Heat transport in catalytic sponge packings in the presence of an exothermal reaction: Characterization by 2D modeling of experiments

Abstract

Heat transfer in catalytically coated sponge packings (open-cell foams) was investigated by experiments in a tubular cooled-wall reactor while conducting an exothermal reaction. A two-dimensional (2D) reactor model was developed to analyze quantitatively the steady-state temperature distributions, which were measured at 108 different positions in the reaction zone at well-defined reaction conditions of varied severity. The heat transport inside the packings was described by correlations for the effective axial and radial two-phase thermal conductivities. The key model parameters are the effective static two-phase thermal conductivities and the axial and radial dispersion coefficients, which have been assessed for sponge supports made of mullite and of α-Al2O3 with different porosities. The resulting simulations of conversions and spatial temperature distributions were in very good agreement with the experimental data. The reactor model was also used as a predictive tool to evaluate other sponge types. The simulations indicate that packings made of well-conducting solids like SiC or Al-alloys are useful supports for reactions with high enthalpy change, when hot spot or catalyst bed temperatures need to be controlled.