Study on differences of pore structure of typical soft and hard coal

The study of coal pore structure research mainly focuses on a certain pore structure measurement technology method, but a single measurement cannot accurately characterize the characteristics of the multi-scale pore and fissure structure of coal in principle. Based on the analysis of the test principles, applicable conditions and coal physical properties of four test methods are proposed: mercury intrusion, nitrogen adsorption, carbon dioxide adsorption and small angle X-ray scattering method. and an integrated measurement and characterization method of pore structure of coal with full pore size based on data fusion is formed. In this paper, the differences of pore structure of soft and hard coal with two different metamorphic degrees are analyzed by using a new method from the aspects of pore shape, pore volume, specific surface area and pore size distribution. The results show that the integrated measurement and characterization method for the full pore structure of coal combines the advantages of the above four methods to determine the pore structure, and the results are more reliable and reasonable;the total pore volume of soft coal is larger than that of hard coal, and the soft and hard coals have large pores, and the difference between the two stages is mainly in the mesopore and macropore stages, in which the gap between the middle pore is the most obvious.The specific surface area of micropore of soft coal is much larger than that of hard coal. Tectonic effecthas the greatest influence on the development of mesopore pore volume of high-metamorphic coal, and has the greatest influence on the development of macropore volume of low-metamorphic coal, while it has little effect on the micropore surface area of low metamorphic coal.The above research results lay a physical foundation for the study of gas adsorption and migration laws and mechanisms of multi-scale pores in coal.