Problems that occur when pressurizing molecular sieves
Thread Content
When our company’s small nitrogen generation unit was under pressurization, the opening degree of the air compressor inlet guide vanes was already at 100%, yet the gas production pressure dropped and the gas could not be delivered; as a result, dumping had to occur, which triggered the activation of the backup system. At the same time, the air compressor’s dump valve also opened. Experts, I’m confused – clearly the air compressor’s pressure is insufficient, so why is there still dumping occurring? Thank you so much!
It is a constant pressure setting; having the guide vanes fully open and the vent valve open at the same time is contradictory. Therefore, it is recommended to check the settings of the vent valve as well as the mechanical and control systems. Additionally, compare the pressures at the molecular sieve and the air compressor outlet to determine whether there is a fault with the transmitters~~
I guess: when the inlet guide vanes are set to 100%, the PSA pressure increase does not meet the requirements, resulting in nitrogen purity that is not up to standard, which in turn causes the nitrogen generator’s vent valve to open. What is the pressure when the inlet guide vanes are set to 100%? What is the normal value? If the pressure when the guide vanes are fully open does not meet the requirements, it indicates that there is a problem with the air compressor; check whether there is an issue with the actuator of the guide vanes (we have encountered situations where the actual opening degree of the guide vanes did not match the value indicated on site). Is the air compressor vent valve opening because the system pressure became excessively high after the nitrogen generator stopped, causing the vent valve to open? Check the pressure curve to see if the pressure is too high; if so, there is no problem with the relief valve.
When the air compressor is operating normally, the pressure setting is 8.3 bar. At the beginning of the pressure filling process, the inlet valve is fully open, and the pressure drops to around 7.9 bar; it then gradually returns to the normal level as the filling process comes to an end
The aforementioned situation does not occur when the ambient temperature is low; it tends to happen when the temperature is high!
Temperature shouldn’t have such a significant impact on the gas flow rate; it seems to me that the pressure buildup is too rapid, which prevents the inlet guide vanes from adjusting in time, and once the pressure rises, the vanes close back down.
Although you say it’s a small issue, I think it’s related to excessive heat loss in the summer setup – that is, the temperature of the circulating water is too high, which prevents the air compressor from raising pressure properly. I assume your guide vanes are used for flow control, while the venting system is used for pressure control; thus, this conflict occurs because the air cannot be compressed. Has this situation happened before? ? ?
Wow, then there’s no need to think further – that’s exactly the reason. Our production unit has to import 90% of what it needs every summer, and moreover, it isn’t able to achieve the required flow rate. Additionally, if it seems uncomfortable to let things go to waste, or if you consider it too wasteful, you can reduce the pressure in the distillation tower; that will do. As for how to do that, you should know how