Fuel And Combustion

Question 1

What is a fuel?

Answer 1

Fuel can be defined as the substances which undergo combustion in the presence of air or oxygen to produce a large amount of heat or energy that can be used commercially for domestic and industrial purposes.

Question 2

State the different types of fuels.

Answer 2

1. On the basis of occurrence.
   a. Primary fuels: Fuels which occur in nature as such are called primary fuels. These can be used either without processing or after little processing which does not change the chemical composition of the fuel.
   Example: Wood,Coal.
   b. Secondary Fuels: The fuels which are derived from primary fuels by further chemical processing are called secondary Fuels.
   Example: Charcoal,LPG
   2.On the basis of physical state
   a.Solid Fuels- eg:Wood
   b. Liquid Fuel-eg:Crude oil
   c. Gaseous fuel -eg: Natural gas, coal gas

Question 3

What are the requirements of the fuel to be used in the industry ?
OR
Characteristics of fuels.

Answer 3

1.High calorific value.
2. Proper ignition temperature (neither too low nor too high)
3. Cause no pollution to the atmosphere on combustion.
4. Combustion of fuel should be controllable.
5. Easy to handle and transport.
6. Fuel should have low residue or ash.
7. Easily available in planting and cheap in cost.

Question 4

Define calorific value.

Answer 4

It is defined as total quantity of heat liberated when power unit mass of fuel is burnt completely.

Question 5

Explain the working of bomb calorimeter.

Answer 5

1. Known mass is placed in crucible.
2. Crucible is attached with electrode.
3. With the help of Mg wire, connect the fuel with electrode.
4. Bomb is filled with O2 and make that air tight.
5. (Bomb) place it in calorimeter.
6. We will start the stirrer and note down the initial temperature.
7. Electrodes is then connected to battery.
8. Combustion of fuel then takes place.
9. Transfer of heat takes place from fuel to water
10. Note down the final maximum temperature.

Question 6

How would you determine the calorific value of fuel by bomb calorimeter?

Answer 6

Principle:known mass of fuel
Known mass of water

Heat liberated by burning of fuel( known mass)=heat absorb by H2O (known mass)

GCV/L( Gross calorific value) in cal/g:(W+w)(t2-t1)/x
W=mass of water taken in calorimeter
w=mass of water equivalent in g of calorimeter
t1= initial temperature of water in calorimeter
t2= final temperature of water in calorimeter
x=mass of fuel in grams

Question 7

Explain the construction of bomb calorimeter.

Answer 7

Bomb
1. It is stainless steel cylindrical container.
2. Two electrodes are connected to battery.
3. One crucible is attached with one electrode.
4. Piece of fuel in crucible.
5. Mg wire is attached with fuel and connected to electrode.
6.O2 valve.
Calorimeter
1.Made up of copper
2. Having known mass of water.
3. One stirrer.
4.Beckmann’s thermometer
(Air jacket: air
Water jacket:water )→To prevent transfer of heat