A problem of level-flow cascade control
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In the level control of the intermediate tank, cascade control is generally used based on both the liquid level and the feed flow rate. I would like to ask if anyone has used cascade control in relation to the incoming material as well. The output of this intermediate tank goes into batch reactors; I hope experts can share their insights. Thank you very much
I was wrong; it usually has to do with discharge control, as the next device is a batch reactor. Is it possible to use cascade control in this case?
If a single-loop control for one liquid level is sufficient to meet the requirements, then using only one level controller is ideal. If higher control precision is needed, a cascade control system that combines level and flow control can be employed; it offers better control performance compared to a single-loop system, but it also requires more investment.
Aren’t feed flow rate and incoming material the same thing?
The level of the intermediate tank is stabilized through feed-level cascade control, thereby ensuring a stable flow rate to the reaction vessel. If discharge is used for cascade control, then the discharge flow rate will inevitably fluctuate, which can affect the reaction vessel and pose a safety risk.
The control design on the flowchart is correct. What the poster is trying to say is–should it be changed to a discharge control method? Time-program control is possible, but it is too imprecise and unreliable.
What happens to liquid level fluctuations if it is controlled in cascade with the incoming material flow? What to do when the jar is empty?
Thank you; there seems to be an issue with the control in this area – one controller is used to control two feed valves, and it doesn’t represent either proportional control nor simple cascade control. :P
First, determine the relationship between the flow rates of these two feed streams: selection, addition, or ratio? Only after understanding the relationship between these two can the control scheme be implemented.