catalytic cracking

Generally, crude oil obtained by atmospheric and vacuum distillation can be obtained from gasoline, kerosene and diesel oil, such as 10 to 40%, and the rest are heavy distillate and residual oil. If you want more light oils, you must reprocess the heavy and residual oils. Catalytic cracking is the most common production process for producing gasoline and diesel. Gasoline and diesel are mainly produced through this process. This is also the most important production link for general petroleum refining companies.

Raw material

Residual oil and wax oil are about 70%. Catalytic cracking is generally based on vacuum distillate oil and coking wax oil. However, with the increasing crude oil and the increasing demand for light oil, most of the refining and chemical enterprises have begun. The vacuum residue is added to the raw material, and even the atmospheric residue is directly used as a raw material for refining.

  1. Product

Gasoline, diesel, oil slurry (heavy distillate), liquid propylene, liquefied gas; each accounted for 42% of gasoline, diesel accounted for 21.5%, propylene accounted for 5.8%, liquefied gas accounted for 8%, and slurry accounted for 12%.

  1. Basic concepts

Catalytic cracking is the main process for processing heavy oil (such as residue) into light oil (gasoline, kerosene, diesel) in the presence of a catalyst. It is the main secondary processing method in the refining process. Belongs to the chemical processing process.

  1. Production process

The normal slag and the wax oil enter the riser, the settler and the regenerator through the feedstock buffer tank to form oil and gas, and enter the fractionation tower.

A part of the oil and gas enters the crude gasoline tower, the absorption tower, and the air compressor enters the condensed oil tank, passes through the re-absorption tower, the stabilization tower, and finally performs gasoline refining to produce gasoline.

A part of the oil and gas passes through the fractionation tower and enters the diesel stripper, and then the diesel is refined to produce diesel. A part of the oil and gas passes through the fractionation tower and enters the slurry circulation, and finally the oil slurry is produced.

A part of the oil and gas enters the liquid hydrocarbon buffer tank through the fractionation tower, and passes through the desulfurization adsorption tank, the sand filter tower, the water washing tank, the desulfurization alcohol extraction tower, the pre-alkaline washing tank, the amine liquid recovery unit, the desulfurization extraction tower, the buffer tower, and finally enters the liquid state. A hydrocarbon tank forms a liquefied gas.

A part of the oil and gas enters the depropanizer, reflux tower, deethanizer, propylene column, reflux tank through the liquid hydrocarbon buffer tank, and finally enters the spheroidal tank of the propylene zone to form liquid propylene. The liquid propylene is further processed by the polypropylene workshop to produce polypropylene.

  1. Production equipment
  1. Regenerator

The primary function of the regenerator is to burn off the coke on the coked catalyst to restore the activity of the catalyst while also providing the heat required for cracking. The regenerator consists of a casing, a cyclone, an air distributor, a secondary combustion chamber and a heat extractor.

  1. Riser reactor

Straight pipe type: It is mostly used for high and low side-by-side anti-re-rear system. It is characterized by direct insertion from the bottom of the settler, simple structure and small pressure drop.

Folding type: mostly used for coaxial anti-re-system.

  1. Settler

The function of the settler is to separate the reaction oil and gas from the riser and the catalyst. The oil and gas are separated from the entrained catalyst by the cyclone and then passed through the gas collection chamber to the fractionation system; the catalyst from the rapid separator falls down by gravity in the settler. , falling into the gas section.

  1. Three machines

Main fan: Supply regenerative scorch air.

Air press: used to boost the rich gas from the fractionation system and then sent to the absorption stabilization system.

Supercharger: Supply the type IV reaction regeneration unit dense phase riser to adjust the catalyst circulation amount.

  1. Three valve

Single-acting slide valve: In the type IV catalytic cracking unit, it is fully open during normal operation, closed in an emergency, and the two devices are disconnected to prevent backflow of the catalyst; the circulation of the two catalysts is adjusted in the riser catalytic cracking unit.

Double acting slide valve: installed between the regenerator outlet and the venting chimney, adjusting the pressure of the regenerator to maintain the pressure balance of the two devices.

Plug valve: The amount of circulation of the catalyst is adjusted in a coaxial catalytic cracking unit