Synthetic Ammonia Process Technology Exchange Area [Daily Question 2009-03-07]
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Synthetic Ammonia Process Technology Exchange Area [Daily Question 2009-03-07] How to protect the catalyst during short-term shutdown and hot work in the ammonia synthesis tower? This post was last edited by jindin312 on 2009-3-7 22:13]
If it’s stopped for just one or two hours, it’s not necessary; after all, it’s needed to maintain temperature and pressure, and the key is to keep the levels of liquid nitrogen and ammonia at low levels, waiting until it’s time to restart operation. If pressure relief and cooling are needed, it’s possible to fill in some nitrogen at a pressure of four nines to maintain a slight positive pressure. If maintenance is required, the synthesis tower and the system must be isolated first, after which nitrogen is introduced to maintain a slight positive pressure.
Should we specify the exact location where the hot work will be carried out?
Since welding is to be carried out, nitrogen should first be used for purging, and it is considered acceptable if the combustible gas concentration is below 0.5%. After the replacement is completed and the synthesis tower is depressurized, blind flanges are installed on all the inlet and outlet pipelines of the ammonia synthesis tower to prevent air from entering the catalyst layer and causing catalyst oxidation. After the maintenance is completed, the blind flange should be removed; replacement is also required, as the oxygen content analyzed is below 0.5%.
Since welding is to be carried out, in the main process, it is necessary to first relieve pressure, purge with nitrogen, and maintain a slight positive pressure.
After the system is depressurized, air cannot enter the system until the temperature drops below 150 degrees. At this point, remove the pipelines where welding will take place and leave the area; use dry powder from a fire extinguisher to fill those pipelines. If the time is long, blind plates should be installed at the inlet and outlet of the synthesis tower