Coal And Different Types Of Coal

 Coal is mainly composed of elements such as carbon, hydrogen, oxygen, nitrogen, sulfur, and phosphorus. The combined proportion of carbon, hydrogen, and oxygen accounts for more than 95% of the organic matter. It is a very important energy source and a key raw material for metallurgy and the chemical industry. It is classified into several types, including lignite, bituminous coal, anthracite, and semi-anthracite.

 As of 2011, China was the world's largest coal producer, with a coal output of 3.24 billion tons, equivalent to 1.8004 billion tons of oil equivalent, accounting for 48.3% of the world's total. The United States came in second, accounting for 14.8% of the world's output, followed by Australia in third place with 6.3%. India and Indonesia ranked fourth and fifth, accounting for 5.8% and 5.0% of the world's output, respectively.

 Coal is divided into three types: lignite, bituminous coal, and anthracite. Different types of coal have different compositions and qualities, and their calorific values also vary.

1. Lignite: Mostly in block form, dark brown in color, with a dull luster and a loose texture; contains about 40% volatiles, has a low ignition point, and is easy to ignite; burns quickly with a large flame and produces black smoke; has a low carbon content and heat value (heat value varies greatly depending on the coal grade of the origin), burns for a short time, and requires frequent refueling.

2. Bituminous coal: Generally comes in granular or small block form, and can also be powdery. It is mostly black and shiny, with a fine texture, containing more than 30% volatiles. It has a relatively low ignition point and is easy to ignite; it has a high carbon content and heat value, ignites quickly, produces long flames, and generates a lot of black smoke. The combustion time is relatively long; most bituminous coals are sticky and tend to form slag during combustion.

3. Anthracite coal: Available in both powder and small lump forms, it is black in color with a metallic luster and is shiny Low impurities, dense texture, high fixed carbon content, reaching over 80%; low volatile matter content, below 10%, high ignition point, not easy to ignite; but high calorific value, slow to ignite initially, large flame once lit, strong heat output, short flame, less smoke, long burning time, weak adhesiveness, and not prone to slag formation during combustion. It should be mixed with an appropriate amount of coal soil for burning to reduce the intensity of the heat.

4. Peat coal: The least carbonized type, with low carbon content and high moisture content, the Mar value can reach up to 90%, so it needs to be air-dried before use; peat coal's ash easily melts, has low calorific value, and contains a lot of volatile matter, making it highly flammable.