Combustion is a chemical process in which a substance reacts with oxygen to give off heat. It is a rapid exothermic reaction that liberates substantial energy as heat and flames. The substances which undergo combustion are known as combustible substances. Combustion is a result of dynamic or time-dependent events that occur on a molecular level among atoms, molecules, radicals, and solid boundaries. The process of combustion generates air pollution, and pollutant formation and oxidation kinetics, as well as their reduction techniques, are explained in the chapter.
There are three necessary conditions for combustion:
- Presence of a combustible substance
- Presence of oxygen
- Ignition temperature
Types of combustion include:
- Rapid combustion: When combustion occurs rapidly
- Incomplete combustion: Typically caused by inadequate air-fuel mixing, insufficient residence time, insufficient temperature, and low total excess air
- Explosion: When a sudden reaction takes place with the release of heat and light and evolution of a large amount of gas takes place, it is called an explosion. For example, firecrackers.
Some examples of combustible substances include:
- Wood
- Coal
- Petrol
- Diesel
- Natural gas
- LPG (Liquefied Petroleum Gas)
