Dynamic modeling, simulation and optimization of the partially-autothermal reforming of biogas in coated monolith channels

Abstract

A dynamic model is proposed describing a catalyst-coated SiSiC monolithic structure taking as a case study the autothermal reforming of biogas (SCR=3; OCR=0.66) in an adiabatic mode of operation. A single channel 2-D representation is assumed including dimensionless mass and energy transport equations solved in gPROMS platform resembling the performance of the whole monolith by breaking down the channel topology into three computational layers, namely the channel, the porous catalytic washcoat, where catalytic reforming and oxidation reactions take place, and the supporting wall. The model is verified using literature kinetics data in comparison with thermodynamic equilibrium analysis in HSC Chemistry software, which hints an optimization scheme for the optimal washcoat thickness to maximize H2 formation. The optimal values are applied to the three-layer model in order to track the dynamic evolution of the dependent variables of temperature and compositions from start-up of the monolith to the introduction of the biogas-O2 feed at the desired temperature to the response of the system to any disturbances being imposed after steady-state is reached. The overall dynamic model can interpret various aspects of the combined combustion and reforming of biogas in catalytic monolithic structures and can be used as an assistance for experiment design and process optimization.