NOVELTY - The reformer unit comprises a burner (3) including a combustion chamber (4), a reformer (5) arranged in the combustion chamber, and a first conduit (6) for supplying the reformer with process gas. The process gas comprises recirculated anode off-gas and hydrocarbons. The reformer comprises a manifold into which the first conduit opens out. An outer surface of the manifold is spaced apart from an opposite surface of the combustion chamber. The reformer unit further comprises a starting burner (11) connected to the combustion chamber, and a flame tube.    USE - The reformer unit is useful in a fuel cell system (claimed) that is useful as an energy source for providing electrical and/or thermal energy to a vehicle such as lorry, and in power and heat cogeneration unit in buildings.    ADVANTAGE - The reformer unit has compact size, and is energy efficient to operate.    DETAILED DESCRIPTION - The reformer unit comprises a burner (3) including a combustion chamber (4), a reformer (5) arranged in the combustion chamber, and a first conduit (6) for supplying the reformer with process gas. The process gas comprises recirculated anode off-gas and hydrocarbons. The reformer comprises a manifold into which the first conduit opens out. An outer surface of the manifold is spaced apart from an opposite surface of the combustion chamber. The reformer unit further comprises a starting burner (11) connected to the combustion chamber, a flame tube connected and projecting into the starting burner, a bypass conduit for exhaust gas of the starting burner to a heat exchanger, and a deflecting unit provided between a flame tube and the reformer. The reformer, the burner and/or the starting burner are arranged such that a central longitudinal axis of the reformer, a central longitudinal axis of the burner and/or a central longitudinal axis of the starting burner are oriented in parallel manner and are coaxially arranged to each other. The manifold has a shape of a cone or a truncated cone. An angle between a flow direction of the first conduit and the central longitudinal axis of the Reformer at an inlet point to the reformer is 90 degrees . A tangent of the flow direction of the first conduit at an inlet point to the reformer divides or intersects the central longitudinal axis of the manifold. A distance is determined between the central longitudinal axis of the manifolds and the side surface, which is perpendicular to a tangent of the longitudinal central axis of the manifold. A ratio of tangents is 1:4. A second conduit for a cathode exhaust air is provided on the burner, and a third line for fuel gas such as an anode exhaust gas is provided on the burner. The second conduit and third conduit are open into the combustion chamber. An angle between a flow direction of the second conduit and/or the third conduit and the central longitudinal axis of the burner at an inlet point is 90 degrees . The burner further includes a catalyst combustor, which is present thermal contact and to disposed around the reformer. The reformer includes a catalytic converter. A substrate of the catalyst combustor supports the reformer. The reformer catalytic converter overlaps with the burner catalyst in an axial direction. A ratio of a flow volume of the reformer catalytic converter to a flow volume of the catalyst combustor is 1:3.7. The manifold is partially disposed in the combustion chamber.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic cross sectional view of a reformer unit.    Burner (3)    Combustion chamber (4)    Reformer (5)    First conduit (6)    Starting burner. (11)