A fuel processor for producing a hydrogen-rich product gas suitable for direct use in fuel cell applications includes a housing, an annular shift/methanator reactor vessel at least one reactor vessel wall disposed within the housing and forming an outer annular space between the at least one reactor vessel wall and the housing. A combustion chamber having at least one combustion chamber wall and forming a first inner annular space between the at least one combustion chamber wall and the at least one reactor vessel wall is disposed in the interior space formed by the annular shift/methanator reactor vessel, and a reformer reactor vessel having at least one reformer vessel wall and forming a second inner annular space between the at least one reformer vessel wall and the at least one combustion chamber wall is disposed within the combustion chamber.