What is meant by petroleum ? Explain in detail the refining of petroleum.

Petroleum: Petroleum is defined as the mineral oil that has been originated from the fossils of plants and animal kingdoms buried under the surface of sea in prehistoric times.

Refining of petroleum:

•The impure oil which is available from the wells is transported to the refinery for purification by pipelines or by tankers. The natural gas is separated from it in the initial stage. The oil is allowed to settle in many large tanks in the refinery and the wastewater is separated.

•Then the fractional distillation of the oil is being carried out. In distillation, hydrocarbons are separated in fractions having specific useful properties for the industries. Each of these fractions is being distilled at a definite range of temperature, and it is a mixture of certain compounds. A typical distillation tower is as shown below: -

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•Here petroleum is heated in a furnace and then sent to a fractionating column in the vapour form. The column is 2 to 4 meter in diameter and 30 to 60 meter high. Perforated shelves are fixed in it, and on each of these shelves, there is a cover like a cap.

•The substances which do not distill are collected at the lower part of the column. The vapour petroleum gets cooled while going up in the column and falls down in the form of liquid.

•The vapour passed through the liquid is collected on the shelves. Thus substances having higher boiling points come down in the form of the liquid and the substances having lower boiling point go up in the form of the vapour.

•In this way distillation continues near each shelf where compounds having nearby boiling points are separated.

•Here substances having a lower boiling point are collected in the shelves of the upper part while those having lower point are collected in the shelves of the lower part. The number and distance of the shelves are so arranged that a certain fraction is collected in the shelves at a certain height.