Distillation tower pressure heat bypass control
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This post was last edited by Refiner on 2016-1-23 22:04. Why must the cooler be located below the reflux tank when controlling the heat bypass of the distillation tower? What is the principle behind this? Please explain
There are also coolers that are higher than the reflux drum, similar to those in the deethanizer reflux drum. In this case, the pressure in the reflux tank must be equal to the pressure at the top of the tower plus the height of the liquid column in the heat exchanger. If the remaining coolers are below the reflux drum, then the pressure difference between the reflux drum and the top of the tower is equivalent to the height difference, which facilitates thermal bypass control. The pressure control method in the deethanizer is mainly to discharge vapor to the low-pressure non-condensable gas network through reflux at the top, or to control the pressure in a manner similar to that of low-power compressors used in vacuum distillation processes.
The stabilizer here is similar to the thermal bypass control scheme you mentioned. The liquefied gas distilled from the top of the tower first passes through four air coolers located at a higher elevation than the reflux tank, then through four water coolers situated at a lower elevation than the reflux tank. It then enters the reflux tank from the bottom. When the thermal bypass is opened wide, communication is established between the tower and the reflux tank, resulting in a reduced pressure difference between them; as a result, less fluid needs to be cooled by the cooler, and the pressure in the tower rises. When the thermal bypass is closed, the pressure difference between the tower and the reflux tank increases, allowing a large amount of fluid to be cooled by the cooler, which lowers the pressure in the tower.