Underground » Health and Safety
This report summaries the results of shearer dust scrubber design and field trials at the final stage of the project C14036 under the Australian Coal Association Research Program (ACARP), entitled "Dust Control Technology for Longwall Faces - Shearer Scrubber System".
Extensive CFD modelling studies of longwall shearer dust scrubber system have been conducted and results indicate that the design of the scrubber system should be aimed to capture a proportion of the dust particles and modify the face flow patterns to divert respirable dust clouds off the shearer operator's position. This can be achieved by correctly matching the scrubber capacity with the face ventilation, positioning the scrubber inlet, discharge direction, and in combination with an air curtain.
By incorporating CFD modelling results, the shearer scrubber has been designed and manufactured as a modular unit consisting of an intake hood directed into the intake ventilation, a hydraulic driven fan sucking the air into a filtration system and a discharge duct forcing the cleaned air under the shearer body towards the face. A series of water sprays are embedded into the sides of the intake hood to create the first agglomeration impact point for the dust/ water mixture prior to impact filtration removal and also to provide firstly an 'air curtain', to stop dust entering the walkway and secondly to entrain airborne dust out of the walkway. The combination effect of the spray pressure, flow and design adds additional collection and dust behaviour modification to the system.
Field trials were conducted at BMA's Broadmeadow Mine in Queensland's Bowen Basin. The shearer scrubber system was installed on the MG side of the shearer body during a scheduled maintenance shift and successfully trialled during four cutting cycles. The shearer scrubber motor is driven from the cowl circuit and functioned via the shearer remote control to turn on or off independently of any other function; the hood sprays are linked into the maingate shearer head spray circuit and activated when the head sprays were functioned.
Field observations of the scrubber operating indicated a significant reduction in the amount of shearer generated dust entering the walkway. This was evident in both the maingate to tailgate floor cut and the tailgate to maingate roof cut. The impact of the scrubber on longwall coal dust can be clearly observed when standing in the walkway next to the shearer during the cutting cycle. Real-time dust collection analysis conducted showed a 56% reduction in average dust concentration (from 1.59 to 0.7mg/m3) in the shearer operator position with the scrubber turned on. In the position four chocks outbye of the operator position, average dust concentrations were reduced up to 49% (from 1.59 to 0.77mg/ m3). The new shearer scrubber system has been deemed a success by the mine personnel involved with the project.
The major challenge has been the design of a scrubber system that would stay on the shearer and survive the harsh environment during the operation of longwall shearers. The current scrubber system can be viewed as work in progress and continued improvements need to be made on scrubber operation and cleaning to fully integrate the scrubber into the longwall shearer automation system. Specific training and operating protocols will also need to be implemented at the mine to ensure the working life and effectiveness of the scrubber system.