Sharing of issues encountered during the maintenance of catalytic cracking units
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Gentlemen, the maintenance of catalytic cracking units is a very important task in a refinery; after all, once the catalytic process stops, almost the entire refinery is affected. So, what problems have everyone encountered during maintenance work and during startup and shutdown processes? Equipment failure? Inner component fallen off? Coke block falling off? The lining has fallen off? Coking in the settler? Coking in the distillation tower? Burnthrough in the auxiliary combustion chamber? Wait
Coking in the settler is perhaps the most common phenomenon; there are also issues such as breaks in the pressure guiding pipes inside the regenerator and at loose connections. During our maintenance work, we encountered a large hole that appeared on the outer wall of the area where the fluidizing air flowed inside the regenerator’s inner sleeve
Encountered quite a few problems: 1. The material broke during withdrawal :)； 2. The fuel combustion nozzle has burned out ； 3、The slurry steam generator has few openings left unblocked ； 4. It is very common for the lining to peel off and the turtle-shell mesh to get damaged ； 5. Large lining blocks are blocking the cyclone separator and material return ； 6. There are way too many deformed trays in some sections of the fractionation tower. I haven’t been doing catalysis work for a long time; how I miss it
This post was last edited by longziyun on 2020-9-14 at 11:00. During shutdowns, one of the most hazardous phenomena is the spontaneous combustion of iron sulfide. Special attention should be paid to numerous areas, including distillation tower trays, the reflux drum at the top of the distillation tower and its pipelines, the stripper in the acidic water treatment system, various heat exchangers and pipelines, fuel gas pipelines, and the dry gas knock-out drum. Therefore, during shutdown and line purging, one must think clearly: steam purging must be carried out thoroughly, sufficient cooling time must be allowed for proper cooling, and comprehensive contingency plans must be in place. The established emergency cooling measures should also be effective to ensure the safety of the equipment. After all, compared to the so-called potential waste of steam and fire-fighting water, the damage to equipment and pipelines caused by the spontaneous combustion of iron sulfide results in losses that are practically negligible.
We have also experienced incidents where the inner tube of our sleeve was worn through.
Due to the spontaneous combustion of iron sulfide, the shell side of our heat exchanger became red-hot, resulting in the complete destruction of the heat exchanger. Consequently, operations had to be halted.
With technology being so advanced these days, I think the only real problems are coking and lining issues; as for our slurry steam generators, we’ve never had any blockages (as long as the flow rate is sufficient, there should be no problems). Ferrous sulfide can be used for passivation, and we’ve never encountered tower tray deformation (it’s either due to excessive gas flow or poor maintenance). Do anyone have any tips to avoid these problems?
I would like to ask: can acidic water systems also be passivated?
The more serious issue is that corrosion and wear lead to premature damage of equipment. Nothing else has been found for now
The more serious issue is that corrosion and wear lead to premature damage of equipment. Nothing else has been found for now
The cause of the spontaneous combustion of ferrous sulfide is likely more related to physical changes