A steam reformer is use in a fuel processor system to create a water gas shift reaction between a hydrocarbon fuel and water. A hydrocarbon fuel and water are provided. The water is heated to superheated steam. The hydrocarbon fuel is mixed with the superheated steam to produce a vaporized fuel/steam mixture. The vaporized fuel/steam mixture is directed into a gap space between separate surfaces. The gap space between the separate surfaces is very small. Within this confined gap space, at least one of the separate surfaces is heated to maintain a reaction temperature range that induces the water gas shift reaction. The water gas shift reaction produces reactant gases that include hydrogen gas and contaminant gases. At least some of the contaminant gases are burned to heat the gap space.