A reformer (10) for reacting fuel (12, 14) and oxidizer (16, 18) into reformate (20), with a plurality of reaction zones (22, 24) to which the fuel (12) and oxidizer (16) are supplied and in each which the fuel and oxidizer are reacted into reformate. The process for reacting fuel and oxidizer into reformate separately adjusting the fuel and/or oxidizer supplied to the reaction zones for varying the reformate output produced.