Correct Answer - Option 4 : Anthracite
Calorific value: It is the amount of energy released or produced when 1 kg of fuel burns or any other substance is burnt in the presence of oxygen and the products of combustion are cooled to STP. Its SI unit is kJ/kg.
Types of coal:
Coal is classified into four main types: anthracite, bituminous, subbituminous, and lignite.
The ranking depends on the types and amounts of carbon the coal contains and on the amount of heat energy the coal can produce. The rank of a coal deposit is determined by the amount of pressure and heat that acted on the plants over time.
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Anthracite contains 86%–97% carbon and generally has the highest heating value of all ranks of coal.
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Bituminous coal contains 45%–86% carbon. It is used to generate electricity and is an important fuel and raw material for making cooking coal or use in the iron and steel industry.
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Subbituminous coal typically contains 35%–45% carbon, and it has a lower heating value than bituminous coal.
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Lignite contains 25%–35% carbon and has the lowest energy content of all coal ranks. Lignite coal deposits tend to be relatively young and were not subjected to extreme heat or pressure. Lignite is crumbly and has high moisture content, which contributes to its low heating value.
