NOVELTY - The processor (10) has reactant gas passage (22) that is extended from reactant gas port (30) to catalyst bed (44). Product gas passage (24) is extended from catalyst bed to product gas port (32). A layer of gas permeable support structure (52,54) e.g. corrugated fin or turbulizer is located between fixed end and free end of separating wall and in contact with separating wall (20) and outer wall (12). Separating wall is extended from fixed end to catalyst bed. Product gas passage is in heat exchange contact with reactant gas passage between fixed end and free end of separating wall.    USE - Fuel processor used in fuel cell system for converting hydrogen-containing fuels such as hydrocarbons and low molecular weight alcohols to reformate containing molecular hydrogen.    ADVANTAGE - The fuel processor featured with simple structure and low manufacturing cost can retain the ability to minimize thermal stresses. The gas permeable support structures can support the walls to maintain their concentric arrangement and can increase turbulence in the reactant gas and reformate, so that the heat transfer through the separating wall can be increased. The layer of heat resistant insulating material is provided between the outer gas permeable support structure and the inner surface of the outer wall, so as to prevent blow-by and to decrease heat transfer loss to the outside environment.    DETAILED DESCRIPTION - The separating wall is used to separate the reactant gas passage from the product gas passage. The fixed end is proximate to reactant gas port and product gas port. The catalyst received inside the separating wall is proximate to the free end. The fixed end of the separating wall is joined to the outer wall. The portions of the reactant gas passage and product gas passage are located between the separating wall and the outer wall. The outer wall is included with a housing having an end wall. The end wall is spaced from the free end of the separating wall so as to form an inlet space (42). The separating wall and the outer wall are included with cylindrical walls extended parallel to a gas flow axis and arranged concentrically with one another, such that a portion of one of the reactant gas passage and the product gas passage is located in an annular space between the separating wall and the outer wall. Annular space is formed between the separating wall and the outer wall of the reactant gas passage. Reactant gas port is located in the outer wall. First layer of gas permeable support structures is located in annular space surrounding the separating wall along a portion of its length. Third cylindrical tube having closed end is located inside the separating wall and arranged in parallel to the gas flow axis such that an inner annular space is provided between the third tube and the separating wall. Second layer of gas permeable support structure is provided in the inner annular space such that surrounds the third tube along a portion of its length. The second layer of gas permeable support structure in the inner annular space is a corrugated fin or turbulizer. Third cylindrical tube is included with a first closed end proximate to the catalyst and a second end with a hole proximate to the fixed end (26) of the separating wall.    DESCRIPTION OF DRAWING(S) - The drawing shows a longitudinal cross-sectional view of the fuel processor.    Fuel processor (10)    Outer wall (12)    Separating wall (20)    Reactant gas passage (22)    Product gas passage (24)    Reactant gas port (30)    Product gas port (32)    Inlet space (42)    Catalyst bed (44)    Gas permeable support structures (52,54)