A multiple adiabatic bed reforming apparatus and process are disclosed in which stage-wise combustion, in combination with multiple reforming chambers with catalyst, utilize co-flow and cross-flow under laminar flow conditions, to provide a reformer suitable for smaller production situation as well as large scale production. A passive stage by stage fuel distribution network suitable for low pressure fuel is incorporated and the resistances in successive fuel distribution lines control the amount of fuel delivered to each combustion stage.

In a catalytic reactor including catalyst carriers inserted into a plurality of channels defined by corrugated fins, the corrugated fins include a first corrugated fin, and a second corrugated fin arranged to adjoin the first corrugated fin. When viewed from the first corrugated fin toward the second corrugated fin along the channels, at least a portion of side walls of the second corrugated fin is located between two adjacent ones of side walls of the first corrugated fin at adjoining end faces of the first and second corrugated fins.