Dust Control on Longwall Faces by Fine Mist (Atomising) Sprays - Can They Really Work?

The ongoing efforts to suppress dust emissions from longwall face shearing and transporting operations have met with varying degrees of success. A particular of concern has been the thicker, gas drained seams where both respirable and combustible fallout dust production has not always met with successful suppression methods using water spray system. There are current programs planning to use very fine atomising sprays that give a water droplet size approaching the respirable dust particle size, and mines are waiting to see how well these systems will work. Some peripheral science such as fluid mechanics and aerodynamics are discussed to determine whether other factors are present that may inhibit the ability of water spray systems to successfully reduce fine dust emissions to acceptable levels. It appears from the initial investigation that water droplets cannot capture all the dust particles generated during coaling operations, and that chemical additives to the spray water may also be limited in their success. The paper also looks at possible methods to better suppress dust, and suggests that far more research and engineering may be warranted. In particular the risks from use of ultra fine water droplets for longwall dust suppression may in fact have health risks that outweigh any potential benefits.