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Bomb Calorimeter for Coal analysis

The procedure for coal analysis using a bomb calorimeter typically involves the following steps:

1. A small weighed amount of powdered coal sample (around 1 gram) is taken and placed either in a silica or platinum crucible.
2. The crucible with the coal sample is positioned inside the stainless steel “bomb” chamber, which is a high-strength vessel designed to withstand high pressures.
3. An ignition wire (usually a fine nichrome or fuse wire) is placed in contact with the coal sample and connected to electrodes that go through the bomb lid.
4. The bomb is sealed, and pure oxygen is introduced into the bomb to a high pressure (about 20 to 25 atmospheres
5. The bomb is placed inside a calorimeter cup filled with a known quantity of water.
6. The water is stirred continuously to ensure uniform temperature.
7. The initial temperature of the water is recorded.
8. An electric current is passed through the ignition wire, igniting the coal sample
9. The combustion releases heat which raises the temperature of the water bath surrounding the bomb.
10. The temperature rise is recorded until it reaches a maximum and stabilizes
11. The change in temperature, along with the known water equivalent of the calorimeter and accessories, is used to calculate the gross calorific value (energy content) of the coal.
12. The calorific value is often calibrated using a standard of benzoic acid, which has a known heat of combustion.

This method provides the gross calorific value (higher heating value), representing the total heat released including the latent heat of vaporization of water formed. The net calorific value (lower heating value) can be calculated by adjusting for water vapor heat loss, usually requiring the hydrogen content of the coal sample.

This analysis is critical for assessing the energy content of coal for classification, combustion efficiency, and industrial use. The process is guided by standards such as ASTM D5865.

Equipment typically involved includes the oxygen bomb calorimeter, calorimeter water bath with stirrer, thermometer, oxygen supply, and ignition circuit.

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