High-temperature-high-pressure cascade impactor design, performance, and data analysis methods

A high-temperature - high-pressure, seven-stage cascade impactor has been designed, built, calibrated, and used to obtain size-classified samples of entrained fly ash from process streams of a pressurized low Btu coal gasifier. The cascade impactor was designed for an effective cutoff diameter (ECD) range of 12 ..mu..m down to about 0.5 ..mu..m aerodynamic diameter. Methods for calculating gas mixture viscosity, density, and mean free path have been developed and used to calculate impactor stage characteristics at operating temperatures and pressures for the gas mixture sampled. Process stream conditions were 400 to 700/sup 0/C and 900 to 1370 kPa. The measured size distribution at stream conditions indicated a mass median aerodynamic diameter (MMAD) of 2.88 +- 0.47 ..mu..m with a geometric standard deviation (sigma/sub g/) of 2.35 +- 0.35.