Control of inventory in the coaxial catalytic cracking stripping section
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During normal production, if the inventory level in the stripping section cannot be controlled due to issues with the equipment in the raw material line, can safety measures for operating the main air supply and pressure relief measures for the reactor be adopted?
There is a problem with the raw gas check valve or the raw gas riser.
Regarding the fault in the standby line you mentioned, what exactly do you suspect to be the problem? If it’s a broken riser, or if there’s a hole in the riser, or if the stop valve isn’t functioning properly and can’t be opened or closed, then an emergency shutdown is necessary. If there’s a blockage in the line, try cutting off the feed to adjust the differential pressure; if that doesn’t work, you must shut it down. What you’re referring to seems to be emergency measures for situations where the inventory level drops too low. Our minimum allowable inventory level must not fall below 20%; otherwise, it becomes dangerous. If the block valve opens wider or fully opens for no apparent reason, and the inventory level remains above this threshold, we can use the flare to release pressure and restore the inventory level before addressing the issue with the block valve. Otherwise, we won’t be able to shut off either unit, and we’ll have no choice but to cut off the main air supply.
Irreparable? The pressure balance between the two devices must not be altered casually, unless it is irreparable
We kept the riser perforated and the valves fully closed, using differential pressure to control the inventory in the stripping section; this situation persisted for over a month
How did it come to a safe stop? Avoid cross-contamination before the oil and gas are completely removed, right?
If it is a small perforation, it is possible to maintain the inventory in the stripping section; keeping a high inventory there is feasible. However, if the inventory in the stripping section cannot be maintained, operations must be halted
We have encountered this situation as well; it is necessary to determine whether there are signs of expansion in the perforation of the feed riser based on the differential pressure or the opening degree of the plug valve, as such perforations tend to get larger over time. It is also important to assess whether there is a perforation in the cone section by checking the oxygen content in the dry gas or any abnormalities. It seems like the situation you described is quite serious; it’s better to stop to ensure safety if it’s hard to control.
How to avoid a large number of cross-talks during shutdown?
Ensure that the pressure in the settler is higher than that in the regenerator; increase the steam supply. After fluidization and coking, switch to agent injection and agent removal. Reduce the main air flow to maintain a positive pressure difference between the two vessels. As soon as the conditions for installing blind flanges are met, do so promptly, then resume the supply of main air – this will make things much safer