Fuels

FUELS

THE NATURALLY OCCURING OR MANUFACTURED COMBUSTIBLE SUBSTANCES WHICH ACT AS SOURCE WHEN BURNT.

“THE FUEL UNDERGOES EXOTHERMIC REACTION WITH OXYGEN PRODUCING HEAT.”

FUELS

CLASSIFICATION OF FUELS:

Depending on their physical state may be classified into Solid fuels Liquid fuels Gaseous fuels

They are further divided intoPrimary or natural Secondary or derived fuels

TYPE NATURAL (PRIMARY ) DERIVED (SECONDARY )

Solid

Wood, lignite coal , anthracite

Charcoal , coke.

Liquid Crude petroleum Fuel oil , diesel, gasoline, kerosene

Gaseous Natural gas Producer gas , water gas , coal gas , bio gas .

CHARACTERISTIC OF FUEL :

High calorific value Composition of the fuel Specific heat of combustion Flame temperature Fire point Flash point Pour pointCloud point Explosive range

HIGH CALORIFIC VALUE3 of solid or liquid fuel or 1*10ˆ-6 at one atmosphere pressure of a gaseous fuel is completely burnt in excess : The total quantity of heat liberated , when 1*10ˆ-of air or oxygen and the products of combustion cooled to room temperature .

COMPOSITION OF FUEL: low moisture content , less volatile matter, high carbon content or combustible substance, ballast must be low.

FLAME TEMPERATURE: The minimum temperature to which an object can be heated by a flame of fuel. FIRE POINT : Temperature in which the oil vapor will catch fire and continue to burn.

FLASH POINT: It is the minimum temperature at which a sample of a fuel oil gives off enough vapors to catch fire (but don’t continue to burn) by the naked flame or electric discharge . It depends on vapour pressure.

POUR POINT: The temperature at which cloudiness appear in a sample of oil due to the separation of wax under standard condition .

CLOUD POINT : The temperature at which oil ceases to flow , when cooled under standard conditions.

EXPLOSIVE RANGE : The limiting composition of a gas –air mixture , beyond which the mixture will not igniteand continue to burn .

They should have high carbon content high calorific value.It should give low ash content or no ash or carbon.Should possess low moisture and volatile matter.Rate of combustion should be uniform and moderate.Should have moderate ignition temperature. Combustion should be easily controllable. It should not produce toxic gases during combustion.

Quality of a good fuel

GASEOUS FUELS

The important gaseous fuels are Water gas Coal gas Producer gasAcetylene Bio gas Liquefied petroleum gas etc..

Advantages of gaseous fuel:

Gaseous fuels have high calorific value. Rate of combustion is very high but can be easily controlled.The higher temperature is obtained and can be easily controlled.It can be easily distributed through pipes from the source of production. They neither produce smoke nor ash .

Natural gas

Natural gas It is found in nature in association with

or without petroleum deposits.

methane ethane hydrogen CO2, CO, H2S, N,& INERT GAS

0%

10%

20%

30%

40%

50%

60%

70%

80%

70%

5% 3%

22%

COMPOSITION OF NATURAL GAS

Used as an excellent industrial and domestic fuel.Used as raw material for the manufacture of carbon black and hydrogen gas.Employed as a member of chemicals in various synthetic processes.

APPLICATION

ADVANTAGE OF NATURAL GASES it can be conveyed to over large

distances through pipelines It burns with blue flame and gives no

smoke or ash. It has high calorific value 12000-14000

kcal/m3 It is cheap and convenient fuel.

Water gas

It is a mixture of combustible gas, CO, and hydrogen with little non-combustible gases like CO2 and nitrogen .

hydrogen51%

carbon monoxide 41%

nitrogen 4%

carbon dioxide 4%

composition of water gas

MANUFACTURECup and cone feeder

PROCESS

1) C + H2O ----------> CO +H2 H=121.5 KJ (STEAM) (WATER GAS)

2) C(s) +O2(g) -----------> CO2 (GAS)

3) 2C (s) + O2 (g) --------> 2CO

APPLICATIONUsed as a source of hydrogen

gas.As a fuel gas and as an

illuminating agent.In the manufacture of methanol

and synthetic petrol.As reducing agent.

PRODUCER GAS It is a mixture of carbon monoxide

and nitrogen.

Composition of producer gas

hydrogen 18%

carbon monoxide 20%

carbon dioxide

10%

nitrogen 49%

oxygen 0%

saturated hydrocarbon 3%

unsaturated hydrocarbon 0%

Calorific value

The calorific value of producer Gas is 1308kcal/m3

The low calorific value is due to the presence of large excess of non combustible gases like nitrogen and carbon dioxide.

MANUFACTURE Cup & cone feeder

Producer gas outlet

Distillation zone

Reduction zone

Combustion zone

Refractory fire bricks

Ash zone

PROCESS C (s)+ O2(g) ----------->CO2(g)

H= -394 kj CO2(g) +C (s)-------> 2CO(g) H= +163 kj

The overall reaction

2C(s)+O2(g)----------->2CO(g) H= -231 kj

APPLICATION It is used as a fuel for heating retorts in preparing coal gas.It is used as a fuel for heating open hearth furnace in the manufacture of steel and glass.It is used as a reducing agent in metallurgy.

BIO GAS

BIO GAS Biogas is obtained by the degradation of

biological matter by the bacterial action in the absence of free oxygen

COMPOSITION OF BIO GAS

methane 55%

carbon dioxide 35%

nitrogen 2.6%

Hydrogen 7.4%

PRODUCTION OF BIO GAS

ADVANTAGE OF BIO GAS The production of biogas is more economical.It also yields simultaneously excellent manure. The nitrogen content of the manure is about 2% as against 0.75% in farm yard manure.The biogas has all the advantages of gaseous fuel.It does not contain any poisonous gas like carbon monoxide.It can burn with pale blue flame and gives temperature of 813K with proper burner.

LPG

LPG

LPG is a mixture of lower hydrocarbon of C3 and C4, which are mainly propane, butane, isobutylene and butylene with little or no propylene and ethane.

COMPOSITION

Hydrocarbon In a cylinder In bulk

n-butane 27.2% 68.9%

Iso-butane 24.7% 18.3%

Butylene 42.8% 1.2%

Propylene 2.5% ---

propane 2.8% 11.5%

Ethane ---- 0.1%

APPLICATION

• It is widely used as a domestic fuel for cooking.

• As industrial fuel.• As motor fuel.

It has high calorific value.It burns with a smokeless flame and does not cause pollution.It does not produce any poisonous gas on combustion.It is easy to handle and convenient to store.

ADVANTAGES OF LPG

ADVANTAGES OF LPG AS MOTOR FUEL

It is less costlier than gasoline. It mixes easily with air and gives better

distribution. Residue and oil contamination is small

as it burns clearly. Engine life is increased.

DISADVANTAGE OF LPG AS MOTOR FUEL Handling has to be done with utmost care.Due to its faint odor, leakage can not be detected easily.It is advantageous only in engines working under high compression ratio.It has low octane number and road sensitivity is very high.

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