A process and a related equipment for producing ammonia synthesis gas from a hydrocarbon-containing feedstock (20), the process comprising the steps of: primary reforming with steam (21), secondary reforming with an oxidant stream (23), and purification of the effluent of said secondary reforming, said purification comprising a step of shift conversion (13) of carbon monoxide, wherein the synthesis gas (25) produced by said secondary reforming is subject to a medium-temperature shift over a copper-based catalyst, and the global steam to carbon ratio of the process is not greater than 2.