Numerical analysis on the evolution of CO concentration in return corner: A case study of steady U-type ventilation working face

Abstract

A good understanding of the evolution of the CO concentration in the return corner is of great value for predicting and controlling the spontaneous combustion of coal. This study investigated the characteristics of the CO distribution in a gob with a steady U-type ventilation working face and the relationship between CO concentration in the return corner and the intensity of the coal oxidation reaction in the gob area. Coal spontaneous combustion generated by CO was modeled using COMSOL Multiphysics simulation software. The results showed that the CO concentration distribution exhibits “peaks” on the horizontal section in the gob and that the CO concentration is highest in the middle of the gob. With thermal accumulation in the residual coal over time in the gob, the CO concentrations in both the gob and return corner increase. When the self-heating temperature of coal in the gob reaches the critical temperature of 75 °C, the CO concentration in the return corner is a quadratic function of the ventilation flux and grows linearly with the increase in the seam thickness of the residual coal, the maximum width of the oxidation zone, and the CO-generation rate of coal.