A detailed chemistry model for transient hydrogen and carbon monoxide catalytic recombination on parallel flat Pt surfaces implemented in an integral code

Abstract

A detailed chemistry model has been adapted and developed for surface chemistry, heat and mass transfer between H 2 /CO/air/steam/CO 2 mixtures and vertical parallel Pt-coated surfaces. This model is based onto a simplified Deutschmann reaction scheme for methane surface combustion and the analysis by Elenbaas for buoyancy-induced heat transfer between parallel plates. Mass transfer is treated by the heat and mass transfer analogy. The proposed model is able to simulate the H 2 /CO recombination phenomena characteristic of parallel-plate Passive Autocatalytic Recombiners (PARs), which have been proposed and implemented as a promising hydrogen-control strategy in the safety of nuclear power stations or other industries. The transient model is able to approach the warm-up phase of the PAR and its shut-down as well as the dynamic changes within the surrounding atmosphere. The model has been implemented within the MELCOR code and assessed against results of the Battelle Model Containment tests of the Zx series. Results show accurate predictions and a better performance than traditional methods in integral codes, i.e., empirical correlations, which are also much case-specific. Influence of CO present in the mixture on the PAR performance is also addressed in this paper.

PARUPM: A simulation code for passive auto-catalytic recombiners

“…The developed model, PARUPM, is a numerical code to simulate the operational behaviour of a PAR device through a physicochemical approach. The PAR itself is considered a series of vertical parallel plates which form vertical flow channels [7]. PARUPM takes into account relevant phenomena involved in PAR operation: convective/diffusive heat and mass transfer between the gaseous mixture and the catalytic surface in a vertical flow driven by the chimney model, the adsorption/desorption of species on the plate surface, chemical surface reactions with subsequent heat release, and radiative heat exchange with the surrounding structures.…”

“…These phenomena occur simultaneously and must be resolved in a coupled manner. The coupling is carried out through expressions of the mass and energy balance at the interface between the catalytic plate and the gaseous current that runs constantly over it [7].…”

Mathematical Modelling of Turbulent Combustion of Two-Phase Mixtures of Gas and Solid Particles with a Eulerian–Eulerian Approach: The Case of Hydrogen Combustion in the Presence of Graphite Particles

“…In this case, there are undesirable subproducts in the H 2 -graphite combustion whose concentration should be reduced to the minimum possible in order to avoid the poisoning of the catalyser. Specifically, because of the large sticking coefficient of CO compared to the other adsorbed species within a PAR and its high activation energy for desorption, the presence of CO in the mixture would poison the catalytic surface; this would prevent the desired recombination reaction in the PAR from occurring [68]. Besides, the lean limit concentration of hydrogen combustion decreases as the CO concentration increases and the flammable region widens for H 2 -CO mixtures.…”

A Mechanistic Model of a Passive Autocatalytic Hydrogen Recombiner

“…On the contrary, few mechanistic models of PAR have been formulated so far allowing for quick engineering calculations. For example, Avakian and Braillard (1999) and Jimenez et al (2007) modelled PAR as a continuously stirred tank reactor assuming that the gas phase inside PAR is perfectly mixed. However, the key catalytic reactions have non-linear kinetics according to Fridell et al (1994) and Rinemo et al (1997).…”