Open Cut » Health and Safety
This report covers ACARP project C18029, Building, Fitting and Testing an Acoustic Agglomerator to Reduce or Eliminate Dust Loading from the Machine House on Draglines. The aim of the project is to use acoustic agglomeration techniques to reduce respirable dust particulate mass (<10 microns) entering dragline machine rooms by up to 90%.
The project was initially planned in three stages and later increased to four stages to allow for the initial investigation of the suitability of the DusTrak DRX 8533 particulate measuring instrument. The specification for the DusTrak DRX 8533 indicated that the instrument was suitable for dust measurements, but there was some question regarding the accuracy of the instrument when used in the coal mining industry. Two DusTrak competitors, Thermo Scientific pDR-1500 and Dwyer dust probe, were also assessed and found to be unsuitable as they did not combine gravimetric measurement with particle sizing.
The outcome of this initial investigation appears to support the experience of the mining industry as to the reliability of the DusTrak instrument. For reliable DusTrak results, the instrument requires a clean area of operation with relative humidity controlled to below 60%: conditions that are difficult to maintain in the coal mining environment. In other industries such as grain, power station and some process engineering plants, the DusTrak appears to perform well.
During the C18029 project, two DusTrak DRX 8533 instruments were used for prolonged dust measurement, verified by gravimetric measurement and good correlation was found.
A visit to the Goonyella Riverside Moranbah open cut coal mine Dragline 4 proved very informative and subsequent analysis of dust samples taken on site provided a better understanding of the makeup of dust found in dragline machine rooms. The visit also provided an opportunity to measure the physical size and power required by the six air handling units if acoustic agglomeration was fitted upstream of the Dynavane inertial separators.
The fitting of acoustic agglomeration to existing dragline machine room air handling units is feasible with very little modification of inertial separation units. The additional electrical power required by the acoustic agglomerators is only a fraction of the power required by the existing air handling units and overall should not be difficult to supply from the existing motor control switchboards.
Computer modelling of the performance of the initial prototype microcyclones and then Dynavane inertial separators both with and without acoustic agglomeration proved very effective compared with test results. There was a good correlation with dust particulate mass and average particle size projected by the computer modelling and the actual measured agglomerated dust.
As the dragline manufacturers have already discovered, the Dynavane inertial separation process operates very efficiently on dust particles >10 microns, requiring very little ongoing maintenance and exhibiting high reliability. The addition of acoustic agglomeration increases the performance of Dynavane inertial separation on dust <10 microns at the lower mass range of mine site dust to the extent that an integrated system with acoustic agglomeration upstream of a Dynavane will extract ~90 % of dust down to 4 microns.
An e-newsletter has also been published for this project, highlighting its significance for the industry.