Crude Oil Refining Processes

This chapter introduces and discusses the major processes used for refining crude oil. After a brief historical perspective of crude oil refining, refinery objectives are introduced and an overall refinery flow diagram is presented to show how the major processes are integrated to produce the desired petroleum fuels and nonfuel materials from crude oil. In the order of increasing boiling point ranges, the major refinery products include liquefied petroleum gases (LPGs), naphtha, gasoline, kerosene, jet fuel, diesel, fuel oil, lubricating oil, and asphalt. Refinery processes may be classified into four categories: separation, conversion, finishing, and supporting processes. Separation processes make use of the differences in physical properties of crude oil components to remove inorganic impurities present in crude oil (e.g., desalting) or to separate groups of hydrocarbon compounds in crude oil or other refinery streams, such as distillation, deasphalting, and dewaxing. On the other hand, the conversion processes are performed to make chemical changes in the hydrocarbon composition of crude oils to meet the demands for the quantity and quality of desirable products, including gasoline, jet fuel, and diesel fuel. Thermal and catalytic cracking processes (e.g., visbreaking, coking, and fluid catalytic cracking) break up larger molecules into the boiling range of light and middle distillates to make blending stocks for LPG, gasoline, and feedstocks for making diesel and jet fuel. Catalytic reforming, alkylation, isomerization, and polymerization processes produce high-octane number gasoline components for the blending pool. Finishing processes include hydrotreating to remove heteroatoms (S, N, and metals) and product blending to attain the product specifications and compliance with environmental and government regulations. Finally, supporting processes provide the recovery of the removed heteroatoms, additional production of hydrogen necessary for the conversion and hydrotreating processes, and the treatment of the effluent water and other environmental emissions. After the discussion of individual processes, an evolutionary path of crude oil refining processes is presented with a timeline for the introduction of new processes and changing refinery configurations as the demands for the petroleum products have evolved. Finally, a future outlook for the market and technology is presented to provide projections for the future refinery configurations.