Filtration of underground ventilation air by wet dust-scrubbing.

The possible use of wet dust scrubbing methods for the control of dust in the recirculation of underground ventilation air is examined. A theoretical model is developed that describes the combined effects of dust filtration and recirculation on dust concentrations in a working area. Conclusions drawn from the model, and measurements of the quartz particle size distribution in underground airborne dust, are used to estimate the required dust filtration efficiencies that would ensure acceptable dust concentration in a recirculation system. The dust filtration characteristics of a typical direct contact spray bulk air cooler are described. It is shown that such a cooler is incidentally capable of removing large dust particles, but is relatively ineffective in removing dust particles in the respirable size range. A laboratory investigation into the dust scrubbing characteristics of a spray cooling chamber consisting of a bank of atomizing nozzles situated upstream of a set of air cooling type spray nozzles is described. The measured dust collection efficiencies are compared with the required efficiencies predicted by the model. It is concluded that wet dust scrubbing may well be effective in controlling dust concentration in South African gold mines. (A)