Better Fractionation Hikes ULSD Yields, Hydrotreater Run Lengths



Improved CDU, FCC and Coker main column fractionation maximizes diesel boiling range yields while eliminating hard-to-treat sulfur components from the hydrotreater feed.  Hydrotreater run lengths can be materially improved by improving the segregation of easy-to-treat and hard-to-treat sulfur species in upstream distillation units.



Improved fractionation will allow many refiners to increase their ultralow-sulfur diesel (ULSD) yields and hydrotreater run lengths by segregating the easy and difficult-to-treat sulfur species.

When ULSD specifications take effect in the US, refiners will have to control hydrotreater feed stream yields tightly so that the ULSD product sulfur specification is met at an acceptable catalyst life. New high-pressure hydrotreaters are being built based upon assumed feed-stream compositions.

In some instances, high endpoint straight-run (SR) diesel, FCC light cycle oil (LCO), and light coker gas oil (LCGO) stream compositions are assumed to remain unchanged after ULSD production begins. Yet many refiners will have to undercut the ULSD hydrotreater feed streams to lower the endpoint, which will reduce the amount of difficult-to-treat sulfur species feeding the ULSD hydrotreater…


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Tags: CDU, VDU