Influence of water evaporation on dust minimisation efficiency using enclosed water spraying systems

Dust minimisation with water spraying resonance nozzles in enclosed hand over points stand out due to advantageous low water consumption, but the evaporation of water droplets can strongly reduce the water flow remained for dust precipitation. A model and a calculation method were worked out, by which the loss of water due to evaporation can be calculated. The dust suppression mechanism during water spraying can be divided into the moistening of the bulk solids, which prevents dust generation and the precipitation of the still generated dust by water droplets. The precipitation of the generated dust was experimentally investigated at a lab- scale test equipment and the fractional efficiency and the PM10 separation efficiency were determined. Further, the sum of PM10 separation efficiency of moistening and precipitation of the water spray was experimentally investigated at a lab- scale bulk solids falling apparatus and usable model equations for estimation of dust minimisation efficiency were developed. It can be stated that the moistening of the bulk solids compared to the dispersed dust particle precipitation has the predominant influence on dust minimisation. Further the established model equations can be a tool for optimal design of water spraying dust minimisation devices.