What is the reason for liquid backflow in the synthesis tower when it is shut down for parking? How should it be handled?

The \"backflow\" phenomenon during shutdown refers to the situation where the material inside the synthesis tower flows back through the gas and liquid pipelines from the synthesis tower to the high-temperature cooler, and then flows into the stripping tower. The reason is that when the vehicle stops and CO2 is removed, the steam pressure on the shell side of the high-temperature cooler does not increase in a timely manner; as a result, excessive condensation occurs within the high-temperature cooler, causing a sudden drop in pressure. There is a liquid column of several dozen meters in height inside the synthesis tower (the exact value varies depending on the process equipment). This liquid column exerts a high static head pressure on both the high-temperature cooler and the stripping tower, and once this static head pressure is broken, a backflow occurs instantly. To prevent this phenomenon, it is necessary to raise the steam pressure on the shell side of the condenser to above 0.5 MPa in a timely manner during the parking process. Regarding his approach, CO2 is first introduced after driving the system before ammonia can be added. If emission is required for long-term parking, then it has to be emitted.

“The term “Haina Chuan River” is used very accurately

Increase the pressure in the drum of the ammonium pressurized condenser to prevent excessive condensation of high-methane, which could cause its pressure to drop below the static pressure in the synthesis tower and lead to backflow

The cold pressure for Gaojia must be set above 0.5, and it’s also important that the CO2 machine not be turned off too early – it needs to maintain a pressure that is 6 minutes higher than that of the system! With these two safeguards, there will be no leakage.

I agree with the opinion of the moderator of “Haina Chuan River”! !

If a \"liquid backflow\" has occurred, the steam pressure on the shell side of the stripping tower should be reduced to below 0.9 MPa. In practice, as long as the steam pressure on the shell side of the stripping tower is reduced to below 0.9 MPa, equipment corrosion is not as severe as one might imagine. For starting up with a short shutdown, it is recommended to first add ammonia (unless the ammonia pressure boost pump is controlled by the urea plant, while CO2 is controlled separately), and then add CO2; meanwhile, monitor the liquid level in the stripping tower ； Otherwise, if coordination is not proper, it’s possible that the liquid level shown in the synthesis tower indicates that ammonia has not yet been added. It should be noted that even if CO2 is added later, the liquid level in the stripping tower can still be emptied before discharge. When the system needs to discharge, it should do so following the normal procedures; steam from the stripping tower should only be discharged after the synthesis tower has emptied itself through the high-pressure discharge pipeline.