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Determination of a novel mine tracer gas and development of a methodology for sampling and analysis of multiple mine tracer gases for characterization of ventilation systems
Patterson, Rosemary Rita
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Ventilation in underground mines is vital to creating a safe working environment. Though there have been numerous improvements in mine ventilation, it is still difficult to ascertain data on the state of the ventilation system following a disaster in which ventilation controls have been potentially damaged. This information is important when making the decision to send rescue personnel into the mine. By utilizing tracer gas techniques, which are powerful techniques for monitoring ventilation systems, especially in remote or inaccessible areas, analysis of the ventilation system immediately following a mine emergency can be more rapidly ascertained. However, the success of this technique is largely dependent on the accuracy of release and sampling methods. Therefore, an analysis of sampling methods is crucial for rapid response and dependable results during emergencies. This research project involves evaluating and comparing four well-accepted sampling techniques currently utilized in the mining industry using sulfur hexafluoride, an industry standard, as the tracer gas. Additionally, Solid Phase Microextraction (SPME) fibers are introduced and evaluated as an alternative sampling means. Current sampling methods include plastic syringes, glass syringes, Tedlar bags, and vacutainers. SPME fibers have been successfully used in a variety of industries from forensics to environmental sampling and are a solvent-less method of sampling analytes. To analyze these sampling methods, samples were taken from a 0.01% standard mixture of SF6 in nitrogen and analyzed using electron capture gas chromatography (GC). The technical and practical issues surrounding each sampling method were also observed and discussed. Furthermore, the use of multiple tracer gases could allow for rapid assessment of the functionality of ventilation controls. This paper describes experimentation related to the determination of a novel mine tracer gas. Multiple tracer gases greatly increase the level of flexibility when conducting ventilation surveys to establish and monitor controls. A second tracer would substantially reduce the time it takes to administer multiple surveys since it is not necessary to wait for the first tracer to flush out of the mine which can take up to a few days. Additionally, it is possible to release different tracers at different points and follow their respective airflow paths, analyzing multiple or complex circuits. This would be impossible to do simultaneously with only one tracer. Three different tracer gases, carbon tetrafluoride, octofluoropropane, and perfluoromethlycyclohexane, were selected and evaluated on various GC columns through utilizing different gas chromatographic protocols. Perfluoromethylcyclohexane was selected as the novel tracer, and a final protocol was established that ensured adequate separation of a mixture of SF6 and perfluoromethylcyclohexane. Since there is limited literature comparing sampling techniques in the mining industry, the findings and conclusions gained from the sampling comparison study provide a benchmark for establishing optimal sampling practices for tracer gas techniques. Additionally, the determination of a novel tracer gas that can be used with and separated from SF6 using the same analytical method increases the practicality and robustness of multiple mine tracer gas techniques. This initial work will contribute to the larger project scope of determining a methodology for the remote characterization of mine ventilation systems through utilizing multiple mine tracer gases and computational fluid dynamics (CFD). This will be completed through several phases including initial laboratory testing of novel tracer gases in a model mine apparatus to develop a methodology for releasing, sampling, and modeling a mine ventilation plan and tracer gas dispersion in CFD and eventually completing field trials to validate and enhance the multiple tracer gas methodology.
- Masters Theses