Petroleum product refining process
The oil produced by each device is generally not directly used as a commodity. In order to meet the requirements of the commodity, in addition to blending and adding additives, it is often necessary to further refine, remove impurities and improve performance to meet actual requirements. Common impurities are compounds containing sulfur, nitrogen, and oxygen, as well as undesirable components such as waxes and gums mixed in oil. They can make oils smelly, dark in color, corrode mechanical equipment, and difficult to store. Commonly used methods for removing impurities include acid-base refining, deodorization, hydrogenation, solvent refining, white clay refining, and dewaxing. Acid refining is the treatment of oils with sulfuric acid to remove certain sulfur compounds, nitrogen compounds and gums. Alkali refining is the treatment of oils such as gasoline, diesel, and lubricating oil with an aqueous solution of caustic soda to remove oxygenates and sulfides, and to remove sulfuric acid remaining during acid refining. Acid refining and alkali refining are often combined, so it is called acid-base refining. Deodorization is the production of steam, coal, and diesel oil from high-sulfur crude oil, which produces malodor due to the presence of mercaptans. When the mercaptan content is high, the oil will be gelatinous and difficult to store. It can be treated with an alkali solution and then oxidized with air in the presence of a catalyst. Hydrogenation is carried out in the presence of a catalyst at 300 to 425 ° C and 1.5 MPa pressure to remove compounds containing sulfur, nitrogen and oxygen and metal impurities to improve the storage properties, corrosion and flammability of the oil. For a variety of oil products. Dewaxing is mainly used to refine aviation kerosene, diesel and so on. The oil contains wax, which forms crystals of wax at low temperatures, affects flow properties, and is prone to plugging pipes. Dewaxing is very important for aviation oil. Dewaxing can be adsorbed by molecular sieves. Refinement of lubricating oils often uses solvent refining to remove undesirable components to improve composition and color. Sometimes you need to dewax. The white clay refining is generally placed at the end of the refining process, and the harmful substances are adsorbed by clay (mainly composed of silica and alumina).