The Asia Miner

SEP-OCT 2014

The ASIA Miner - Reporting Important Issues to Mining Companies in the Asia Pacific Region

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September/October 2014 | ASIA Miner | 79 Supplier News The three locations in which collection buckets were placed in a dragline machine house used to study the effciency of an existing dust fltration system. Moths were identifed as a major problem. They clogged up intake screens and scavenge systems on the fltration units and reduced their performance. Some practical means of addressing this include not positioning lighting too close to the intakes of the fltration units because it attracts the moths and, when modifying ventilation systems, maintainers should make the intake screens as large as possible so the moths can't get trapped so easily onto the screen mesh. The performance of existing fltration systems could also be im- proved by making the fltration systems easier to maintain, re-con- fguring the air entry points, introducing weather protection, regular flter cleaning, utilization of effective dust scavenge systems and regular mechanical maintenance of fans to maintain consistent and adequate house pressurization. Several alternative concepts were investigated to determine whether technologies existed that could be readily incorporated into a dragline ventilation system in order to secure enhanced ef- fciencies. Such technologies included acoustic agglomeration, cyclone designs, traditional baghouses and cartridge flter based technology. The latter ultimately became the preferred option of the researchers, after seeing the fltration results from an electric rope shovel which was part of the studied group of machines that had a small cartridge flter based system installed. To be viable on a drag- line, it was felt that the normal operational pressure drop across the flters would need to be decreased somewhat from standard cartridge flter design practice, so as to bring the fan power con- sumption requirements within acceptable limits. The more recent study moved on to identifying whether an al- ternative cartridge flter design with improved fow and pressure drop characteristics, compared to those normally used in the P&H AirScrubProâ„¢ system, could be developed and then tested on an operating shovel. On completion of the frst stage of laboratory testing, it became evident that a signifcant reduction in pressure drop across a clean flter was unlikely to be realzed by attempting to develop an alternative flter cartridge design. The focus of the study moved away from the manufacture and testing of an alterna- tive cartridge flter design to the feld testing of the cartridge flters used in a standard AirScrubPro system to establish how quickly the pressure drop across the flter changed with time as the flter elements tended to clog up with dust. Perhaps the biggest surprise of the study was to fnd how much appearances can infuence perceptions. One of the older ma- chines that was deemed by mine staff to be one of the worst per- formers was found from early testing to indeed be the worst (only about 70% dust collection effciency compared to more like 75% to 85% for the other draglines; but when the fltration system was completely cleaned it became the best performer across all of the draglines being tested (about 95% overall dust collection effciency - only the shovel with the cartridge based system performed better, about 98% to 99% overall dust collection effciency), yet only the researchers noticed the change. The projects have provided the Australian coal industry with a better understanding of dragline cooling and dust control issues and further provided operators with tools to assess the potential for improving the situation on a particular machine experiencing cooling or dust issues. This has particular relevance for operators planning an overhaul or replacement of the ventilation system on a dragline in order to get the most beneft from the works.

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