Lube Vacuum Column Revamp



The basis of a lube vacuum column revamp and its results are discussed. The primary goals were to increase lube product fractionation, minimise HVGO product contaminants and improve vacuum bottoms specifications for asphalt production.



The lube column at Marathon Petroleum Company's (MPC) Cattlesburg, Kentucky, USA, refinery was revamped in 2006 to improve lube product fractionation, reduce the heavy vacuum gas oil (HVGO) product's micro-carbon residue (MCR) and metals, and improve the vacuum bottoms specifications for the production of asphalt. Prior to the revamp, the HVGO product was black and cylinder stock yield was excessive. Cylinder stock was fed to another vacuum unit so that the lube column bottom product could meet the asphalt product specifications, as well as recover a portion of the HVGO boiling range material in the cyclinder stock. However, reprocessing this stream consumed some of the other unit's capacity and increased its heater firing. All the project's justification benefits were met following startup. Moreover, a lower column operating pressure and improved stripping efficiency led to a 4.0 Mbpd higher crude charge rate due to the lower heater's cracked gas production freeing up some compressor capacity to process more crude.

The previously mentioned Figure 1 shows the simplified process flow scheme for the atmospheric and vacuum column prior to the revamp. Off-gas from the atmospheric crude and lube vacuum columns was handled with a common compressor. Atmospheric column heavy gas oil (HGO) product was routed to the vacuum column to recover some of the lube-quality material. The vacuum column produced light vacuum gas oil (LVGO), side stream (SS) #2, HVGO, cyclinder stock and asphalt products. It was necessary to yield cylinder stock to meet the ashpalt specifications on the bottom product. LVGO and HVGO were routed to cat feed hydrotreating...



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Tags: CDU, VDU