Problems with the catalyst bed feed line in coaxial catalytic cracking
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This post was last edited by sdwfsgyykai on 2018-10-2 at 11:47. Four months have passed since the unit was restarted after a major overhaul; during that overhaul, the valve head and seat of the control valve were replaced, and the control valve itself was also thoroughly repaired. However, a abnormal phenomenon has occurred recently: without any significant changes in the catalyst circulation rate, the opening degree of the control valve keeps decreasing, until it reaches its minimum position (during cold-state tests, the control valve was fully closed over a distance of 100 mm; under hot conditions, it reached a closing distance of 260 mm. Based on the expansion of the feed pipe, the control valve should be fully closed). The amount of material stored in the stripping section remains low. Currently, the valves are all at their minimum opening position. I was wondering if there are any good ways to address this issue. Could this phenomenon be due to the valve not being aligned properly?
Is the circulation rate of the catalyst too low? Increase the termination dose and raise the catalyst circulation rate to see what happens.
Since the processing load doesn’t change much, it’s possible to consider whether there is a problem with the Sepa valve head, or whether the lining of the valve head has fallen off
The valve head and seat have been replaced, and the valve body has been repaired
My personal analysis is that there’s a problem with the plug valve; it’s probably not a misalignment issue. (Does increasing the opening of the plug valve cause the amount of material in the stripping section to decrease?) ) Maintain production first; if that’s not possible, stop operations for maintenance.
Now with the valve fully closed, the reserve can no longer be maintained.
Have you considered using differential pressure to control the reserve? It’s the only option left!
Give it a try and see if the reserve level goes down
We are also facing such a problem at the moment. The initial valve opening is 31, and when the valve opening reaches around 39, it is possible to maintain a reserve of about 24 tons in the regenerator ； Currently, the valve needs to be closed to a minimum of 38.2, with a stroke of 262 mm; the valve then needs to be opened to 35 in order to barely maintain a stable inventory level in the stripping section, but this still does not result in an inventory level of 24 tons.
Reduce the differential pressure of the descender; try reducing the fluidization air for the sleeve