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A laboratory-scale apparatus has been used for unattended, long duration, continuous flow through testing of a vacuum formed chopped ceramic fiber filter under reducing conditions at atmospheric pressure. Four candle specimens were exposed from 150 to 3550 h to 600°C gas containing 4 percent CO, 11 percent H2, 12 percent CO2, 14 percent H2O, 59 percent N2, 1 ppmv NaCl, 50 ppmv H2S, and 1000–2000 ppmw ash from a transport reactor operated in gasification mode. A database was established on pressure drop of the as-received and exposed filter as a function of face velocity and temperature. Tests were conducted to investigate the effects of back-pulse parameters on filter regenerability. Results are reported on the critical reservoir pressure and pulse duration for maintaining a stable saw-tooth profile of pressure drop across the filter element. Data are obtained to characterize the effect of chemical and thermal aging on the apparent bulk density of the filter, pore size distribution, fast fracture strength, and microstructure. It is suggested that the compliant filter undergoes a slow process of rigidization upon exposure to the test environment.

An electrostatic powder dispenser was constructed to dispense particles without the use of a carrier gas. This device consisted of two contoured, outer stainless-steel plates that were electrically grounded and a fiat, inner copper grid that was electrified and contained a central powder reservoir. Experiments were performed to investigate the levitation of various powders from the reservoir in the presence of an applied de electric field. Eleven materials including metals, oxides, and conductively coated oxides were studied under vacuum and atmospheric conditions, The electric field required to remove particles from the powder reservoir was found to be a function of particle density and size. An equation was developed that predicted the minimum voltage necessary to remove conductive particles larger than 10 lJ,m in diameter from a conductive surface in a vacuum environment: E = [4.85 (pD) 112 + 0.362] X 10 5 , where E is the field strength (V !m), p is the particle density (kg/m 3 ), and D is the mass median particle diameter (m). For particles in this size range, gravitational and electrostatic forces appeared to dominate, whereas for particles with a mass median diameter less than 10 flm, adhesive forces appeared to dominate. This equation was also found to hold for the removal of glass beads in air. A semiquantitative model was developed that was consistent with experimental results. This model calculated the force and charge induced on the particles in an electric field while taking into account the neighboring particles. 3242