Catalytic cracking unit diagram

The basic process flow of the catalytic cracking unit is as follows: The feed oil is pumped from the storage area to the feed oil buffer tank in the unit using a feed oil pump. It is then drawn out from this tank, pressurized, and after heat exchange with intermediate oil, it undergoes heat exchange with light diesel and slurry oil until its temperature reaches around 200°C. Subsequently, it enters the first reaction zone of the heavy oil lift tube reactor through the feed oil atomization nozzle, where it comes into contact with a high-temperature catalyst at around 680°C, resulting in vaporization and cracking reactions. The exit temperature of the first reaction zone is controlled at around 510°C by a regeneration slide valve. The reprocessed oil and reprocessed oil slurry from the self-distillation zone are mixed and then enter the internal riser from the bottom of the heavy oil riser reactor. The reaction products of the crude oil and reprocessed oil are mixed at the exit of the first reaction zone; their temperature is reduced to around 490°C by injecting a quenching medium (acidic water), after which they enter the second reaction zone via a gradually changing diameter cone. Under appropriate reaction conditions, the second reaction zone can inhibit secondary cracking reactions, increase isomerization and selective hydrogen transfer reactions, raise the content of isoparaffins and aromatics in gasoline, and reduce the olefin content. The reaction gas and oil at the outlet of the heavy oil riser reactor are rapidly separated from the raw catalyst by a coarse spinner and then enter the settler. To ensure that the regenerator can burn off heat under appropriate temperature conditions, an air-controlled external heat exchanger is installed outside the regenerator to remove excess heat. That is, the catalyst is drawn out from the dense-phase bed in the regenerator and flows through inclined tubes into the upper shell side of the external heat exchanger. Under the action of the fluidizing air, it flows downward in a dense phase. As the high-temperature catalyst passes through the finned tube bundle, it transfers heat to the water inside the tubes, generating medium-pressure steam. The cooled catalyst then flows back to the lower part of the heat exchanger, where it is lifted back up by the lifting air and returned to the middle of the dense-phase bed in the regenerator. The external heat-fluidized air is supplied, while the lift air is provided by a pressure booster. The flue gas generated by the coking of the regenerator enters the regenerator in a dilute phase, and three sets of two-stage cyclone separators within the regenerator are used to recover the catalyst from this flue gas, which is then returned to the dense-phase bed of the regenerator via the material leg. After leaving the regenerator, the flue gas passes through a third-stage cyclone separator to further remove catalysts, and then enters the flue gas turbine, where the physical energy in the flue gas (pressure energy and some heat energy) is recovered and used to drive the main fan through expansion work. Finally, the flue gas is introduced into a waste heat boiler to further recover thermal energy, reducing the flue gas temperature to below 220°C, before it is discharged into the atmosphere through a chimney. Light diesel flows by gravity from the 11th and 13th layers of the light diesel fractionation tower to the light diesel stripping tower. The stripped light diesel is pumped out using a light diesel pump, and its temperature is reduced to 40°C through a light diesel–feed oil heat exchanger, a light diesel–rich absorbent oil heat exchanger, a light diesel air cooler, and a light diesel cooler. The resulting light diesel is divided into two streams: one stream is used as the product and exits the plant, while the other stream is sent to the reabsorption tower as an absorbent. The excess heat in the fractionation tower is removed respectively by the top circulation reflux, the intermediate section circulation reflux, and the slurry circulation reflux. The top circulation stream is drawn from the fourth tray of the distillation column; it is pressurized by a top circulation oil pump, passes through an air cooler for the top circulation oil first, and then through a liquid cooler for the top circulation oil. After its temperature drops to 80°C, it is returned to the first tray of the distillation column. The middle-stage reflux oil is drawn from the 17th stage of the distillation column; it is pressurized by a middle-stage circulation reflux oil pump. After passing through the circulation oil slurry–middle-stage oil heat exchanger, the stabilizer bottom reboiler, the desorption tower bottom reboiler, the feedstock–middle-stage oil heat exchanger, the middle-stage oil–deoxidized water heat exchanger, and the middle-stage oil cooler (E209), its temperature is reduced to 190°C before it is returned to the 14th stage of the distillation column. After the slurry is pumped out from the bottom of the slurry distillation tower by a slurry pump, it splits into two streams: one stream goes directly to the riser reactor as recycled slurry ； Along the way, it passes through the circulating slurry-distillate intermediate oil heat exchanger and the circulating slurry-feedstock oil heat exchanger, as well as the slurry steam generator; the temperature is reduced to 280°C, after which it is divided into two streams and sent back to the distillation tower. The slurry cooling tank is used to lower the temperature of the slurry to 90°C before it is sent outside the plant. The reprocessed oil flows by gravity from the 27th stage of the reprocessing distillation tower to the reprocessed oil tank; it is then pumped out by a reprocessing pump and divided into two streams – one stream goes to the lift tank for further reprocessing, while the other stream returns to the 28th stage of the distillation tower. The rich gas coming from the overhead vapor separator of the fractionation tower enters the first stage of the compressor for compression; after being cooled by the compressor intercooler, it goes to the compressor intermediate gas-liquid separator where gas and liquid are separated. The separated rich gas then enters the second stage of the compressor. The rich gas from the second stage outlet of the compressor, along with the wash water for this rich gas, is cooled in a compressed rich gas air cooler. It is then mixed with the gas from the top of the desorption tower and the oil from the bottom of the absorption tower. After being further cooled to 40°C in a compressed rich gas condenser, it enters an oil-gas separator at the compressor outlet where gas and liquid are separated. The gas resulting from this separation goes into the absorption tower, where it is absorbed using crude gasoline and stabilized gasoline as absorbents. The heat generated during this absorption process is removed by the reflux stream within the absorption tower. The lean gas is sent to the reabsorption tower, where it is further absorbed using light diesel as an absorbent. The dry gas then exits the top of the tower and passes through a dry gas liquid separation tank before being sent on to product purification. The condensed oil is drawn from the oil-gas separator at the exit of the compressor by a feed pump in the desorption tower; it is then divided into two streams: one stream is heated to 80°C in a stabilizer gasoline-condensed oil heat exchanger before entering the 9th layer of the desorption tower, while the other stream goes directly to the top of the desorption tower. Heat is provided by the bottom reboiler to desorb the C2 components from the condensed oil. The reboiler of the desorption tower is heated by fractional distillation and intermediate oil; the deethanized oil flows out from the bottom of the tower, and after exchanging heat with stable gasoline in the feed heat exchanger of the stabilization tower, it is sent to the stabilization tower for multi-component distillation. The stabilizer bottom reboiler is heated by the circulating reflux oil from the middle section of the distillation column. Liquefied petroleum gas is obtained as the overhead distillate; after being cooled to 38°C by the dry air cooler and the condensation cooler at the top of the stabilizer, it enters the reflux tank at the stabilizer’s top. The liquefied petroleum gas is pumped out by the reflux pump located at the top of the stabilizer, with part of it being used for reflux within the stabilizer and the remainder being sent as a liquefied petroleum gas product for further purification. The stabilized gasoline flows out from the bottom of the stabilizer tower; after exchanging heat with deethanized gasoline, condensed oil, and deoxygenated water through the stabilizer tower feed heat exchanger, stabilized gasoline-condensed oil heat exchanger, and stabilized gasoline-deoxygenated water heat exchanger respectively, it is cooled to 40°C in the stabilized gasoline cooler. Part of this gasoline is pumped using a stabilized gasoline pump to the absorption tower as a supplementary absorbent, while the remaining portion is sent to the gasoline desulfurization unit, where it is refined via desulfurization before being discharged as a product.

I don’t know how to upload pictures from our factory for you to study*study*, but here is a link: http://bbs.hcbbs.com/viewthread.php?tid=95587&highlight=%B4%DF%BB%AF%C1%D1%BB%AF%CD%BC