Problems with distillation

Insufficient information; an accurate judgment cannot be made. It is speculated that this is due to a change in the composition of the material inside the tower; at the beginning, the proportion of heavier components in the rising gas was higher, resulting in a higher temperature at the same pressure inside the tower. Thereafter, the proportion of light components in the rising gas increases; at the same pressure, the temperature decreases, which is a normal phenomenon

It’s unlikely; this manufacturing process has been in normal use for a long time already! There will be no changes detected in the material components

Has the reflux temperature not changed? Has the feed rate not changed?

Analyze the feed components. With lighter feed components and unchanged operating conditions, the situation described by the original poster occurs.

Thank you to the folks upstairs; I’m using a 8000L tower reactor；

We analyzed it on our own: it turns out to be a primary condenser (chilled brine)； It was later changed to a two-stage condenser: primary circulating water and secondary chilled brine, with the possibility of unstable flow rate of the primary circulating water. Then the workshop shuts off the primary circulating water, and the same problem reoccurs! !

In case of batch distillation, after the distillation column is started up, there is a mass transfer equilibrium process; the temperature at the top of the column gradually increases from room temperature until reflux begins to occur – this is a process of warming up the column； If you take a sample from the reflux, you will find that the content of the reconstituted components is very high. As the reflux gradually returns to normal, the top temperature will slowly decrease. Sampling will show that the content of heavy components also decreases gradually, until the top temperature reaches its lowest level and the content of heavy components is at its minimum. As the light components are distilled off, the top temperature gradually rises; at this point, it is necessary to increase the reflux ratio in order to control the top temperature and thus regulate the content of heavy components in the distillate. Otherwise, it will be a reverse process: the top temperature will keep rising, and the content of the recombined components will also increase. This is the law revealed by mass transfer theory. If the abnormal situation mentioned by that gentleman occurs, I think a chemical reaction must have taken place in the distillation vessel; as the temperature rises, some of the materials inside the vessel may decompose, resulting in the formation of new light components. I hope my analysis can help you find the cause and solve the problem.

Thank you; this process was indeed developed by us last year! But we conducted pilot tests before putting it into production, and this device has been in operation since last September until now without any problems! It only exists starting this time! Affecting production capacity.:lol

Has your fractionation component not changed? In thermal equilibrium, it involves the tower bottom, the feed, and the tower top; the feed temperature must remain stable. Either the condensate at the tower top is undercooled, or there is a problem with the liquid at the bottom of the tower. Ideally, as the distillation time increases, the material should gradually move upward, resulting in an increase in temperature. . . . If it doesn’t work, dismantle the tower for inspection

That’s not right. According to the principles of distillation, an increase in the reflux ratio should lead to a decrease in the temperature at the top of the tower. If all other conditions remain unchanged, and since the temperature brought in by the feed remains constant as well as the temperature at the bottom of the tower, an increase in the reflux ratio means that more heat will be removed, so the temperature at the top of the tower should decrease