The vacuum level of the vacuum system does not meet the process requirements
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Dear teachers: Our company has a continuous vacuum distillation system consisting of one vacuum pump (200 L/S) and three tower systems. Each tower represents a complete distillation unit, equipped with pumps, reboilers, reflux tanks, condensers, etc. In total, there are 4 towers in this unit: Tower 1, Tower 2, Tower 3, and Tower 4. Towers 1, 3, and 4 operate under negative pressure, while Tower 2 operates at atmospheric pressure. Each of the reflux tanks in Towers 1, 3, and 4 is connected to a vacuum line, and these three vacuum lines lead to a main vacuum pipe. The main vacuum pipe then passes through a cooler and a buffer tank before reaching the vacuum pump. During the initial pump testing, the vacuum pump was connected to just one column, and the vacuum level inside that column could quickly reach -0.095; each of the three columns could also achieve this pressure on its own ； However, when all three towers are connected and used together, Tower 1 can only reach -0.084, Tower 3 can reach -0.090, and Tower 4 can only reach -0.067 ； The vacuum pump was checked and there are no issues. Could everyone please help analyze the possible reasons for this situation? Thank you!
The suction power isn’t enough; what else could be the reason?
Insufficient load on the vacuum pump can also be caused by poor condensation performance in the overhead condenser, or by excessive resistance in the vacuum piping at the tower top.
It’s not a problem with insufficient suction power; the vacuum level remained unchanged even after more than a day of continuous pumping
Insufficient suction means that the amount of suction generated by the three towers is >200....
Empty the liquid from all three towers before trying to pump it out; if it can’t be pumped out, there’s a leak. When the dry tower can be lowered to allow liquid to flow in, it cannot be lowered again – the pumping speed is not sufficient
Does it mean that the three towers cannot be brought up together under normal operating conditions? If that’s the case, it’s either because the condenser isn’t effective at condensing, the gas flow is too high, or there’s an issue with the vacuum pump ； There’s not enough time for pumping; if the condensation effect is good, it means the pump was sized too small when it was designed, and it’s unable to handle three columns
The vacuum levels of the three towers are inconsistent; it’s likely due to insufficient suction power. Turn off the steam first and then pump; if the vacuum level remains the same, it means it’s not sufficient
The sealing effect is poor, and the pump’s pumping power is insufficient!
The vaporization rates of the three towers are different, which means the amounts of oil and gas vary. Drawing from all three of them at once will certainly not yield good results. Have you considered the leakage issues in towers 1 and 4? It is possible to achieve the required pressure when pumping separately, as the leakage is low and it’s easy to meet the pressure requirements in such cases. However, when pumping together, if there are some leakage points, it’s normal for the vacuum pump not to be able to meet the requirements due to the load imposed on it. It is recommended to locate the leakage points first, and then adjust the opening degrees of the inlet pipelines coming from the three towers: increase the opening for those towers with higher vaporization rates and decrease it for those with lower rates. Overall, it seems that your vacuum pump is not powerful enough.
Check the sealing of each tower. Also, send me the distillation diagram to take a look