Experimental study of drag characteristics and dust removal performance of a hybrid wet-filter precipitator

With their advantages of high dust removal efficiency and low drag characteristics, hybrid wet-filter precipitators have great potential for dust control in coal mines, but the underlying mechanisms are not well understood. In this study, to help fill this knowledge gap, a hybrid wet-filter precipitator consisting of a 40-layer metal filter and a defogger device is designed and a prototype is constructed. Experiments are conducted to investigate its drag characteristics under wind velocities from 0.85 to 5.68 m/s and its dust removal performance under wind velocities of 2 and 4 m/s. On the basis of results with the initial design, which show that the dust removal efficiency does not meet the target value of 99%, two rounds of improvement are implemented to enhance the dust removal efficiency. Results show that the defogger device contributes ∼80% of the total drag. The drag from the metal filters is found to increase by over 80% on average after sampling, since some of dust particles are left on the filters, decreasing their porosity. The installation of two-layer air filters on the leeside of the metal filter unit is found to increase the efficiency to 99.89% and 99.80% under wind velocities of 2 and 4 m/s, respectively, although this is at the cost of increased drags. Additionally, it is found that the replacement of the defogger by a 20-layer metal filter is not desirable, since this increases the downstream air humidity to more than 100%, which can cause damage to the centrifugal blower system. Therefore, new designs for the defogger device need to be examined in future studies.