The national standard divides coal into three major categories, namely anthracite, bituminous coal and lignite, with 29 subcategories. Anthracite is divided into 3 subcategories, the numbers are 01, 02, and 03. The "0" in the number indicates anthracite coal, the single digit indicates the degree of coalification, and the small number indicates a high degree of coalification; bituminous coal is divided into 12 coal categories, with 24 small Class, the ten digits (1~4) in the number indicate the degree of coalification, the smaller number indicates the higher degree of coalification; the single digit (1~6) indicates the cohesiveness, the larger number indicates the stronger cohesiveness; lignite is divided into 2 Small category, the numbers are 51 and 52, the "5" in the number indicates lignite, the single digit indicates the degree of coalification, and the small number indicates the low degree of coalification.

In the digital numbers of various types of coal, the ten-digit number represents the size of the volatile matter. For example, anthracite has the smallest volatile matter, and the tens-digit number is 0; lignite has the largest volatile matter, and the tens-digit number is 5. The tens digit of bituminous coal is between 1 and 4. For bituminous coal, the single digit represents its cohesiveness or coking properties. The larger the single digit, the stronger the cohesiveness. For example, The bituminous coals with a single-digit number of 6 are all fat coals or gas-fat coals with a maximum thickness Y value of the colloid layer greater than 25mm. The bituminous coals with a single-digit number of 1 are coals without caking, such as lean coal. Coal, non-caking coal and long bituminous coal. For bituminous coals whose single digits range from 2 to 5, their cohesiveness increases as the number increases.

Distinguish various types of coal with the naked eye:

Anthracite: Anthracite has high fixed carbon content, low volatile component yield, high density, high hardness, high ignition point, and does not emit smoke when burned. Black is hard and has a metallic luster. Rubbing with grease will not cause staining, the fracture will be shell-shaped, and the flame will be short and smokeless when burning. No coking.

Lignite: Lignite, also known as firewood, is the mineral coal with the lowest degree of coalification. A brown-black, dull, low-grade coal between peat and bituminous coal. Because it is rich in volatiles, it burns easily and produces smoke. Traces of the original wood can be clearly seen in the cross-section. Contains humic acid soluble in alkali solution. The carbon content is 60% to 77%, the density is about 1.1-1.2, and the volatile content is greater than 40%. No colloid layer thickness. The calorific value is approximately 23.0-27.2 MJ/kg (5500-6500 kcal/kg). Mostly brown or brown-black, with a relative density of 1.2 to 1.45. Lignite can be divided into two types: (1) brown coal, which is loose and soft in texture; (2) lignite, which is dense and hard in texture. It can be directly used as household fuel, industrial heat source fuel and fuel for power generation. It can also be used as raw material for gasification, low-temperature carbonization, etc.

Bituminous coal: coal with a long and smokey flame when burned, coal with a greater degree of coalification. The appearance is gray-black to black, and the powder is from brown to black. The shiny and matte parts are combined into layers to form a layer. Asphalt, grease, glass, metal, diamond, etc. are all shiny, and have obvious strip-like and convex mirror-like structures.