Study on Methane Distribution in the Face Zone of the Fully Mechanized Roadway with Overlap Auxiliary Ventilation System

Dariusz Obracaj,Marek Korzec,Paweł Deszcz

doi:10.3390/en14196379

Abstract

An overlap auxiliary ventilation system is very often used for driving roadways in methane-rich coal seams. An overlap zone between the outlets of the forcing duct ends with a whirl flow air-duct (WFAD) and the exhaust duct ends with a dust scrubber that is created by applying the overlap system. This study examines the distribution of methane concentrations at various distances in the overlap zone. Maintaining a long overlap zone could increase the advance of the face. Therefore, the impact of overlap zone length on the methane concentration distribution, in and beyond the overlap zone, is investigated. The evaluation of methane concentrations is performed utilizing a well-established computational fluid dynamics (CFD) approach. The mathematical model of methane emissions into the roadway is adopted. Moreover, the CFD model is validated. A vortex of the return air, caused by the free airstream flowing out of the dust scrubber, is found. This air vortex is responsible for higher methane concentrations at the end of the overlap zone. Therefore, the conclusion can be drawn that maintaining the length of the overlap zone at 5 m to 10 m should be done to control permissible methane concentrations.

Highlights

Appropriate working conditions in mining excavations are ensured using throughflow and auxiliary ventilation systems
The purpose of using an auxiliary ventilation system during roadway drivage in a methane-rich coal seam is to supply the desired amount of air to the face so that a permissible methane concentration is not exceeded along the entire length of the roadway [1,2,3]
5, to the face—Figure a distance of 32 m location of the M4 outlet)—Figure

Summary

Introduction

Appropriate working conditions in mining excavations are ensured using throughflow and auxiliary ventilation systems. The purpose of using an auxiliary ventilation system during roadway drivage in a methane-rich coal seam is to supply the desired amount of air to the face so that a permissible methane concentration is not exceeded along the entire length of the roadway [1,2,3]. One of them is called a primary forcing with an exhaust overlap system, and the other is called a primary exhaust with a forcing overlap system [1,4,5,6,7] These ventilation systems are selected depending on the technology of roadway drivage and environmental threats, such as methane, coal dust, and thermal conditions, which can result in explosions and/or health issues for miners

Methods

Results

Conclusion