Calorific Value Of Fuels

Calorific Value of Fuels: The amount of heat produced by the complete combustion of a unit weight of fuel is known as its calorific value.

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Calorific Value of Fuels

Calorific value indicates the amount of heat available from a fuel.

The greater the calorific value of fuel, the larger is its ability to produce heat.

Calorific value of a fuel is expressed in

In case of solid and liquid fuels, the calorific value is expressed in cal/gm or kcal/kg.

However, in case of gaseous fuels, it is generally stated in cal/litre or kcal/litre.

Calorific value and Composition of fuels

The details of various types of fuels and their calorific values along with composition isgiven below.

Solid fuels

(i) Lignite – 5,000 kcal/kg , C = 67%, H = 5%, O = 20%, ash = 8%
(ii) Bituminous coal – 7,600 kcal/kg ,C = 83%, H = 5·5%, O = 5%, ash = 6·5%
(iii) Anthracite coal -8,500 kcal/kg ,C = 90%, H = 3%, O = 2%, ash = 5%

Liquid fuels

(i) Heavy oil – 11,000 kcal/kg, C = 86%, H = 12%, S = 2%
(ii) Diesel oil – 11,000 kcal/kg, C = 86·3%, H = 12·8%, S = 0·9%
(iii) Petrol – 11,110 kcal/kg, C = 86%, H = 14%

Gaseous fuels

(i) Natural gas – 520 kcal/m3, CH4 = 84%, C2H6 = 10% Other hydrocarbons = 5%
(ii) Coal gas 7,600 kcal/m3 , CH4 = 35%, H = 45%, CO= 8%, N = 6% ,CO2 = 2%, Other hydrocarbons = 4%

Calorific value and Composition of fuels

Advantages of liquid fuels over the solid fuels

The following are the advantages of liquid fuels over the solid fuels

(i) The handling of liquid fuels is easier and they require less storage space.
(ii) The combustion of liquid fuels is uniform.
(iii) The solid fuels have higher percentage of moisture and consequently they burn with great
difficulty. However, liquid fuels can be burnt with a fair degree of ease and attain high
temperature very quickly compared to solid fuels.
(iv) The waste product of solid fuels is a large quantity of ash and its disposal becomes a problem.
However, liquid fuels leave no or very little ash after burning.
(v) The firing of liquid fuels can be easily controlled. This permits to meet the variation in load
demand easily.

Advantages of solid fuels over the liquid fuels

The following are the advantages of solid fuels over the liquid fuels :

(i) In case of liquid fuels, there is a danger of explosion.
(ii) Liquids fuels are costlier as compared to solid fuels.
(iii) Sometimes liquid fuels give unpleasant odours during burning.
(iv) Liquid fuels require special types of burners for burning.
(v) Liquid fuels pose problems in cold climates since the oil stored in the tanks is to be heated in order to avoid the stoppage of oil flow.