Energy Fuels

Fuel may be defined as the storing of energy. The higher is the concentration of energy storage, better is the fuel.

Classification of Fuels:-

1). Solid Fuels:- Solid fuels are mainly classified into two categories as mentioned below:

a). Natural fuels such as Wood, Coal, etc.
b). Manufactured fuels such as Charcoal, coke, briquettes, etc.

Wood:-

• Ash Content:-  It varying degrees of calcium, magnesium and sodium carbonate as well as minute quantities of iron oxides, alumina and silica.
• Moisture Content:- It varies from about 40 to 60%. It strongly depends upon the type of the tree as well as the season of the year.
• Characteristics of the flame:- It depends on the tar content of wood.
• Combustion characteristics:- They have observed that the lighter wood burns more intensely with a long flame as compared to hick wood.
• Ignition Temperature:- It depends upon the different kinds of woods for eg. Pine at 295 C, Oak at 287 C, Larch at 290 C and Fir at 292 C.

Coal:-

Coal properties are determined by following two processes:

• Proximate analysis for determining heating value.
• Ultimate Analysis for determining chemical composition.

Proximate Analysis:-

• Moisture: All varieties of coal contain some moisture.
• Volatile matter: It is that part which is driven off as a gas when the coal is heated such as that discharged from a beehive type coke oven.
• Fixed Carbon and Ash: In the above process, coke is left and is composed of fixed carbon and ash. The sum of the carbon in the volatile matter and the fixed carbon gives the total carbon. This total carbon, together with the percentage, by weight of hydrogen, oxygen, nitrogen, sulphur and ash gives the ultimate analysis.

Ultimate Analysis:-

• It is used to find more precisely the chemical composition of coal like carbon, hydrogen, oxygen, nitrogen, sulphur and ash.

Charcoal:-

• Is a product derived from destructive distillation of wood, being left in the shape of solid residue.
• It applications but also for cooking purposes.
• It burns rapidly with a clear flame producing no smoke and developing heat of about 6050 Cal/Kg.

Coke

• It  is also obtained from destructive distillation of coal, being left in the shape of solid residue.
• There are two categories of coke:- Soft and Hard Coke

Soft Coke: It is obtained as the solid residue from the destructive distillation of coal in the temperature range of 600-650 C. It contains 5 to 10 % volatile matter. It burns without smoke. It is extensively used as a domestic fuel.

Hard Coke: It is obtained as solid residue from the destructive distillation of coal in the temperature range of 1200-1400C. It burns to smoke and is a useful fuel for metallurgical processes.

Briquettes:-

• It is usually defined as the dust, culm, slack and other small and other small size waste remains of lignite, coke, peat etc. compressed into different shapes of regular form with or without a binder.
• Good quality briquettes should be quite hard and as little friable as possible.
• They must withstand the hazards of weather and must be suitable for storing and handling.

Bagasse:-

• It is referred to as residue of suger-cane, which is left as waste in the sugar mill after extraction of sugar juice.
• It is fibrous fuel which can be compared to wood. It contains 35-45% fibre, 7-10% sucrose and other combustible constituents, 45-55% moisture and possesses an average calorific value of 2200 Cal/Kg.
• It is dried in an open sun after spreading it in an open field. If dried properly, it is a quick burning fuel with good efficiency.
• Now with the energy conservation culture getting momentum, waste flue gases are being used in dryers to reduce the moisture of bagasse.

2). Liquid Fuels:-

Gasoline or Petrol:-

• Must be cheap and readily available.
• Must burn clean and produce no corrosion on combustion.
• Should mix readily with air and also should easily vaporize.
• Should not pre-ignite easily.
• Must have a high calorific value.

Diesel:-

• Diesel or gas oil is obtained between 250-320 C during he fractional distillation of crude petroleum. It is used in diesel engines as heating oil and for cracking to get gasoline.
• Contains 85% Carbons, 12 % hydrogen.
• Calorific Value is about 11000KCal/Kg.

Kerosene Oil:-

• It is obtained between 180-250 C during fractional distillation of crude petroleum.
• It is used as an illuminant, jet engine, tractor fuel and for preparing laboratory gas.
• Kerosene when used in domestic appliances, gets vaporized before combustion.
• By using a fair excess of air it burns with a smokeless blue flame.

Heavy Oil:-

It is obtained between 320-400 C during fractional distillation of crude petroleum. This oil on refractionation gives.

• Lubricating oils which are used as lubricants.
• Petroleum jelly (vaseline) which is used as lubricants in medicines and in cosmetics.
• Greases which are used as lubricants.
• Paraffin wax which is used in candles, boot polishes, wax paper, tarpolin cloth and for electrical insulation purposes.

3). Gaseous Fuels:-

They occur in nature and are manufactured from solid and liquid fuels. The gaseous fuels need very large storage tanks and are highly inflammable, so chances of fire hazards in their use is high.

Coal Gas

• Colourless gas having characteristic odour.
• Lighter than air.
• Burns with a long smoky flame.

Water Gas

• Mixture of combustible gases, Carbon monoxide and hydrogen with a little non-combustible gases
• Burns with blue flame.

Producer Gas

• Cheap, clean and easily preparable gas.
• Bruns with blue flame.

Blast Furnace Gas

• By product of flue gas obtained during the reduction of iron ore by coke in a blast furnace.
• Contain dust.
• Needs to be cleaned before use.

Video regarding:- Classification of Fuel.

GAURAV SARASWAT