Chemical Fuels

INTRODUCTION:

A chemical fuel is any substance used to produce heat and power by combustion nuclear fuels are also now used. By common usage the term fuel also implies that it can be stored and transported. Fuels are primarily used for heating but they have other very important functions. Eg. Several metallurgical operations, as in a blast furnace, coke not only supplies heat but also acts as a reducing agent.

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CLASSFICATION:
Fuels are classified according to whether they occur in nature (Primary fuel) or are
prepared manually and according to whether they are in the solid, liquid or
gaseous state.
The classification is summarized as follows:

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1) WOOD:-

In India wood is used to a considerable extent as a domestic fuel. Its uses as an engineering fuel are restricted.
 On a moisture free basis, wood contains about 50% C, 6% H, 4% O2 and less than 1% ash.
 Freshly cut wood contains 5 to 40% moisture and air dried wood contains about 15% moisture.
 The calorific value of common air dried wood is about 3500cal/g, but in some case it may be as high as 5000 cal/g.
 Bagasse is also important fuel in sugar mills. It calorific value on 15% moisture basis is 3800 cal/g.
Brazil which is the eleventh largest steel producing country of the world, meets 40% of its energy needs of the steel industry by burning wood. Sweden, meets 60% of energy needs for paper and pulp industries by burning wood.

WOOD CHARCOAL :-

Wood charcoal is obtained by the destructive distillation (heating out of contact with air) of wood. Water and various kinds of volatile matters are expelled.
 Charcoal consists about 20% C, 15% O2 and N2, 2% H2 and 3% ash.
 Its calorific value is high, being 8000cal/g.
 Usually the weight of charcoal obtained does not exceed 20% of the weight of wood. Its volume in 50-75% of the original volume.

Because of its purity and low as content charcoal was the most important metallurgical fuel.
Because of its low mechanical strength it has become largely replaced by
coke.

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2)COAL:-

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INTRODUCTION:
Coal is a complex substance which originated several million years ago from the various plants that existed profusely on the surface of the earth. The plants were caught up in swamps, buried underground and slowly changed due to heat, pressure and biochemical and chemical processes. The fact that on proper processing it yields gas, oil, fertilizer and chemical which increases its usefulness.
ORIGIN:
Coal has been defined as a stratified rock consisting of the more or less altered remains of plants together with associated mineral matter. This process which
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changed plant into coal has taken millions of years.
Geologists have put forward two theories of coal formation.
1) “In situ” theory contends that the coal formation took place where the vegetation grow and accumulated.
2) "Drift” or “Transportation " theory holds that the trees etc were uprooted and the material drifted or was transported by rivers to lakes and estuaries and deposited there.
The great purity of many coal seems can be better explained by the “in situ” theory and great thickness of coal seems to appears more reasonable on the basis of the "drift" theory.
It is interesting to note that in most cases, although there are some exceptions with the increase in vertical depth, the carbon content increases and volatile matter decreases. Anthracite and graphite are formed under extreme conditions.
The stage in the formation of coal from vegetation can be best be summarized thus:
Plant debris - Peat - lignite - brown coal - sub-bituminous coal - bituminous coal - semi-anthracite coal - anthracite coal - graphite.
This series is known as "Peat" to anthracite series.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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