Regarding the removal of large blind plates in catalytic units

1. Basic conditions for removing the blind plate: ① During fluidization, the process proceeds normally, the equipment is free of faults, there is minimal catalyst loss, or any issues that arise during fluidization have been resolved. ②The three off-tower circulations for the crude oil, reprocessed oil, and slurry systems are operating normally, and heating and tightening have been carried out. ③The compressor passed the trial run without any issues and is now ready to be operated at any time. 2. Operating conditions before removing the large blind flange: ① Transfer all of the catalyst from the settler to the regenerator – approximately 120 tons – close the regenerator slide valve and the unregenerated catalyst plug valve, so that flow occurs only in one of the units. ②Slowly reduce the pressure in the regenerator to 0.03–0.05 MPa, while simultaneously reducing the air flow rate. ③ Open the vent at the bottom of the lift column to minimize the amount of steam used in various processes related to the lift column and settler – namely, stripping steam, atomization steam, lift steam, and anti-coking steam. ④Open the vent at the top of the settler, the vent on the oil-gas line, and the vent in front of the large blind flange on the oil-gas line, to maintain a slight positive pressure in the settler. ⑤After replacing the air in the distillation tower with steam, reduce the steam injection into the tower, open the vent at the top of the tower as well as the drain at the bottom, to maintain a slight positive pressure. 3. Remove the large blind plate: ① After removing the large blind plate, restore the steam flow rates in the reaction system to their normal levels (under the same fluidization conditions as those of the two reactors). Steam will be observed at the top of the settler; after 10 minutes, the air will be expelled and the process will be completed. ②The distillation system is fed with the following steams: stirrer steam at the bottom of the tower, light oil stripping steam. About 10 minutes after a large amount of vapor appears at the top of the distillation tower, the air expulsion process is completed. ③Turn off the vent at the top of the settler, the vent on the main oil and gas pipeline, the vent in front of the blind flange, as well as the vent at the top of the distillation tower; use the butterfly valve for the vapor and oil at the top of the distillation tower to control the reaction pressure. ④The oil feed into the distillation tower has been changed to in-tower circulation. ⑤Recover the fluidization of the two reactors; to prevent some of the catalyst from entering the fractionation tower during the catalyst transfer process and affecting the slurry circulation, a certain amount of external discharge should be maintained. And periodically analyze the solid content of the slurry.

The information provided by the poster seems to refer to the situation when a new or modified unit is put into operation for the first time, with the blind flanges removed after the fluidization tests are completed. Of course, it’s not ruled out that work is carried out on regular days; some do that. However, during normal operation, the packing is usually removed first and the fractionation system is switched to internal tower circulation before the regenerative system starts to be loaded with material.

Every time we start work, we remove the blind flanges according to the plan for the 2nd floor. The problem is that it’s difficult to control the amount of steam when expelling air; every time, the maintenance staff complain that there’s too much steam and it’s impossible to disassemble it