Distillation reflux cascade fluctuation
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Since we started operating the plant, the reflux from several of our distillation columns has not been able to be fed into the cascade control system (when it is fed in, the reflux flow rate fluctuates greatly, and the opening degree of the control valves also changes frequently). In fact, the pumps are fine, and the columns are operating normally. Could everyone please help analyze what could be the cause of this? Is there any solution? Thank you! ! ! ! 1
It is inseparable from process reasons. We used to have a distillation tower, but it wasn’t good. I haven’t used cascade control since then.
The reflux at the tower top is generally controlled through a cascade control system based on the liquid level in the reflux tank and the reflux flow rate; the main interfering factors are fluctuations in the amount of condensate from the tower top condenser and fluctuations in the tower top pressure. Level fluctuations ultimately cause fluctuations in the reflux adjustment cycle.
Reply to 2# Fish Skin Beans: What process conditions are related to it? I would appreciate your advice.
Reply to 3# zhuye99: But it’s very stable when we do manual adjustment; I don’t know what’s going on
Adjusted using a uniform loop; the liquid level is kept within 10%. The main loop has a weaker effect, while the secondary loop has a stronger effect