1. Coal is the most abundant and widely distributed fossil fuel on the earth. The main elements that make up coal organic matter are carbon, hydrogen, oxygen, nitrogen and sulfur, and there are also very few elements such as phosphorus, fluorine, chlorine and arsenic.
2. Carbon, hydrogen and oxygen are the main organic matter in coal, accounting for more than 95%; The deeper the coalification, the higher the carbon content and the lower the hydrogen and oxygen content. Carbon and hydrogen are the elements that generate heat when coal is burned, and oxygen is the combustion-supporting element. When coal is burned, nitrogen does not generate heat, but is converted into nitrogen oxides and ammonia at high temperature and precipitated in a free state. Sulfur, phosphorus, fluorine, chlorine and arsenic are harmful components in coal, of which sulfur is the most important. When coal is burned, most of the sulfur is oxidized into sulfur dioxide (SO2), which is discharged with flue gas, polluting the atmosphere, endangering the growth of animals and plants and human health, and corroding metal equipment; When high sulfur coal is used in metallurgical coking, it will also affect the quality of coke and steel. Therefore, the content of "sulfur" is one of the important indexes to evaluate coal quality.
3. The combustible gas produced by the decomposition of organic matter in coal under certain temperature and conditions is called "volatile matter", which is a mixed gas composed of various hydrocarbons, hydrogen, carbon monoxide and other compounds. Volatile is also the main coal quality index, which plays an important reference role in determining the processing and utilization mode and technological conditions of coal. Coal with low coalification degree has more volatile matter. If the combustion conditions are not suitable, the coal with high volatile content will easily produce unburned carbon particles when burning, commonly known as "black smoke"; And produce more pollutants such as carbon monoxide, polycyclic aromatic hydrocarbons and aldehydes, and the thermal efficiency is reduced. Therefore, suitable combustion conditions and equipment should be selected according to the volatile matter of coal.