A beginner asking about the issue of dual impulse adjustment
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I encountered a problem related to a reaction vessel in which, under the action of catalyst C, raw material A reacts with raw material B to produce the main product D and the by-product E. The reaction equations are as follows: Main reaction: 2A + B → D; Side reaction: A + B → E. Here, the main product D is the desired product, while the by-product E is an impurity. Both the main reaction and the side reaction are highly exothermic. To achieve a higher reaction conversion rate, a process with an excess of raw material A is employed. The feed ratio of A, B, and C is approximately 9:3:1. The reactor temperature range is 20 – 110 degrees, while the reactor liquid level range is 0% – 100%. The pressure range in the flash tank is 20 – 120 KPa. The concentration of the material exiting from the bottom of the flash tank should be above 75%. What the original poster intends is to determine the feed amounts for B and C based on those for A, in order to stabilize the liquid level in the mixing tank; the opening degree of the feed valve for A is controlled accordingly. But what to do regarding the reaction tank is unclear It is required that the temperature and liquid level of the reaction tank be within reasonable ranges, while the conversion rate should be increased as much as possible. Therefore, there are two sampling parameters: temperature and liquid level. What should be the controlled variable? Shouldn’t the feed valve at the front of the reaction tank and the discharge valve at the back be controlled? Is it possible to manually lock the discharge valve and adjust only the feed valve? Should the control objective be to stabilize the pressure and temperature of the reaction tank? How should a PID algorithm be written? How is this double impulse calculated?
1. The liquid level in the reaction tank is related to the residence time of the material, in order to control the reaction time. This is not specified in the question. 2. The reaction temperature is related to catalyst activity, which is not specified in this question either. Although not specified, these two values are definitely fixed. Therefore, level control is achieved through a cascade connection between the opening degree of the discharge valve and the liquid level, in order to maintain a constant feed rate of material A; while materials B and catalyst C are controlled proportionally using a proportional controller. Temperature control is achieved by adjusting the valve on the CWS side according to the temperature required for the reaction, while keeping the valve on the CWR side fully open.
Hello, this is a competition question – all the materials involved are virtual, so it’s not possible to find a time-based reference. In general practice, is the change in liquid level inside the reaction tank particularly delayed? Is it then necessary to include an integral term in the PID control?
Yes, the integrals of both the liquid level and temperature are very large
Yes, the integrals of both the liquid level and temperature are very large