Autothermal Reactor Concepts for Endothermic Fixed-Bed Reactions

Abstract

Autothermal reactor concepts for the heat integrated coupling of endothermic and exothermic reactions are required for an efficient on-site production of hydrogen from alcohols or hydrocarbons for use in fuel cells. Existing experience with countercurrent reactors and reverse-flow reactors for weakly exothermic reactions can be utilized for their design. However, specific features of coupling endothermic and exothermic reactions must be taken into account. The respective considerations are presented and discussed for different modes of operation: the simultaneous coupling of both reactions; coupling with cocurrent recuperative heat exchange between the two process streams in the reaction zone; and asymmetric operation with counter-current recuperative or regenerative heat exchange. It is shown that asymmetric operation requires spatial distribution of the feed for the exothermic reaction in order to prevent excess temperatures and to ensure stable operation. Both simulation and experimental results are presented for methanol steam reforming, gasoline reforming and methane steam reforming.