The impact of airway geometry on the distribution of methane concentrations at the outlet from a longwall

Abstract

In underground hard coal mining, there are various types of natural hazards, which is related to human interference with the natural environment and the consequent disturbance of its equilibrium. The mining industry is an important component of the Polish economy, because coal is the basic raw material for power generation in the country. Therefore, there are numerous tests and studies to make the mining activities safe and effective. As a result, a crucial role is played by research and scientific work that result in the improvement of safety in this branch of industry. One of the areas undertaken by such research is dedicated to limiting the methane hazard in mines. The underlying cause of this problem is methane release from the body of coal and excavated coal, because this gas is flammable and explosive. These properties place the methane hazard amongst one of the most dangerous mining phenomena. The paper concentrates on the determination of methane concentrations in the area of ongoing exploitation, depending on airway geometry. The analysis is based on the model-based tests using computational fluid dynamics (CFD). The related calculations were performed by means of ANSYS Fluent based on the finite volume method (FVM). The analysis was conducted on a numerical model, reflecting the real-world region of the exploitation. The input data for the calculations were obtained from the results of measurements carried out in real-world conditions. The model developed takes into account a series of solutions that are the original scientific achievement of the Authors. This particularly refers to the modelling of goaves with caving as a porous medium. The calculations made it possible to determine the physical and chemical parameters of an air-methane mixture in each point of the region analysed. This is particularly true of the most dangerous area, namely the outlet from a longwall. In the case at hand, the calculations were carried out for several variants of airway geometry. The methodology of model-based testing presented in the paper, taking into consideration the real-world measurements and the results obtained, is an example of how advanced calculation methods can be used for solving practical problems.