Two distillation towers share one vacuum pump – is the pressure regulation unstable?
Thread Content
This post was last edited by luckyyjjun on 2017-9-5 at 12:53. The operating pressure of the two distillation towers is 60 kPa; a single vacuum pump is shared to create negative pressure in each of the two towers. Use the control valve on the return line of the vacuum buffer tank to adjust the vacuum level. 1. It was found that the pressures in both towers could not be maintained at below 60 kPa; one tower had a pressure of 62 kPa and the other of 68 kPa, and the pressures in both towers fluctuated frequently. 2. Later, the vacuum systems of the two towers were modified by installing a control valve in each tower; these valves open when the pressure is high to allow air to be introduced. After the modification, the tower pressure can be stabilized at 60 kPa, but fluctuations still occur. Is there a better way? 3. Another column in the unit is equipped with its own vacuum pump, resulting in relatively stable pressure. Is it more stable to use one vacuum pump per tower in the design of vacuum distillation, with separate control? 4. Can vacuum pumps of the same specification in a vacuum tower be combined? If merging is possible, how should it be designed to stabilize the pressure at the design value?
Settings like yours will interfere with each other! It is recommended to use two control valves, with one of them being set for manual adjustment. Once the pressure is stable, adjust the manual control valve slightly as needed to reach the desired value!
You mean one tower is controlled by a control valve, another tower is controlled manually, and the vacuum pump buffer tank is controlled by a control valve. Is my understanding correct?
If all four distillation columns are under-pressure columns, each with a vacuum level of 50 kPa, how should they be designed? How to control it?
I’m telling you an approach for a smooth adjustment; as for whether to use manual or automatic control, it depends on your specific circumstances! Otherwise, following your previous adjustment approach, they will affect each other and it won’t be possible to maintain control!
You can barely manage with one vacuum pump for 2 units; you already have four towers – do you really not have the money for those three more vacuum pumps?
The pressure in both towers is higher than the set value, which indicates that the vacuum pump is not powerful enough. Regarding the utility systems, when multiple systems share a single vacuum pump, it essentially forms a vacuum pipeline network. It might be possible to use the design principles applied to water supply networks as a reference; in such designs, the resistance losses are distributed among the various branches, while the pressure loss in the main pipeline is kept low. So, could it be that the main vacuum pipeline is too small?
The original designer did not develop a process system for multiple vacuum towers. Is the poster using one tower and one pump?
Does the poster mean that the diameter of the vacuum main pipe is smaller?
Yes! This way, the mutual influences are eliminated!