Combustion is an exothermic chemical reaction, which is
accompanied by development of heat and light at a rapid rate, so that
temperature rises considerably. for example, combustion of carbon in oxygen:
+ 5 O2 ––> 3 H2O + CO2 + Heat
For proper combustion, the substance
must be brought to its kindling or ignition temperature, which may be defined
as “the minimum temperature at which the substance ignites and burns without
further addition of heat from outside”.
Many other substances other than hydrocarbons
can be used as fuels like the alcohols, such as methanol (CH3OH) and
ethanol (CH3CH2OH) are often used in racing cars. When Ethanol
is mixed with gasoline it is called as gasohol which is currently being
explored as a substitute for gasoline. Among the simplest fuels is molecular
hydrogen (H2) which readily reacts with oxygen forming water as
2 H2 + O2 ——>
2 H2O + Energy
This oxidation-reduction reaction has a non-
polluting aspect, the amount of energy generated, and the relative presence of
both H2 and oxygen in environment, makes H2 a very attractive
alternative fuel source. Research efforts are being made to focus on further
development of the technology to broaden its use as a source of energy.
primary use of the combustion of fuel is
energy. The most common fuels used for the production of this energy are fossil
fuels, which are made up of ancient and decomposed organic matter. Oil, coal,
and natural gas are three most commonly used fossil fuels in fuel combustion reactions. The energy produced by
the combustion of these fuels can be used to power vehicles varying from cars to
normal household appliances.
TYPES OF FUELS USED COMBUSTION:
Solid fuels: Solid
fuels generally burn in the following 3 phases:
1)Preheating stage: their temperature is
increased till they reach their flash point and start releasing flammable
2)Distillation phase: the gases are released
from the solid which is burning, the flames are
also visible, and an extreme amount of heat is released.
3)Charcoal Phase: It is the final
stage which is also called as charcoal phase, in which the solid does not have
enough flammable gas to burn consistently, so it simply only glows and have a smoldering
Liquid fuels: Liquid fuels are
likely to burn only in the gaseous phase. They are heated until they begin to
evaporate, and the vapor catches fire.
Gas fuels: Gases tend to burn
quickly and easily as they are already in an energized state and their
particles are far apart, allowing them to mix with oxygen and
USES OF FUEL COMBUSTION:
Most of the electricity produced worldwide results from
the combustion of
oil, coal and natural gas. Natural gas(methane, CH4) is a
relatively clean fuel and coal is
The primary use of fuel
combustion is energy which is used for various purposes.
Rocket engines, internal combustion, or piston engines,
and jet engines all
depend on the burning of fuel to produce power..
Combustion of fossil
fuels in sufficient amount of oxygen produce carbon dioxide gas, and a lot of
smoke is released into the atmosphere. Increased
Proportions of carbon
dioxide in the atmosphere could lead to undesirable changes in the climate.
If the oxygen supply is
insufficient, fossil fuel burns to produce poisonous gas, carbon monoxide,
unburnt carbon, hydrocarbons (like CH4), acids, alcohols, etc., and these enter
the atmosphere, and pollute the latter.
1)Hydrocarbons produce a number of petrochemical oxidants, and smog (due to
photochemical reaction with oxygen, and nitrogen oxides), which possesses
physiological damaging effects on human-beings.
2) Carbon monoxide reacts with haemoglobin forming
carboxy-haemoglobin, thereby the normal exchange of oxygen-carbon is checked,
which can lead even to death.
3)Petrol on burning in vehicles produces carbo dioxide, water vapour,
CO, unburnt hydrocarbons, lead compounds etc. moat of these products of
combustion are poisonous in nature and no method is available by which we can
control air pollution caused by moving vehicles.
Hence, we say that it is difficult to control air pollution produced by combustion