The petrographic compositions of Chinese commercial coals: A national survey and statistical analysis

•The weighted average contents of vitrinite, inertinite and liptinite are 61.3%, 36.5%, and 2.2%, respectively, in Chinese commercial coals.•Relatively high content of inertinite and low content of liptinite are characterized for Chinese commercial coals. As liptinite is a much lesser component, the distribution trend of inertinite is generally opposite to that of vitrinite. An updated survey and statistical analysis were conducted about the petrographic compositions of Chinese commercial coals nationwide. 727 commercial coal samples were systematically collected from 25 provinces in China and the spatial distributions of the samples were consistent with the resources and capacities of the coal mines in China. The petrographic characteristics of different coal-forming ages, and coal-accumulating areas were analyzed in detail. The average petrographic compositions based on reserves weight were put forward. The weighted average contents of vitrinite, inertinite, liptinite were 61.3%, 36.5%, and 2.2%, respectively. Relatively high content of inertinite and low content of liptinite were found of Chinese commercial coals. The average contents of vitrinite were the highest in Cenozoic coals (93.5%) and Late Jurassic and Early Cretaceous coals (87.1%) while that was the lowest in Early and Middle Jurassic coals (52.4%). The average contents of vitrinite were the highest in Northeast (87%) and lowest in Shanxi-Shaanxi-Inner Mongolia-Ningxia (58.8%) and Northwest (59.9%). The coals in Northwest and Shanxi-Shaanxi-Inner Mongolia-Ningxia were characterized by high content of inertinite, which were mainly Early and Middle Jurassic coals. Diverse distributions of vitrinite and inertinite were found of coals in Northwest. Considering the layout of coal production, the vitrinite content will be decreased in the western areas and increased in the east areas.