Why are large gas blind flanges installed when a catalytic cracking unit is shut down?
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Why are large gas blind flanges installed when a catalytic cracking unit is shut down? What will happen if it’s not added?
Because when restarting, fluidization must occur first to prevent the catalyst from entering the distillation tower. .
It involves separating the regeneration system from the distillation and stabilization units; during shutdowns for maintenance, coking in the regeneration unit can be carried out separately from operations in the distillation and stabilization columns. This approach also prevents catalyst from entering the distillation unit when the system is restarted and put back into operation
During shutdown, the reaction system is separated from the diversion system; the distillation tower is purged with steam. The catalyst in the reactor system is drained, the system is cooled, manholes are opened, and inspection of the two units is carried out in advance. If blind plates are not used, air from the two vessels can mix into the distillation system, and oil and gas from the distillation system may also enter those two vessels. Any such mixing of different media is dangerous, and it can lead to fires or even explosions.
To prevent the mixing of oil and gas, and to stop the catalyst from entering the distillation unit during reaction catalysis and thereby blocking the slurry pumps and trays, in order to prepare for subsequent operations.
After the shutdown, steam purging is required to stabilize the oil and gas in the fractionation unit; moreover, the regenerator has a lined structure that cannot tolerate large amounts of water. Additionally, the regenerator system has a heavy workload during plant maintenance, with many tasks needing to be carried out in advance. By installing blind flanges, the regenerator is no longer restricted by the purging time required for stabilizing the oil from the fractionation unit.
A steam seal must be installed both during assembly and disassembly. Prevent air from entering. An explosion and fire broke out.
To prevent air and oil/gas from mixing, for safety reasons
During shutdown, the diversion system needs to be purged with steam; at this time, the reaction system has not yet had all of its contents removed, and there is main air inside both vessels to prevent cross-contamination and fires or explosions