Flash steam temperature and pressure
Thread Content
With the amount of reformate gas remaining unchanged and the temperature of the methanol-poor stream being low, the temperature of the flash vapor in the flash drum is also low; why then is the pressure low as well? Apart from the composition of the reformate gas, what other factors are involved?
I’m not quite sure what the original poster means. The analysis should be as follows: the temperature of the lean methanol is low------the temperature of the flash vapor also decreases------which results in a reduced amount of flash vapor------and consequently, the pressure in the flash system is low
Reply to 1# Liu Ran: If the poster is referring to the medium-pressure flash system, here are some additional points: 1. It is primarily affected by the load on the shift gas； 2. Fluctuations in the level of the flash tank also have a significant impact, as the space available in the flash tank is limited ； 3. In fact, the operating condition of the heat exchanger before entering the flash tank also has an impact ； 3. The reason for the PID parameters of the pressure control valve in our flash evaporation system is that it closes slowly at low opening degrees, resulting in a drop in pressure ； 4. (If any) the load regulation of the recycle hydrogen compressor also has an impact ；
It’s likely that the pressure in the flash tank is low, which results in a lower temperature of the flash vapor. The lower the pressure, the more gas is flashed; since more heat is released during flashing, the temperature of the flashed gas becomes lower.
Reply to 4# 654262293: I think it’s probably the lack of flash steam that causes the low pressure. And the reason for this is the low temperature of the methanol coming from the scrubber tower (only mention the low temperature of the methanol used in scrubbing).
It is mainly due to the too low flow rate of low-temperature methanol washing; too little gas is released from the flash tank, while the flash gas compressor draws in too much gas, resulting in a pressure in the flash tank that is lower than the specified process values. The lower the pressure in the flash tank, the lower the temperature of the flashed gas!
It is mainly high system pressure that causes high pressure at the compressor outlet, which in turn leads to obstruction at the compressor inlet and high pressure in the flash drum. High pressure is not conducive to flashing; therefore, the temperature of the flashed gas is high, while the low temperature of methanol is just a coincidence