The influence of inhibitor solution on pore-fracture structure of coal body and its seepage law

ZHENG Sanlong; CHEN Mengqiao; SUN Lulu; YANG Xu; ZHANG Likui; LIU Longfei; DUAN Shoulei

doi:10.13347/j.cnki.mkaq.20241419

Abstract：Pre-injection of inhibitor solution is the source prevention technology of coal spontaneous combustion,which can effect-ively solve the fire problem caused by oxidation of coal.In order to study the effect of the inhibitor solution on the pore and fracture structure of the coal body and its seepage law,based on CT scanning experiments and CT three-dimensional reconstruction techno-logy,we constructed a three-dimensional pore and fracture structure model of the coal body,elucidated the effect of the inhibitor solution on the microscopic pore and fracture structure of the coal body.Based on the real pore and fracture structure of the coal body,Comsol was used to simulate the seepage characteristics of the inhibitor solution in the microscopic pore and fracture of the coal body,and to study the influence of the pore and fracture structure of the coal body and different pressure injection conditions on the seepage effect of the inhibitor solution and its role in the law.The results show that the pore and fracture structure of the original coal is denser than that of the inhibited coal samples.In the range of pore size of 0-100 μm,the number of pore and fractures in treated coal samples of inhibitor solution was smaller than that of the original coal,and the fractal dimension and porosity of the coal samples were reduced by 0.63%and 19.30%,respectively.The degree of throat development of the original coal was more signific-ant than that of the inhibited coal samples,and the inhibitor solution hindered the development of the coal body throat to a certain ex-tent.After the original coal was treated with the inhibitor solution,the average coordination number decreased by 17.9%,and the connected pore area and connected volume percentage of the coal samples decreased by 32.4%and 4.7%,respectively.With the in-crease of seepage pressure,the average seepage velocity gradually increased,and the maximum seepage velocity appeared at the pore with larger pore diameter,specifically at the position of section 192 μm;within the range of 0-192 μm at the cross-section position,the pressure field changes were more gentle due to the existence of well-connected pore channels with larger pore diameter.From the above analysis,it can be concluded that inhibitor solution inhibits the development of the pore throat structure and connectivity of the coal body to a certain extent,and the change of the structure affects the seepage characteristics of the inhibitor solution inside the coal body,which in turn affects the coverage area of the inhibitor solution inside the coal body,reduces the contact area between the coal body and oxygen,and slows down the rate of coal-oxygen composite reaction to achieve the flame retardancy purpose.