NOVELTY - Preparing hydrogen in fuel processor assembly involves preheating air with shifted reformate forming preheated air and cooled shifted reformate; combusting preheated air and combustion feed gas in catalytic combustor (20) to form exhaust; heating water with exhaust; heating a methane-containing gas (3) and the heated water with unshifted reformate to form steam and heated methane-containing gas; reforming the steam and heated methane-containing gas to form the unshifted reformate; and reacting cooled unshifted reformate in a water gas shift reactor (22) to form the shifted reformate.    USE - For preparing hydrogen in a fuel processor assembly.    ADVANTAGE - The process and apparatus utilize heat exchangers that thermally integrate the reaction steps such that heat generated by exothermic reactions e.g. combustion and water gas shift, are arranged closely to the endothermic reaction, e.g. steam reformation, and heat sinks, e.g. cool methane, water and air, to minimize heat loss and maximize heat recovery. Effectively, this thermally integration eliminates excess piping throughput, reduces initial capital and operating costs, provides built-in passive temperature control, and improves hydrogen production efficiencies. The process is thermally neutral, such that a supplemental fuel such as methane is no longer needed in order to achieve high reforming efficiency and conversion. This directly translates to lower operating costs. The surface areas and flow configurations of the heat exchangers are designed such that they serve the dual purposes of heat recovery/pre-heating and passive temperature control of process streams. The heat exchanger can also cool the reformate to a desired pressure swing adsorption unit operating temperature and utilize this heat to convert water to saturated steam and/or to preheat a combustion reactant such as air. This thermal pinching/passive temperature control technique not only simplifies and adds robustness to the process controls, but also eliminates control valves and various other moving parts throughout the apparatus as well as the need for external cooling. Thus the only active control parameters of the process are setting and adjusting the air flow to the combustor and the natural gas and water flows to the reforming reactor. The uniqueness of this process flow design significantly drives down the capital cost of the system. An annular design in a single vessel allows for operating the combustor and reforming reactor at two different pressure regimes without sacrificing heat loss.    DETAILED DESCRIPTION - Preparing hydrogen in a fuel processor assembly involves preheating air with a shifted reformate to form pre-heated air and cooled shifted reformate; combusting the preheated air and a combustion feed gas in a catalytic combustor (20) to form exhaust; heating water with the exhaust of the catalytic combustor to form heated water; heating a methane-containing gas (3) and the heated water with an unshifted reformate to form steam, a heated methane-containing gas and a cooled unshifted reformate; reforming the steam and the heated methane-containing gas in a reforming reactor (21) to form the unshifted reformate; reacting the cooled unshifted reformate in a water gas shift reactor (22) according to a water gas shift reaction to form the shifted reformate.    An INDEPENDENT CLAIM is included for an apparatus for preparing hydrogen comprising a combustor, a water gas shift reactor, a reforming reactor, and at least three heat exchangers arranged in a manner to carry out the process.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic process flow diagram of a hydrogen generation system.    Methane-containing gas (3)    Heat exchangers (13,14)    Catalytic combustor (20)    Reforming reactor (21)    Water gas shift reactor (22)