70% limit on methanol wash inlet gas

I saw a flow chart in which the minimum inlet flow rate is 70%; if this value is lower, the recycle gas compressor will trip! May I ask what kind of chain this is? Is it because of the reduced volume of circulating gas that this value causes the circulating gas compressor to surge? But this process is designed with an additional gas line leading from the V1 separation tank to the inlet of the recycle gas compressor; doesn’t this additional gas serve any purpose? Answer: Firstly, the cycle gas compressor is designed with a return line, and it is not restricted by the inlet flow rate in the process section. Unless you close the entrance tightly. In the design of conventional low-temperature methanol washing cycle gas compressors, when the inlet flow rate is too low, the interlock reflux line control valve opens, allowing the flow to return from the outlet to the inlet in order to maintain the pressure at the compressor outlet. What is meant by interlocking refers to this. There is also a interlock at the compressor inlet; if the pressure becomes too high, it is discharged to a safe location, ensuring that the compressor operates under its designed conditions.

The anti-surge valve also has a certain margin of safety; it’s not the case, as you said, that the compressor can keep operating normally no matter how much the inlet flow is reduced!

The interlocks for the recycle gas compressor generally include conditions such as low inlet pressure, low oil pressure, or abnormalities in other utility systems. The inlet pressure is automatically regulated; if it is insufficient, air is supplied from the outlet, and any excess is vented. Generally, three load levels of 0%, 50%, and 100% are available for adjustment, depending on factors such as the feed gas volume to the methanol wash unit, energy savings, and economic benefits.

The interlocks for the recycle gas compressor generally include conditions such as low inlet pressure, low oil pressure, high compressor outlet temperature, high alarms, and abnormalities in other utility systems. The inlet pressure is automatically regulated; when the pressure is low, it can be increased through a return line, and when the flow rate is low, the flow rate can also be increased via the return line to maintain the pressure at the compressor outlet. If the pressure at the primary inlet is too high, it can be automatically released to the flare for combustion through the pressure control valve. Generally, three load levels of 0%, 50%, and 100% are available for adjustment, with the specific setting determined by the load on the methanol washing unit, in order to ensure that the compressor operates under the most economical conditions.

The lower limit for gas volume is 70%; I think another reason is economic factors! The compressor consumes electricity to operate; if the cost of recovering the flash vapor is lower than the cost of running the motor, there is no need to keep it running. Additionally, opening the inlet circuit of the compressor raises its temperature, which in turn increases the exhaust temperature of the compressor

The last edit to this post was made by 654262293 on 2013-6-14 at 15:29. It isn’t necessary to interlock the flash vapor compressor with the inlet flow rate of the low-temperature methanol wash unit; the pressure of the flash vapor compressor can be adjusted using settings such as one-in-one and three-in-one. The amount of gas that returns has a tolerable impact on the compressor’s inlet temperature, and it does not cause any harm to the compressor. There is a water cooler at the compressor’s outlet, so it won’t have a significant effect on the raw gas fed into the low-temperature methanol wash unit.

Hehe, I need to reply to this post! ! ...

I think \"chain\" also refers to stopping the circulating gas compressor; it’s likely that running the circulating gas compressor at 70% capacity is not cost-effective. The inlet pressure relief flare is a self-regulating valve; when the pressure is low, it operates in open-loop mode and is also a self-regulating valve, thus it is not part of the interlock system

Circulation gas compressors are generally reciprocating, right? Will it surge?

Insufficient inlet pressure can be compensated for by adding pressure at the outlet; this is achieved through stepwise regulation； In terms of operation, the compressor stops working at 70% load; this is likely due to a high inlet gas temperature, which results in a high outlet gas temperature after compression. The increased thermal stress within the equipment can pose a risk