Resid hydrocracker

Also known as: RHCU, H-Oil, LC-Fining, Hycon

The resid hydrocracker upgrades vacuum resid through cracking while injecting hydrogen. This yields a high volume of high-quality diesel and kerosene product. It is similar to the more common gasoil hydrocracker, except that it is capable of running a heavier feed and is more expensive to build and complex to operate.

The resid hydrocracker is particularly valuable in a refinery that is trying to maximize diesel production and reduce residual fuel oil. The resid hydrocracker yields a high volume of kerosene and light gasoil (distillate) of good quality (high cetane and low sulfur). However, its volume yield of naphtha is low and of low quality (low N+A). Also, it yields some heavy product (VGO and vac resid range) that must be further processed (FCC or coker) or blended into fuel oil.

How it works

A mixture of hydrocarbon feed and hydrogen is heated and injected into a series of vessels containing a hydrotreating catalyst. The catalyst in the first reactor typically removes metals, and subsequent reactors have catalysts to remove sulfur. The resulting mix of converted and unconverted hydrocarbon is then separated. Unconverted hydrocarbon can then be recycled to the hydrocracking step for further conversion, sent to a second hydrocracking vessel, or sent to another conversion unit as feed (e.g., an FCC).


A resid hydrocracker can produce a wide range of products depending upon what feed it processes and how it is designed and operated. Typical products are:

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