Vent line for use in ammonia and hydrogen plants

In an ammonia or hydrogen plant comprising a desulfurisation section, a reforming section and a shift section, where the shift section comprises a low temperature shift converter and a medium temperature shift converter, a vent line is arranged downstream from the low temperature shift converter and the medium temperature shift converter in order to allow the shift converters to be re-heated with process gas at a low pressure (typically 3-7 bar). This way condensation of water vapour in the process gas is avoided. By applying this vent line it becomes possible to save significant time, more specifically 8-24 hours, for restarting the production after temporary shut-down thereof, because a heat-up of the LTS/MTS converter in circulating nitrogen is avoided.