The second is external water (Mf), which is the water attached to the surface and cracks during coal mining and transportation. Total water quantity is the sum of external water quantity and internal water quantity of coal. Generally speaking, the greater the degree of coal metamorphism, the lower the internal moisture. The inherent moisture of lignite and long-flame coal is generally high, while the inherent moisture of lean coal and anthracite coal is low.
Extended data:
Introduction to index
I. Humidity (m)
The existence of water is extremely unfavorable to the utilization of coal, which not only wastes a lot of transportation resources, but also when coal is used as fuel, the water in coal will become steam when it evaporates, consuming heat. In addition, the moisture of clean coal also has a certain influence on coking. Generally, for every 2% increase in moisture, the calorific value decreases 100kcal/kg (kcal/kg); For every 65438 0% increase in clean coal moisture, the coking time is prolonged by 5-65438 00 minutes.
Second, the ashes (a)
The residue left after coal is completely burned is called ash, especially in ash and inherent ash. External ash comes from rock fragments and research in the roof, which has a great relationship with the rationality of coal mining methods.
Most of the external ash can be removed by sorting. Intrinsic ash is an inorganic substance contained in primitive plants that form coal. The higher the inherent ash content, the worse the washability of coal.
Ash is a harmful substance. The ash content in power coal increases, the calorific value decreases, the slag discharge increases, and the coal is easy to slag. Generally speaking, for every 2% increase in ash, the calorific value will decrease by about 100kcal/kg.
The ash content of refined coal increases, the utilization coefficient of blast furnace decreases, the strength of coke decreases and the consumption of limestone increases; When the ash content increases by 65438 0%, the coke strength decreases by 2%, the blast furnace production capacity decreases by 3%, and the limestone consumption increases by 4%.
Three. volatile
When coal is heated at high temperature and isolated from air, the gaseous and liquid products are called volatiles. The main components of volatiles are methane, hydrogen and other hydrocarbons. It is one of the important indexes to identify the type and quality of coal. Generally speaking, with the increase of coal metamorphism, the volatile matter of coal decreases. Lignite and gas coal have higher volatiles, while lean coal and anthracite have lower volatiles.
References:
Baidu encyclopedia-basic indicators of coal quality