What is Crude Oil & Crude Oil Refining? Crude oil, also known as black gold, is a thick, dark brown or greenish flammable liquid, which is found in the upper strata of some regions of the Earth's crust It is a complex mixture of various hydrocarbons, (mainly, alkanes), along with trances of other chemicals and compounds (e.g. Sulphur) When extracted from underground, it ranges in density from very light to very heavy and in color, from yellow to black Crude oil can be categorized as either "sweet crude" (where the sulphur content less than 0.5%) or "sour crude," (where the sulphur content is at least 2.5%) An Oil Refinery Crude oil must undergo several separation processes so that its components can be obtained and used as fuels or converted to more valuable products The process of transforming crude oil into finished petroleum products (that the market demands) is called crude oil refining
Distillation of Crude Oil We can separate the components of crude oil by taking advantage of the differences in their boiling points. This is done by simply heating up crude oil, allowing it to vaporize, and then letting the vapor to condense at different levels of the distillation tower (depending on their boiling points). This process is called fractional distillation and the products of the fractional distillation of crude oil is called fractions A fraction from crude oil can be categorized into two categories: Refined Product: A crude oil fraction which contains a lot of individual hydrocarbons (e.g. gasoline, asphalt, waxes, and lubricants) Petrochemical Product: A crude oil fraction which contain one or two specific hydrocarbons of high purity (e.g. benzene, toluene, and ethylene).
AT THE TOP OF THE DISTILLATION COLUMN AT THE BOTTOM OF THE DISTILLATION COLUMN Short carbon chains Long carbon chains Light moleculesHeavy molecules Low boiling points High boiling points Gases & very runny liquids Thick, viscous liquids Very volatileLow volatility Light colourDark colour Highly flammableNot very flammable Crude Oil Refining
Fractions of Crude Oil & Their Properties Name Number of Carbon Atoms Boiling Point ( °C ) Uses Refinery Gas3 or 4below 30 Bottled Gas (propane or butane). Gasoline7 to 9100 to 150 Fuel for car engines. Naphtha6 to 1170 to 200 Solvents and used in gasoline. Kerosene (paraffin)11 to to 300 Fuel for aircraft and stoves. Diesel Oil11 to to 300 Fuel for road vehicles and trains. Lubricating Oil18 to to 400 Lubricant for engines and machines. Fuel Oil20 to to 450 Fuel for ships and heating. Greases and Wax25 to to 500 Lubricants and candles. Bitumenabove 35above 500 Road surface and roofing.
Chemical Processing The fractions from crude oil are liable to undergo chemical processing to alter its structure and thus its properties The sort of chemical processing employed depends largely on the market demand Examples of chemical processes are as the following: Cracking: the process obtaining relatively simple and small hydrocarbon molecules from the breaking down of large, heavier and more complex hydrocarbon molecules. Coking: the process of breaking down bitumen into its fractions (done by a Coker) Alkylation: A process where the structure of a hydrocarbon molecule in one fraction is altered to produce another hydrocarbon molecule with another structure. In alkylation, compounds with a low molecular weight, such as propylene and butylene, are mixed in the presence of a catalyst such as hydrofluoric acid or sulfuric acid Unification: a process where two or more hydrocarbons are combined to produce a larger one. The major unification process is called catalytic reforming and occurs in the presence of a catalyst (platinum, platinum-rhenium mix) to combine low weight naphtha into aromatics
Treatment Processes Chemical sweetening, acid treating, clay contacting, caustic washing, hydro treating, drying, solvent extraction, and solvent dewaxing. Sweetening compounds and acids desulphurize crude oil before processing and treat products during and after processing. Clay Treating Use clay to soak up and remove unwanted components in petroleum Dilute the oil with solvent and freeze the oil During the freezing process, wax will be solidify leaving only the pure oil in liquid phase Acid treating Using concentrated sulphuric acid to convert sludge from the oil Expensive SO 2 Treating Using a very toxic recyclable solvent to remove the worst components in oil
Treatment: The Finishing Touch Impurities such as organic compounds containing sulphur, nitrogen, oxygen, water, dissolved metals and inorganic salts must be removed from the distillated and chemically processed fractions Treating is typically done by passing the fractions through the following: a column of sulphuric acid - removes unsaturated hydrocarbons (hydrocarbons with carbon-carbon double-bonds), nitrogen compounds, oxygen compounds and residual solids (tars, asphalt) an absorption column filled with drying agents to dehydrate the fraction sulphur treatment and hydrogen-sulphide scrubbers to remove sulphur and sulphur compounds Today, a major portion of refining involves blending, purifying, fine-tuning and improving products to meet specific requirements Example: Refinery workers carefully blend together a variety of hydrocarbons to make petrol. Moreover to distinguish the various grades of fuel, technicians add performance additives and dyes. At the end of the production of petrol, the petrol contains more than 200 hydrocarbons and additives
Why Upgrade An Oil Refinery? Oil refining releases carbon dioxide into the atmosphere Response to changing market demands for certain products Government regulations Clean Air Act Amendments of 1990 (CAAA90) Changing consumer demand for better and different products Decrease the number of non-hydrocarbons, impurities, and other constituents Potential physical, mechanical, chemical, and health hazards are recognized in air
Accomplishment of Oil Refinery Upgrading The emissions of pollutants from oil refining decreased significantly over the past decade due to the new technology implemented into the oil refining techniques
Solvent-Refining Process Uses chemicals (fairly safe recyclable solvent) to dissolve one part of the oil from another Removes heavy materials and wax (undesirable component by extraction)
References How Stuff Works How Oil Refining Works?. [Online]. UTS Energy Corporation Glossary. [Online] Products of Oil. [Online] Alan G. Lucas Modern Petroleum Technology Volume 2. New York: John Wiley & Sons Inc. Douglas M. Ruthren Encyclopaedia of Separation Technology Volume 2. New York: John Wiley & Sons Inc.