In the class of G>85 bituminous coal, the coal needed to determine colloid layer maximum thickness value Y or Oaxaca expansion degree B value to limit coal, gas coal and other sub bituminous coal type. When the Y value is greater than 25mm, such as Vdaf>37%, is divided into gas. Such as Vdaf<37%, are divided into fat. If the Y value of <25mm, according to the size of its Vdaf and divided into the corresponding other types of coal. Such as Vdaf>37%, should be divided into gas coal, such as Vdaf>28%-37%, should be divided into 1/3 coking coal, such as Vdaf is below 8%, it should be divided into coking coal.
Types of coalAccording to the classification Chinese coal, coal volatile, all coal is divided into lignite, bituminous coal and anthracite; for lignite and anthracite, respectively according to the characteristics of the degree of coalification and industrial use is divided into 2 and 3 categories; four stages, according to the >10%~20% bituminous coal volatiles >20%~28%, 28%~37 and >37% divided into low, medium, high and high volatile bituminous coal. As for the caking property of bituminous coal, it is distinguished by the bond index G: 0~5 is non caking and slightly caking coal; >5~20 is weakly caking coal; >20~50 is medium weak caking coal; >50~65 is moderately strong caking coal; >65 is strong caking coal. For the strong caking coal, and the plastic layer maximum thickness of Y>25mm or b>150% (for Vdaf>28% AoYa dilatation of bituminous coal, b>220% coal) into strong caking coal. In the name of coal type, taking into account the continuity of the new classification, still retain the gas coal, coking coal, lean coal, lean coal and weakly caking coal, non caking coal and long flame coal 8 coal.
It should be noted that the G value is greater than 100 of the coal, especially coal mine average G or several samples were above 100, generally can not measure Y value determined for coal or gas coal class.Also stipulated in China's coal classification standard, the G value is greater than 85 of the coal, if not measured Y, also available Oaxaca expansion degree B value (%) to determine the boundaries of coal and gas and other types of coal, namely Vdaf<28% coal, tentative b value of >150% for coal to Vdaf>28%; coal, provisional b value of >220% for coal (when the value of Vdaf <37% (Vdaf) or gas when the value of >37%). When there is a contradiction between the classification of coal according to the b value and the type of coal classified according to the Y value, the coal class determined by the Y value shall prevail. Thus in determining the new classification of strong caking coal brand, can only measure the Y value and temporarily B value.
