How is the tower pressure in a distillation column generated?
Thread Content
How is the pressure in a distillation tower generated? Is it through the non-condensable gas carried by itself or through the addition of nitrogen? If it is a full condenser, will negative pressure be generated? A new tower has been installed in the unit; the packing in the distillation section is DN500, while the trays in the stripping section are DN800. It’s a very small tower. When driving the plant, a phenomenon occurs: when the reflux at the top of the tower is high, the pressure at the top rises; when it is low, the pressure drops. Moreover, the size of the pipe from the tower top condenser to the reflux tank is DN32, with a height of approximately 10 meters, connecting to the upstream elbow. The liquid density is 0.865. It is common for the pressure at the top of the tower to be higher than that in the tank; there are control valves on the tank to allow for venting and nitrogen supplementation. It seems that this pipeline is filled with liquid, and nitrogen cannot be introduced into the tower. Let’s analyze what the reason is and how to deal with it. By adding a balance tube, some of the material gas will be released, thereby reducing the yield
Is there no gaseous product at the top of the reflux tank?
The pressure in a distillation column is caused by the evaporation rate being greater than the condensation rate; it is also related to the packing resistance, of course. An increase in the tower top reflux indicates an increased total amount of reflux of low-boiling compounds, and the boiling of these low-boiling compounds leads to a rise in pressure. Reducing the reflux increases the output rate of low-boiling substances, and the pressure decreases.
1. The pressure in the distillation tower is caused by the evaporation rate being higher than the condensation rate; adjusting the flow rate of the reflow pump at the top of the tower can help improve this situation! 2. Blockage of the packing inside the tower is also a direct cause of increased tower pressure
This post was last edited by HEJIYUER on 2015-10-1 at 19:56, version 1. Is the tower top designed for complete condensation? 2. Is the condensate supercooled? If it is not too cold, there is no need to introduce N2; the condensate tank has an evaporation pressure (corresponding to a temperature). 3. The introduction of N2 into the system reduces the cooling capacity of the heat exchanger, which in turn increases the tower pressure. If the pressure of N2 entering the tower is used to maintain that pressure, then this tower pressure has little meaning. Is there a vent on the condenser? Release some pressure; it’s possible that N2 accumulates there, which reduces the condensation capacity. As a result, the pressure at the top of the tower is often higher than the pressure in the tank. The testing setup tends to replenish N2 in order to control the tower pressure, and the response is indeed fast. However, there are side effects – when N2 is introduced, we refer to this as the “Dulengding treatment” approach. You can manually turn off N2 and then increase the reflux flow to see if the column pressure can rise further If you are from Quan Ning Design, the tower pressure is determined by the heat transfer capacity of the condenser. @jiaguoyun