Categories of fuels

Categories of fuels

Fuels can be classified into three groups according to the physical state of the fuel. A fuel can be in any of the three states of matter namely, solid, liquid or gaseous state.

Fuels according to their states

Solid fuels

Solid fuels include wood, charcoal, peat, lignite, coal, coke, etc. The immediate use of all these fuels is for heating and lighting. Coal was the fuel for the industrial revolution, from firing furnaces to running steam locomotives and trains.

Liquid fuels

Liquid fuels include petrol (gasoline) diesel, alcohol (spirit), kerosene (paraffin), liquid hydrogen, etc. Liquid fuels have advantage over solid fuels because they produce no solid ashes, and can be regulated by automatic devices. They are relatively more convenient to handle, store and transport than solid fuels.

Gaseous fuels

The use of gaseous fuels for domestic heating is common in urban areas. Compressed gas that is delivered to our homes in steel cylinders is liquefied propane, butane, or mixture of the two.

The following is a list of types of gaseous fuels:

1. Fuel naturally found in nature: natural gas, methane from coal mines.
2. Fuel gas from solid fuels or materials: gas derived from coal (water gas and producer gas), gas derived from wastes and biomass (biogas).
3. Fuel gas made from petroleum.

Qualities and characteristics of a good fuel

1. It should be environmentally friendly (not harm the environment) in the course of its production and use, that is, it should not produce harmful or toxic products such as much smoke, carbon dioxide, carbon monoxide, sulphur dioxides, etc.
2. It must be affordable to most people, i.e. it must be cheap.
3. It should not emit or produce dangerous by-products such as poisonous fumes, vapor or gases.
4. It should have high calorific value, i.e. it must burn easily and produce a tremendous quantity of heat energy per unit mass of the fuel.
5. It should be easy and safe to transport, store, handle and use.
6. It should be readily available in large quantities and easily accessible.