μCT quantitative assessment of the pore–fracture structures and permeability behaviors of long-flame coal treated by infrared rapid heating

Abstract

To explore the evolution features of the pore–fracture structures and permeability behaviors of coal under high temperatures and nitrogen atmospheres, an infrared rapid heating apparatus was employed to heat coal samples up to 100–500 °C at intervals of 100 °C. The coal samples were then scanned using high-precision micro-CT, and a three-dimensional (3D) pore–fracture structure and equivalent pore network model of the coal samples were established. The changing laws of Ep, Cn, Et, and Lc that varied with the heating temperature were first quantitatively analyzed. The distribution of the surface area and volume of the pore fracture was then statistically characterized. The results showed that the number of pore fractures and throats reached a maximum at 200 °C. Pore and fracture structures in coal tend to develop more with increasing temperature. In addition, the variations in the fractal dimension, porosity, connectivity, and permeability of coal with temperature are discussed. The fractal dimension and porosity increased significantly with increasing temperature. Dc and φc are more linearly dependent on temperature than Df and. φf The interconnection between the pores and fissures caused by the temperature increase is responsible for the increase in connectivity and permeability. This study provides theoretical guidance for coal fire prevention and coalbed methane extraction.