Simulation of hydrogen mitigation in catalytic recombiner: Part-I: Surface chemistry modelling

Prabhudharwadkar, Deoras; Aghalayam, Preeti; Iyer, Kannan N.

doi:10.1016/j.nucengdes.2010.09.032

Cited by 45 publications

(13 citation statements)

References 16 publications

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“…Even then, according to Friedel, Rosen and Kasemo [16], at least seven reaction steps must be considered when modelling heterogeneous recombination kinetics. Fortunately, at low hydrogen concentrations in the gas phase (less than 5% v/v) and low gas humidity, Kasemo's kinetic model can be reduced to a single kinetic equation in the catalyst ignition regime [17] (7) where c i [kmol/m 3 ] is the molar concentration of the reactants. Kasemo's model in its simplifi ed one equation version should not be used in the case of strong oxygen defi ciency.…”

Section: Model Descriptionmentioning

confidence: 99%

Modelling of a passive autocatalytic hydrogen recombiner – a parametric study

Rożeń

2015

Nukleonika

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Abstract. Operation of a passive autocatalytic hydrogen recombiner (PAR) has been investigated by means of computational fl uid dynamics methods (CFD). The recombiner is a self-active and self-adaptive device used to remove hydrogen from safety containments of light water nuclear reactors (LWR) by means of a highly exothermic reaction with oxygen at the surface of a platinum or palladium catalyst. Different turbulence models (k-, k-, intermittency, RSM) were applied in numerical simulations of: gas fl ow, heat and mass transport and chemical surface reactions occurring in PAR. Turbulence was found to improve mixing and mass transfer and increase hydrogen recombination rate for high gas fl ow rates. At low gas fl ow rates, simulation results converged to those obtained for the limiting case of laminar fl ow. The large eddy simulation technique (LES) was used to select the best RANS (Reynolds average stress) model. Comparison of simulation results obtained for two-and three-dimensional computational grids showed that heat and mass transfer occurring in PAR were virtually two-dimensional processes. The effect of hydrogen thermal diffusion was also discussed in the context of possible hydrogen ignition inside the recombiner.

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Section: Model Descriptionmentioning

confidence: 99%

Modelling of a passive autocatalytic hydrogen recombiner – a parametric study

Rożeń

2015

Nukleonika

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“…The Shortly, a mixture of PdCl 2 and H 2 PtCl 6 aqueous solutions of appropriate volume ratio was introduced to cyclohexane-surfactant solution and the obtained reactors [1,2]. These studies showed that the catalysts with well dispersed metal particles are preferred [8].…”

Section: Preparation Of Catalystsmentioning

confidence: 99%

“…At first the Pd-Pt particles were prepared in the microemulsion medium of the same compositions and then they were deposited on SiO 2 or MoO 3 supports. 2 . The Pd/Pt atomic ratios determined from the EDS analysis is determined to be within the range 0.89 -1.06, e.g the values which are close to the nominal compositions from the preparation procedure.…”

Section: Characterization Of Catalystsmentioning

confidence: 99%

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Hydrogen and oxygen reaction on SiO2 and MoO3 supported Pd-Pt catalysts

Lalik¹,

Kołodziej²,

Kosydar³

et al. 2015

Recyclable Catalysis

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Abstract:The thermal effects and activity of SiO 2 and MoO 3 supported bimetallic Pd-Pt catalysts (Pd:Pt = 1) in the exothermic H 2 and O 2 recombination reaction have been investigated in view of their potential use in the passive autocatalytic recombiners (PAR), which are applied at an industrial stage of development in the nuclear plant to lower the explosion risk associated with hydrogen release. The catalysts have been prepared using the colloid-based reverse "water-in-oil" microemulsion method and characterized by BET, XRD, SEM, EDS techniques. The recombination reaction of hydrogen and oxygen has been monitored using Microscal gasflow through microcalorimeter. This technique was also applied to follow hydrogen sorption by the Pd-Pt/ MoO 3 catalyst resulting in the formation of molybdenum bronzes (H X MoO 3 ). The pattern of changes in both the heat evolution and the conversion of hydrogen clearly show much better performance of Pd-Pt/SiO 2 catalyst. On Pd-Pt/ MoO 3 catalyst the conversion of H 2 was lower whereas the amount of evolved heat was higher because of exothermic reaction of bronzes formation. In contrast to Pd-Pt/SiO 2 catalyst offering stable activity, the activity of Pd-Pt/MoO 3 decreased during the catalytic test.

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“…Thus the reaction has been modeled as a one step reaction mechanism as proposed by Schefer [18]. Prabhudharwadkar et al [19] have numerically compared the approaches described above to model the process of recombination in order to obtain the most accurate one and shown that single step reaction gives reasonable good results compare to detailed mechanism. Gera et al [20] have carried out numerical simulation with CFD using single step reaction for separate effect recombiner used in Battelle Model Containment.…”

Section: Introductionmentioning

confidence: 99%

2D numerical simulation of passive autocatalytic recombiner for hydrogen mitigation

2011

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Resolving hydrogen related safety issues, pertaining to nuclear reactor safety has been an important area of research world over for the past decade. The studies on hydrogen transport behavior and development of hydrogen mitigation systems are still being pursued actively in various research labs, including Bhabha Atomic Research Centre (BARC), in India. The passive autocatalytic recombiner (PAR) is one of such hydrogen mitigating device consisting of catalyst surfaces arranged in an open-ended enclosure. In the plate type recombiner design sheets made of stainless steel and coated with platinum catalyst material are arranged in parallel inside a flow channel. The catalyst elements are exposed to a constant flow of a mixture of air, hydrogen and steam, a catalytic reaction occurs spontaneously at the catalyst surfaces and the heat of reaction produces natural convection flow through the enclosure. Numerical simulation and experiments are required for an in-depth knowledge of such plate type PAR. Specific finite volume based in-house 2D computational fluid dynamics (CFD) code has been developed to model and analyse the working of these recombiners and has been used to simulate one literature quoted experiment. The validation results were in good agreement against literature quoted German REKO experiments. Parametric study has been performed for particular recombiner geometry for various inlet conditions. Salient features of the simplified CFD model developed at BARC and results of the present model calculations are presented in this paper.

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Simulation of hydrogen mitigation in catalytic recombiner: Part-I: Surface chemistry modelling

Cited by 45 publications

References 16 publications

Modelling of a passive autocatalytic hydrogen recombiner – a parametric study

Modelling of a passive autocatalytic hydrogen recombiner – a parametric study

Hydrogen and oxygen reaction on SiO2 and MoO3 supported Pd-Pt catalysts

2D numerical simulation of passive autocatalytic recombiner for hydrogen mitigation

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