Vacuum distillation is the distillation process of separating liquids boiling above 150°C at 1 atm from Nonvolatile impurities. Another liquid is boiling at least 25°C higher than the first. For vacuum distillation of crude coal tar, (specifically creosote oil), the crude coal tar is produced from coke ovens of steel plant, 50% of this crude coal tar in pitch. Coal tar is essentially the thick & black viscous liquid which is obtained by the carbonization of coal, and is a by product in the ordinary manufacture of coal gas. It should be differentiated from all the other forms of tar. Its composition varies enormously according to the mode of its formation in the gas or coke works. Properties: Coal tars are by-products of the destructive distillation (carbonization) of coal to produce coke or gas. The composition and properties of a coal tar depend primarily on the temperature of the carbonization and to a lesser extent on the nature (source) of the coal used as feedstock. In general, coal tars are complex combinations of hydrocarbons, phenols, and heterocyclic oxygen, sulfur, and nitrogen compounds. Coal tars typically are black or almost-black viscous liquids or semisolids with a characteristic naphthalene like odor. They are slightly soluble in water, partially soluble in acetone, carbon disulfide, chloroform, diethyl ether, ethanol, methanol, petroleum ether, and sodium hydroxide, and soluble in benzene and nitrobenzene. Low-temperature coal tars (formed at temperatures below 700°C) are black, viscous liquids that are denser than water and contain a lower percentage (40% to 50%) of aromatic compounds than high-temperature coal tars. Coal tars are highly flammable and corrosive, and toxic gases may be released when they burn. Their vapors can form explosive mixtures with air. Uses & Applications:Coal tars and coal-tar pitches have many uses in industry and in consumer products. Coal tars are used primarily for the production of refined chemicals and coal-tar products, such as creosote, coal-tar pitch, and crude naphthalene and anthracene oils from the distillation of crude coal tar. Coal tar has been used as a fuel in open-hearth furnaces and blast furnaces in the steel industry, as a binder and filler in surface-coating formulations, and as a modifier for epoxy resin surface coatings. Coke oven pitch is used to produce pitch coke, which is used as the carbon component of electrodes, carbon brushes, and carbon and graphite articles. Distillation fractions and residues from high temperature coal tars are used for road paving and construction and in the production of naphthalene, recovery of benzene, production of anthracene paste, briquetting of smokeless solid fuel, impregnation of electrodes and fibers, and manufacture of electrodes and graphite. Market Scenario: The downstream markets of coal tar mainly include coal tar deep-processing (phenol, anthracene, industrial naphthalene, and coal tar pitch), carbon black, substitute for heavy oil and exportation. Among these applications, coal tar consumption for deep processing ranked No.1 with 66.4% of the total consumption volume in 2009, followed by carbon black raw oil sharing 28.1% of the total. During 2005-2011, China's coal tar deep processing capacity increased from 5.4 million tons to 16.35 million tons, with a CAGR of 20.3%. From 2010 to Q1 2012, the capacity of the coal tar deep-processing projects planned or construction totaled 8.50 million t/a.
