Hard coal is a general term for bituminous coal and anthracite, which refers toConstant humidity ash free basis gross calorific valueCoal greater than or equal to 24MJ/kg.Black has strong luster, which means that it will not be contaminated by friction, and the specific gravity is more than 1.7.[1]
Bituminous coal is a kind of coal.The carbon content of this kind of coal is 75%~90%, without freehumic acid。Most of them are adhesive;Calorific valueHigher.When burning, the flame is long and smoky.Most cancoking 。The density is about 1.2-1.5.VolatilesAbout 10% - 40%.relative density1.25~1.35, calorific value about 27170-37200Kilojoule/Kg (6500-8900 kcal/kg).Volatile matterMedium content is called medium bituminous coal;The lower is called sub bituminous coal.Coal with long and smoky flame when burning,Coalification degreeLarger coal.The appearance is grayish black to black, and the powder is brown to black.Glossy and matt parts gather together to form a layer, with asphalt, grease, glass, metal, diamond and other luster, with obvious banded and convex mirror structure.
anthracite
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Anthracite, commonly known as white coal or red coal.yesCoalification degreeLargest coal.Anthracite has high fixed carbon content,Volatile matterLow yield, high density, high hardness, high ignition point, no smoke when burning.Black hard, withMetallic luster。Rub with grease to prevent contamination,fractureShell shaped, short flame with little smoke when burning.nocoking 。Generally, the carbon content is more than 90%,VolatilesBelow 10%.nothingThickness of colloid layer。Calorific value is about 6000-6500 kcal/kg.Sometimes, semi anthracite coal with extremely large volatile content is called;Very small coal is called high anthracite.
Hard coal classification
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Classification criteria
The international classification of hard coal takes dry ash free volatile matter as the first indicator, which indicates the degree of coal gasification. When the volatile matter is greater than 33%Constant humidity ash free basis gross calorific valueIs the auxiliary index to indicate thefree swelling index Or Roga index is the second indicator, which is the Gejin coke type orOa expansionIs the third indicator.[2]
Group indicators
The specific classification of hard coal is as follows: first, hard coal is divided into 10 categories from 0 to 9 based on volatile matter, while 6 to 9 types of coal need to be classified according to the high calorific value of ash free coal at constant humidity (30 ℃, relative humidity 96%).In Class 1 coal, it can be divided into two groups according to the volatile matter.Vdaf of Group A coal is more than 3% ～ 6.5%, and Vdaf of Group B coal is more than 6.5% ～ 10%.Then, among the above 0-9 hard coals, they are divided into 4 groups (0-3 in total) according to the coal cohesion index (free expansion number or Rogar index).
Index of international classification group of hard coal
group
free swelling index
Roga index
Bonding degree
zero
one
two
three
0～1/2
1~2
5/2～4
>4
0~5
>5～20
>20～45
>45
Unbonded to slightly bonded
Weak bond
Medium bond
Medium to strong bond
Finally, each group is divided into six subgroups (0~5 in total) according to the coking index of hard coal (Ao'a swelling test or Gejin test).
Phase group index of international classification of hard coal
Subgroup
Ao'a expansion b/%
Glenn test coke type
Coking characteristic
zero
one
two
three
four
five
Non softening
Shrink only
>0～50
>50～140
>140
A
B～D
E～G
G1～G2
G5～G8
>G8(≤G15)
Non coking
Very weak coking
Weak coking
Moderate coking
Strong coking
Extra strong coking
The international hard coal classification uses three Arabic numerals to indicate the type of coal, in which the hundred digit number represents the type of coal, the ten digit number represents the cohesiveness of coal, and the single digit number represents the coking of coal.The stronger the hundred digit number (i.e. the first digit) is, the higher the volatile matter is. The larger the ten digit number and the single digit number are, the stronger the cohesiveness and coking ability are.
Hard coal related data
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Figure 1 shows the world coal (hard coal) trade volume from 1996 to 2006[3]
Figure 1
Figure 2 shows the hard coal output of major coal producing countries in the world from 1990 to 2002[4]
