Abstract: A fuel gas selective oxidizer assemblage for use in a fuel cell power plant is formed from a series of repeating components, each of which includes a plurality of separate selective oxidizer gas passages and a plurality of adjacent coolant passages. The selective oxidizer gas and coolant passages are preferably formed by corrugated metal sheets which are interposed between planar metal sheets. One of the planar metal sheets forms a common wall between the selective oxidizer gas passages and the coolant passages so as to provide enhanced heat transfer between the reformate gas in the selective oxidizer gas passages and the coolant. Each of the components includes a first outer planar metal sheet, a medial planar metal sheet, and a second outer planar metal sheet. Each of the planar metal sheets is separated from the next by the corrugated metal gas and coolant passage sheets.