Abstract: Disclosed herein is a process for the separate control of the methane and rare gas contents of an ammonia-hydrogen recovery-rare gas plant complex. By the controlled withdrawal of a purge gas from the synthesis gas circulation, splitting of the purge gas into two partial streams and recycling of a partial stream to the synthesis gas generation section, the increase in inert gas to be taken out of the synthesis gas circulation as a result of the modernization of the ammonia plant can be prevented negative effect on the downstream hydrogen recovery/rare; thus energetic disadvantages or costly expansions or modifications of the ammonia-hydrogen recovery-rare gas plant complex are voided.