Influence of section return dust levels as an exposure indicator and assessment parameter of engineering control in coal mines

摘要

Return air quantity and quality in an underground mine section are important indicators of both ventilation effectiveness as well as the environmental control systems in place in the section. From an explosion control perspective, high return air dust levels indicate the possibility of a large amount of dust being deposited in the return way, thereby aiding the catastrophe in the event of an explosion. This parameter can be effectively used to monitor the occupational health and safety of workers in the mine. The history of return dust measurement originates from the United Kingdom in the 1970s. To assess the dust conditions at the workplaces in the face, measurements were carried out using fixed-point sampling located in the return airways approximately 70 m behind the face. The reason for this choice of location was that the results are no longer influenced by the coarse dust or the unequal distribution of the respirable dust in the air. This paper highlights the data on return dust levels measured worldwide that were available from the literature and the section return dust levels measured in South African underground coal mining sections. The average sampling period of all section return samples was 336 minutes and the average return dust level for the sampling period was 2.36 mg/m~3. Some of the high dust levels measured was due to the application of stone dusting during the beginning or in the middle of the shift. The dust samples, which were tainted by the stone dust, were nearly 4% of the total return dust samples collected and were significantly greater than 2 mg/m3. It must be noted that, unlike in the past, in the existing operating coal mines workers generally do not spend any time in the section return. The return dust level can be easily monitored using real-time fixed point or area monitors (where the movement of machinery is limited) and requires limited human intervention. The intention to use the return dust levels is that they can be used to indicate the exposure levels of the section workers to coal dust and the effectiveness of the ventilation system and the dust control system. The application of return dust level as an exposure parameter is discussed to judge a coal section for various identified parameters influencing dust exposures.