Fuels—A Source of Energy
Concept: Formation and Uses of Fuels
What is fuel?
- Anything which burns in the presence of air to produce energy is called fuel.
- The energy produced by burning a fuel comprises both light and heat energy.
- The heat produced by 1 kg of fuel is known as its calorific value. It is expressed in kilojoules (kJ).
- Approximate calorific values of some common fuels are given below—
- The amount of energy produced by burning a fuel varies.
- Based on their origin, fuels can be either natural or derived.
|Name of the fuel||Calorific Value(kJ/kg)|
Examples: Small amounts of liquid hydrogen can produce massive energy, whereas burning a large amount of firewood would not produce energy equivalent to liquid hydrogen.
- Every fuel initially requires a small amount of heat to burn. This amount of heat needed to initiate the burning of fuel is called its ignition temperature.
Examples: We rub a matchstick by striking it on a rough surface which initiates the burning of the matchstick
Characteristics of an ideal fuel:
A fuel that possesses all the following characteristics is called an ideal fuel.
- High calorific value: Higher the calorific value, the more is the amount of heat produced by the fuel.
- Optimum ignition point: A fuel must have an optimum ignition temperature, which is neither too low nor too high.
- Less polluting: Burning fuel leads to the production of gases like carbon dioxide, methane, etc., which causes environmental pollution. Hence, the emission of less-polluting gases on burning a fuel makes it ideal for use.
- Cost-effective: A fuel should be readily available at a low cost.
- Easy to store and transport: A fuel that can be stored easily and transported conveniently is considered ideal.
- Fuels that are formed as a result of the decomposition of plants and animals buried under the soil for millions of years are called fossil fuels.
- The word ‘fossil’ stands for the remains of dead plants and animals.
- The remains of dead plants and animals get converted into coal and petroleum respectively, over a long period.
Formation of fossil fuels:
- The formation of fossil fuels is a gradual and slow process.
- Natural disasters like earthquakes and volcanic eruptions led to the burial of large masses of plants and animals below the Earth’s surface millions of years ago.
- These buried plants and animals got converted into coal and petroleum, respectively, due to the high temperature and pressure below the Earth’s surface.
- Carbon comprises the major portion of coal. Based on the percentage of carbon found, coal is divided into the following categories—anthracite, bituminous, lignite and peat.
- Anthracite is the hardest of all the varieties, with the highest percentage of carbon content.
- Peat has the least amount of carbon content in it.
- The heating of coal in the absence of air leads to the production of coke, coal tar and coal gas. Their uses are as follows—
Uses of coke:
- It is used as fuel. It is a good fuel and burns without the production of any smoke.
- It is used to make fuel gases like water gas.
- It is used while extracting metals from their ores.
Uses of coal tar:
- It is used for preparing dyes, paints, artificial fibres, pesticides, and drugs.
- It is used to make the top layer of roads.
- Naphthalene balls that we use as insect repellent are also made from coal tar.
Uses of coal gas:
- Coal gas is a mixture of methane, hydrogen and carbon monoxide.
- It is used as fuel.
- The word petroleum is made of two words—‘petra’ meaning rock and ‘oleum’ meaning oil.
- Therefore, we can say that the oil derived from the rocks is called petroleum.
- Petroleum is lighter than water and hence, floats on it.
- It occupies the cavities of impervious rocks below the seabed from where it is extracted using machines.
- Natural gas is found floating on top of the petroleum reserves.
- The petroleum extracted from the interior of the Earth cannot be used directly. It has to be purified by the process of fractional distillation.
- Petroleum or crude oil is also called ‘black gold’ because of its wide array of uses.
Fractional distillation of crude oil/petroleum:
- Fractional distillation is the process where the components of crude oil are separated based on their different boiling points.
- The crude oil is heated at a high temperature, and its components get converted into vapours at different temperatures. This is how each component is separately isolated.
- The principle of fractional distillation is based on the fact that different components have different boiling points, which is what is utilised in this method.
Products obtained after the fractional distillation of crude oil/petroleum:
The products of fractional distillation of crude oil and their uses are as follows—
- Fuel Gas/LPG:LPG stands for Liquified Petroleum Gas, which is compressed and transported after filling in cylinders and is used as domestic cooking fuel.
- Petrol: Petrol is used as fuel in vehicles.
- Naptha: It is used as a raw material to prepare a wide range of chemical compounds.
- Diesel: It is used as a fuel in heavy vehicles like trucks, lorries, etc.
- Lubricating oil/grease: These are used to lubricate. Grease is also used in the synthesis of various chemicals.
- Bitumen and tar: These are black-coloured water-resistant substances and are often used as waterproofing materials on roads and buildings.
Conservation of fossil fuels:
Fossil fuels take years to form. So, overuse of fossil fuels may lead to their depletion, and there won’t be anything left for future generations. So, the conservation of fossil fuels is necessary for sustainable development.
Some of the ways which would help in minimising the use of fuels are as follows—
- Switching to renewable sources of energy:The advancement in technologies has allowed us to use various renewable sources of energy like wind energy and solar energy. Using these forms of energy would reduce the use of fossil fuels for meeting the daily energy demands.
- Using public transport as far as possible:The use of public transport would reduce the use of fuels like petrol and diesel to a large extent.
- Using efficient electrical appliances:
Examples: Wind energy can be used to produce electrical energy instead of coal.
- Using efficient electrical appliances would help decrease the use of extra electricity. This, in turn, would help reduce the demand for coal used to produce electricity in thermal power plants.
- Also, inculcating habits like switching off the electrical appliances when not in use would help save electrical energy on a large scale.
- Nowadays, most of us depend on objects made of plastic.
- Synthesis of various plastic products involves a lengthy process, which requires a lot of energy.
- Hence, reusing the things made of plastic would decrease the amount of extra energy used to create new plastic objects.
- This principle is also valid for other materials we use in daily, like paper and metals.
Impervious: Something which does not allow fluid to pass through.
Decomposition: It is the conversion of complex substances into simpler substances by the process of decaying.
Sustainable development: It is the development that can fufill the demands of the present generation while saving the resources for the future generations as well.
Did You Know?
- Anthracite is a variety of coal that is believed to be 300 million years old.
- Fossil fuels fulfil the demand for 85% of the energy we consume daily.
- Natural gas is supplied to our homes through pipelines, which are directly connected to the gas reservoir.
- Burning fossil fuels is one of the major causes of environmental pollution because it contributes to acid rain, air pollution and global warming.
- Natural gas has no characteristic smell and cannot be detected if it leaks. Hence, a chemical called mercaptan is added to it, which helps detect gas leakage as mercaptan has quite a unique smell of its own.