NOVELTY - The fuel stream and oxygen containing stream are supplied to a primary reactor portion (30) of combined primary reactor and heat exchanger (12). The fuel stream and oxygen containing stream are reformed in the presence of catalyst in primary reactor portion to form product gases. The heat energy is supplied to oxygen containing stream by counter flow of product gas with respect to oxygen containing stream.    USE - For synthesizing hydrogen gas for fuel cell system (claimed) for automobiles and domestic applications.    ADVANTAGE - The method economically and quickly provides hydrogen gas. Close-coupling the reformate to steam and air heat exchanger with the primary reactor inlet, results in minimum thermal energy loss, maximum dynamic response, improved primary reactor performance, and durability from the improved mixing of steam and air with fuel. The heat exchanger results in improved fuel processor efficiency.    DETAILED DESCRIPTION - The fuel stream and oxygen containing stream are supplied to a primary reactor portion of combined primary reactor and heat exchanger through several inlet conduits (40). The heat exchanger portion (28) is annularly disposed with respect to primary reactor portion. The fuel stream and oxygen containing stream are reformed in the presence of catalyst in primary reactor portion to form product gas. The heat energy is supplied to oxygen containing stream by counter flow of product gas through several outlet conduits (41) with respect to oxygen containing stream.    INDEPENDENT CLAIMS are included for the following:    (1) apparatus for synthesizing hydrogen gas; and    (2) fuel cell system.    DESCRIPTION OF DRAWING(S) - The figure shows partially fragmented sectioned side view of combined primary reactor and heat exchanger for method for synthesizing hydrogen gas from fuel.    combined primary reactor and heat exchanger (12)    heat exchanger portion (28)    primary reactor portion (30)    inlet conduits (40)    outlet conduits (41)