Maximising Diesel Recovery From Crude



The CDU/VDU process flow scheme is reviewed, including equipment design and operating fundamentals used to maximise straight-run diesel recovery. Factors important to increasing diesel yield are discussed in detail.



Increased recovery of straight-run (SR) diesel from crude oil improves refinery profitability.  Low  crude/vacuum  unit  (CDU/VDU)  SR  diesel recovery  is  caused  by  existing  unit process  flow  schemes,  equipment designs and operating conditions. Since many FCC or hydrocracker feeds contain 25–35% or more diesel boiling-range material, there is significant opportunity to improve recovery.  Low  or  moderate capital  investments  have  increased refinery  ULSD  product  yields  by  more than 5% on whole crude.

Refiners in the US have until recently targeted maximum gasoline production with little focus on CDU/VDU SR diesel recovery.  Not surprisingly, few US refiners achieve good SR diesel recovery. This  is  because  most  of  the  existing process  flow  schemes  and  equipment were  not  designed  to  maximise  the  SR diesel  yield  from  crude,  nor  were  the operating variables associated with these flow  schemes  optimised  for  maximum SR  diesel  recovery.  Most US refiners produce SR diesel only from their atmospheric crude columns. Even some of  the  new  CDU/VDUs  have  not  been designed for maximum recovery, because many  major  E&Cs  (and  some  refiners) continue to believe that diesel should be produced  only  from  the  atmospheric column. Even though diesel margins are very strong, there are still many misunderstandings about maximising CDU/VDU diesel production.

Many non-US refiners have designed their CDU/VDU to maximise diesel recovery.  Their atmospheric crude columns have 10–14 trays between the flash zone and…


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Tags: CDU, VDU