Adsorption and deformation characteristics of coal under liquid nitrogen cold soaking

Abstract

The research on gas adsorption deformation characteristics of coal under liquid nitrogen cold soaking deserves investigation, as most of the investigation efforts in this field are in a preliminary stage. In this article, the experiments of coal adsorption deformation under different times of liquid nitrogen cold soaking (0, 1, 3, 5, 7 and 9) were carried out. The variation of coal gas adsorption capacity and volumetric strain under different times of liquid nitrogen cold soaking were investigated. Based on thermodynamics, the adsorption strain model of coal was developed, and the relationship between coal adsorption capacity and volumetric strain was discussed. The research results show that: (i) the coal adsorption capacity and volumetric strain both gradually decrease with the increase of the number of liquid nitrogen cold soaking; (ii) the saturated gas adsorption capacity and limit volume strain of coal both show a decreasing trend with the increase of liquid nitrogen cold soaking times; (iii) the volumetric strain of coal under the different times of liquid nitrogen cold soaking first accelerates and then slowly rises with the increase of adsorption capacity. After liquid nitrogen cold soaking, the volumetric strain growth rate of coal gradually decreases; (iv) the coal under different cold soaking times reaches the limit volumetric strain at a pressure (P) that is higher than the pressure (p) required to reach the saturation adsorption capacity, and the values of p and P both show a decreasing trend with the increase of liquid nitrogen cold soaking times; (v) the model results have good predictive effect.