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, it's 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 catalyst 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 converson unit as feed (e.g. an FCC).

Products

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:

Hydrocracked distillate - This is a high quality diesel blend stock (high cetane and low sulfur)

Hydrocracked kerosene - This is a high quality jet fuel (or diesel) blend stock with low sulfur and high smoke point.

Heavy hydrocrackate - This is a good quality reformer feed, with moderate N+A and low sulfur

Light hydrocrackate- This is a low quality gasoline blend stock with low octane but also low sulfur.

Isobutane - This is valuable in a refinery with an alkylation unit that requires isobutane as a feed stock

Hydrocracked vacuum gasoil - A low sulfur VGO range material that makes a good FCC feed.

Hydrocracked vacuum resid - A low sulfur vac resid material that can be sent to a coker for further conversion or blended into fuel oil. Frequently, this is recycled back into the resid hydrocracker to drive higher overall yield.