FUELS & COMBUSTION
· Fuel can be defined as a combustible substance which contains carbon as its main components, which gives large amount of heat on proper burning.
· Carbon can be used economically for domestic and industrial requirements.
· Common example involving wood, charcoal, coal, kerosene, petrol, diesel, producer gas, oil gas, etc.
· During combustion process of a fuel (like coal), the atoms of carbon, hydrogen, etc. combine with oxygen with the simultaneous release of heat at a speedy rate.
· This energy is released due to the “rearrangement of valence elections” in these atoms, resulting in the formation of new compounds like methane and water.
FUEL + OXYGEN —> PRODUCTS + HEAT.
· Coals and petroleum oils are the main source of the fuel; the available quantity of these sources is reduced day by day.
· Fossil fuels are composed by natural resources such Fossil Fuels as anaerobic decomposition of buried dead organisms.
· The age of the organisms and their resulting fossil fuels is more than millions of years.
· They are non-renewable resources because they take thousands of years to form, and reserves are being decomposed much faster than new ones are being made.
· Its uses and production raise environmental issue.
1. Solid fuel
· Solid fuel is defined as raw materials which are used as a primary fuel to produce energy and provide heating.
· Common example under this category includes wood, charcoal, peat, coal, Hexamine fuel tablets, and pellets made from wood, wheat, rye and other grains.
· It also used in solid fuel rocket technology.
· For creating fire, it has been used.
· Coal is used for firing furnaces, to running steam engines.
· Steam locomotives engines are operated by using wood as fuel.
· In electricity generation, peat and coals are used.
· Due to unsafe levels of toxic emissions, use of some solid fuels is restricted or prohibited in some urban areas.
2. Liquid Fuel
· Liquid fuels are defined as combustible or energy-generating molecules which are used to produce mechanical energy.
· Fumes of these fuels are flammable instead of the fluid.
· Most liquid fuels which are used for various purpose in now days, are derived from petroleum.
Types of liquid fuel:
· It is a by-product of petroleum, contains carbon and hydrogen.
· Gasoline or petrol is produce by hydrocarbon molecules forming aliphatic compounds, or chains of carbons with hydrogen atoms attached.
· Engines that use unleaded gasoline releases fewer hydrocarbons, have fewer combustion chamber deposits, and provide a longer life for spark plugs, exhaust system and carburetors.
· It is generated by distillation of crude oil.
· The desirable liquid is taken out from the crude oil in refineries.
· For the formation of gasoline, petroleum must first be removed from crude oil.
· Gasoline itself is actually not burned, but the fumes it creates ignite.
· It is a mixture of aliphatic hydrocarbons extracted from petroleum.
· Diesel may cost less than gasoline; it costs less for production because the extraction processes used are simpler.
· It can hold dirt particles in suspension longer than gasoline because it is heavier and more viscous.
· Its efficiency varies with the type of engine.
· Use of a polluted fuel or an improper grade of fuel can cause hard starting, incomplete combustion, and a Smokey exhaust.
· Kerosene is defined as flammable hydrocarbon oil usually obtained by distillation of petroleum and used as a fuel, solvent, and thinner.
· It is sometimes used as an additive in diesel fuel to prevent gelling or waxing in cold temperatures.
· Heat of combustion of kerosene is similar to that of diesel
· It is generally used for heating and fueling vehicles.