The fuel mostly used in boilers is lignite.

Lignite is a type of coal that is commonly used as fuel in boilers. It is a low-grade coal with high moisture content and low carbon content. Lignite is formed from peat through the process of coalification, which involves the transformation of organic matter under high pressure and temperature over millions of years.

Reasons for using lignite as fuel in boilers:

1. Abundance: Lignite is one of the most abundant coal resources globally. It is found in large quantities in many countries, including Germany, Russia, the United States, and India. Its availability in large quantities makes it an attractive fuel option for boilers.

2. Low cost: Lignite is a relatively cheap fuel compared to other types of coal. Its low cost makes it economically feasible for use in boilers, especially in applications where a large amount of fuel is required.

3. High moisture content: Lignite has a high moisture content, typically ranging from 20% to 40%. This high moisture content means that lignite has a lower calorific value compared to other types of coal. However, boilers designed to burn lignite are equipped with drying systems to reduce the moisture content of the fuel before combustion. These drying systems ensure efficient and effective combustion of lignite in boilers.

4. Low carbon content: Lignite has a low carbon content, typically ranging from 25% to 35%. This low carbon content means that lignite produces lower amounts of carbon dioxide (CO2) emissions compared to other types of coal. This makes lignite a relatively cleaner fuel option for boilers.

5. High volatile matter: Lignite has a high volatile matter content, typically ranging from 30% to 45%. Volatile matter refers to the combustible gases and vapors released during coal combustion. The high volatile matter content of lignite makes it highly combustible and facilitates efficient combustion in boilers.

In conclusion, lignite is the fuel mostly used in boilers due to its abundance, low cost, high volatile matter content, and relatively lower carbon content compared to other types of coal. Despite its high moisture content, lignite can be effectively burned in boilers with the help of drying systems.

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