- Practice · 5 marks
Classification of traditional fuels with examples
Short answer
Traditional fuels are classified by physical state and source: solid (wood, coal; cheap, easy to store but smoky, low calorific value); liquid (petrol, diesel; high calorific value, clean, easy control but costly, fire hazard); gaseous (natural gas, LPG; high efficiency, no ash, but storage risk of explosion).
Classify traditional fuels according to their physical state and the way they are obtained. Give two examples in each class and state the main advantages and disadvantages of solid, liquid and gaseous fuels.
A fuel is a substance that releases heat energy on combustion. Traditional (conventional) fuels are the carbon-based fuels used for centuries: wood, coal, petroleum products and natural gas.
Classification
| Physical state | Natural (primary) | Prepared (secondary) |
|---|---|---|
| Solid | Wood, peat, lignite, coal | Charcoal, coke, briquettes |
| Liquid | Crude petroleum | Petrol, diesel, kerosene, furnace oil, alcohol |
| Gaseous | Natural gas | LPG, producer gas, water gas, coal gas, biogas |
Fossil fuels (coal, crude oil, natural gas) were formed over millions of years from buried plant and animal remains. Wood and charcoal are non-fossil but are also traditional fuels.
Solid fuels
- Advantages: cheap, easy to store and transport, no explosion risk in storage.
- Disadvantages: low calorific value, ash and smoke, difficult to control the flame, low thermal efficiency, labour needed for handling.
Liquid fuels
- Advantages: high calorific value (about 42–46 MJ/kg), clean burning with little ash, easy to transport by pipe, easy to control flow and flame, no ash handling.
- Disadvantages: costly, fire hazard, need closed storage tanks, many are imported, give CO and unburnt hydrocarbons if burnt badly.
Gaseous fuels
- Advantages: highest efficiency, complete combustion with little excess air, no ash or smoke, easy control, can be preheated, transported by pipeline.
- Disadvantages: need large storage volume or pressure cylinders, high risk of leakage and explosion, costly equipment.
✓ Answer checked by Claude Opus 5.5 (high effort)
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