A combustor for oxidizing a combustion fuel and pre-heating one or more reactants for fuel reforming. The combustor includes an elongated housing having an inlet for receiving a combustion fuel and an outlet for exhausting combustion products. The elongated housing further includes a cylindrical side wall, a bottom wall, and a top wall. Inert particles are disposed within the housing adjacent the inlet. A combustion catalyst bed is disposed within the housing above the inert particles that is a mixture of inert particles and combustion catalyst. The inert particles and the combustion catalyst preferably have a volumetric ratio of inert particles to catalyst between about 2:1 and about 4:1. The combustor has at least one heat exchanger within the combustion catalyst bed for heating a reformer reactant and generating steam. Preferably, the combustor includes at least two heat exchangers within the combustion catalyst bed, the heat exchanging elements have different surface areas. The combustor can include at least one sensor for measuring temperature within the combustor, and preferably the reactor includes two or more sensors for measuring temperature at two or more locations within the combustion catalyst bed. A power-generating apparatus comprising the combustor, a fuel processor and fuel cell is also provided. Methods for pre-heating a reactant and generating steam for use in a fuel reformer and for manufacturing a combustor for use in fuel reforming are provided.