TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Component: A perimeter bounding the modules is irregular. The housing has a regular cross-sectional geometry bounding the two modules. The regular geometry is a round, circular, obround, oval, elliptical, square, rectangular, triangular or regular polygonal shape. The housing provides mechanical support for the modules. The fuel processor further comprises end closures for the housing; vent(s) to the atmosphere from the interstitial space; a housing inlet in communication with the interstitial space; a housing outlet in communication with the interstitial space; a heat exchange conduit positioned within the interstitial space for exchanging heat with fluid flow in the interstitial space; a reaction catalyst disposed in the interstitial space; an auxiliary burner incorporated in a first module; a process conduit in the interstitial space and in operative association with the modules for conducting their respective unit operations; and an anode gas combustion burner incorporated into the module(s). End(s) of each module is/are attached to an end closure in a way that permits relative movement due to thermal expansion between or among the modules and the housing. The housing comprises an integral path for fluid communication between the modules. The integral path comprises a conduit integrated with the end closure of the housing. Each module conducts unit reactions from combustion of fuel for heat, partial oxidation of a hydrocarbon fuel, desulfurization of a feed stock, adsorption of impurities in a reformate or feed stock, steam reforming of a hydrocarbon feed stock or a pre-oxidized (reformate) stream, water-gas shifting of a pre-processed steam reformed or preferential oxidation of pre-processed (reformate) stream, heat exchange for preheating fuel, air or water, reactant mixing and/or steam generation. The fuel processor is configured to provide a flow through the interstitial space of a process fluid for thermal insulation(s) of the modules and/or heat exchange. The interstitial space contains a material for insulating the modules. The modules are positioned in close proximity to each other to achieve a compact, efficient utilization of a volume within the housing. Each module has an elongated dimension. The modules are positioned so that the elongated dimensions align in parallel. The auxiliary burner comprises an exhaust that heats a thermal conductor disposed about the module(s) or disposed about the auto-thermal reforming module. The process conduit is heat exchangers, boiler/steam tubes, electrical conduit and/or fluid conduit.Preferred Material: The insulating material is a flowing process fluid, a solid or semi-solid (e.g. metal or ceramic fibers), a porous support and/or a foamed material.Preferred Method: The reforming method includes catalyzing a reaction in the heat exchange fluid simultaneously with the step of exchanging heat. A catalyst is used in the catalyzing step to promote preferential oxidation of carbon monoxide. It is provided on a porous monolithic support aligned in the direction of flow of the heat exchange fluid. The heat exchange fluid is reformate generated in the second unit operation.