linker backbone of two thymidine residues of one of the strand of the DNA duplex. Using spectroscopic and calorimetric techniques, we observed that TANA destabilizes the DNA helix by lowering the favorable enthalpy parameter of duplex formation. TANA center dot DNA duplexes were found to adopt a conformation toward an A-type duplex as shown by circular dichroism spectroscopy studies. Analysis of differential scanning calorimetry data indicated a nonzero heat capacity change, Delta C(p), accompanying the duplex formation. The average Delta C(p) change per duplex was found to be 832.5 cal mol(-1) K(-1), giving an average base-pair change of 59.5 cal (mol of base pairs)(-1) K(-1). Hybridization kinetic measurements using surface plasmon resonance indicated a decrease in binding affinity parameter (K(A)) that originates from higher dissociation rate constants (k(d)). Furthermore, optical melting studies showed that increasing the number of modifications results in a modest change in the number of counterions taken up during duplex formation.

}, issn = {1520-6106}, doi = {10.1021/jp808747g}, author = {Kaur, Harleen and Arora, Amit and Gogoi, K. and Solanke, P. and Gunjal, Anita D. and Kumar, Vaijayanti A. and Maiti, Souvik} } @article { ISI:000369937200001, title = {Biosurfactant as a promoter of methane hydrate formation: thermodynamic and kinetic studies}, journal = {Scientific Reports}, volume = {6}, year = {2016}, month = {FEB}, pages = {20893}, publisher = {NATURE PUBLISHING GROUP}, address = {MACMILLAN BUILDING, 4 CRINAN ST, LONDON N1 9XW, ENGLAND}, abstract = {

Natural gas hydrates (NGHs) are solid non-stoichiometric compounds often regarded as a next generation energy source. Successful commercialization of NGH is curtailed by lack of efficient and safe technology for generation, dissociation, storage and transportation. The present work studied the influence of environment compatible biosurfactant on gas hydrate formation. Biosurfactant was produced by Pseudomonas aeruginosa strain A11 and was characterized as rhamnolipids. Purified rhamnolipids reduced the surface tension of water from 72 mN/m to 36 mN/m with Critical Micelle Concentration (CMC) of 70 mg/l. Use of 1000 ppm rhamnolipids solution in C type silica gel bed system increased methane hydrate formation rate by 42.97\% and reduced the induction time of hydrate formation by 22.63\% as compared to water saturated C type silica gel. Presence of rhamnolipids also shifted methane hydrate formation temperature to higher values relative to the system without biosurfactant. Results from thermodynamic and kinetic studies suggest that rhamnolipids can be applied as environment friendly methane hydrate promoter.

}, issn = {2045-2322}, doi = {10.1038/srep20893}, author = {Arora, Amit and Cameotra, Swaranjit Singh and Kumar, Rajnish and Balomajumder, Chandrajit and Singh, Anil Kumar and Santhakumari, B. and Kumar, Pushpendra and Laik, Sukumar} } @article { ISI:000367235100139, title = {Effect of different fixed bed media on the performance of sodium dodecyl sulfate for hydrate based CO2 capture}, journal = {Materials \& Design}, volume = {90}, year = {2016}, month = {JAN}, pages = {1186-1191}, publisher = {ELSEVIER SCI LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

Sodium Dodecyl Sulfate (SDS) is used as a kinetic promoter in gas hydrate formation. In this work, the performance of SDS for carbon dioxide gas hydrate formation in two different fixed bed media: silica sand and zeolite (5A and 13X) has been evaluated. The concentration of SDS was fixed at 0.5 wt\%. The experiments were carried out in batch mode with the initial pressure fixed at 3.0 MPa, and the temperature kept constant at 274.65 K. The results showed that hydrate of carbon dioxide with fixed bed of silica sand was significantly promoted by the addition of SDS as compared to the other fixed bed medium used in this study: zeolite 13X. (c) 2015 Elsevier Ltd. All rights reserved.

}, keywords = {Carbon dioxide, Fixed bed media, Hydrate formation, Kinetic promoter, Silica sand, Zeolite 5A and 13X}, issn = {0261-3069}, doi = {10.1016/j.matdes.2015.06.049}, author = {Arora, Amit and Kumar, Asheesh and Bhattacharjee, Gaurav and Kumar, Pushpendra and Balomajumder, Chandrajit} } @conference {45823, title = {Role of Rhamnolipid: A biosurfactant in methane gas hydrate formation kinetics}, booktitle = {Proceedings of The First International Conference on Recent Advances in Bioenergy Research}, year = {2016}, month = {FEB}, publisher = {Sardar Swaran Singh Natl Inst Bio-Energy}, organization = {Sardar Swaran Singh Natl Inst Bio-Energy}, address = {7th Floor, Vijaya Building, 17, Barakhamba Rd, New Delhi, 110 001, India}, abstract = {

Naturally occurring methane gas hydrate is a vast source of methane gas which is trapped in crystalline ice-like structure present in permafrost regions and under the sea in outer continental margins. It is purposed that total amount of carbon in the form of methane hydrates is almost twice the carbon content in all the fossil fuel reserves put together, and hence these are supposed to be the future potential energy resource. This paper investigates the laboratory investigations on effect of a biosurfactant rhamnolipid on methane hydrate formation kinetics. Rhamnolipid was produced by Pseudomonas aeruginosa strain A11. The presence of P. aeruginosa has been reported in Gulf of Mexico gas hydrate samples. Biosurfactant reduced the surface tension of water from 72 to 36 mN/m with CMC of 70 mg/L. The biosurfactant dose is studied at two different concentrations in the solution at 100 and 1000 ppm. Kinetic of hydrate formation and growth is compared at 0, 100, and 1000 ppm of rhamnolipid showing that rhamnolipid acts as a hydrate promoter at these concentrations. Thus, small dosages of rhamnolipids produced by P. aeruginosa strain A11 must clearly affect the gas hydrate formation kinetics in natural sites (as in Gulf of Mexico).

}, keywords = {Induction time, methane hydrate, Potential energy resource, Pseudomonas aeruginosa, Rhamnolipid}, isbn = {978-81-322-2773-1; 978-81-322-2771-7}, doi = {10.1007/978-81-322-2773-1_25}, author = {Arora, Amit and Cameotra, Swaranjit Singh and Kumar, Rajnish and Singh, Anil Kumar and Kumar, Pushpendra and Balomajumder, Chandrajit and Laik, Sukumar}, editor = {Kumar, S and Khanal, SK and Yadav, YK} } @article {47049, title = {Hydrate-based carbon capture process: assessment of various packed bed systems for boosted kinetics of hydrate formation}, journal = {Journal of Energy Resources Technology-Transactions of the ASME}, volume = {143}, year = {2021}, month = {MAR }, pages = {033005}, type = {Article}, abstract = {

The case for developing novel technologies for carbon dioxide (CO2) capture is fast gaining traction owing to increasing levels of anthropogenic CO2 being emitted into the atmosphere. Here, we have studied the hydrate-based carbon dioxide capture and separation process from a fundamental viewpoint by exploring the use of various packed bed media to enhance the kinetics of hydrate formation using pure CO2 as the hydrate former. We established the fixed bed reactor (FBR) configuration as a superior option over the commonly used stirred tank reactor (STR) setups typically used for hydrate formation studies by showing enhanced hydrate formation kinetics using the former. For the various packing material studied, we have observed silica gel with 100 nm pore size to return the best kinetic performance, corresponding to a water to hydrate conversion of 28 mol\% for 3 h of hydrate growth. The fundamental results obtained in the present study set up a solid foundation for follow-up works with a more applied perspective and should be of interest to researchers working in the carbon dioxide capture and storage and gas hydrate fields alike.

}, keywords = {air emissions from fossil fuel combustion, Carbon dioxide capture, combustion of waste, Fixed bed reactor, fuel combustion, Gas hydrate, hydrates, kinetics, Silica gel}, issn = {0195-0738}, doi = {10.1115/1.4048304}, author = {Arora, Amit and Kumar, Asheesh and Bhattacharjee, Gaurav and Balomajumder, Chandrajit and Kumar, Pushpendra} } @article {47051, title = {Rhamonolipids produced by Pseudomonas aeruginosa promotes methane hydrates formation in fixed bed silica gel medium}, journal = {Marine Geophysical Research}, volume = {42}, year = {2021}, month = {MAR}, pages = {5}, type = {Article}, abstract = {

Natural gas hydrates are seen as an alternative future energy source. They have also been valued for their carbon dioxide capturing capability, gas separation, desalination, natural gas storage and transportation. Developing economical and viable gas hydrate based technology is one of the most promising research areas of present decade. Successful commercialization of gas hydrate based technology is often curtailed due to slow formation rate. The present study evaluates biosurfactant as a kinetic promoter of methane hydrates formation in a fixed bed C type silica gel medium. Biosurfactant was produced by growing Pseudomonas aeruginosa strain A11 in glycerol supplemented mineral salt medium. Biosurfactant characterization with FTIR, NMR and MALDI-TOF spectroscopy reveled it to be a glycolipids type biosurfactant namely rhamnolipids. Saturating C type silica gel with of 100 ppm rhamnolipids solution enhanced the rate of methane hydrates formation by reducing the induction time. Mole of methane consumed and percentage of water to hydrate conversion was observed to be more in 1000 ppm rhamnolipids saturated C type silica gel as compared to quiescent water system and water saturated silica gel system. Overall results suggest that rhamonolipids produced by strain A11 in combination with silica gel can be utilized as environmentally safe kinetic promoter for methane hydrate formation.

}, keywords = {Biosurfactant, Energy, Glycolipids, Induction time, Kinetic promoter}, issn = {0025-3235}, doi = {10.1007/s11001-020-09426-6}, author = {Arora, Amit and Cameotra, Swaranjit Singh and Balomajumder, Chandrajit and Kumar, Rajnish and Singh, Anil Kumar and Santhakumari, B. and Kumar, Pushpendra and Laik, Sukumar} }