DURABLE, LOW COST CERAMIC MATERIALS FOR USE IN HOT GAS FILTRATION EQUIPMENT

CERAMIC CANDLE FILTERS HAVE PROVED TO BE EFFECTIVE FOR REMOVING PARTICULATES TO LEVELS EXCEEDING NEW SOURCE PERFORMANCE STANDARDS IN HIGH TEMPERATURE APPLICATIONS. HOWEVER, THE TRADITIONAL "HARD" CERAMIC FILTER ELEMENTS, FORMED TYPICALLY FROM GRANULES OF SILICON CARBIDE, MULLITE, ETC., HAVE BEEN SHOWN TO BE SUSCEPTIBLE TO FAILURE FROM PHYSICAL SHOCK, THERMAL STRESS, AND CHEMICAL ATTACK. IN ADDITION, THESE HARD, DENSE CANDLES CAN BE COSTLY AND CAN CAUSE INTERNAL FILTER DESIGN PROBLEMS BECAUSE OF THEIR RELATIVELY HIGH WEIGHT. UNLIKE THE DENSE, GRANULAR CERAMIC FILTER ELEMENTS, VACUUM-FORMED CHOPPED CERAMIC FIBER (VFCCF) FILTERS REPRESENT AN ATTRACTIVE ALTERNATIVE. BECAUSE VFCCF FILTERS ARE MADE FROM COMMERCIALLY AVAILABLE CHOPPED CERAMIC FIBERS AND UTILIZE EXISTING VACUUM-FORMING MANUFACTURING TECHNOLOGY, IT IS POSSIBLE TO PRODUCE THEM AT A LOW COST AND WITH EXCELLENT PHYSICAL AND THERMAL SHOCK RESISTANCE. THE CERAMIC FIBER SKELETON CAN BE FURTHER POST-TREATED WITH REFRACTORY MATERIALS TO ENHANCE STRENGTH AND CHEMICAL RESISTANCE AND CHANGE PERMEABILITY TO SUIT A PARTICULAR APPLICATION. ALSO, BECAUSE THE CERAMIC FIBER SKELETON HAS GREATER POROSITY AND IS COMPOSED OF LOW DENSITY MATERIALS, THE FINAL PRODUCTS ARE SIGNIFICANTLY LIGHTER IN WEIGHT THAN THE TRADITIONAL DENSE CERAMIC ELEMENTS, MAKING OVER-ALL FILTER DESIGN AN EASIER TASK. PHASE I STUDIES INCLUDE INVESTIGATIVE EFFORTS ON BOTH VFCCF FILTER CANDLES AND VFCCF FILTER TUBE SHEET COMPONENTS. CANDIDATE FILTER ELEMENTS ARE BEING PREPARED, POST-TREATED WITH SELECT COATINGS, AND TESTED TO OPTIMIZE PHYSICAL STRENGTH AND PERMEABILITY. PROTOTYPE VFCCF FILTER TUBE SHEET COMPONENTS ARE ALSO BEING TESTED FOR STRENGTH IN A SIMILAR FASHION.