Evaluate fundamental approaches to longwall dust control: Subprogram H, Air canopies for longwalls

This report describes the laboratory development and evaluation of an air canopy concept for longwall faces. The objective in an underground application would be to create a clean air zone along the face walkway by equipping the shields with water-powered scrubbers or other devices. Contaminated air would be extracted, cleaned and reinjected into the breathing zone of face personnel. The concept was evaluated in a full scale longwall test facility by equipping alternate shields with simulated air canopies. A variety of canopy configurations and airflow capacities were tested under different face ventilation situations to determine the quality and extent of the clean air zone developed by the canopy. The results revealed that even the most optimum configurations were unable to create a suitable clean air zone. Low effectiveness, coupled with high projected costs for underground application, showed the concept to be unfeasible and further development effort was cancelled. 21 figs.