What is LPG?

LPG, an acronym for Liquefied Petroleum Gas, is the most popular cooking fuel used in urban households. It is a mixture of gases, liquefied by compression, consisting of volatile and flammable hydrocarbons such as ethane, propane, butane and pentane. It is obtained either from crude oil or from natural gas. Crude oil, recovered from underground oil deposits, is a mixture of heavy hydrocarbons. In a petroleum refinery, this oil is heated and turned into a mixture of gases and liquids. This mixture is then passed into a huge tower called fractionating column which is hotter at the bottom and cooler at the top. The heavier hydrocarbons with large number of carbon atoms condense at higher temperatures at the bottom whereas the lighter components with fewer carbon atoms condense at a lower temperature at the top. For LPG, the lower hydrocarbon fraction is collected from the top of the fractionating column in the gaseous form. These gases become liquid when kept under pressure. When pressure is released, they again turn into gaseous forms as happens when the valve in the gas is released. LPG is volatile and highly inflammable and hence needs extra care while using. Since the hydrocarbons do not have any smell a small quantity of methyl, ethyl or terbutyl mercaptans, which have strong disagreeable odour, are added to LPG to make it easily detectable in case of leakage. LPG is also being used in automobiles as a fuel which is much cleaner than petrol.