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4.
An
ideal fuel
There are a number of fuels that one can choose from,
starting from petrol, diesel to methane gas and synthetic fuels. The choice
of the fuel will depend on its cost, easy availability and its efficiency.
There are a number of criteria, which may be check listed before choosing a
fuel for its application.
The criteria for an ideal fuel is as follows :
1.
The fuel should have high calorific value. A fuel that gives more
calories per unit of weight would be an ideal choice. We have seen earlier
that fuels that have oxygen in them have less calorific value.
2.
The fuel should have a moderate rate of combustion. The burning of
the fuel should release heat in a controlled manner so that the fire neither
dies nor explodes. The fuel should burn smoothly and sputter. Thus the rate
of oxidation reaction of the fuel should be moderate.
3.
The fuel should have a suitable ignition temperature. We have seen
that a fuel will catch fire only if its ignition temperature is reached. If
the ignition temperature is too low, them the fuel is not suitable as it
will cause fire easily. If the ignition temperature is too high, then again
it is not suitable, as reaching the ignition temperature will not be
practical. Thus the ignition
temperature of an ideal fuel should not be too high nor too low.
4.
The fuel should have low content of non combustible materials. Non
combustible materials in a fuel are its impurities. When heated these
impurities may cause pollution and give out undesirable harmful gases. Thus
an ideal fuel should not pollute the air by emanating harmful gases.
5.
The fuel should be easily available and cost effective. Some fuels
have all the characteristics of an ideal fuel like high calorific value, low
pollution causing gases, etc. but these fuels can be very expensive. An
example of this is high octane petrol. On this petrol, a car runs very
efficiently. But the cost of this fuel is very high and is not readily
available at petrol filling stations. High octane petrol is therefore not
widely used. Thus an ideal fuel
should be available easily and should also be cost effective.
6.
The fuel should be easy to store and transport. Fuels are extracted
and purified in factories and have to be transported to either homes for
domestic use or to industries for industrial use. Quite a large number of
precautions have to be taken to handle, store and transport fuels. These are
highly flammable substances. For example it is easier to transport gaseous
fuels like LPG or methane in cylinders than to transport petrol or kerosene
in tankers.
7.
The fuel should not be more useful for other purposes other than its
use as fuel. For example, wood is a fuel but that denudes forest cover and
is environmentally harmful to fell trees. Hence it is not a suitable or
ideal fuel. Similarly, coke is a good fuel but it is better that coke is
used as a reducing agent in industrial applications. Thus it is better that
coke be used for reduction reactions than be used as a fuel.
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