Comparison of tower pressure control methods
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bk13.jpg As shown in the figure, two different tower pressure control methods! I hope the seniors in the design institute and the chemical industry can point out when to use the control method in Figure 1 and under what circumstances to use the control method in Figure 2?
The second kind of control is common, but the first kind has never been seen before. It usually controls the pressure by controlling the cooling water.
Neither method is common, and it is difficult to control the pressure of the gas phase through valves. The control of gas phase pressure is generally adjusted and controlled by increasing the tower top cooling load + vacuuming degree. The main adjustment is the cooling load of the tower top condenser, that is, the amount of cooling water used, and vacuuming to discharge non-condensable gas.
There is also a third method to control the opening degree of circulating water return water.
I have never seen the first one, but with this pressure control method, if the regulating valve fails to open and cannot be opened, is there no fear of overpressure in the tower?
The first is a partial condenser, the second is a total condenser, and the second mainly adjusts the heat exchange area to control the tower pressure.
The first type of gas volume should be small, the reflux temperature requirement is not high, the top pressure of the tower reacts sensitively, and energy consumption is saved when returning to the tower. The second type relies on changing the liquid level in the cooler to change its heat exchange area. The cooling effect is better than the first type. However, since there is no regulating valve in the circulating water line, it is a bit of a waste of energy to rely on manual adjustment of the water volume.
The first type of valve needs to be as large as it needs to be. Is it unstable?