Catalytic cracking shift gas seal
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This post was last edited by chengkang on 2010-4-23 19:41. Is the flow in the unit maintained during catalyst cracking gas seal switching, or is the bed dead? What is the difference in their effects? For single-unit fluidization, what pressure should the regenerator be controlled at? If it’s too high, it’s not possible to remove the blind flange. Let’s discuss this
Wow, when switching to the steam seal during startup, the system still doesn’t contain any catalyst – so how can there be single-vessel fluidization or a bed that becomes stagnant?
We use the method of covering the bed. The regenerator is under pressure relief, while the settler is at a slight positive pressure.
Using a sealed bed and removing the blind flanges is the original method for starting up operations. These days, it is common to remove the blind flanges first before adding the agent.
What if the agent leaks? They’ve all gone into the distillation tower. We use the method of covering the bed. The regenerator is under pressure relief, while the settler is at a slight positive pressure.
During charging, fractional distillation is already a process of circulation within the tower, and this can be achieved by increasing the amount of slurry returning to the tower. By the time of simultaneous charging, the two reactors have already been disconnected, so not much catalyst will flow into the fractionation unit.
Nowadays, the blind flanges are removed first, and then additives are added. I’ve seen this practice at Sinopec, PetroChina, and some of CNOOC’s refineries as well. Such fractionation allows for earlier circulation within the tower, reducing startup time. However, when removing the blind plates, the main air supply to the regenerator usually has to be stopped, which requires extinguishing the fire in the auxiliary combustion chamber; ignition is then carried out after the agent has been installed. This method demands a precise and time-consuming process for switching the steam seal, and the pressure in the settler must be higher than that in the regenerator during the installation of the agent. The method of installing the agent first and then removing the blind flange is commonly used in local refineries as it is safer. The internal circulation in the distillation tower is delayed, so the reaction process has to wait for the distillation process; this results in a longer startup time, but only 3 or 4 hours. This method is safe, involving fluidization experiments with blind plates. There is no such thing as switching the steam seal; once fluidization is complete, the blind flange is removed. At that point, the settler itself uses steam to remove the blind flange and then allows \"air\" to flow out from the top of the distillation tower for a while to evacuate it. Our factory uses this method for catalysis
The method of installing the agent first and then removing the blind flange is commonly used in local refineries as it is safer. Our factory uses this method for catalysis; of course, the startup time is longer.
We separated the two units after fluidization; during separation, we maintained a slight positive pressure in the bed settler to minimize steam usage during the reaction