Precautions for catalytic shutdown
Thread Content
What should be considered during catalytic shutdowns? What problems have arisen during such shutdowns, and how should they be handled?
The key procedure is installing the large blind flange. Risks are not easy to control.
During this shutdown, we failed to control the valve opening properly, which caused the valve head to become misaligned; the joint between the start-up riser and the start-up sleeve was also cracked as a result
Reply to 2# karamay: What are the precautions when installing blind plates? Or have there been any problems? Thanks for the exchange
Reply to 4# gengzhe a: Open the double-acting slide valve to reduce the pressure in the regenerator, cut off the main air supply; meanwhile, gradually open the anti-surge valve bypass and close the primary and secondary main air hand valves. Main air cut off, bed blocked. After sealing the bed, close all loose air vents on the two devices; if necessary, cut off the pressurized air. b. After sealing the bed, open the vent at the top of the settler or the DN200 oil-gas line for drainage; shut off the emergency steam feed, and reduce the flow of stripping steam and atomizing steam (complete shutdown is prohibited as it may cause clogging of the nozzles). Keep the settler under slight positive pressure. c. Assist in installing the large blind flange. Conditions for installing a large blind flange: 1. The oil and gas in the settler and fractionation tower must be purged completely. 2. The distillation tower should be maintained at a slight positive pressure to prevent air from entering the tower, as well as to stop oil and gas from the tower from entering the settler. 3. Steam is observed at the bottom vent of the distillation tower. d. After installing the large blind flange, increase the pressure in the regenerator and the main air supply. Spray burning oil to raise the bed temperature to around 450°C. Check all loose points and backflow points to ensure they are unobstructed. e. Remove the catalyst. After the deslagging is complete, when the bed temperature drops to the main air temperature, stop the main fan ； This is ours.
Unlike what’s done upstairs, here we first remove the agent and then install the blind flange.
These days, the agent is removed first before a blind flange is installed; otherwise, it is very difficult to install the blind flange and it is also dangerous.
Reply to 5# yiransunny: May I ask if this is a shutdown blind plate? If so, that would be too troublesome! It’s still easier to pour it after removing the agent!
Why is everyone talking so little? During shutdowns, someone needs to monitor the control panels; otherwise, overheating and overpressure can be very dangerous. In one factory, the catalytic processing unit experienced pressure buildup due to lack of monitoring in the control room, as everyone was busy with other tasks, which led to an explosion in the flare tank and heavy losses； The next issue is oil leakage; the key is to remove the oil properly. Those responsible for cleaning the lines need to be careful, as one might think that everything is fine once steam is detected, but often oil will still leak out. It is recommended to pump the oil into the tower at the initial stage in order to remove it uniformly, which can help prevent oil leakage incidents ； Another issue is water hammer in the light oil line; the steam needs to be properly dehydrated, and the overhead circulation flow should be sent out as much as possible. Otherwise, it must be discharged collectively, as water hammer in the light oil at lower levels can lead to flange leaks ； When sweeping the torch over the surface, if it encounters cold areas, it is necessary to control the temperature carefully; otherwise, uneven thermal expansion can pose risks to the equipment.
After installing the blind flanges, how is the temperature of the settlers reduced? Is it entirely thanks to steam, or is it the main air flow? How can spontaneous combustion of coke masses after the manhole is opened be prevented? Assume that the sedimentators are all cooled with steam. What are the main factors considered when deciding when to increase the blind plate? I learned from all the masters*. . .
Reply to 9# dugutianzuo5: What is the relationship between the explosion of the torch filling system and pressure buildup during distillation? I think the water seal wasn’t established properly