Subject:- Applied Chemistry 2.

Topic:- Fuels.

Difficulty:- Medium

Q3.8 Discuss the steps involved in refining of crude oil. [Difficulty level-low] Refining of petroleum : It is the process by which petroleum is made free from impurities and separated into various useful fraction having different boiling points by the process of fractional distillation is known as refining of petroleum This refining of petroleum is done in following stages. 1. Demulsification - First the emulsified water along with salts dissolved, is removed by passing the crude oil between highly charged electrodes. The colloidal water droplet unite to form large drops which separate from oil. 2. Removal of harmful impurities – The emulsion free crude oil is then subjected to electrical desalting to remove NaCl & MgCl2 which may corrode the refining equipments and causes scale formation in heating pipes. The oil is then treated with copper oxide to remove sulphur compounds as copper sulphide which is removed by filtration. 3.Fractional Distillation: Fractional Distillation is carried out in fractionating still which consists of pipe still in which crude petroleum is heated at 4000 C Temp. A different fraction present in oil gets converted into gaseous vapours. These gaseous vapours are then passed through fractional column which consists of number of horizontal trays. As these fractions moves upward gradual cooling takes place & gets separated. High boiling point fraction separated first & low boiling point remains at the bottom of fractional column which contains variable products, therefore subjected to refractionation.