Emergency shutdown of low-temperature methanol washing

During an emergency stop, first stop the circulation process, primarily to prevent pressure from building up in the high, medium, and low pressure systems; promptly close all level control valves, and close the manual valves if possible； Subsequently, the pressures in the high-pressure and medium-pressure systems can be reduced at a certain rate ； Finally, stop the heat regeneration and methanol separation tower; also be sure to shut down the ammonia cooler in a timely manner

In an emergency shutdown, the boundary valve leading to the downstream section should be closed first, the startup pipeline for methanol washing should be opened, and the isolation valve on the cold synthesis gas pipeline coming from the cryogenic tank should be closed. If the methanol synthesis unit is also in use, it should be shut down as well. Then the feed gas supply should be cut off, the recycle gas compressor should be stopped, and the control valves that regulate pressure from high to low should be closed. Subsequent actions include dealing with issues such as overpressure and excessive liquid levels; other procedures are carried out in accordance with the normal shutdown procedure

In an emergency shutdown, the boundary valve leading to the downstream section should be closed first, the startup pipeline for methanol washing should be opened, and the isolation valve on the cold synthesis gas pipeline coming from the cryogenic tank should be closed. If the methanol synthesis unit is also in use, it should be shut down as well. Then the feed gas supply should be cut off, the recycle gas compressor should be stopped, and the control valves that regulate pressure from high to low should be closed. Subsequent actions include dealing with issues such as overpressure and excessive liquid levels; other procedures are carried out in accordance with the normal shutdown procedure

Wrong, an emergency stop includes power outages, lack of steam and feed gas, as well as internal issues such as pumps. At this time, proceed to Step 3: shut down the reboiler via the central control system. Nitrogen is stripped off using air lift; there is a valve on site for this purpose. The cycle compressor also shuts down via low-pressure interlock. In the second step, the control system shuts down the ammonia cooler while a valve is closed on site; moreover, the valves related to sulfur recovery, urea production, shift reaction, and methanol synthesis are closed on site. In the first step, the control system immediately shuts down all pressure relief valves, stops the pumps, and orders that a valve be closed on site. After that, cut off the exhaust gas scrubber, reduce the amount of water used for washing; if the pressure drops, use a safety valve to release pressure or rely on the pressure relief system in the control room to do so.

In an emergency stop, the first actions are to shut off the valves for the process gas flowing in, as well as those for the process gas going to the next unit. It is also necessary to prevent high pressure from leaking into low pressure systems