Electrostatic Enhancement of Fabric Filtration of Fly Ash and Spray Dryer By-Product

摘要

The paper describes small pilot-scale experiments, showing that the pressure drop increase during the fabric filtration of redispersed spray dryer by-product (chiefly calcium salts and fly ash) is significantly reduced by electrostatic enhancement of the filtration. The pressure drop rise for a typical electrostatically augmented fabric filtration (ESFF) is only 25% or less of that of the rise for a conventional filtration cycle. The ESFF takes advantage of the electrical characteristics of the spray dryer by-product, specifically the higher natural electrical charge, as compared to fly ash, and the relatively lower electrical resistivity of the spray dryer by-product at the high moisture and the low temperature conditions of filtration of spray dryer by-product. The low resistivity of the spray dryer by-product and certain fly ashes allows application of high corona voltages in the new Center-wire ESFF to produce an even slower pressure drop increase over the filtration cycle. Center-wire ESFF proved to be operable under conditions of high gas velocities and grain loadings which were beyond the range for successful conventional reverse-air fabric filtration. Results of tests on the Center-wire ESFF are presented and compared with conventional fabric filtration.