and avoid high-cost solutions that cannot be implemented during a turnaround or within a constrained capital envi - ronment. Some solutions are simply too expensive and do not warrant consideration, whereas others are clearly more constructible and lower cost. It is essential for process design engineers to have equipment expertise so that prac - tical, cost-effective solutions can be the focus. Little or no time should be wasted on unrealistic options. When con - ceptual and feasibility work is done properly, scope growth is minimised, with late-stage cost cutting rarely required. The following discussion demonstrates how creative solu - tions can lead to focused revamps, which often result in big unit improvements. Identifying opportunities and challenges CV1 is a modern integrated crude and vacuum distillation unit commissioned in 2005 to process very heavy crude oils. 1 The vacuum column was designed for deepcut oper - ation to maximise gasoil recovery from vacuum resid. The column was built with a diesel recovery section to capture diesel from vacuum gasoil. The other crude units in the refinery produce HGO products with large amounts of diesel boiling range material. The other vacuum units do not have diesel recovery sections, and the LVGO streams contain roughly 50% diesel. CV1 was originally designed to process HGO and LVGO streams from these other units in its vacuum unit to recover incremental diesel. The other vacuum units in the refinery are an older design, lacking stripping steam and overflash recycle. With the lack of VR stripping, their HVGO product cutpoints are much lower than CV1’s. These units produce more coker feed and less gasoil.² CV1 vacuum unit was designed to process excess atmospheric residue (AR) to improve RGO recovery from coker feed. Over time between turnarounds, as the vacuum system deteriorates and operating pressure increases, HVGO cut - point suffers. As VR production increased, less RGO and excess AR could be processed. It was readily apparent that reducing the vacuum column pressure would increase HVGO cutpoint, reduce the VR rate, and give flexibility to increase the amount of heavy crude in the blend. In addi - tion, more RGO and excess AR could be processed. Fixing the vacuum was a major opportunity to improve overall refinery diesel and gasoil recoveries (see Figure 2 ). Preliminary engineering work identified other equipment shortcomings that would need to be addressed to maxim - ise gasoil and diesel recoveries while increasing RGO and excess AR processing. The atmospheric and vacuum heat - ers were operating at maximum capacity, and the duties could not be increased. This was a hard constraint that needed a workaround. Increasing the heater outlet temperature would require a higher inlet temperature as major retrofitting to the existing heaters or building new heaters was infeasible within the turnaround window. Therefore, engineering work focused on opportunities to improve preheat train utilisation. The atmospheric column was originally designed with a heavy gasoil (HGO) pumparound, which provided high-tem - perature heat for crude preheat and steam generation.
Slop oil
LVGO
Diesel
RGO
MVGO
Hydrocracker or FCC
Atmospheric column
HVGO
FCC
LGO
HGO
Hydrocracker
Crude
Vacuum column
Steam
Steam
Re nery AR
Coker feed
Figure 2 CV1 LVGO product draw maximises refinery diesel product yield
process design package (PDP) detailed any process flow scheme changes and equipment design requirements for a focused capital revamp. Focused capital revamps require a different engineering approach than highly structured large capital projects that often focus on rigid process design basis development, strict project scope, milestones, and schedule controls. During the conceptual and feasibility design phases, the refiner has the best opportunity to maximise return through identification of creative solutions. Project scope is shaped by practical alternatives developed and investment scope prioritised. During these phases, experienced process design engineers should focus on constructible solutions
Crude
Atmospheric column
Naphtha
Kero PA Crude oil
398
Kerosene
Side stripper not shown
LGO PA
520
Crude oil & steam
LGO
Diesel
HGO PA reduces LGO/HGO section re ux
Crude oil & steam HGO
630
HGO
Hydrocracker
670
Desalted crude
Stripping steam
Temperature, ˚F
670
AR
Figure 3 Atmospheric crude column simplified PFD
20
PTQ Q3 2023
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