Mining Project: Developing and Improving Respirable Dust Controls in Coal Mines

Research Summary

Flooded-bed scrubbers and water sprays are used to control respirable dust in the underground environment. Both the Mine Safety and Health Administration (MSHA) and the National Institute for Occupational Safety and Health (NIOSH) have identified instances of poor dust control due to inadequate spray operation and loss of flooded-bed scrubber airflow on continuous mining machines (CMMs). Research is needed to evaluate common dust controls, including water sprays and surfactants, flooded bed scrubbers, and foam, to develop improvements for respirable dust control, with emphasis on RQD. Advances in each of these areas can contribute to the reduction of silicosis in the U.S. mining workforce, which is thought to be the current source of the resurgence of the prevalence of coal workers’ pneumoconiosis (CWP). CWP occurs through exposure to respirable coal dust (RCMD) while silicosis occurs through exposure to RQD dust, with both dusts consisting of airborne dust particles less than 10 µm in size.

This project will evaluate different water sprays for their airflow induction and airborne respirable dust capture capabilities on RQD. Using water sprays with specific properties for airflow induction and airborne dust capture and applying them to appropriate situations can lead to lower exposures to RQD dusts and thereby reduce the occurrences of CWP and silicosis. Testing the addition of surfactants to water sprays will be conducted to determine optimum parameters for the type of spray, water pressure, type of surfactant, etc. The evaluation of the flooded bed scrubber, used on CMMs to improve their performance for airborne dust capture, through re-evaluation of scrubber flow design, redesign of filter, re-configuration of filter arrangement, evaluation of surfactant use, etc. will also help researchers to address CWP and silicosis. The use of foam for longwall shield dust control and other respirable dust generation sources is another area of interest in the mining industry for improved dust control. Higher dust capture with the use of a lesser amount of water, especially in areas where water is a limited resource, can be advantageous for reducing the occurrences of CWP and silicosis.

This project research will address this need by way of three research aims and related tasks, as summarized below.

1. Examine and evaluate water spray systems for knockdown performance on RQD and the use of additives to improve airborne capture. Water spray nozzles will be tested in the laboratory for airflow induction using a water spray nozzle air induction measurement device. Testing will also be conducted to measure dust capture of different nozzles. Parameter to be evaluated are spray nozzle type, water pressures, water additives and dust composition. Computer models of airflow induction and dust capture of different spray nozzle types will be created, and simulations will be run to determine optimal water spray use in a water powered scrubber design.
2. Examine and evaluate flooded-bed scrubber systems to improve operation and develop associated techniques to maintain and/or restore performance when subjected to both RCD and RQD. In-mine studies will collect clogged filter panels for further analysis along with data collected about production and the mine environment (depth of cut, material mined, face ventilation, the amount of time filter was in-place since last cleaned, etc.). A series of laboratory evaluations will repeatedly load an original equipment manufacturer flooded-bed scrubber with synthesized feed dust material to match the composition of the material found in clogged filters. Dust sampling before and after the filter panel will determine the dust collection efficiency. Tests will vary the filter construction, filter arrangements, etc. Additional modifications varying the spray nozzle operation, the number of filter panels installed in series, and the use of surfactants will be completed. The effects of the differing parameters on airflow will be monitored. The highest performing configurations will be installed in a production CMM for field evaluation. It is anticipated that these controls will be compared to an unmodified CMM in the same super-section.
3. Evaluate aqueous foams to control dust emissions resulting from longwall shield movement, surface blasthole drilling, and the operation of stageloaders/crushers. Laboratory tests will evaluate the foam properties of newly constructed field-deployable foam generators. Subsequent field studies will compare airborne dust levels following the application of foam to those measured during the use of either no dust control or the use of an existing water-based control.

Outcomes from this project research will contribute to coal mine operators adopting control interventions, such as technologies and work practices, to reduce overexposure to RCD and RQD. Further, this project specifically targets those coal mining occupations with the highest exposures to RQD. Industry adoption of improved technologies and practices derived from this project will result in improved mine environments that will reduce the respirable dust exposure of mine workers and minimize the burden of detrimental health effects from respirable dust overexposure. Development of these technologies will also be of interest to many other dust-producing industries, such as construction and agriculture, as they may benefit by adapting the controls to their applications.