A hydrogen production apparatus includes a first separation device that separates hydrogen from a steel by-product gas and discharges a first mixed gas containing carbon monoxide and methane, a pre-reforming device that receives the first mixed gas and a first water vapor, converts hydrocarbon into methane, and discharges a second mixed gas containing the methane, a mixed reforming device that receives the second mixed gas and a second water vapor and discharges a third mixed gas containing the hydrogen and the carbon monoxide, and a second separation device that individually separates the hydrogen and the carbon monoxide from the third mixed gas.

A method is described for retrofitting a hydrogen production unit, said hydrogen production unit having, a purification unit that separates the hydrogen-enriched gas into a hydrogen product stream and an off-gas stream, said method comprising the steps of: (a) installing a gas-heated reformer, and installing a carbon dioxide removal unit; (b) feeding a mixture of hydrocarbon and steam the gas-heated reformer, (c) combining the gas recovered with a second gas recovered and using the combined synthesis gas to heat reformer tubes in the gas-heated reformer; (d) recovering a cooled gas and passing the cooled gas to the water gas shift unit; (e) feeding the gas to the carbon dioxide removal unit to produce a carbon dioxide stream and a crude hydrogen stream, and; (f) passing the crude hydrogen stream to the purification unit. The invention further includes a process and system for producing hydrogen using the production unit.

A plant, such as a hydrocarbon plant, or synfuels plant, is provided, with effective use of various streams, in particular carbon dioxide and hydrogen. A method for producing a product stream, such as a hydrocarbon product stream, is also provided. The plant and method of the present invention provide overall better utilization of carbon dioxide and hydrogen, while avoiding build-up of inert components.