Coal

• Coal is a readily combustible, black or brownish-black sedimentary rock, predominantly made of carbon. 
• Coal is classified as a nonrenewable energy source because it takes millions of years to form.
• Coal is a fossil fuel and  comprises a mixture of carbon, ash, moisture and other impurities.
•  Coal is primarily used for Power generation in Thermal Power Plants, in steel production. It also finds application in alumina refineries, paper manufacturing, and chemical and pharmaceutical industries.

Grade of coal

• The Gross Calorific Value (GCV), or the amount of heat or energy that can be generated from burning the coal, determines the grade of coal.
• The higher the available carbon in a unit of coal, the greater is its quality or ‘grade.’ 
• As per the Coal Ministry, there are 17 grades of coal. 

Types of coal found in India

• Anthracite: It is the highest grade of coal containing a high percentage of fixed carbon. It is hard, brittle, black and lustrous. It is found in smaller quantities in regions of Jammu and Kashmir.
• Bituminous: It is a medium grade of coal having high heating capacity. It is the most commonly used type of coal for electricity generation in India. Most bituminous coal is found in Jharkhand, Odisha, West Bengal, Chhattisgarh, and Madhya Pradesh.
• Subbituminous: It is black in colour, dull (not shiny) and has a higher heating value than lignite.
• Lignite: It is the lowest grade coal with the least carbon content. It is found in the regions of Rajasthan, Tamil Nadu, and Jammu & Kashmir.

Characteristics of Indian Coal

• Indian coal has been evaluated as being high in ash content and low in calorific value compared to imported coal. 
• The average GCV of domestic thermal coal ranges from 3,500-4,000 kcal/kg compared to imported thermal coals of +6,000 kcal/kg of GCV. 
• The average ash content of Indian coals is more than 40% compared to imported coal which has less than 10% ash content.
• High-ash coal when burnt results in the emissions of  higher particulate matter, nitrogen and sulphur dioxide

Sources

• https://uttam.coalindia.in/about.html

• https://www.britannica.com/science/coal-fossil-fuel