What is the specific process for the three external circulation paths in the fractionation tower during the start-up of catalytic cracking? Thank you!
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This post was last edited by h*ng on 2017-11-12 09:11. What is the specific process for the three external circulation circuits in the fractionation tower during the start-up of catalytic cracking? What is the process of the three-way circulation inside the tower? What issues need attention? Thank you!
The three external circulation paths around the tower involve slurry, the middle fraction from distillation, and crude oil. The external circulation refers to the circulation outside the distillation tower; the slurry is drawn from the bottom of the reprocessing tank and sent back to either that tank or the crude oil tank. Internal circulation is the normal circulation process. Before the catalyst is added in the reaction vessel, the slurry passes through the distillation tower, with it being drawn from the bottom of the distillation tower. Precautions: 1. During external circulation, it is strictly prohibited for oil to enter the distillation tower; keep the vent at the bottom of the distillation tower slightly open and check regularly to ensure no oil enters. 2. Control the temperature well during the heating process to prevent rapid heating, which could cause water inside to vaporize too quickly and damage the equipment. 3. Reach 150 degrees quickly to avoid vacuum conditions in the pumps
They are crude oil, reprocessed oil, and slurry circulation. Crude oil follows the normal heating process before being returned to the crude oil tank via the emergency bypass. Reprocessed oil follows the normal process and is returned to the reprocessed oil tank through the external circulation line of the second tower. The slurry is drawn out from the bottom of the reprocessed oil tank through a connection line; it then follows the slurry circulation path and returns to the crude oil tank. The amount of slurry that returns can be controlled, thereby regulating the liquid levels in the crude oil tank and the reprocessed oil tank
The re-refined oil returns to the re-refining tank via the external circulation line of the second intermediate tower, following the normal process. Are there some plants that do not have such an external circulation line for the second intermediate tower?
Before oil is fed into the distillation tower, there should be no slurry circulation; at this stage the three types of circulation involve light diesel, feedstock oil, and reprocessed oil. It’s not available at No. 2 Middle School either; what goes back to the refining line is actually crude oil, which then proceeds along the startup cycle line along with the crude oil.