Process and plant for producing a synthesis gas by catalytic steam reforming of a hydrocarbon feedstock in a steam reforming unit, wherein water is removed from the synthesis gas as a process condensate, wherein boiler feed water is introduced in the process, and wherein the process or plant produces at least two separate steam streams: a pure steam which is generated from at least a portion of the boiler feed water by the cooling of synthesis gas, and a process steam which is generated by evaporating at least a portion of the process condensate by using synthesis gas, optionally together with pure steam and/or flue gas from the steam reforming unit.