Distillation column operation problems
Thread Content
There is currently a continuous vacuum distillation process. In Tower 1, the liquid level at the bottom of the tower is lowered in order to increase the temperature at the bottom of the tower; however, once the liquid level is reduced, a vacuum is created, which leads to significant fluctuations in the liquid level as well as in the flow rate and pressure of the steam from the reboiler. These fluctuations greatly affect the operation of the system. I would like to know what the reason for this is What are the solutions?
Don’t understand the principle? What is the relationship between raising the temperature at the bottom of the tower and lowering the liquid level? ? To increase the temperature at the bottom of the tower, it is necessary to reduce the amount of product taken from the bottom of the tower or increase the amount of heating steam used.
““A drop in liquid level will create a vacuum.” It must be caused by low feed volume; it certainly isn’t due to temperature. The flow and pressure of the reboiler steam experience large fluctuations; this is due to issues with the temperature of the steam itself or the steam trap, and it has nothing to do with distillation. Your logic is incorrect, so it’s impossible to analyze the information provided
Increasing the feed temperature at the same time should be able to solve it
I also think that if we want to increase the temperature at the bottom of the tower, we can just increase the amount of steam supplied to the reboiler. What is the principle behind lowering the liquid level? If it is indeed necessary to lower the liquid level to avoid creating a vacuum, considering increasing the tower pressure appropriately might be an option.
Is there a flowchart? What the original poster is referring to is the increase in the reboiling in the tower bottom, which leads to an increase in the temperature of the tower bottom and a decrease in its liquid level
According to the available information, the temperature of the reactor bottom is related to the level of liquid in it. The current problem is that it’s not possible to increase the amount of steam used; therefore, attempts are being made to raise the temperature by lowering the liquid level in the reactor bottom
Some information suggests that the liquid level in the tower bottom can affect the temperature at the bottom of the tower. At present, the opening degree of the reboiler’s automatic control valve is already quite high, but the low temperature still does not meet the process requirements; therefore, attempts are being made to reduce the liquid level in the tower bottom in order to increase the low temperature
In practice, lowering the liquid level in the tower bottom does not increase the evaporation rate; the evaporation rate can only be increased by increasing the steam supply along with the feed rate. The reason for instability is the reduction in the liquid level at the bottom of the tower, which leads to a decrease in evaporation and an increase in vacuum, thereby causing an artificial liquid level.
I’ve never heard that lowering the liquid level can increase the temperature at the bottom of the tower; there’s a logical error in this. Generally, increasing the heating power of the reboiler leads to an increase in the amount of vapor rising inside the tower, which results in a decrease in the liquid level ； At the same time, as more light components evaporate, more heavy components remain in the bottom of the tower. With pressure remaining constant, an increase in the amount of heavy components leads to a rise in temperature, thereby increasing the temperature at the bottom of the tower.
Stable liquid level is the basis for the operation of a distillation tower. There are several methods to increase the temperature at the bottom of the tower, such as reducing reflux, increasing the amount of heating steam (or heat) at the bottom of the tower, and reducing the discharge volume there. Lowering the liquid level at the bottom of the tower is an incorrect approach.