#1 Crude/Vacuum Distillation Unit (#1 CDU/VDU)

The #1 Crude & Vacuum units (#1CDU/VDU), Unit 11, separate the crude oil feedstock into its primary boiling point fractions, producing both saleable products and providing the feedstocks for secondary, downstream processing units. The #1 unit has a nominal design capacity of 42,000 BPSD on a sweet crude feed. This unit can also process asphaltic crudes at somewhat lower throughputs. The nominal design capacity of the VDU section of this integrated unit is 26,100 BPSD. The unit incorporates a desalter, preheat exchanger train, preflash column, atmospheric column, vacuum column, 2 side strippers, a stabilizer and 4 fired heaters.

The raw crude feedstock is heated in the preheat exchangers through heat exchange against the hot products leaving the unit and internal circulating streams. Fresh water is injected into the hot crude feed, then the mixture is fed to the desalter where the salt, water, and sediment are removed to prevent corrosion, plugging of exchangers, or potential catalyst poisoning in the downstream units. The desalted crude feed is further heated in the preheat exchangers and charged to the preflash column where unstabilized straight run gasoline is removed as an overhead product.

This overheads light naphtha stream is charged to the naphtha stabilizer where light ends, such as butanes and lighter gaseous components, are removed to produce a stabilized light straight run gasoline product that is run down to storage or routed to Unit 24, the Iso-Ref Unit. The bottoms from the preflash tower are pumped through the fired heaters and charged to the primary atmospheric distillation column.

In the atmospheric distillation column the crude is separated into primary boiling range fractions or component products of naphtha, No. 1 distillate, virgin light gas oil, and atmospheric bottoms. The heavy naphtha is routed directly to the naphtha hydrotreater. The No. 1 distillate and virgin light gas oil flow into side strippers, where they are steam stripped of residual entrained light ends to meet flash point specifications. The atmospheric bottoms (or reduced crude) from the primary atmospheric separation column are pumped through the Vacuum section fired heaters into the vacuum column. This column is operated under vacuum so that distillation can be carried out at temperatures below the thermal cracking temperature. Light and Heavy Vacuum Gas Oils are recovered as side cuts. They are then combined and used as FCCU feedstock. The vacuum tower bottom product, depending on the type of crude being charged, is either sent to storage as asphalt, or is blended with cutterstock (primarily Light Cycle Stock) and sent to Heavy Fuel Oil storage.