Problems that have occurred during the operation of catalytic cracking coaxial two-reactor units
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Could everyone please introduce and discuss the problems that have occurred during the operation of coaxial dual-device systems? I am particularly concerned about the condition of the startup riser and the startup plug valve. This post was last edited by DAC The army rules the world on 2007-9-26 at 16:35.]
How is it that no one is participating in the discussion on such an important issue?
I have never operated such devices; I’ve heard that issues can arise including pipeline breakage at loose points in the feed pipe, perforations in the stripping section, jamming of the feed pipe when it is hot, and breakage when it is cold.
Yes. There have indeed been many instances of perforation in the stripping section of coaxial catalytic units. As far as I know, the cause was a fracture at the root of the loose point in the stripping section cone. Due to the different pressures in the regenerator and the settler, the flue gas carries catalyst into the settler through the breakage points, causing wear. Observationally, the flue gas components in the dry gas gradually increase, that is, the levels of N2 and CO2 rise. During normal production, the problems are not too serious, but accidents can easily occur if appropriate measures are not taken during shutdown periods.
The answer upstairs was excellent. The serious issue is how to prevent perforation or cracking in the stripping section during shutdown. Is it because, after stopping the feed, the catalyst does not circulate sufficiently, causing the temperature in the stripping section to drop too rapidly? Such sharp temperature changes lead to changes in thermal stress on the material, resulting in cracking. If the differential pressure is not well controlled at this time, or no other measures are taken, the consequences will be unimaginable.
What I mean is not that the break in the air ducts occurred during the shutdown period. In my experience, this tends to occur under normal production conditions; if you pay attention to the data on the flue gas components in the catalytic dry gas, you will find that their levels tend to increase during the first half of the cycle. What I mean is that the flue gas that leaks during normal operation (as the oxygen content is already low at the upper part of the regenerator) will not cause serious problems when diluted by a large amount of oil and gas. However, when production is stopped and feed is cut off, the amount of oil and gas decreases significantly, and the oxygen concentration in that oil and gas rises. The danger **increases at this time!**
I see what you mean; it’s the loosening of the pipeline that causes the break. I am talking about the cracking of the tube wall in the stripping section. Additionally, there are many other issues that I hope we can discuss together.
The problem of perforation in the stripping section occurred in our plant last month; the dry gas flow rate increased from 3000 to around 5800, creating a very dangerous situation. Even a slight decrease in differential pressure would cause the temperature in the dilute phase to rise, and the load on the compressor was significantly higher than normal. After analysis, it was determined that the perforation in the stripping section was likely caused by a leak in the stripping steam pipeline, with catalyst being carried along and leading to wear and perforation in that section. Shutdown for maintenance was carried out on September 20, and a perforation was found at the cone of the stripping section with a diameter of approximately 200 mm.
The loose air ducts have broken; due to thermal expansion, there are issues with the placement of manholes at the location of the main air distribution plates and the raw material risers, and the exterior of the perforations in the stripping section is severely oxidized