Candles, medicines, make up, fertilizers, synthetic rubber, synthetic fibre, furnace oil, automobile fuel, detergents, plastics, jet fuel, ship fuel – what magical ingredient links this wide range of products?
The liquid gold, petroleum!!!
Petroleum is a complex mixture of hydrocarbons that are found on Earth in solid, liquid and gaseous states. In common usage the word petroleum refers to liquid form called crude oil, but includes the gaseous form, natural gas and the solid form bitumen. The liquid and gaseous phases of petroleum are the most important primary fossil fuels used on Earth.
Gasoline, also spelled gasoline, is referred to as gas in North America. Elsewhere it is known as petrol. It is a transparent liquid derived from petroleum and used as fuel in internal combustion engines. It is also used as a solvent for fats and oils. Gasoline (gas) was originally considered as a by- product of the petroleum industry. The principal product was meant to be kerosene. However the discovery of the useful properties of gas soon made it the most preferred automobile fuel. Gas produces high energy on combustion. In addition it mixes readily with air in the carburettor.
Gasoline is a mixture of volatile flammable hydrocarbons. It is a complex mix of 100’s of different hydrocarbons. Most of the hydrocarbons contain between 4 and 12 carbon atoms per molecule. It boils between 300 and 2000, depending on the blend.
Gas was first produced by distillation, a process that involves the separation of crude petroleum into its various fractions. The more volatile fractions were considered more valuable. Gas soon became the most valuable fraction, as American cars began to guzzle 180 million gallons of the liquid in a day. In order to extract greater volumes of gas from crude oil, new processes replaced distillation. Cracking, polymerization, alkylation, isomerization and reforming are the process now being used to yield more gas from crude oil.
Diesel oil or diesel fuel is a combustible liquid used as fuel for diesel engines. Diesel is also obtained from fractions of petroleum. Diesel is extracted from crude oil (petroleum) at temperatures of 2000 to 3500 at atmospheric pressure. This creates carbon chains. Each molecule in the chain contains between 8 and 21 atoms of carbon.
Diesel freezes at temperatures of -80C and changes into a gel at – 190. It vaporises at between 1490C and 3710C. The flash point occurs between 520C and 960C, making it unsuitable for combustion engines. A flash point is the temperature at which the vapours of a liquid will ignite.
In a diesel engine, fuel is not ignited by a spark. Instead the fuel is injected in a spray into hot air that is compressed in a cylinder.
On combustion, diesel releases more energy than an equal volume of gasoline. This makes for better fuel economy. The refinement of diesel from petroleum is a simpler process than that of refining gas from petroleum. For these reasons diesel is a cheaper fuel and preferred by commercial vehicles.
Diesel as an automobile fuel emits higher greenhouse gases. Additional refining required to remove the sulphur has increase the cost of diesel. Diesel spills are dangerous as the liquid evaporates leaving behind a slick that is very dangerous for vehicles especially two wheelers.