TECHNOLOGY FOCUS - MECHANICAL ENGINEERING - Preferred Component: The fuel processor further comprises a second combustion heater system (24); a control valve system; a heat exchanger (16); a water spray; and a catalyst combustor (26). The second combustion heater system is coupled to at least another of the reformer (14), the shift reactor and the preferential oxidation reactor. It is operable to produce thermal energy as a product of the combustion of air and fuel in the form of a second heated exhaust stream (70). It comprises an air inlet or a first inlet providing fresh air; and a second inlet in fluid communication with the first heated exhaust stream. It is positioned in series with the first combustion heater system. The first heated exhaust stream (32) is used to dilute the fresh air to control the temperature of the second heated exhaust stream. The control valve system selectively diverts the first heated exhaust stream from the first combustion heater system from passing through the shift reactor. It selectively routes an oxygen-containing cathode effluent from a fuel cell stack (22) to the catalyst combustor and the second combustion heater system. It comprises a combustor air control valve (64), and a cathode back pressure valve (66). The combustor air control valve selectively routes air or the oxygen-containing cathode effluent to the catalyst combustor. The cathode back pressure valve selectively applies a fluid back pressure to facilitate routing of the oxygen-containing cathode effluent to the catalyst combustor. The heat exchanger is operatively associated with the reformer, shift reactor or preferential oxidation reactor. It is exposed to the first or second heated exhaust stream for heating the reformer, shift reactor or preferential oxidation reactor. The water spray is coupled downstream from the second combustion heater system. It is operable to maintain a predetermined temperatures of the second heated exhaust stream. The catalyst combustor is positioned in series upstream or downstream from the second combustion heater system. It is positioned such that an output of the catalyst combustor is input downstream of the second combustion heater system.