How to control the liquid level drop rate?

This post was last edited by Ku Liang Zhi Le on 2023-7-24 at 15:28. A single-loop level control system is designed, in which the level detection signal is sent to the level controller, and the output from the level controller is fed to the control valve located on the outlet pipeline of the metering tank. Unlike constant level control, the setpoint signal for a level controller is a ramp signal, that is, the setpoint is a ramp signal with a constant rate. To enable the liquid level to decrease at a constant rate in order to follow this ramp waveform setpoint, the controller must have a 2nd-order integration function.

It seems that OMEGA has a mass flow controller

Based on your description, the control of the liquid level drop rate can be achieved through the following steps: 1. Configure the remote liquid level gauge: Connect the remote liquid level gauge to the Hollyland K-series Macs 6.5.4 system to ensure that real-time liquid level data can be obtained. 2. Set the target liquid level drop rate: Calculate the amount by which the liquid level needs to drop per second, based on the quantity of nitric acid to be added and the time required. Set this value as the target liquid level drop rate. 3. Set valve control: Perform feedback control based on real-time liquid level data and the target liquid level drop rate. When the real-time liquid level is higher than the target level, open the valve to add nitric acid drop by drop ； When the real-time liquid level is below the target level, close the valve to stop the addition of nitric acid. 4. Calibration and tuning: Based on actual conditions, the rate at which the target liquid level drops and the valve control parameters are continuously adjusted to ensure stable and precise control over that rate of decline. Please note that due to the lack of a flow meter, there may be some error in controlling the rate of liquid level drop. To improve accuracy, it is recommended to add a flow meter to the system in order to more precisely control the dripping rate. .

Feedback control is carried out based on real-time liquid level data and the target rate of liquid level decline. This idea is correct; the key point is that both the real-time liquid level and the decline rate are variables – so how can feedback control be implemented? I just don’t know how to use this control method

If it is indeed not possible to add more flow meters, try using pure proportional control or a calculation module. The tasks that need to be carried out are as follows: 1. Adjust the linear characteristics of the control valve. 2. Calibrate the flow rates at various opening degrees of the control valve to create a characteristic curve; strive to make this curve linear, such that the relationship between flow rate and opening degree is given by Flow Rate * K = Opening Degree. Control can be achieved using a calculation module. 3. It is necessary to regularly calibrate the relationship between opening degree and flow rate. 4. The flow rate can be controlled by modifying the K coefficient according to the required flow rate. 5. It is essential to have a good quality control valve. Try looking for some information on proportional control methods

The process of adding nitric acid seems to be a rather dangerous one; it is necessary to monitor and alert for changes in liquid level rate (calculating an appropriate rate based on the process requirements). The flow rate should be kept as uniform as possible.

When considering the options, please pay attention to a few key terms: nitric acid, dropwise addition, reaction vessel, uniform addition

Use cascade control; do not use a single-loop PID

Which one should be connected in series with a level gauge?

Well, is it mainly just one liquid level, or is it a variable? It seems pretty complicated!