Reason for the rapid drop in regeneration pressure after the catalytic unit stops feeding

This is how I understand it: if the feed is stopped, the carbon buildup on the catalyst decreases rapidly, and the amount of coke sent to the regenerator also drops quickly. Meanwhile, the volume of gases produced by the combustion of that coke, such as carbon dioxide and carbon monoxide, also decreases rapidly in the regenerator； As the coke decreases, the temperature in the regenerator drops, which in turn reduces the amount of gas expansion; as a result, the pressure in the regenerator falls rapidly. This post was last edited by chengkang on 2009-4-12 12:09]

After the feed was cut off, the amount of burnout during regeneration gradually decreased, and the total heat generated during regeneration fell. Meanwhile, steam such as accident steam continued to be supplied to the reaction section; as a result of this circulation between the two units, the heat balance between regeneration and reaction was disrupted and declined rapidly.

The regeneration temperature drops, followed by a sharp decrease in the amount of flue gas used for regeneration, which results in a rapid drop in regeneration pressure.

In my opinion, after the feed is cut off, the temperature of the regenerator drops rapidly. The volume of the flue gases decreases due to this temperature drop. To prevent the lift pipe from overheating, the regeneration slide valve closes quickly; yet catalyst continues to flow from the lift pipe into the settler. In order to control the level of material in the settler, the speed at which the unreacted catalyst slide valve closes is relatively slow. As a result, catalyst with a relatively lower temperature enters the regenerator, which causes the pressure in the regenerator to drop rapidly. This post was last edited by chengkang on 2009-4-12 12:10]

I thought it was caused by the shutdown of the main fan~:lol

After cutting, the bed temperature drops, and gas expansion decreases. Does the regeneration pressure drop? It should be that simple.

I don’t know how large the decline is

As a supplementary note, what the original poster is referring to is likely an oxygen-enriched regeneration unit. In the case of an oxygen-depleted regeneration unit, once the feed to the lift pipe is stopped, the temperature of the regenerator will rise rapidly, and the pressure in the regenerator will increase as well (as the double-acting slide valve opens wider).

The rapid drop in regeneration pressure upon shutting off the feed is due to the decrease in temperature. The amount of flue gas has not decreased. Due to the high compressibility and thermal expansion of gases, the true reason for the drop in pressure can be understood from the ideal gas law PV=nRT. Additionally, you can refer to a set of data: at 101.33 kPa and 20 degrees Celsius, the density of air is 1.205 kg/m3 ； At 200 degrees, 0.746 ； 500 degrees, 0.456 ； 700 degrees, 0.362. Let’s make a correction to the original post: the amount of flue gas should decrease, as coke is a compound with a high carbon-hydrogen ratio; when it burns, it produces CO2, CO, and H2O. If coke were pure carbon and all of it turned into CO2, then there would be no change in the amount of flue gas. The decline in regeneration pressure is due to two reasons. Correct the mistakes. This post was last edited by chengkang on 2009-4-12 12:08]

The pressure in the regenerator is mainly determined by the amount of flue gas; the effect of a decrease in temperature on pressure isn’t very significant, right?

According to the ideal gas law, in an adiabatic reactor, as the temperature drops, the pressure also drops. . . After the cut-in of feed to the riser, the regenerator generally only reduces the amount of lift steam without reducing the amount of emergency steam. Since there is no more fresh oil, reprocessed oil, or slurry involved in the catalytic reaction, the carbon buildup on the catalyst gradually decreases. Once in the regenerator, the main air flow remains constant at first; the goal at this stage is simply to use this opportunity to burn off the carbon on the catalyst. As the bed temperature continues to drop, the main air flow is then gradually reduced. . . Until the bed is deactivated or even production is halted and the agent is removed. . . It can be seen that the entire process is one of gradual decrease in the amount of gas. . . So the pressure needs to be reduced; if the pressure in the regenerator is to be maintained at this point, then it is necessary to adjust the double-acting slide valve. . . Haha. . . :lol

The feed is cut off, the source of heat for the reaction is terminated, and the gas pressure drops

After cutting, the bed temperature drops, and the decrease in gas-phase load leads to a drop in pressure

The main thing is that there is no charring, and the amount of flue gas has decreased; if the dual valves are automatic, this can be seen from their valve positions.