Londonderry-based Air Quality Technologies has been developing its Portable Diesel Particulate Emission Measuring System for four years, initially for on-road engines. After some successful exploratory work with the New South Wales Department of Minerals and Energy, AQT was approached in 2004 by the Queensland Department of Natural Resources, Mines and Water to explore the feasibility of adapting the technology for testing engines used in underground coal mines.
In the past, regulators and industry had faced the problem of a lack of practical, low-cost equipment that could immediately and reliably identify high DPM-emitting vehicles.
AQT looked at developing a rugged, practical and easily operated DPM measuring instrument, specifically designed for mining engines. The aim was to take the time consuming and expensive process of DPM analysis “out of the laboratory and into the workshop”, according to AQT director Peter Anyon.
“Effective engine maintenance can drastically reduce PM concentrations, but workshop staff must have the tools to identify high PM emitters and to validate the effectiveness of the maintenance performed,” he said.
Anyon said keeping DPM levels down was about good maintenance and weeding the high DPM-emitting engines out.
“Advanced engine technologies and improved fuel quality are gradually reducing PM levels but emissions from existing in-use engines remain a problem, as a badly maintained diesel engine can have PM emissions many times higher than an equivalent, well-maintained example. Fortunately good maintenance can in most cases drastically reduce emissions from the high polluters,” he said.
“Although there is not yet a great deal of data for underground mining engines, the trends are starting to look very similar to those for on-road vehicles, with a relatively small number of badly maintained engines accounting for a disproportionately large amount of total pollution. These engines are, in most cases, also the ones that offer the greatest emission reductions.”
AQT’s analyser uses laser “light-scattering” technology coupled with integrated sample drying and dilution systems. The system gives instant results and can also be used on engines with water-bath exhaust scrubbers.
“Measuring DPM in underground mines is a particularly demanding task, as the whole exhaust stream in most cases passes through a water bath to cool the exhaust and quench sparks,” Anyon said.
“This means that the exhaust sample contains large number of condensing water droplets, which must be removed prior to passing through the laser analyser in order to avoid erroneous reading arising from reflection and refraction of the laser beam by the water droplets.”
The battery-powered instrument gives real-time measurements and could, if there is sufficient commercial demand, also incorporate analysers to measure carbon monoxide, hydrocarbon and nitrogen oxides.
Intrinsically safe certification has not yet been sought, as it will mostly be used for engine maintenance in surface workshops and designated non-IS areas underground.
AQT’s analyser sells for about $A24,000 per unit.
Anyon said trials of the analyser had been “extremely successful” and the first production units were now in service with a number of Queensland and overseas mines.
“Many of the major mining companies operating in Australia are implementing, or planning to implement, the one-minute “stall" test, together with a real-time PM analyser as their primary method of monitoring PM emissions from diesel engines.
“It is possible that the stall test – which was developed by the New South Wales Department of Minerals and Energy – could be developed into a nationally adopted standard for the mining industry.”