On the control methods for liquid stratification and the selection of automatic control instruments

First, extract the material from the upper layer; determine the position of the separation between the upper and lower layers by using the liquid level in the mixing tank. Then place the pipeline above the water surface – the details on how to do this are unnecessary to explain

Thank you for participating in the discussion. If the upper layer of material is to be removed first, should a hose be inserted into the tank to use vacuum for extraction? We intend to pump the material from the outlet at the bottom of the tank outward, aiming to achieve automatic control and reduce the need for manual operation. By using instruments to detect the boundary layer of the material flowing within the pipe, the valve at the pump outlet can be opened and closed automatically, thereby allowing the material to be directed to two different locations: the upper and lower sections of the tank.

Choose a level gauge with a density between that of water and that of organic substances: it should indicate water when the liquid level is high, organic substances when the level is at zero, and shut off when the organic substance level reaches zero. The downside is that the liquid level may fluctuate during pumping, requiring the pump flow rate to be reduced.

Thank you for the suggestion, Haiyou! My tank is quite large; it has an agitator, a jacket, and elliptical end caps at both the top and bottom. As a result, it is rather difficult to install an external level gauge. Even if a level gauge is used, it isn’t easy to determine the boundary between the different layers. Although the principle of a communicating vessel applies, once the layered material enters the level gauge, the level indicated by the gauge may not correspond to the actual boundary between the layers in the tank. The main goal is to achieve automatic control; therefore, it is required that the instruments detecting the points at which material exits the tank respond quickly and accurately.

This same or similar issue has been mentioned several times; since I often read about it, I have paid attention to it and come up with solutions. It is possible to use a material that combines water and organic density to create a float for controlling the liquid level. There are even better solutions available – you can search for this post on the site. Actually, what I wanted to say today is…； Another option could be to establish an operation interface on the device, with a connection point at that interface for attaching a branch pipe equipped with a probe; a conductivity meter can also be used. Under normal coating conditions, if the water level exceeds a certain threshold, an organic overflow valve will open. When the organic liquid level reaches the lowest value indicated by the level gauge, the water supply valve is opened; and when the water level again reaches that lowest value, the water supply valve is closed. After feeding and stirring for a certain period of time, and after the mixture has separated into layers, the valve connected to the conductivity meter is opened, and the conductivity probe starts to function. In other words, at the start of feeding, the conductivity meter should not operate yet, as otherwise, overflow would occur before the mixture has properly separated. Once feeding is complete, the feeding valve is closed. Of course, this branch pipe valve opens only after the feeding valve has been open for a certain time and then closed, taking into account the time required for feeding to be completed, the stirring time, and the time needed for the mixture to separate into layers. It’s written in a messy way; please organize it.

If you release water first, it will end up coming out along with the material. You can install a detection device on the tank – as long as it can detect water. Make an opening in the part of the tank where there is material; during operation, you can draw out the material through this opening. Then slowly pour water into the tank until it reaches below the opening at the top. Once the detection probe detects water, stop pouring water. After all the material has been drawn out, then remove the water. In this way, the material will not contain any water. Eventually, there will be a small amount of material in the water. Make the discharge outlet rectangular in shape. Detection devices for water are available, but it’s difficult to find devices for detecting material; using such devices can provide greater accuracy.

It’s simple; you can first determine the process parameters by manually observing the time it takes for the pump to draw up a certain volume of fluid. Then, precise flow delivery is achieved through an external control system. Achieve automatic control

Thank you for participating in the discussion in this post, for offering great ideas and practical solutions. Here, if the time is measured based on manual observation. Theoretically, it is feasible, but inputting the time values obtained through manual observation over time into an automatic control system for time-based control seems unreliable to me. Firstly, there are already errors in the timing of manual observations, and the response may be delayed; even a delay of three to five seconds can result in materials being poured into the wastewater or wastewater being poured into the materials. After all, the flow rate of the pump is quite high – just a few seconds can mean tens or even hundreds of liters of fluid being transferred. Secondly, since it is a batch-based operation, there is a possibility that the amount of material fed into the reactor and the amount of water added may not be exactly the same. The amount of water added can be kept constant across batches, but for the amount of material, as it comes from previous processing steps, there is always a slight variation. This method can achieve control, but not precise control.

Did the original poster manage to solve it in the end? I’m working on a proposal for a client and am facing a similar issue.

There is two-phase separation and batch operation; precise full-automatic control is difficult, as the phase interface is not a straight line. If stirring is excessive, emulsification occurs, resulting in a wider and more blurred interface. Let’s install a glass tube at the discharge port to take a look. You can give it a try by using an extraction tower for continuous operation, and controlling the approximate height of the phase interface with a phase interface level gauge.