Regarding the basic pressure boosting and relief issues of hydrogenation units?
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Is the pressure increase in the hydrogenation unit at startup achieved using a new hydrogen compressor? How does shutting down operations help to reduce pressure?
There was once an account; now I’ve forgotten the username and password, so I’m registering a new one and posting for the first time. The shutdown of a hydrogenation unit generally starts with a temperature drop; as the temperature falls, if no fresh hydrogen is supplied or the amount of fresh hydrogen is insufficient, the system pressure will continue to decrease. Taking a 15 MPa unit as an example, during the cooling phase the pressure can generally be reduced to 12–14 MPa; if there are no requirements regarding product quality during the shutdown process, it is even possible to reduce the pressure further. The reason why the pressure cannot be lowered too much at this stage is that too low a pressure hinders the cooling process. In addition to natural pressure reduction, the system pressure can also be lowered by releasing waste hydrogen, and ultimately it can be reduced further by venting the pressure to a flare or high-pressure gas system; if there is a hydrogen production unit available, the pressure can also be released to that unit during this stage.
«Does lowering pressure result in the emission of waste hydrogen?»
The flare system is discharged through the waste hydrogen valve on the circulating hydrogen buffer tank. In order to save energy and reduce consumption, the newly installed units can feed the gas into the gas recovery system, or they can be connected to the fractionation unit for hydrogen recovery in order to concentrate the hydrogen.
Is the pressure increase in the hydrogenation unit at startup achieved using a new hydrogen compressor? How does shutting down operations help to reduce pressure?
The shutdown of a hydrogenation unit generally starts with a temperature drop; as the temperature falls, if no fresh hydrogen is supplied or the amount of fresh hydrogen is insufficient, the system pressure will continue to decrease.
Yes, new hydrogen compressors are used to increase pressure at the start of operation. During shutdown, pressure is generally reduced from the waste hydrogen discharge system of the cyclohydrogen buffer tank and sent to the flare.
At first, the compressor load can be reduced; once this approach is no longer sufficient to achieve the desired pressure reduction, waste hydrogen can be vented.