- Hydrocracking is a two-stage process combining catalytic cracking and hydrogenation, wherein heavier feedstocks are cracked in the presence of hydrogen to produce more desirable products. The process employs high pressure, high temperature, a catalyst, and hydrogen.
- The process produces a high yield of middle distillates, which are free of sulphur
- Standard Hydrocracking processes are used for cracking Hvgo Heavy Vacuum Gas Oil but alternative processes are capable of utilising much heavier feeds.
How It Works
- In the first stage, preheated feedstock is mixed with recycled hydrogen and sent to the first-stage reactor, where catalysts convert sulfur and nitrogen compounds to hydrogen sulfide and ammonia. Limited hydrocracking also occurs.
- After the hydrocarbon leaves the first stage, it is cooled and liquefied and run through a hydrocarbon separator. The hydrogen is recycled to the feedstock. The liquid is charged to a fractionator. Depending on the products desired (gasoline components, jet fuel, and gas oil), the fractionator is run to cut out some portion of the first stage reactor out-turn. Kerosene-range material can be taken as a separate side-draw product or included in the fractionator bottoms with the gas oil.
- The fractionator bottoms are again mixed with a hydrogen stream and charged to the second stage. Since this material has already been subjected to some hydrogenation, cracking, and reforming in the first stage, the operations of the second stage are more severe (higher temperatures and pressures). Like the outturn of the first stage, the second stage product is separated from the hydrogen and charged to the fractionator.
- The unit consists of two stages of reactor, the first removes the impurities such as sulphur and the majority of the actual cracking takes place in the second
- Fractionating columns separate the different product streams
- Hydrocrackers need a sources of Hydrogen, which is usually provided by a Steam Reforming Unit
- Sulphur removed in the process is separated in a Sulphur Recovery Unit