Treatment at the freezing station after the shutdown of the methanol cycle in low-temperature methanol washing
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Must the ammonia compressor (centrifugal) be shut down after the methanol cycle in low-temperature methanol washing is stopped?
After the methanol cycle in the low-temperature methanol wash unit is stopped, it is not necessarily necessary to shut down the ammonia compressor (centrifugal type); this depends on the duration of the shutdown. If the shutdown period is long, it may be advisable to shut down the compressor; if the shutdown period is short, the compressor can remain running, but the supply of ammonia to the low-temperature methanol wash unit must be stopped. In such cases, a surge valve is used to maintain the compressor’s operation.
The low-temperature methanol wash has been shut down, which indicates that there is no low-pressure nitrogen nor high-pressure nitrogen, meaning that the air separation unit has also stopped operating. It takes at least about 8 hours to drive to the methanol washing unit. So I don’t think it’s necessary to turn on the ammonia compressor. If other work orders still use ammonia, it can be started. If it’s not needed, stop using it.
Could you explain why a low-temperature methanol wash shutdown can prove the absence of low-pressure nitrogen and high-pressure nitrogen? How then can it be shown that the air separation unit has stopped?
If the ammonia compressor is intended for use in methanol washing and will be shut down for an extended period, then it can be shut down. However, if the ammonia compressor serves other users as well, it certainly cannot be shut down casually; in that case, it’s sufficient to simply stop supplying liquid ammonia.
It’s possible to keep driving without stopping for a short period of time; simply keep the anti-surge valve fully open. By keeping it in a low operating mode, this can be achieved
A shutdown of the low-temperature methanol wash does not necessarily mean there is a problem with the air separation unit. If the shutdown duration is long, it is necessary to stop the ammonia compressor; otherwise, there is no need to do so
What is the limit for the duration of shutdown of an ammonia compressor?
If only the purification system shuts down, the refrigeration system does not need to stop; it can simply operate in circulation mode, thereby returning to the state it was in before cold energy was supplied. It’s easy to understand
Purification has stopped despite being parked. The air separation unit is still in operation, and its ammonia cooler must be used in summer as well.
The issue with purification parking is not necessarily due to a problem with the air separation unit; it could also be caused by problems with the purification process itself or by other sections of the facility. If the parking time is short, the cooling system operates in a cycle of turning on and off, which is both wasteful and troublesome