NOVELTY - An apparatus for producing hydrogen comprises a fuel processor for producing a flow of intermediate reformate containing hydrogen and an impurity; a purification unit to produce a flow of hydrogen-enriched reformate; and a controller for determining a calculated flow of intermediate reformate and operating the purification unit in part in response to the calculated flow of intermediate reformate.    USE - In the production of hydrogen (claimed) useful in aerospace; food production; oil and gas production and refining; in industries as a propellant, an atmosphere, a carrier gas, a diluent gas, a fuel component for combustion reactions, a fuel for fuel cells, as well as a reducing agent in numerous chemical reactions and processes; as an alternative fuel for power generation.    ADVANTAGE - The use of fuel processors converts hydrocarbon-based fuels to hydrogen-rich reformate. The purity of hydrogen produced by using the apparatus can be maintained by adjusting the operation of the purification unit in response to change in reformate composition, pressure and/or flow rate. The method removes or reduces the impurities to extremely low levels to render hydrogen product safe and reliable. The apparatus reduces or dampens fluctuations and adjusts the operation of purification unit so as to maintain desired product composition; and provides pure hydrogen product that can be safely and reliably used in any hydrogen-consuming device or process.    DETAILED DESCRIPTION - An apparatus for producing hydrogen comprises a fuel processor capable of producing a flow of intermediate reformate containing hydrogen and an impurity; a purification unit disposed downstream of the fuel processor capable of removing impurity from the flow of intermediate reformate to produce a flow of hydrogen-enriched reformate; and a controller capable of determining a calculated flow of intermediate reformate from a process model of the fuel processor and operating the purification unit in part in response to the calculated flow of intermediate reformate. An INDEPENDENT CLAIM is included for producing hydrogen-enriched reformate involving: producing a flow of intermediate reformate comprising hydrogen and an impurity in a fuel processor; removing impurity from the intermediate reformate to produce a flow of hydrogen-enriched reformate; determining a calculated flow of intermediate reformate to be produced by the fuel processor from a process model of the fuel processor; and operating the purification unit in part in response to the calculated flow of intermediate reformate.