Experimental study of the kinetics of the adsorption of nitrogen by coal containing different amounts of water

Abstract

Useful insight can be gained into the underlying adsorption mechanism by studying the adsorption of nitrogen by primary structure coal with different water content. In this work, a coal-adsorption gas experimental system is used to investigate the adsorption of nitrogen by coal samples containing different amounts of water ( 2.894%, 1.871%, 0.897%, and 0%) and different pressures (0.7, 1.2, 1.7, 2.2, 2.7, 3.2, and 3.7 MPa). The adsorption rates under the different conditions were calculated using a volume method, and the adsorption kinetics investigated using a kinetic model. The results show that an adsorption model based on an opposing process characterizes the adsorption behavior better than the pseudo-first order kinetic model and pseudo-second order kinetic model. The adsorption rate constant, k, reflects the rate at which the gas can get into the pores of different sizes in the coal a greater k value, implies a greater increment in the rate. The k value is found to decrease when the initial pressure is increased for the same moisture content. Also, the greater the water content, the smaller the value of k for a given initial pressure. As the moisture content continues to increase, the k value tends to a certain value. The results presented can provide an experimental basis for the study of the mechanism responsible for the adsorption of nitrogen by primary structure coal with different moisture content.