How to handle a dead catalyst bed due to external heat removal when the catalytic unit has to be shut down urgently?
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After the external heat exchanger of the catalytic unit activated its self-protection function, there was no accident steam available; therefore, it was necessary to wait for manual intervention to supply unpurified air in order to maintain fluidization, but this could easily lead to a dead bed in the catalyst. How do you guys, who are into the sea, handle this?
With such a high temperature in the regenerator after bed fouling, and no sludge formation, how can the bed die?
Firstly, it’s normal for the bed to die; this shows that the safety valves in your plant are effective. Moreover, companies these days require production at maximum capacity – which facility doesn’t experience leaks 2 or 3 times a year due to external heat extraction? By adding an unpurified air line after each of your control valves, this air can flow through the orifice plates along with the pressurized air into the external heat extraction and regenerator sleeves. When there is catalyst backflow, the manual valves can be closed to purge the control valves – so why not do this? :)
We encountered a situation where the catalyst in the external heat exchanger became dead, and there were no specific techniques for dealing with it; we simply opened the bypass line of the pressurized air control valve and hit the pipeline with a sledgehammer, and fortunately, this method managed to unblock it.
Our external heat exchanger also doesn’t experience any accident steam. If the pressurized air supply is interrupted, it’s sufficient to activate the unpurified air right away. Dead beds hardly ever occur; and even if one does arise, the walls of the external heat exchanger have multiple layers of loose air available. By using this loose air in combination with the unpurified air, it should be easy to achieve fluidization.
The probability of heat death in the external heat extraction section is quite low; the temperature for external heat extraction is high, and the catalyst does not get mixed with sludge. Even if the non-purified air cannot be replenished in a timely manner, by opening the valve for external heat extraction and adding loosening air, it is still relatively easy to transfer the catalyst.
There is another method: even if it’s truly stuck, move the agent at the unloading point on the unloading line, and then ventilate.
The solutions provided by the users above are all very good; they can be used as references in similar situations in the future. The person on the 7th floor from Haiyou said that the agent should be removed from the agent-unloading line, but we don’t have such a line for removing heat from the outside. In general, specialized medium-pressure air is used for prolonged and repeated purging during processing.