Compact fuel processor

A fuel processor for producing a hydrogen-containing product stream from a fuel stream and an oxidant stream incorporates a particulate filter assembly comprising a plurality of filter segments separated by expansion joints to accommodate dimensional changes that result from temperature fluctuations. Other embodiments of a fuel processor incorporate, instead or in addition, one or more of: a flame rod as a temperature sensing device for a reforming reaction; a two-sleeve concentric type heat exchanger; a mixing tube manufactured from an alumina-silica based material; and a wet blanket type of insulation.