Emergency shutdown of the catalytic cracking unit

The feed auto-protection can be activated under the following conditions: 1. The low feed flow rate is less than 40 t/h； 2. The raw materials contain excessive moisture, preventing normal production ； 3. The reaction pressure is extremely high, posing a threat to the safety of the facility ； 4. Severe carbon buildup, requiring the shutdown of feeding when burning occurs ； 5. If the exit temperature of the lift pipe is below 450°C and it cannot function properly for a short period of time ； 6. Interruption of catalyst fluidization ； 7. Main air and spool valve pressure drop self-protection drive ； 8. Severe accidents such as fires or explosions occur in the device ； 9. Other times when the feed needs to be cut off due to the influence of external systems. Handling method: Response: 1. Activate the feed auto-protection system; first, go to the site to check whether the auto-protection valves of the heavy oil lift pipes are functioning. If no action is taken, open the feed accident steam and feed accident bypass line, and close the valve upstream of the feed safety system ； Check whether the pre-lift dry gas is turned off; if not, close its manual valve immediately. 2. Check whether the self-protection valves for each feed line of the light oil lift pipe are activated; if not, close the manual valves ； Check whether the accident steam is open and whether the pre-lift dry gas is closed; if they are not in the correct state, the corresponding manual valves should be opened or closed immediately. 3. Close the manual valves of all feed nozzles and slurry recycle nozzles in the two lift pipes to increase the discharge of slurry. 4. Control the pressure in both reactors; if the feed can be restored quickly, maintain fluidization in both reactors, otherwise transfer the catalyst from the settler to the regenerator to achieve single-reactor fluidization. 4. Discontinue external heat extraction, maintain the drum liquid level, allow flue gas to be discharged directly through the chimney, and control the main steam temperature at no more than 450°C. If the steam volume is very low and cannot be restored for an extended period, direct the steam to waste. 5. Maintain the regeneration temperature at ≮500°C using burning oil; if fluidization occurs in both reactors, the outlet temperatures of both lift pipes shall be ≮530°C. Fractionation: 1. Control the liquid level at the bottom of the tower and the temperature at the top of the tower; the discharge temperature of the oil slurry should be ≤100°C. 2. Introduce the light diesel feed device, establish a light diesel cycle, and maintain the seal oil circulation. 3. Improve the startup cycle process for the crude oil, and maintain the circulation of oil slurry and reprocessed oil. 4. Maintain the liquid levels in various towers and containers. 5. Contact the product team to replace the non-conforming tank. Absorption stability: 1. Establish a three-tower cycle. 2. Maintain the pressure and liquid level of each tower and vessel. 3. Stop injecting water into the rich gas. 4. Transfer the defective products to the unqualified tank. Modify the process by keeping the last manual valve. Desulfurization: 1. Maintain the three-tower cycle, and keep the pressures and liquid levels in each tower and vessel. 2. Control the bottom temperature of the regeneration tower from rising too high. (≯123°C). Crew: 1. Maintain close communication and coordination with the reaction team to ensure a proper supply of main air ； The press cutting system remains operating at low speed (1000 rpm). 2. Control the reaction pressure in conjunction with the reaction process.

Reduce the temperature and volume of the reaction, adjust operations via distillation; stop feeding to the reaction vessel and shut down the extraction pumps on all sides of the distillation system, in preparation for oil removal. Remove the catalyst from the reaction vessel and drain the contents of the distillation tower; install large blind flanges in the reaction vessel, thoroughly purge the pipelines of the distillation system, add more blind flanges to it, purge the pipelines and equipment of the distillation system, and install blocking blind flanges. Remove the manholes from the towers and containers of the distillation system to enter confined spaces for inspection and work. Remove oil from the absorption-stabilization system, as well as water-top gasoline and water-top liquefied gas; relieve pressure in the absorption-stabilization system, thoroughly purge it, and then wash the tower with water.