Reaction-regeneration systems in catalytic cracking processes

In the operation of the reaction regeneration, we must focus on mastering the material balance, heat balance and pressure balance of the two vessels, analyzing and judging the change trend of the production of the device, adjusting the process parameters in time to make it within the fluctuation range allowed by the process card, and producing qualified products of the device.

1. Control of reaction temperature
The reaction temperature is standardized by the sink outlet temperature, and the change of temperature in the middle and lower part of the lifting pipe should also be examined more. The reaction temperature is mainly related to the pre-lift steam and atomization steam entering the reaction system. Other conditions remain unchanged, but the amount of pre-lift steam and atomization steam varies, and the amount of heat brought in will change accordingly, thus affecting the temperature of the reaction system. The amount of gas steam used has an effect on the yield of the vaporizable carbon, which in turn affects the coking temperature and regeneration catalyst temperature, and therefore the reaction temperature. Factors such as feed preheat temperature, total feed volume, catalyst regeneration temperature and catalyst cycle volume all affect the reaction temperature. The feed preheat temperature is the temperature of the feed oil into the lift tube. An increase in preheat temperature means that the heat brought into the reaction system becomes larger, and then the reaction temperature increases; conversely, it decreases. The reaction temperature increases as the feed volume decreases; conversely, it decreases. Increase in catalyst circulation, the reaction temperature increases; conversely, it decreases. Catalyst regeneration temperature rises, reaction temperature rises.
The general lifting tube reactor outlet temperature control target is 485~535°C. The control method is mainly controlled by regeneration slide valve opening and feedstock oil preheating temperature auxiliary adjustment.

2. Settler pressure control
The pressure at the top of the settler, i.e. the reaction pressure, is the main control parameter in production. The reaction pressure will affect the reaction rate, product distribution, smooth operation and safe operation.
product distribution, smooth operation and safe operation.
During the production process, the amount of feed, the total amount of steam, fractionation tower bottom level, reaction depth, the number of revolutions of the rich gas compressor and other factors will affect the reaction pressure.
The reaction pressure is affected by the feed volume, the total amount of steam, the liquid level at the bottom of the fractionator, the reaction depth, the number of revolutions of the rich gas compressor, etc. When the feed volume increases, the settler pressure rises; conversely, it falls. When the total amount of steam is increased, the settler pressure increases.
The sinker pressure increases when the total amount of steam is raised; conversely, it decreases. Since the reaction pressure directly affects the pressure balance of the reverse-reactor system, the reaction pressure also affect the operation of the fractionation and absorption stabilization system, so it is generally used as a constant value control on the device, not as a frequently adjusted variable. The general sink pressure control target is 0.11~0.20MPa, and the control method is mainly through adjusting the anti-fluttering flow rate and gas compressor rotation to control the pressure.
The control method is mainly controlled by adjusting the back-flash flow rate and the rotation number of the air compressor.

3. Control of reactor storage volume
The reactor storage capacity of the lift tube mainly refers to the storage capacity of the settler and the steam extraction section. Generally, the sinker is operated at zero level, and the storage capacity is mainly in the steam lift section. The sink level can ensure the catalyst has enough residence time in the vapor extraction section, so that the oil and gas on the surface and in the internal pore space of the agent to be produced can be vaporized by water vapor to reduce the vaporizable carbon. Maintaining a certain level of material can also make a positive pressure seal on the material leg of the rotary separator in the sinker to prevent the oil and gas from backing up and causing a large amount of catalyst run-off. At the same time, it also has the role of providing sufficient propulsion for the line to be born. However, the material level of the sinker should not be too high, otherwise it will cause the material leg to be discharged poorly.
Factors affecting the reactor collection volume are pending raw slide valve opening, catalyst circulation volume, etc.
Under normal conditions, the sinker storage volume regulator is used to adjust the opening of the pending raw plug valve to make the storage volume of the steam extraction section meet the process index.
 

4. Regenerator temperature control
The regeneration temperature is an important factor affecting the coking rate. Increasing the regeneration temperature can greatly accelerate the coking rate and reduce the carbon content of the regenerated catalyst. The regeneration temperature is also a reflection of the heat balance of the two devices. If there is excess heat, the regeneration temperature increases.
Factors such as feed rate, refining ratio, reaction depth, heat extraction and main air volume can affect the regeneration temperature. The increase of feed quantity and refining ratio can cause the increase of bed temperature. If the reaction depth is large, the bed temperature will increase. If the external heat extraction increases, the bed temperature decreases. When the main air volume is insufficient, the bed temperature decreases.
The general regenerator temperature control target is not more than 700°C. The control method in production is to adjust the steam volume to change the raw coke volume, adjust the regenerator main air volume, and adjust the coke volume.
The control method in production is to adjust the steam volume of steam extraction to change the coke volume, adjust the main air volume of regenerator to change the ratio of coke burning in regenerator, and adjust the heat extraction volume of external heater to control the dense phase temperature of regenerator.

5. Regenerator pressure adjustment
Regeneration pressure is also an important parameter that affects the pressure balance of the two devices, and increase the regeneration pressure (oxygen partial pressure = regeneration pressure*molar fraction of oxygen in regeneration flue gas, increase the regeneration pressure can increase the oxygen partial pressure, the coking rate is proportional to the oxygen partial pressure of regeneration flue gas) can improve the coking rate.
The coking rate is proportional to the oxygen partial pressure of regenerated flue gas) can increase the coking rate. In order to obtain a higher flue gas energy recovery rate, a higher regeneration pressure is generally used.
The regenerator pressure is affected by the opening of the flue gas population butterfly valve and double-action slide valve, the main air volume, and the total steam volume of the regenerator. When the fume machine inlet butterfly valve and double-action slide valve opening increases, the pressure drops; the main air volume increases, the pressure rises; the total regenerator steam volume rises, the pressure rises.
Under normal conditions, the regeneration pressure is automatically selected for the control system, and the control target is 0.15~0.24 MPa. The automatic control of regeneration pressure is achieved by adjusting the opening of the flue machine inlet butterfly valve and double-action slide valve.