Settler level issue
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During normal shutdowns, power outages, or emergency shutdowns of the unit, the material level in the settler always drops to zero very quickly, and the density of the catalyst train also becomes 0 immediately (the catalyst train stop valves are fully closed, and sometimes they are manually operated on-site). What’s going on? Is this phenomenon dangerous? I hope to receive guidance from all the teachers!
The pressure dropped quickly because the pressure in the settler was too high, right?
It’s not high (150 Kpa); at that time, the pressure in the regenerator was even higher than that in the settler
It’s too dangerous. The reason is that the plug valve closes too late (it’s also possible that the leakage through the plug valve is too high), resulting in a positive differential pressure between the two vessels.
Upon seeing that the settler had no level indication, we immediately reversed the differential pressure
Emptying the two devices is a very dangerous task; such emptying usually occurs due to poor control of pressure or pressure differences! In the operation of catalytic cracking, three types of equilibrium are important, among which pressure equilibrium is of utmost significance.
How does it work? As soon as an accident occurs, the dead-end valve is closed right away (sometimes by hand on site), but it’s still not possible to control the level of material in the settler!
Is the flare valve at the compressor inlet open? You can ask the experienced workers or supervisors there for advice and see how they do it!
Is there a hole in the settler or at the top of the raw oil riser?
Does this kind of problem occur in every accident, or only occasionally? When the compressor stops working and pressure rises, it is necessary to immediately open the inlet of the compressor and use a flare to release the pressure. Is the 150 kPa value you mentioned related to maintaining pressure?
Isn’t it supposed to increase the stripping steam in the stripping section?