Process for producing hydrogen and method of retrofitting a hydrogen production unit

A plant is described for production of hydrogen comprising: a fired reformer containing a plurality of catalyst-containing reformer tubes and having a shell side to which fuel is fed, producing a crude synthesis gas from a feed stream; an autothermal reformer arranged to be fed with an oxygen-containing gas and crude synthesis gas from the fired reformer, producing reformed synthesis gas; a water-gas shift unit arranged to be fed with reformed synthesis gas from the autothermal reformer, producing hydrogen-enriched gas; a carbon dioxide removal unit arranged to be fed with hydrogen-enriched gas from the water-gas shift unit, producing a crude hydrogen stream and a carbon dioxide stream; a purification unit arranged to be fed with crude hydrogen stream gas from the carbon dioxide removal unit, producing a hydrogen product stream and an off-gas stream; wherein the plant is such that a portion of the crude hydrogen stream from the carbon dioxide removal unit and/or a portion of hydrogen product stream from the purification unit is fed as fuel to a shell-side of the fired reformer. The invention includes; process for producing hydrogen; method of retrofitting hydrogen plants.