Development and quantification of a dust reduction program in longwall mining at metropolitan colliery - a case study

Harmful respirable dust produced during longwall mining is a major concern for production, safety and the health of workers in the underground coal mining sector both in Australia and globally, Longwall personnel are exposed to harmful dust from multiple dust generation sources including, but not limited to intake entry, belt entry, stageloader/cnisher, shearer, shield advance and dust ingress from falling goal or over pressurisation of the goal the increase in production created from the advancement in longwall equipment, dust loads have significantly increased and this has resulted in a potentially greater exposure level to personnel. Metropolitan Colliery, located at Helensburgli in NSW, Australia, in conjunction with the University of Wollongong, P11/116 Laboratories and EnviroCon, has implemented a dust reduction program Utilising a recently developed Dust Mitigation Efficiency Model to quantify dust loads produced during the cutting cycle. With the quantification of.this benchmark dust load production along with the quantification of installed control efficiencies at independent sources of dust generation, Metropolitan Colliery, with the installation of the latest shearer scrubber technology has successfully reduced the respirable dust levels in excess of 70% of benchmark levels on their operating Iongwali This reduction will have a significant and immediate positive effebt on employees, production and operating costs which will be maintained throughout the life of the mine

A critical evaluation of dust sampling methodologies in Longwall Mining in Australia and the USA

Questions relating to the validity and subsequent suitability of the current dust sampling methodologies utilised in Australia and the USA have recently come under scrutiny. The reason for this scrutiny is that there has been a significant increase in Coal Workers‟ Pneumoconiosis in the USA over the last few years despite recorded conformance to exposure level legislation. The opinion by many in the underground coal mining operators in Australia is that the current testing regime tells them very little about the actual operational production of dust on the longwall face in relation to where it is produced, how much is produced or how efficient installed controls are at preventing this dust from entering the atmosphere. Evaluation of the current testing regimes in Australia and the USA are proposed, which identify limitations that are raising questions relating to its suitability to ensure worker health in the underground coal mining operator

Design and field trials of water-mist based venturi systems for dust mitigation on longwall faces

Dust generation from longwall chock movement and the Beam Stage Loader/crusher (BSL) is a major source of air contamination on modern longwall faces. If not controlled effectively, much of these respirable dust particles would disperse quickly into the longwall due to high face ventilation velocities, contributing significantly to higher dust levels. A new water mist based venturi system has been developed for the purpose of suppressing respirable dust from longwall chock movements close to the maingate (MG). The unit is powered by compressed air and water using an ultrasonic nozzle embedded in a venturi body. The ultrasonic nozzle is capable of producing ultra fine water mist with droplet sizes ranging from 1 to 100 μm. Laboratory tests indicate that the ultrasonic nozzle (MAL-1300-B), when combined with a 70 mm (diameter) x 143 mm (length) venturi body, was can produce an optimum spray covering a distance over 10 m. Further tests show that a combination of air supply at 6 bar and water at 4 bar produces the optimum water mist thrust with inducted air velocity over 8 m/s. The venturi system was built as a stand alone unit using fire resistant and antistatic materials and can be easily hooked under the chock canopy with a magnetic base. The system can be powered by compressed air and water supplied to the longwall face and adjusted with the spray angle to achieve the droplet size and velocity needed for dust suppression and diversion. Computational Fluid Dynamics (CFD) modelling was undertaken to gain a better understanding of face ventilation and dust flow patterns to optimise the spray orientation of the venturi system for field trial installation. CFD modelling results show that the operating conditions of sprays with the best mitigation performance vary according to the source of dust, a better dust mitigation effect can be achieved when the venturi units on longwall chock are installed at 20o down towards the floor and tilted 45o along the face. Field trials were conducted at two underground longwall mines in QLD and NSW. Three venturi units were installed on Chock No 6 on the longwall with an additional unit trialled at the BSL to mitigate dust from longwall outbye. Dust measurements with real time monitoring Personal Dust Monitor (PDM) and gravimetric samplers indicate dust mitigation efficiency up to 30% has been achieved in both trials

Respirable and inhalable dust measurement and control efficiency determination in high production longwalls

Dust sampling in Australian coal mines is carried out with cyclone separation and collection of the sized particles for weighing, generally over the period of a full shift to measure personal exposure levels to airborne contaminants of employees. This testing methodology is described in AS2985 for determination of respirable dust and AS3640 for inhalable dust. These testing methodologies give an accurate figure for the personal dust exposure levels of employees for the period sampled, but cannot be related to any specific longwall operational sources of dust generation or to the efficiency of dust mitigation controls installed at those sources. Fugitive dust on longwalls has always been an issue of concern for production, safety and the health of workers in the underground coal mining industry both in Australia and globally. Longwall personnel can be exposed to harmful respirable and inhalable dust from multiple dust generation sources including, but not limited to: intake entry, belt entry, stageloader/crusher, shearer, and chock advance. With the increase in production created from the advancement in longwall equipment, dust loads have also increased and this has resulted in an increase in exposure levels to personnel. The main objective of this thesis was to develop a new dust monitoring methodology to quantify and document both respirable and inhalable dust magnitudes generated from different sources, and assess the efficiency of installed controls for the mitigation of produced dust, using gravimetric sampling as per statutory requirements. The resulting Dust Mitigation Efficiency (DME) model has been developed to identify respirable and inhalable dust loads at independent sources of dust generation on longwall faces and quantify the efficiency of installed controls for the mitigation of this produced dust. The DME model will shed some fundamental and scientific insights into an area of genuine concern to the mining community and will enhance the current practices of statutory dust monitoring. It will also offer a significant benefit to the coal mining industry by providing a benchmark or signature dust load monitoring procedure along with the implementation of quantified best mitigation practices. The DME model has been used to identify respirable and inhalable dust loads at independent sources of dust generation on longwall faces and quantify the efficiency of installed controls for the mitigation of this produced dust. The data collected from each of the sampled mines during the field trials has been used to create a benchmark or signature for each longwall of those mines in relation to dust loads from different sources of generation to ensure maximum efficiency in removing respirable and inhalable dusts. The DME model has also successfully identified the most efficient installed engineering controls operating at individual sources of respirable and inhalable dust generation on operating longwalls in Australia. The use of the DME model as opposed to the statutory measurement process will allow mine operators to establish a dust mitigation regime based on the measured best practice for installed engineering controls. A total of 360 samples were taken for data analysis to quantify the robustness of the DME model and determination of the best practice engineering controls. Of these, 190 were respirable samples and the remaining 170 were inhalable samples. With the DME model, it is envisaged that a greater reduction in both respirable and inhalable dust can be achieved with best practice engineering, which will have a direct reduction in exposure levels to workers on the face and significantly reduce the risk of lung disease in employees. The establishment of the DME model for respirable and inhalable dust load identification and control efficiency determination has shown to be a valuable and robust informational tool that will have a significant benefit to not only the underground coal industry, but all industries that are affected by airborne contaminants less than 10 m in size (PM10). The ability to understand the actual dust production, coupled with the quantification of performance of installed engineering controls for dust mitigation, will give all operators of dust producing activities a valuable tool to better control their airborne contaminants. It is suggested that further studies be undertaken to include; - the use of Personal Dust Monitors (PDM’s) for data collection with the DME model used to calculate efficiencies; - use of the DME model to better understand respirable and inhalable dust production and control in development panels and bord and pillar mining; - medical research be conducted to understand how much respirable and inhalable dust is actually required to be ingested to create medical problems, and; - comprehensive research into the accuracy of current exposure level limits and their suitability to the continually increasing production in the global mining industry. By better understanding respirable and inhalable dust production and application of a best management practice to mitigate airborne contaminants, a significantly healthier workplace and environment will be achieved

A Critical evaluation of dust sampling methodologies in Longwall Mining in Australia and the USA

Questions relating to the validity and subsequent suitability of the current dust sampling methodologies utilised in Australia and the USA have recently come under scrutiny. The reason for this scrutiny is that there has been a significant increase in Coal Workers‟ Pneumoconiosis in the USA over the last few years despite recorded conformance to exposure level legislation. The opinion by many in the underground coal mining operators in Australia is that the current testing regime tells them very little about the actual operational production of dust on the longwall face in relation to where it is produced, how much is produced or how efficient installed controls are at preventing this dust from entering the atmosphere. Evaluation of the current testing regimes in Australia and the USA are proposed, which identify limitations that are raising questions relating to its suitability to ensure worker health in the underground coal mining operators

Dust controls and monitoring practices on Australian longwalls

Fugitive dust on longwalls has always been an issue of concern for production, safety and the health of workers in the underground coal mining industry globally. Longwall personnel can be exposed to harmful dust from multiple dust generation sources. With the increase in production created from the advancement in longwall equipment, dust loads have also increased and this has resulted in an increase in exposure levels to personnel. Control processes in place for the mitigation of dust vary from mine to mine, with each individual mine having a dust mitigation setup that is only effective for that particular mine operation. While the focus in the past has quite correctly been on improving the controls on dust exposure, the future lies in identifying the efficiency of installed controls on operating longwalls, evaluating them through robust and quantitative sampling methods to ensure the most effective controls are in place to prevent occupational disease from occurring. This paper will examine the current controls for dust mitigation on longwalls and propose a new testing methodology to determine dust mitigation efficiency (DME) of installed controls for both respirable and inhalable dust. The main objective of this proposed sampling method is to identify dust loads at independent sources of dust generation in mg/tonne produced on longwall faces and quantify the efficiency of installed controls for the mitigation of produced dust on longwall faces

Dust Monitoring and Control Efficiency Measurement in Longwall Mining

Occupational hygiene has been an integral part of the mining industry for centuries; however its importance has grown with developments in mechanisation. While the focus in the past has quite correctly been on improving the controls on dust exposure, the future lies in identifying the efficiency of installed controls on operating longwalls, evaluating them through robust and quantitative sampling methods to ensure the most effective controls are in place to prevent occupational disease from occurring. The current statutory testing regime identifies the exposure levels of personnel on an operating face, which gives a snapshot of the dust that these persons will be exposed to over the duration of a mining shift. Although this testing process clearly determines exposure levels, it does not give mine operators any indication of where dust is produced, how much dust is produced nor how efficient the installed controls are at mitigating produced dust. This paper proposes a new testing methodology to determine installed control efficiency for both respirable and inhalable dust and reports the initial dust measurement results based on this methodology. The main objective of this sampling method is to identify dust loads at independent sources of dust generation on longwall faces and quantify the efficiency of installed controls for the mitigation of produced dust. The use of this new methodology will provide mine operators with a complete dust production signature of their operating longwall and allow the implementation of more efficient controls at independent sources of dust generation

Dust monitoring and control efficiency measurement in longwall mining

Occupational hygiene has been an integral part of the mining industry for centuries; however its importance has grown with developments in mechanisation. While the focus in the past has quite correctly been on improving the controls on dust exposure, the future lies in identifying the efficiency of installed controls on operating longwalls, evaluating them through robust and quantitative sampling methods to ensure the most effective controls are in place to prevent occupational disease from occurring. The current statutory testing regime identifies the exposure levels of personnel on an operating face, which gives a snapshot of the dust that these persons will be exposed to over the duration of a mining shift. Although this testing process clearly determines exposure levels, it does not give mine operators any indication of where dust is produced, how much dust is produced nor how efficient the installed controls are at mitigating produced dust. This paper proposes a new testing methodology to determine installed control efficiency for both respirable and inhalable dust and reports the initial dust measurement results based on this methodology. The main objective of this sampling method is to identify dust loads at independent sources of dust generation on longwall faces and quantify the efficiency of installed controls for the mitigation of produced dust. The use of this new methodology will provide mine operators with a complete dust production signature of their operating longwall and allow the implementation of more efficient controls at independent sources of dust generation

A scientific approach to quantifying the efficiency and efficacy of dust curtains on a Sandvik mb650 continuous miner at kestrel colliery whilst mining a full face of roof stone during an overcast construction

With the correct identification and continued increase in CWP and related occupational lung disease in the Australian coal mining industry since May 2015, the industry’s focus has been directed at mining operations achieving statutory respirable dust level compliance to AS2985. The majority of dust control techniques currently installed and operational in Australian coal mines have been developed in the USA, UK and other western countries and their application is more suited to low to medium coal seam heights up to 3m. The Australian mining experience has indicated that the efficiency of some of the existing respirable dust control methods reduce significantly in thick coal seams, under high production environments and when mining roof stone. As the current trend in the industry is to substantially increase production levels, there is an urgent need for detailed investigation of various dust control options and development of appropriate dust management strategies based on quantifying the efficiency and efficacy of installed controls to mitigate respirable dust from the working environment. This paper details the approach taken to quantify the efficiency and efficacy of installed face curtains for respirable dust mitigation on a Sandvik MB650 continuous miner whilst mining a full face of roof stone cutting an overcast in the mains at Kestrel Colliery. Results of the project have shown that the installed face curtains are not suitable as a dust mitigation control

Dust monitoring and control efficiency measurement in longwall mining

Occupational hygiene has been an integral part of the mining industry for centuries; however its importance has grown with developments in mechanisation. While the focus in the past has quite correctly been on improving the controls on dust exposure, the future lies in identifying the efficiency of installed controls on operating longwalls, evaluating them through robust and quantitative sampling methods to ensure the most effective controls are in place to prevent occupational disease from occurring. The current statutory testing regime identifies the exposure levels of personnel on an operating face, which gives a snapshot of the dust that these persons will be exposed to over the duration of a mining shift. Although this testing process clearly determines exposure levels, it does not give mine operators any indication of where dust is produced, how much dust is produced nor how efficient the installed controls are at mitigating produced dust. This paper proposes a new testing methodology to determine installed control efficiency for both respirable and inhalable dust and reports the initial dust measurement results based on this methodology. The main objective of this sampling method is to identify dust loads at independent sources of dust generation on longwall faces and quantify the efficiency of installed controls for the mitigation of produced dust. The use of this new methodology will provide mine operators with a complete dust production signature of their operating longwall and allow the implementation of more efficient controls at independent sources of dust generation