Porosity and Fracture Changes of Bituminous Coal under Action of Dry–Wet Cycles in Acid Environment

The application of acetic acid to coal seams can significantly impact the coal’s microstructure and properties. In this paper, micro-CT was used to perform CT scanning on two bituminous coal samples before and after 72 h of dissolution with different concentrations of acetic acid solution to quantitatively identify the changes in the components and microstructures of pores, coal matrices, and minerals in the coal with acetic acid concentration. Research has shown that the erosion effect of acetic acid concentration on bituminous coal exhibits a positive correlation, with high concentrations causing more significant open-pore erosion. Additionally, the porosity of coal samples increases with the concentration of acetic acid, and the mineral volume fraction generally decreases. The minerals inside the coal samples are constantly eroded by dissolution and hydrolysis, leading to changes in their state. The interaction of acid corrosion and the dry–wet cycle ultimately causes the deterioration of the physical form of coal and an increase in porosity.