NOVELTY - The method comprises providing an outer tube concentrically surrounding an inner tube, mixing a hydrocarbon fuel (12) with the steam to produce a fuel/steam mixture, flowing the fuel/steam mixture in a gap space, and heating the outer tube to maintain a reaction temperature range within the gap space that induces a water gas shift reaction. The gap space exists between the inner tube and the outer tube, and positioned between the separate surfaces is less than 1000 microns. The step of heating the outer tube includes positioning a part of the outer tube within a combustion chamber.    USE - The method is useful for inducing water gas shift reaction between hydrocarbon fuel and steam, where the water gas shift reaction is useful for creating hydrogen gas and waste raffinate gases (claimed) and the hydrogen gas is useful for a fuel cell.    ADVANTAGE - The method is capable of efficiently inducing the water gas shift reaction between hydrocarbon fuel and steam thus producing the hydrogen gas with high purity.    DETAILED DESCRIPTION - The method comprises providing an outer tube concentrically surrounding an inner tube, mixing a hydrocarbon fuel (12) with the steam to produce a fuel/steam mixture, flowing the fuel/steam mixture in a gap space, and heating the outer tube to maintain a reaction temperature range within the gap space that induces a water gas shift reaction. The gap space exists between the inner tube and the outer tube, and positioned between the separate surfaces is less than 1000 microns. The step of heating the outer tube includes positioning a part of the outer tube within a combustion chamber, burning fuel within the combustion chamber, providing supply tubes that extend into the combustion chamber, and introducing combustion gases into the combustion chamber through the supply tubes. The step of burning fuel includes burning some of raffinate gases (23). The supply tubes contain a concentric fuel supply tube and a concentric air supply tube. INDEPENDENT CLAIMS are included for:    (1) a method of producing hydrogen rich gases from a supply of hydrocarbon fuel; and    (2) a method of operating a steam reformer for use in inducing a water gas shift reaction between steam and a hydrocarbon.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of an exemplary embodiment of a fuel processor system.    Hydrocarbon fuel (12)    Initial heat exchanger (18)    Micro-channel steam reformer (20)    Hydrogen separator (22)    Raffinate gases. (23)