Study on the change law of physical and mechanical properties and wetting mechanism of coal body under the synergistic effect of chelation-adsorption

Abstract

ABSTRACT A chelating agent dissolves minerals in the coal body through chelation, and a surfactant increases the permeability of the solution by reducing surface tension of the solution. The chelating agent and the surfactant are compounded into the compound wetting agent, and the wetting effect of the coal body can be significantly improved by using different infiltration mechanisms. By measuring the surface tension of different kinds of surfactants and their contact angles with the coal body, the surfactant with the best effect was selected and combined with the chelating agent. The change law of moisture content and compressive strength of the coal body and other mechanical properties were determined after soaking in the solution. The results showed that surface tension of different surfactants SAS, BS-12, and JFCS and contact angle with the coal body all decrease with the increase of the mass concentration and the effect of JFCS is the best under the same concentration. When the concentration of surfactant increases to 0.05%, the surface tension and contact angle with the coal body will no longer decrease significantly. By soaking coal with the compound wetting agent consisting of 0.05% surfactants JFCS and 0.4% chelating agent, the water content of the coal body is 21%, which is 2.0 times that of the raw coal. The uniaxial compressive strength, elastic modulus, and impact energy index of the coal body are 6.5 MP, 547 MPa, and 1.1, respectively, which are 63%, 22%, and 91% lower than those of the raw coal, respectively. The dynamic failure time is 12271 ms, which is 17 times that of the raw coal. Through the chelation and wetting effect of the chelating agent and the adsorption and wetting effect of the surfactant, the compound wetting agent can promote seepage and migration of water in the coal body under the chelating-adsorption synergistic effect and improve the effectiveness of water injection in the deep coal seam.