Some issues encountered during the commissioning of a vacuum distillation unit

Thread Content

Recently, the company’s pressure relief units have been in operation, but they have not been functioning properly. The current problem is that the temperatures of the various side streams in the pressure relief tower cannot be increased; although the liquid levels in these side streams have been established. All streams from Stream 1 are sent back to the reactor (through reflux from Stream 1 and reflux from the top of the tower). Stream 2 is mixed with the material returning to the feed tank, while Stream 3 is discharged from the unit. The temperatures of these side streams differ by about 50 degrees from the design values. The temperature at the furnace outlet exceeds 370 degrees (due to certain reasons, this temperature fluctuates between 370 and 390 degrees). It is not possible to increase the distillation temperatures of these side streams, and the steam used for stripping at the bottom of the tower already reaches the design value； The top temperature fluctuates between 80 and 150; the instrument cannot be set to automatic mode for the time being, and the vacuum level in the tower remains very stable ； The pressure drop at the top and in the middle of the tower is very small, around 500 Pa ； After looking at some materials on Kaichuan, many people mentioned that the stress-reduction startup cycle is established from top to bottom, but we establish our cycle from bottom to top. What is the difference between these two approaches?