Tham khảo tài liệu 'lubricants and hydraulic fluids episode 2 episode 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | EM 1110-2-1424 28 Feb 99 Chapter 3 Lubricating Oils 3-1. Oil Refining Most lubricating oils are currently obtained from distillation of crude petroleum. Due to the wide variety of petroleum constituents it is necessary to separate petroleum into portions fractions with roughly the same qualities. a. General scheme of the refining process. The refining process can be briefly described as follows 1 Crudes are segregated and selected depending on the types of hydrocarbons in them. 2 The selected crudes are distilled to produce fractions. A fraction is a portion of the crude that falls into a specified boiling point range. 3 Each fraction is processed to remove undesirable components. The processing may include Solvent refining to remove undesirable compounds. Solvent dewaxing to remove compounds that form crystalline materials at low temperature. Catalytic hydrogenation to eliminate compounds that would easily oxidize. Clay percolation to remove polar substances. 4 The various fractions are blended to obtain a finished product with the specified viscosity. Additives may be introduced to improve desired characteristics. The various types of and uses for additives are discussed in Chapter 7. b. Separation into fractions. Separation is accomplished by a two-stage process crude distillation and residuum distillation. 1 Crude distillation. In the first stage the crude petroleum is mixed with water to dissolve any salt. The resulting brine is separated by settling. The remaining oil is pumped through a tubular furnace where it is partially vaporized. The components that have a low number of carbon atoms vaporize and pass into a fractionating column or tower. As the vapors rise in the column cooling causes condensation. By controlling the temperature the volatile components may be separated into fractions that fall within particular boiling point ranges. In general compounds with the lowest boiling points have the fewest carbon atoms and compounds with the highest boiling .
