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How is Crude Oil Refined?

At the refinery, thousands of tons of oil are turned into useful substances every day.

What is Crude Oil?

Crude oil is a mixture of many different chemicals called hydrocarbons. 
Hydrocarbons are useful because they can be used to make many different substances, such as butane gas, gasoline and diesel fuel, plastics, medicines, and paints.

Crude oil refining process

Before it can be used, crude oil has to be refined.
In the refinery, the crude oil is heated and turned into a mixture of gases and liquids.
The mixture is then passed into a huge fractionating column. 
Inside the column, there are trays at different levels.
The column is hotter at the bottom and cooler at the top.
The gases pass up the column and condense into liquids on the trays at different temperatures.
The gases that have longer molecules, with more carbon atoms, condense at higher temperatures.
Those with shorter molecules and fewer carbon atoms condense at lower temperatures.
This process is another example of fractional distillation.

Different hydrocarbons have different numbers of carbon atoms.

Hydrocarbons with 1 to 5 carbon atoms remain as gas at the top of the column. The gas is used as bottled fuel.
Gasoline has 5 to 10 carbon atoms and is used as fuel for cars.
Naphtha has 8 to 12 carbon atoms and is used to make chemicals.
Kerosene has 9 to 16 carbon atoms and is used as jet fuel.
Diesel oil has 15 to 25 carbon atoms and is used as fuel for trains and ships.
Bitumen has over 20 carbon atoms and is used for sealing roofs.

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