Coal quality indicators

"Interpretation of Coal Quality Indexes"

The first indicator: moisture.
The moisture in coal is divided into intrinsic moisture, external moisture, crystallization water and decomposition water.
Excessive moisture in the coal is not conducive to processing, transportation, etc., it will affect the thermal stability and heat conduction when burning, coke production will reduce the coke yield and prolong the coking cycle.
Now we often report the moisture indicators:
1. Total moisture (Mt) is the sum of all internal moisture and external moisture in coal. It is also commonly referred to as Mar. Usually set below 8%.
2. Air-dried base water (Mad) refers to the moisture content of coal in air-dry conditions. It can also be regarded as intrinsic moisture, and the old national standard calls it "analysis of basic water."

The second indicator: ash refers to the residue of coal left after burning.
It is not the sum of the minerals in the coal, but the chemical and decomposed residues of these minerals.
The high ash content indicates that the combustible composition in coal is low. Heat is low.
At the same time, in the coking of refined coal, the ash content determines the ash content of coke.
The usual ash indicators are air dry base ash (Aad), dry base ash (Ad), etc. Also useful for receiving basic ash (Aar).

The third indicator: volatiles (full name volatile yield) V
Refers to the thermal decomposition products of organic matter and some minerals in coal, not all of them are inherent components in coal, and some are pyrolysis products, so they are called volatile yields.
The amount of volatiles is related to the degree of coal metamorphism. The higher the degree of coal change, the lower the volatile yield.
In combustion, it is used to determine the boiler model; in coking, it is used to determine the proportion of coal blending; it is also an important indicator of vaporization and liquefaction.
Commonly used are air-dried based volatiles (Vad), dry-based volatiles (Vd), dry ashless volatiles (Vdaf), and received-based volatiles (Var).
Among them, Vdaf is one of the important indicators for coal classification.

The fourth indicator: fixed carbon is different from elemental analysis of carbon and is calculated based on moisture, ash, and volatiles.
FC+A+V+M=100

The formula is as follows: FCad=100-Mad-Aad-Vad
FCd=100-Ad-Vd
FCdaf=100-Vdaf

The fifth indicator: Full *St
It is a harmful element in coal, including organic*, inorganic*. Less than 1% can be used for fuel. Some areas require below 0.6 and 0.8. Nowadays, environmental protection coal and green energy all refer to lower coal.
Commonly used indicators are: Air Drying Group* (St,ad), Drying Group* (St.d), and Receiving Group* (St,ar).