Application: The Shell Bulk CDU is a highly integrated concept. It separates the crude in long residue, middle distillates and a naphtha minus fraction. Compared with stand-alone units, the total integration of a crude distillation unit (CDU), hydrodesulfurization unit (HDS), high vacuum unit (HVU) and a visbreaker (VBU) results in a 50% reduction in equipment count and significantly lowered operating costs. A prominent feature embedded in this design is the Shell deepflash HVU technology. This technology can also be provided in cost-effective process designs for both feedprep and lube oil HVUs as stand-alone units. For each application, tailor-made designs can be produced.
Description: The basic concept of the bulk CDU is the separation of the naphtha minus and the long residue from the middle distillate fraction, which is routed to a bulk HDS. After desulfurization in the HDS unit, final product separation of the bulk middle distillate stream from the CDU occurs in the HDS fractionator (HDF), which consists of a main atmospheric fractionator with side strippers.
The long residue is routed hot to a feedprep HVU, which recovers the waxy distillate fraction from long residue as the feedstock for a cat-cracker or hydrocracker unit (HCU). Typical flashzone conditions are 415°C and 24 mbara. The Shell design features a deentrainment section, empty spray sections to obtain a lower flashzone pressure, and a vacuum gasoil (VGO) recovery section to recover up to 10 wt% as automotive diesel. The Shell furnace design prevents excessive cracking and enables a five-year run length between decoke.
Yields: Typical for Arabian light crude
Products wt, %
Gas C1–C4 0.7
Gasoline C5 –150°C 15.2
Kerosine 150°C –250°C 17.4
Gasoil (GO) 250°C –350°C 18.3
VGO 350°C –370°C 3.6
Waxy distillate (WD) 370°C –575°C 28.8
Residue 575°C+ 16.0
Licensor: Shell Global Solutions International B.V.