Role of porosity in dust cleaning of silicon carbide ceramic filters

Silicon carbide ceramic filters consisting of highly porous support and fil tration layer were fabricated by cold isostatic pressing. The porosities of the supports were varied near the percolation threshold, 28.7, 33.7 and 35 .8%. The silicon carbide layer with a finer pore size was coated on the sup ports to collect dust particles. The pressure drop (JP) was measured at var ious face velocities, dust loadings, and operation times. The separation ef ficiency was calculated by measuring the dust concentrations at the inlet a nd outlet of the filter vessel, and the cleaning efficiency was calculated by comparing the pressure drops before and after back-pulse cleaning. The r esults indicate that higher porosity of the filter support is favorable for preventing an increase of pressure drop and for improving cleaning efficie ncy. As the porosity in the silicon carbide filter support increased from 2 8.7% to 35.8%, the pressure drop decreased by as much as 30%. Most of dust particles were collected by the finer pores in the coating layer with effic iencies > 99.9%. Additionally, better cleaning efficiency was obtained at h igher porosity. The values of flexural strengths of the filter supports wer e over 20 MPa even though a lower value was found at high porosity.