PrintHeavy Ends Conversion Refinery (1970-)
Oil crises of 1973 and 1979, which created crude oil price shocks, contributed to an increasing emphasis on energy efficiency and independence. These events along with the stricter environmental regulations set up the evolution of the End of the Century Refinery (or Heavy Ends Conversion Refinery) which has focused on efficient processing of heavy crudes as well as the heavy ends of crude oils to produce higher yields of distillate fuels. Producing cleaner fuels and cleaner operation of refining processes have been mandated by environmental regulations.
Figure 11.6 shows the configuration of the Heavy Ends Conversion refinery, with emphasis on processes marked with the red rectangle in Figure 11.6. These processes include hydrotreating of heavy gas oils before catalytic cracking to remove sulfur that contaminates downstream catalysts and to saturate aromatic C-C bonds to produce higher yields of fuel products from catalytic cracking. With better protection from sulfur contamination, FCC units can use modified catalysts to increase gasoline yield and reduce coke yield.
HECR offers four primary heavy oil or residue processing technologies as options for processing heavy crudes or “bottom-of-the barrel” processing. These processes have become more important as the world crude slate becomes heavier and more contaminated with sulfur and other heteroatom species, as sulfur limits become more stringent with environmental regulations.
Hydrocracking of heavy oils removes downstream catalyst contaminants and saturate aromatic compounds to produce higher yields of fuel products. Hydrocracking offers flexibility to choose between gasoline, jet fuel, and diesel fuel by coordinating the operations of fluid catalytic cracking and hydrocracking.
Other options for residue processing include coking, visbreaking, and deasphalting. Coking followed by catalytic upgrading of coking products (naphtha and gas oils) by hydrogenation, or hydrocracking generates high-quality distillates from residua that are not suitable for catalytic processes due to large concentrations of asphaltenes and heteroatom compounds (sulfur, nitrogen, oxygen, metals). Visbreaking and deasphalting removes the highly reactive compounds and asphaltenes from residua making the visbroken and deasphalted oils attractive feedstocks for catalytic hydroprocessing to produce distillate fuels.
The End of the 20th Century Refinery (the present-day refinery) is much more complex and versatile than its predecessor, The Catalytic Refinery. In addition, there are differences that are not so visible in conventional descriptions and flow sheets, such as computerized control of the operations and on-line measurements of product composition and properties.
