Kray Luxbacher

Tracer gas applications in mining and implications for improved ventilation characterisation

Tracer gases have been an invaluable tool for analysis of airflow, especially in the mining industry as they are powerful techniques for evaluating many aspects of the ventilation system. This article highlights applications of tracer gases in coal and non-coal mines, in addition to the developing technology and the future role of tracer gases as a tool for ventilation analysis. Depending on the application, there are many characteristics that aid in the selection of an appropriate tracer gas. Other important considerations in tracer gas studies involve releasing and sampling techniques as well as methods of analysis. In addition to current sampling techniques, solid-phase microextraction (SPME) is introduced as a potential alternative sampling method for underground tracer gas applications.

Passive seismic tomography for three-dimensional time-lapse imaging of mining-induced rock mass changes

Progression of an immature block cave in proximity to a mature sublevel cave was monitored over an 18-month period using double-difference tomography. This method utilizes existing microseismic data to generate time-lapse images of seismic wave velocity changes within the rock mass. The velocity changes are caused by damage zones forming or local high-stress concentrations. In this study, images were generated on monthly intervals. An average of 2000 microseismic events recorded by 25 stations were used to generate each image. Results showed a development of the initial undercut followed by the growing cave and interaction with the adjacent sublevel cave. The goal of the research is to provide a tool that can augment both numerical modeling results and underground geotechnical measurements to allow the mine operator to produce in the safest and most efficient manner possible.

Computational fluid dynamics applied to mining engineering: a review

Abstract This paper provides a review of computational fluid dynamics (CFD) applications in mining engineering, with particular focus on mine ventilation-related flow problems. The basic principles of CFD are reviewed and six turbulence models commonly used are discussed with some examples of their application and guidelines on choosing an appropriate turbulence model. General modelling procedures are also provided with particular emphasis on mesh independence study and CFD validation methods, which can further improve the accuracy of a model. CFD applications in mining engineering research and design areas are reviewed, which illustrate the success of CFD and highlight challenging issues. It is expected that more CFD research will be carried out to solve problems in mining engineering, and the potential benefits from the simulations are enormous if proper modelling procedures are followed and modern computational approaches are implemented.

An Ultra-Trace Analysis Technique for SF6 Using Gas Chromatography with Negative Ion Chemical Ionization Mass Spectrometry

Sulfur hexafluoride (SF6) is widely used as a tracer gas because of its detectability at low concentrations. This attribute of SF6 allows the quantification of both small-scale flows, such as leakage, and large-scale flows, such as atmospheric currents. SF6s high detection sensitivity also facilitates greater usage efficiency and lower operating cost for tracer deployments by reducing quantity requirements. The detectability of SF6 is produced by its high molecular electronegativity. This property provides a high potential for negative ion formation through electron capture thus naturally translating to selective detection using negative ion chemical ionization mass spectrometry (NCI-MS). This paper investigates the potential of using gas chromatography (GC) with NCI-MS for the detection of SF6. The experimental parameters for an ultra-trace SF6 detection method utilizing minimal customizations of the analytical instrument are detailed. A method for the detection of parts per trillion (ppt) level concentrations of SF6 for the purpose of underground ventilation tracer gas analysis was successfully developed in this study. The method utilized a Shimadzu gas chromatography with negative ion chemical ionization mass spectrometry system equipped with an Agilent J&W HP-porous layer open tubular column coated with an alumina oxide (Al2O3) S column. The method detection limit (MDL) analysis as defined by the Environmental Protection Agency of the tracer data showed the method MDL to be 5.2 ppt.

Field test of a perfluoromethylcyclohexane (PMCH) permeation plug release vessel (PPRV) in an underground longwall mine

Perfluoromethylcyclohexane (PMCH) was released in a Midwestern underground longwall mine in the United States using a PMCH permeation plug release vessel (PPRV). The operators of this mine graciously allowed full access to an active longwall panel at two points in time to perform the test. This paper presents a study designed to determine the feasibility of using a PPRV in an underground mine environment for tracer gas studies. The results of this study showed that the PPRV is a feasible tracer delivery system for releasing PMCH at mine scale. Some of the advantages afforded by the PPRV over traditional release techniques are also highlighted.

Tenability analysis for improvement of firefighters’ performance in a methane fire event at a coal mine working face

Due to the high rate of methane ignitions at active continuous miner working faces in underground coal mines, this location has been the focus of many researchers, as well as safety initiatives. Multiple ignitions occur annually in US mines, and outcomes vary widely based on the magnitude of the ignition and the subsequent damage to ventilation controls or development of active fire. Depending on the magnitude of the explosion or fire, auxiliary ventilation controls, such as exhausting line curtain or tubing may be damaged or completely removed, affecting the ventilation into the area. Investigation of a typical dead end continuous miner working face with exhausting ventilation was undertaken to explore firefighting conditions post ignition. Regular mining crews are trained in the fighting of mine fires, while mine rescue or fire brigade teams may also be utilized for firefighting depending upon the conditions. The research in this article develops an approach to analyze the tenable limits in a fire event in an underground coal mine for barefaced miners, mine rescue teams, and fire brigade teams in order to improve safety and training of personnel trained to fight fires. A detailed computational fluid dynamics analysis was conducted to investigate temperature, visibility, radiation, and concentration of combustion products based on different damage assumptions following an ignition at the continuous miner working face. The source of the combustion products analysis and the exposure effects were considered to assess the potential for harm to mine personnel, mine rescue teams, or fire brigades during a firefighting operation, taking into account their training and personal protective equipment during the 5- and 15-min exposure. This study has shown that if the exhausting line curtain was destroyed, the situation would not be tenable for barefaced personnel. The findings were utilized to recommend the tenable limits for barefaced miners, mine rescue team, and fire brigade teams during the 15-min exposure to the methane fire at a continuous miner working face. The outcome of this research, applied to training, will result in the more efficient evacuation, as well as safe and effective firefighting under certain conditions.

A preliminary study of the application of Background Oriented Schlieren (BOS) for the qualitative imaging of methane emissions from coal

Methane presents a pervasive risk in most coal mines, its dilution being one of the primary objectives of the ventilation system. Although many different types of detectors and techniques exist for quantifying methane, little is known about the qualitative aspects of methane, such as visualising how this gas flows from coal. Background Oriented Schlieren (BOS) provides a potential method from qualitative analysis of methane emissions. BOS is an imaging technique designed to visualise normally invisible flows in transparent media. This paper is a preliminary investigation of the feasibility of using the BOS technique for imaging methane release from coal.