Hydrogen production shutdown

Emma, generally, during startup/shutdown or when the circulation rate is low, a large-scale circulation is carried out using gas or nitrogen as the circulating medium; nitrogen displacement is done during startup or after long periods of shutdown. The last question is excessive – the hydrogenation reactor is designed to be used for the saturation of olefins! The methanation reaction you mentioned is a medium-temperature reactor

There are various ways to shut down hydrogen production units. For safety reasons and to simplify on-site operations, a large-cycle shutdown is preferred. From a safety perspective, the feed rate to the hydrogen production unit is first reduced to the minimum level, after which the PSA system is gradually shut down (while maintaining the pressure between 1.5–2.0 MPa through a medium-pressure control and venting system). At the same time, the temperature of the conversion furnace is adjusted promptly to ensure that all parameters remain under proper control. As the feed is gradually reduced, the operation is switched to the large-cycle mode; once this mode is fully established, the hydrogenation reactor is shut down (to prevent the hydrogen atmosphere from reducing the efficiency of the hydrogenation catalysts). After all system parameters have been stabilized, nitrogen is introduced at the compressor inlet for displacement until the nitrogen purity exceeds 99% (the lower the amount of hydrogen and sulfur-containing hydrocarbons present, the better). Once the displacement is satisfactory, cooling can begin gradually. As for the methanation reaction-------it is not easy to encounter it; if it does occur, it is due to excessive levels of CO and CO2 in the medium or the fresh hydrogen, which react with the catalyst to produce methane (the methanation reaction is an exothermic process)