NATURAL SOLID FUELS

Huma Nazir

M.Phill 2nd Smester

Institute of Chemistry Punjab University Lahore

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Fuel Fuel is a substance which, when burnt,

i.e. on coming in contact and reacting with oxygen or air, produces heat.

The substances classified as fuel must necessarily contain one or several of the combustible elements : carbon, hydrogen, sulphur, etc.

•Heat energy

Chemical energy

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TYPES OF NATURAL SOLID FUELS

Wood Peat Lignite Coal

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WOODContents of Wood Cellulose Lignin Resins Inorganic materials Water (25-60%)

Composition of dry wood: C 50% O 35% N 7% H 6% Ash 2%

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Calorific value 6500-9200 BTU/poundCarbonization of Wood

combustibles

• Co,H2

• CH4

Saturated hydrocarb

ons

Non-combusti

bles

• CO2

• N2

Wood charcoal

Wood gas

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Advantages of WoodBurns readilySoot and ash produced is smallAsh is reusedEasily availableSuitable calorific value for domestic use

Disadvantages of WoodHigh percentage of water (decrease calorific

value)

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PEAT Decayed vegetation (moist condition) Usually accumulates slowly, at the rate of

about a millimetre per yearGeneral Composition:Volatile matter 10.4%Fixed carbon 4.6%Moisture 85%Composition in dry condition:C 57%H2 6.1%Oxygen 34.9%Ash content(mostly) 5-10%

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Greater the decomposition greater the carbon lesser the oxygen

Average Calorific value 6000-9000 BTU/lb

Tar

wax

Fuel gases

(NH4)2SO4

Peat coke

Destructive

distillation

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Advantages of Peat Used as fertilizer As packing material As boiler fuel in form of braquettes

Disadvantages of peat: High water content Burns slowly Low calorific value Not economical

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LIGNITE OR BROWN COAL Immature coal May be amorphous, fibrous or woody in

texture It contain small quantity of resins,

moisture (25-40%), high percentage of volatile matter(ignites)

Characterized by high content of noncombustible matter.

Burns with long smoky flame Calorific value 6000-7500 BTU/lb

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carbonization

tar

High pressure hydrogenation

Synthetic petrol

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USES Heating boilers Evaporating pans in industry For domestic purposes Fertilizer manufacture

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COAL

coal

Absence of air

pressure

Heat of earth

Decayed

vegetatio

n 300 million years

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COMPOSITION Highly complex organic matter with Varying quantity of water Nitrogen (0.75-1.75 %) sulphur

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TYPES OF COALOn the basis of origin

Humic or Banded coal Sapropelic coal

Different grades of coal are Anthracite (86-88% C) Bituminous (78-86% C) Sub-bituminous coal or black lignite Pulverised coal

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ANTHRACITE COAL Final stage of coal formation Hard, compact, black coloured coal,

good semimetallic lusture Highest % of fixed C High Calorific value ( 14000-15000

BTU/lb)

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AdvantagesIntense heat with no smokeUseful for metallurgyFor slow combustion stoves for domestic

purposes

DisadvantagesHigh ash contents

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SUB BITUMINOUS COAL Dull black coal Calorific value < bituminous coal Denser and harder than lignite Moisture content 10-25% Calorific value 7000-15000 BTU/lb

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BITUMINOUS COAL Commercial rank coal Very hard and black Burns with yellow smoky flame Distillation product is coke(remove

sulfur and ash contents) Brittle High calorific value

(11000-15000BTU/lb) Low moisture contents

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TYPES OF BITUMINOUS COALOn the basis of fuel ratio Low volatile coal High volatile coal Super bituminous coal (2.5-5.0) (calorific

value = 12000-15500BTU/lb) HVC burns with long flames so used in

gas industry, coal tar distillation,glass industry