Mines routinely monitor the gas profiles in their goafs and roadways to determine the current status of the mine as part of their principle hazard management plan for spontaneous combustion. Many mines typically monitor for hydrogen, oxygen, methane, carbon monoxide, carbon dioxide, ethane and ethylene using micro gas chromatographs.
This paper investigates the existence of other gases which may have the potential to be used to monitor the underground environment for early signs of a heating or developing spontaneous combustion event. Simtars collected goaf and roadway gas samples into Tedlar bags to determine the “normal” background levels of these gases.
The gases analysed for included aliphatic hydrocarbons to C10, Benzene, Toluene, Ethyl Benzene and Xylene (BTEX) and aldehyde compounds. In addition to classical analytical techniques such as Gas Chromatography / Mass Spectroscopy (GC/MS) and High Pressure Liquid Chromatography (HPLC), a new micro gas chromatograph configuration previously developed by Simtars was used to conduct the analysis for aliphatic hydrocarbons to C6 and BTEX.
This paper provides a summary of the extended aliphatic hydrocarbon, BTEX and aldehyde gas profiles found in the longwall goafs and roadways of the surveyed Queensland and New South Wales mines.
Nick Coplin – General Manager, Engineering Services, Orbital Australia Pty Ltd
Australian Coal Association Research Program (ACARP) project C25073 was proposed by industry stakeholders seeking a solution that would both improve underground air quality and reduce the operational costs associated with currently implemented disposable filter technology used to control diesel particulate emissions in the underground coal mining environment. The follow-on C26070 project sought to industrialise the proof-of-concept (PoC) wall-flow diesel particulate filter (DPF) system to comply with relevant safety and health standards.
The technology has demonstrated significant DPM emissions reduction, comparable to the incumbent disposable technology, and has demonstrated the ability to meet NSW MDG43 requirements for year 2020. Testing noted that whilst the technology increased modal NO2 formation, it was compliant over typical operational duty cycles.
One of the key benefits with the use of a wall-flow DPF system is its tamper-proof design, mitigating the risk of operating unfiltered diesel plant in poorly ventilated areas. Elimination of the need for continual replacement of disposable filters provides significant operational savings estimated to be up to 80% of the incumbent technology.
The robustness of the aftertreatment solution can be maintained with both appropriate design and the use of embedded real-time, and near-real-time, electronic monitoring technology.
Dr Ian Webster – Group Engineering Manager, Ampcontrol Pty Ltd
The operation of a diffusion type gas detectors used in fixed, machine mounted and handheld applications is reliant on the natural equalisation of dissimilar gas concentrations driven by partial pressures inside and outside the detector.
Typically, this equalisation is inhibited (to a greater or lesser degree) by protective filters and barriers surrounding the fragile sensing elements from the typically harsh ambient environments. The accumulation of dust and other foreign matter on the protective filters can further inhibit the diffusion of gas into a detector.
The usual calibration process for a gas detector – typically by a ‘bump’ or ‘challenge’ test – will often fail to detect when a detector is blocked, or partially blocked. This can lead to the ‘calibrated’ detector reading high or low, but with no way to determine if that is the case.
Retrospective examination of records and equipment from Pike River Mine lead to the conclusion that critical detectors were affected by filter blockages, resulting in methane detectors reading approximately one-half of the true concentration.
This presentation explores how a blocked detector can give an erroneous reading, and what steps can be taken to avoid replicating previous mistakes.