Underground » Health and Safety
This is the final report for ACARP Project C18017, Triple Chamber Triple Frequency Ultrasonic Diesel Exhaust Soot Scrubber , a follow-on project to the successful outcome of ACARP Project C15021 Ultrasonic Diesel Particulate Agglomeration.
The promising results of Project C15021 using a single-frequency acoustic agglomerator approach led to the current project which investigates the performance of triple-frequency acoustic agglomeration. It expands on the results of the earlier project with the design, development and testing of a number of prototype triple-frequency acoustic agglomerater's combined with a range of microcyclone designs and dynamometer diesel engine DPM reduction tests using these systems to investigate their performance. Five diesel engines; two naturally aspirated and three common rail turbo charged diesels, were fitted with acoustic agglomerater's and the DPM reduction measured. Three methods of DPM removal were tested; micro-cyclone, catalytic converter and fabric filter to ascertain the most efficient DPM mass removal for each diesel engine size and type.
Ultrasonic agglomeration of itself does not affect the DPM mass but conditions the DPM particulates for efficient removal by other means. The purpose of acoustic agglomeration is to increase the size of exhaust DPM particles to a size range that can be extracted from exhaust flows by other means such as microcyclones or filters. The main findings from the computer modelling, laboratory testing and operation on a mine vehicle show triple-frequency acoustic agglomeration technology reduces DPM mass by up to 77% compared to untreated exhaust flows and the technology operates efficiently when fitted to a working mine vehicle. It produces very little backpressure on diesel engines and is able to operate over a wide range of operating loads.
Testing of a pre-production acoustic agglomerator on an operational TORO LHD proved very successful with an 82% reduction in DPM at 75% loading. At 100% loading, it is anticipated this figure will rise to above 90% due to the decreasing efficiency of diesel engine combustion at rated load. Moreover, large DPM reductions were achieved over all operating condition of the TORO machine.
The dynamometer testing of a newly-reconditioned BHP Caterpillar 10.3 litre common rail turbocharged diesel engine gave a >34% reduction in DPM mass and showed a reduction across all engine loading. This is a better than expected result for this engine which is as new, very efficient and produces very little DPM. Because of this we consider these results, although far short of the DPM reduction expected on an average mine diesel engine, to be in line with expected DPM levels for new diesel engines.
The outcome for the underground coal mining industry is a dramatically improved understanding of the combustion behaviour of diesel engines and the efficient removal of much smaller DPM particulates than is achieved with naturally aspirated diesel engines. The outcome of this will be a greatly improved acoustic agglomerator and micro-cyclone DPM extraction method for underground coal mines.
This project has demonstrated the practicality of fitting post combustion DPM treatment that will extend the life of fabric filter material and while there are still challenges in making the acoustic agglomerator suitable for use in ERZ areas of a coalmine this problem could be addressed with a further ACARP funded project.