Permeation Behavior of Oxide Bonded SiC Ceramics at High Temperature and Prediction of Pressure Drop in Candle Filters

Oxide-bonded silicon carbide supports of porosity ranging from 33% to 47% were prepared by heating powder compacts (SiC, clay and alumina) at 1400 degrees C in air with graphite acting as a pore former. The supports were spray-coated with an aqueous slurry of fine SiC powder (d(50)=15 mu m), then sintered to produce a filtering layer with thickness ranging from 116 to 200 mu m and average pore size ranging from 5 to 20 mu m. Airflow tests were performed on both supports and coated filters at temperatures ranging from 25 degrees to 700 degrees C and superficial velocities ranging from 0.02 to 0.9 m.s(-1). Experimental permeability coefficients were used to simulate the pressure drop behavior of hypothetical candle filters for industrial combustion/gasification processes (biomass combustion in water-tube steam boilers (BCSB), pressurized fluidized-bed combustion (PFBC) and integrated gasification combined cycle (IGCC)). The simulated permeation properties of the hypothetical candles were compared to those of commercial hot gas filters.