Question regarding whether to shut down one of the circulators when reducing the capacity of the ammonia synthesis tower
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During normal operation of the ammonia synthesis unit in my company, two circulation pumps are used; when production volume is reduced significantly, one of the circulation pumps has to be stopped. However, I’m not sure when this should be done – is it determined based on the air delivery volume of the circulation pump, or based on the temperature of the bed layer? I would appreciate some guidance from those who know more about this. Thank you very much
Based on a comprehensive assessment, the circulation volume and the amount of fresh gas used in synthesis are in a certain proportion, which allows the temperature in the synthesis tower to remain stable. Theoretically, halving the amount should allow one machine to be used, but in actual production, one machine can handle around 70% of the load. The circulation volume can be reduced first; once it is reduced to the level corresponding to one unit of circulation, then one unit can certainly be switched off.
First, stop one unit that needs to be shut down by turning off the circuit and reducing the gas flow; everything should proceed smoothly during this process. It is also possible not to stop any of the units in operation, as a high space velocity is beneficial for the catalyst
Take a shortcut based on the bed temperature and air supply volume. If the reduction time is short, it is recommended not to stop the circulation machine.
If reducing the flow rate (by opening the circulation valve) is not sufficient to maintain the temperature inside the synthesis tower, or if it is not possible to resume full production in a short time, one of the circulation pumps can be shut down.
Each issue should be analyzed on a case-by-case basis. If production was originally at full capacity, the total circulation volume was 180,000, the circulation machine was also operating at full capacity, and the opening degrees of various cooling air valves were relatively high. I feel that when the circulation volume drops below 100,000, it might be possible to shut down one of the circulators. Everyone is welcome to offer corrections and criticism.
If the furnace temperature cannot be maintained, operation must be stopped; by adjusting the circulation rate and the bypass lines, it is possible to keep the furnace temperature stable without having to stop operation
Based on the opening degree of the system’s bypass valve, if the circulation volume drops to the point where it is necessary to activate the bypass of a circulation pump, then once more than half of one such bypass is in use, it becomes necessary to consider shutting down one of the circulation pumps
When the circulation volume of a circulator is reduced to zero, it is normal for it to stop operating. However, its diameter is definitely smaller than that of the inlet and outlet pipelines; even when the circulation volume has been reduced to zero, there is still some amount of circulation. Whether it will stop or not depends on various factors such as the duration of the volume reduction, the length of time the catalyst is in use, and so on. A high rotation speed is beneficial for the catalyst