Explain in detail with a suitable diagram how you will determine the GCV and NCVof a given coal sample.

To determine the Gross Calorific Value (GCV) and Net Calorific Value (NCV) of a given coal sample, you can use a bomb calorimeter. Here are the steps:

1. Preparation of the Sample: The coal sample should be ground to a fine powder (less than 60 mesh) and dried in an oven at about 108 degrees Celsius for one hour to remove moisture.

2. Weighing the Sample: Weigh about 1 gram of the coal sample and place it in the crucible of the bomb calorimeter.

3. Setting up the Bomb Calorimeter: The bomb calorimeter consists of a strong vessel (the bomb), which can withstand high pressures and is surrounded by a jacket of water. The bomb is filled with oxygen and the coal sample is ignited electrically.

4. Ignition: The coal sample is ignited by passing an electric current through a wire coil or fuse wire which ignites the coal sample. The combustion of the coal sample under high pressure of oxygen results in the production of heat.

5. Measurement of Temperature Rise: The heat produced by the combustion of the coal sample is absorbed by the water jacket and results in a rise in temperature of the water. This rise in temperature is measured using a thermometer.

6. Calculation of GCV: The GCV is calculated using the formula:

   GCV = W x (T2 - T1) x F

   where: W = weight of water in the calorimeter T2 = final temperature of the water T1 = initial temperature of the water F = calorific value factor of the fuse wire

7. Calculation of NCV: The NCV is calculated by subtracting the latent heat of vaporization of the water produced during combustion from the GCV. The formula is:

   NCV = GCV - (9 x H x 587)

   where: H = percentage of hydrogen in the coal sample

The diagram of a bomb calorimeter is as follows:

Image Source: ResearchGate

The bomb (B) is filled with oxygen and the coal sample. It is then placed in a water jacket (W) and the coal sample is ignited. The heat produced is absorbed by the water and the temperature rise is measured.