Understanding the coal rock reflectance index in coking coal

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Since the 1980s, indicators of coal rock reflectance have been introduced from abroad to characterize the degree of metamorphism of coking coal; they show a good correlation with volatile matter content. Their applications are mainly in the following areas: 1. The most prominent use of this indicator is in identifying blended coals. Coal from single seams exhibits a normal distribution, whereas blended coals show multiple peaks on the reflectance distribution graph. According to national standards, a standard deviation greater than 0.1 indicates a blended coal, while a value greater than 0.2 indicates a complex blended coal. Identifying blended coals is key to the usefulness of this indicator. 2. By determining the coal rock components, namely the vitrineinite, inertinite, and inert components, the ratio of active components to inert components can be determined, which is used for coal blending. This is a classical theory in coal rock-based coal blending. However, since the quality of coal in China differs from that abroad, and because the testing procedures are complex and subject to significant human factors, this method is not widely used ； 3. By combining coal rock reflectance indices with other macroscopic indicators, these can be used to guide the selection of coal blends for coking, such as the R–G and R–Y models. This approach is easier to implement compared to method 2, but the accuracy of the models varies depending on the conditions of the coal blend ； 4. Uncovering the information contained in coal and rock reflectance distribution maps and using it, in conjunction with macroscopic indicators, to guide coal blending for coking is one of the development directions for coal and rock reflectance.