Reformers convert light streams like lower octane naphtha into higher octane gasoline with a small chemical change. Cracking units use heat, pressure, and catalysts to break apart large, heavy molecules into smaller, higher-value ones like gasoline and diesel. Alkylation units combine smaller molecules into larger ones. Desulphurization units not on the diagram remove sulphur. Coking units , or cokers, apply high amounts of heat and pressure to break down the molecules in the heaviest streams in smaller molecules, leaving petroleum coke as a bi-product.
Products from a coking unit include butanes, naphtha, diesel, and petroleum coke which can be used in place of coal for some industries, like power generation and steelmaking. Refining Technology and Equipment.
The Science of Crude What is petroleum? Refining Video Series Introducing Refining , a three-part education series on the basics of petroleum refining.
Crude Oil Basics. Distillation Basics. Refinery Configurations. Crude Oil Characteristics Crude oil is classified primarily by its density, measured in API gravity, and its sulfur content, measured in weight percent. Medium Crude Generally, crude oil with an API gravity between 24 and 34 and a sulfur content less than 0.
Our Products. We produce essential fuels and products that are foundational to modern life. Kerosene based fuel used in commercial aviation. Safety is the Foundation for Our Success We are focused on being the safest operator in the industry. Learn More About Safety. There are many different industrial versions of cracking, but all rely on heating. When heated, the particles move much more quickly, and their rapid movement causes carbon-carbon bonds to break.
The major forms of cracking are thermal cracking, catalytic, or cat cracking, steam cracking, and hydrocracking. Because they differ in reaction conditions, the products of each type of cranking will vary.
Most produce a mixture of saturated and unsaturated hydrocarbons. Thermal cracking is the simplest and oldest process. The mixture is heated to around to degrees Celsius, at a pressure of kilopascals That is, around seven times atmospheric pressure.
This process produces alkenes, such as ethane and propane, and leaves a heavy residue. The most effective process in creating lighter alkanes is called catalytic cracking. The long carbon bonds are broken by being heated to around degrees Celsius in an oxygen-free environment, in the presence of zeolite.
This crystalline substance, made of aluminum, silicon, and oxygen, acts as a catalyst. A catalyst is a substance that speeds up a reaction or allows it to proceed at a lower temperature than would normally be required. During the process, the catalyst, usually in the form of a powder, is treated and reused over and over again. Catalytic cracking is the major source of hydrocarbons, with 5 to 10 carbon atoms in the chain.
The molecules most formed are the smaller alkanes used in petrol, such as propane, butane, pentane, hexane, heptane, and octane, the components of liquid petroleum gas. In hydrocracking, crude oil is heated at very high pressure, usually around 5, kiloPascals, in the presence of hydrogen, with a metallic catalyst such as platinum, nickel, or palladium.
This process tends to produce saturated hydrocarbons, such as shorter carbon chain alkanes, because it adds a hydrogen atom to alkanes and aromatic hydrocarbons. It is a major source of kerosene jet fuel, gasoline components, and LPG.
In one method, thermal steam cracking, the hydrocarbon is diluted with steam and then briefly heated in a very hot furnace, around degrees Celsius, without oxygen.
The reaction is only allowed to take place very briefly. Light hydrocarbons break down to the lighter alkenes, including ethane, propane, and butane, which are useful for plastics manufacturing. Heavier hydrocarbons break down to some of these, but also give products rich in aromatic hydrocarbons and hydrocarbons suitable for inclusion in petrol or diesel.
Petroleum refineries are complex and expensive industrial facilities. All refineries have three basic steps:.
Modern separation involves piping crude oil through hot furnaces. The resulting liquids and vapors are discharged into distillation units. All refineries have atmospheric distillation units, while more complex refineries may have vacuum distillation units. Inside the distillation units, the liquids and vapors separate into petroleum components called fractions according to their boiling points.
Heavy fractions are on the bottom and light fractions are on the top. The lightest fractions, including gasoline and liquefied refinery gases , vaporize and rise to the top of the distillation tower, where they condense back to liquids. Medium weight liquids, including kerosene and distillates , stay in the middle of the distillation tower. Heavier liquids, called gas oils, separate lower down in the distillation tower, while the heaviest fractions with the highest boiling points settle at the bottom of the tower.
After distillation, heavy, lower-value distillation fractions can be processed further into lighter, higher-value products such as gasoline. This is where fractions from the distillation units are transformed into streams intermediate components that eventually become finished products. The most widely used conversion method is called cracking because it uses heat, pressure, catalysts, and sometimes hydrogen to crack heavy hydrocarbon molecules into lighter ones.
A cracking unit consists of one or more tall, thick-walled, rocket-shaped reactors and a network of furnaces, heat exchangers, and other vessels. Cracking is not the only form of crude oil conversion. Other refinery processes rearrange molecules to add value rather than splitting molecules.
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