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Kumar R.,Heavy Water Division | Kumar R.,Indian Institute of Technology Bombay | Mohan S.,Heavy Water Division | Mahajani S.M.,Indian Institute of Technology Bombay
Industrial and Engineering Chemistry Research | Year: 2013

A pilot-scale countercurrent trickle bed reactor (TBR), packed with a water-repellent catalyst, is investigated for deuterium exchange between water and hydrogen, to be used for the production of heavy water. The reactant, i.e. heavy water, from liquid phase is stripped by the gas phase wherein, it undergoes an equilibrium limited exchange reaction with hydrogen over a solid catalyst. A two phase mathematical model is developed incorporating reaction kinetics, mass transfer resistances, and dispersion in liquid phase flow to simulate the reactor performance. Model parameters such as kinetic rate constant, mass transfer coefficient etc. were determined by independent experiments. The reactor model is then experimentally validated by performing reactions in pilot scale column. The validated model is further used to arrive at a suitable design for the desired performance. © 2013 American Chemical Society. Source


Bhattacharyya R.,Heavy Water Division | Bhanja K.,Heavy Water Division | Mohan S.,Heavy Water Division
Fusion Engineering and Design | Year: 2015

Reduction of copper oxide by hydrogen at high temperatures to metallic copper is one of the ways of removing hydrogen gas or its isotopes from its mixture with an inert gas like helium which is the coolant for plasma facing first wall of tritium breeding blanket modules in fusion reactor systems. The kinetics of the reaction of hydrogen with copper oxide was obtained from literature and it was used to model the reduction of a single particle of copper oxide using the well-known shrinking core model along with the pseudo-steady state hypothesis. No controlling regime was assumed a priori and the various interfacial gas concentrations were calculated by an iterative procedure based on the pseudo steady state hypothesis as function of the core radius at any time and for given operating conditions. The time required for complete reaction of the pellet was then calculated by numerical integration. A spherical geometry was considered in this work for the purpose of illustrating the technique, but the method is applicable to any kinetic model and any geometry of the pellets after simple modifications to the governing equations. © 2015 Elsevier B.V. Source


Bhattacharyya R.,Heavy Water Division | Bandyopadhyay D.,Heavy Water Division | Bhanja K.,Heavy Water Division | Mohan S.,Heavy Water Division
International Journal of Hydrogen Energy | Year: 2015

Abstract The reaction of metallic uranium particles with hydrogen at ambient or above ambient temperature has been used as the basis for the solid state storage of hydrogen in the form of uranium hydride for various applications in the nuclear industry. This work models the reduction of a single particle of metallic uranium to uranium hydride using available kinetic data, the well known shrinking core model and the pseudo-steady state hypothesis. No single rate controlling regime was assumed apriori and the various interfacial gas concentrations were calculated by an iterative procedure as function of the core radius at any time and for given operating conditions. The volumetric expansion or increase in the outer radius of the uranium particle as it is progressively hydrided was also considered in this work. The time required for complete conversion of the pellet to the hydride was then calculated by numerical integration and the rate controlling regime was identified. A spherical geometry was considered in this work for illustrating the technique, but the method is applicable to any kinetic model and any geometry of the pellets after simple modifications to the governing equations. © 2015 Hydrogen Energy Publications, LLC. Source


Sandeep K.C.,Heavy Water Division | Bhattacharyya R.,Heavy Water Division | Warghat C.,Heavy Water Division | Bhanja K.,Heavy Water Division | Mohan S.,Heavy Water Division
International Journal of Hydrogen Energy | Year: 2014

Catalytic recombination of hydrogen with oxygen is one of the most attractive options to control the hydrogen concentration in air. The basic pre-requisite for the process design of any catalytic reactor is the knowledge of kinetic data. In the present study, the kinetic data for the catalytic recombination of hydrogen in presence of 0.5% Pd on alumina catalyst were generated using a packed bed reactor with complete recycle. The experiments were conducted using low concentration of hydrogen in air at different temperatures and the apparent rate constants were estimated assuming a first order reaction with respect to hydrogen. The resistances due to internal and external mass transfer were decoupled from the apparent kinetics and estimated separately. The activation energy and frequency factor were found out using the slope and intercept of the Arrhenius plot. The effect of different process parameters such as temperature, superficial velocity and the catalyst particle size on the overall reaction rate was also studied. The knowledge of the intrinsic kinetics along with the mass transfer can be easily extended for the design of catalytic recombination reactors during scale up. © 2014 Hydrogen Energy Publications, LLC. Source

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