Introduction

Fractional distillation consist of a tall column is fitted above the mixture, with several condensers coming off at different heights. The column is hot at the bottom and cool at the top. Substances with high boiling points condense at the bottom and substances with low boiling points condense at the top. Crude oil is made up of different substances with different boiling points hence, these substances can be separated by fractional distillation.

Explanation

The steps of fractional distillation:

1. Heat the mixture of crude oil to a high temperature. (High pressure steam + 600 degrees Celsius)
2. The mixture boils, forming vapor (gases); most substances go into the vapor phase.
3. The vapor enters the bottom of a long column that is filled with trays. The trays have many holes in them to allow the vapor to pass through. They increase the contact time between the vapor and the liquids in the column and help to collect liquids that form at various heights in the column. There is a temperature difference across the column (hot at the bottom, cool at the top).
4. The vapor rises in the column.
5. As the vapor rises through the trays in the column, it cools.
6. When a substance in the vapor reaches a height where the temperature of the column is equal to that substance’s boiling point, it will condense to form a liquid.
7. The trays collect the various liquid fractions.
8. The collected liquid fractions may pass to condensers, which cool them further.

References

Fuels from crude oil. (n.d.). Retrieved March 22, from http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/rocks/fuelsrev3.shtml

Freudenrich, C. (n.d.). Retrieved March 22, from http://science.howstuffworks.com/environmental/energy/oil-refining4.htm

The Basic Products From Fractional Distillation. (n.d.). Retrieved March 22, from http://www.spesttmigas.org/2014/07/the-basic-products-from-fractional.html