Hydrogen production shutdown
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Using naphtha； Liquefied gas ； In hydrogen production plants that use natural gas as a raw material, why is it necessary to first cut off the liquid feedstock when shutting down the plant, and wait until all of the liquid feedstock has been removed before cutting off the gaseous feedstock?
To prevent catalyst carbon deposition caused by inadequate oil reactions during the shutdown and cooling process, as well as to facilitate cleaning during shutdown.
Removing the liquid feed first prevents the liquid raw material from remaining in the reactor during shutdown, which could otherwise cause carbon deposition on the catalyst and lead to its deactivation; it also ensures that the catalyst can be easily removed.
It is not easy to replace liquid feedstocks; first cut off the liquid feed, while the gas feed can be easily replaced with nitrogen to prevent hydrocarbons from cracking in the reactor
I agree with the opinions expressed above; the idea is to use the higher temperature of the system to consume any remaining liquid (oil) inside it, thereby cleaning it out
When shutting down the unit (for processing dry gas) with reduced load, it is generally necessary to first reduce the load and cut off the oil supply; thereafter, depending on the circumstances, the dry gas supply can be stopped. This approach helps to consume any remaining oil in the system while it is still at high temperature, thereby ensuring thorough cleaning and preventing residual crude oil from remaining in the reactors or pipelines, which could lead to problems during maintenance……
The liquid feedstock is removed first so that the subsequent gas feedstock can carry away as much of the remaining liquid feedstock as possible, preventing it from accumulating in the reactor and furnace tubes and causing carbon deposition on the catalyst.