Refining Processes Used in Fuel Production

Fuels and other petroleum products are derived from crude oil through the use of a variety of different refining process techniques. Distillation, however, is the first significant processing step taken in crude oil refining. Both atmospheric and vacuum distillation can be utilized to process crude oil into fuels and other products. 

Before distillation, crude oil salts and certain metals must be removed. The process of desalting is applied for this purpose. Desalting involves mixing the crude oil with water at a temperature of about 250°F (121.1°C) under enough pressure to prevent evaporation of both water and volatile crude oil components. The salts are dissolved and removed by the water. Oil/water emulsions often form which also contain salts. The emulsions can be broken by the use of high-voltage electrostatic coalescers or by the use of demulsifying chemicals. 

Single-stage and multistage desalting processes are utilized to remove as much of the salt as possible. Any remaining salts which carry into the distillation unit could initiate corrosion. 

From the desalting unit, crude oil passes through a series of heat exchangers to increase the temperature to about 550°F (287,8°C). From the exchangers, oil passes 

Once in the column, volatile compounds vaporize and less-volatile liquids drop to the bottom of the column. Reflux begins and oil fractions condense and collect in various trays throughout the column. Heating within the column can influence the rate of reflux and holdup within the column. Steam is introduced into the column at the level of the lower trays and strips lighter compounds from the condensed fractions on these trays. As a result, the flash point of the fractions remaining on the lower trays increases. 

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We can notice, incidentally, that the processes used in the refining and primary petrochemicals industries meet the above conditions for the same reasons (massive production, limited differential between fuel and products). Mostly, in these fields, continuous processes are used (as apposed to batch processes) and, when applicable, heterogeneous catalysis is chosen in preference to homogeneous catalysis. 

Waste polymer hydrogenation is a variant of a similar process used in oil refining. Degradation takes place in the presence of high pressure hydrogen over a bed of eatalyst sueh as a zeolite or silica-alumina [9]. Decomposition and hydrogenation oeeur simultaneously, to yield products consisting primarily of liquid hydrocarbons that may be used as fuels [10]. 

Urea has the remarkable property of forming crystalline complexes or adducts with straight-chain organic compounds. These crystalline complexes consist of a hoUow channel, formed by the crystallized urea molecules, in which the hydrocarbon is completely occluded. Such compounds are known as clathrates. The type of hydrocarbon occluded, on the basis of its chain length, is determined by the temperature at which the clathrate is formed. This property of urea clathrates is widely used in the petroleum-refining industry for the production of jet aviation fuels (see Aviation and other gas-TURBINE fuels) and for dewaxing of lubricant oils (see also Petroleum, refinery processes). The clathrates are broken down by simply dissolving urea in water or in alcohol. 

The first gas producer making low heat-value gas was built in 1832. (The product was a combustible carbon monoxide—hydrogen mixture containing ca 50 vol % nitrogen). The open-hearth or Siemens-Martin process, built in 1861 for pig iron refining, increased low heat-value gas use (see Iron). The use of producer gas as a fuel for heating furnaces continued to increase until the turn of the century when natural gas began to supplant manufactured fuel gas (see Furnaces, fuel-fired). 

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