Some nice facts about coal
- Some coals after release of volatile matter become soft and pasty and form agglomerates. They are called caking coals. Extent of caking of coal is determined by swelling index. On the contrary, free burning fuels have high swelling index, expand in volume during combustion.
- Grindability index is inversely proportional to power required to grind coal. Grindability of a standard coal is defined as 100.
- Phosphorous in coal should be <0.01% as it can react with iron to form hard, brittle iron phosphide.
- Sulphur occurs in coal as a) Pyrites: FeS2 b) Organic sulphur coupled with carbon atom of coal molecule. c) In form of gypsum Ca SO4.
- Fixed carbon in proximate analysis is a hypothetical term and not a precise constituent of fuel. It is obtained from subtracting from 100 sum of % of moisture, volatile matter and ash content of fuel sample.
- Moisture can be present in coal as surface moisture(Formed during washing, scrubbing of coal), inherent moisture(Absorbed moisture through water absorbed in capillaries in coal), Combined moisture
- As moisture increases, free hydrogen for combustion decreases as 1/8th of weight of oxygen content is consumed as moisture.
- Organic Sulphur is inseparable from coal. Only pyritic sulphur can be removed.
- Basic contents of volatile matter are a) Gases containing: CO, H2, CH4, C2H6 and H2S
b) Tar: Complex mixture of benzene, toluene, napthalene, xylene, phenols, free carbon, anthracite and cresols.
c) Ammoniacal liquor: Aqueous condensate of nitrogen and sulphur compounds plus cynides.
- Some coals after release of volatile matter become soft and pasty and form agglomerates. They are called caking coals. Extent of caking of coal is determined by swelling index. On the contrary, free burning fuels have high swelling index, expand in volume during combustion.
- Grindability index is inversely proportional to power required to grind coal. Grindability of a standard coal is defined as 100.
- Phosphorous in coal should be <0.01% as it can react with iron to form hard, brittle iron phosphide.
- Sulphur occurs in coal as a) Pyrites: FeS2 b) Organic sulphur coupled with carbon atom of coal molecule. c) In form of gypsum Ca SO4.
- Fixed carbon in proximate analysis is a hypothetical term and not a precise constituent of fuel. It is obtained from subtracting from 100 sum of % of moisture, volatile matter and ash content of fuel sample.
- Moisture can be present in coal as surface moisture(Formed during washing, scrubbing of coal), inherent moisture(Absorbed moisture through water absorbed in capillaries in coal), Combined moisture
- As moisture increases, free hydrogen for combustion decreases as 1/8th of weight of oxygen content is consumed as moisture.
- Organic Sulphur is inseparable from coal. Only pyritic sulphur can be removed.
- Basic contents of volatile matter are a) Gases containing: CO, H2, CH4, C2H6 and H2S
b) Tar: Complex mixture of benzene, toluene, napthalene, xylene, phenols, free carbon, anthracite and cresols.
c) Ammoniacal liquor: Aqueous condensate of nitrogen and sulphur compounds plus cynides.
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