A question regarding the return of slurry to the tower

Bro, you see the fork there, right? Lowering the liquid level in the tower serves to reduce the temperature of the liquid phase at the bottom of the tower. Unless you lower the flow rate in that tower, which results in insufficient flow rate in the upper part of the tower, the liquid level won’t be maintained. See whether it is the diesel component that evaporates from the bottom of the tower, or whether the residue rises to the upper trays.

I checked the book, and it’s indeed the case. He said that when that happens, it’s probably because the amount of material returning to the tower is too large, resulting in an excessive load on the lower part of the distillation tower. When dealing with a flooded tower, it is essential to identify the key points for reducing the load; similarly, when the circulation rate of the slurry is low, it is necessary to first ensure that an adequate amount of fluid flows back up into the tower. My understanding of his statement is that after adjusting the slurry circulation rate, if the amount flowing back down the tower decreases while the amount flowing back up the tower increases, it is necessary to adjust the inlet at the bottom of the tower where the flow returns. This book was written in 1993, and at that time control valves might not have been available for oil slurry. For the lower return tower, there is usually room in the oil circuit via a bypass line, allowing adjustments even for smaller amounts; it is essential to ensure that the upper return tower remains prominent.

If necessary, increase the downward flow rate significantly and reduce the upward flow rate to decrease condensation volume