The report gives results of an evaluation of the Johns-Manville CHEAF system for controlling particulate emissions. Fine particulate collection efficiency as a function of dry particle size was computed from data taken on the CHEAF system, a system used to control emissions from a diatomaceous earth calcining and drying process with an overall collection efficiency of 95%. The unit was operating at a capacity of 710 A cu m/min (25,000 acfm), at 63C (145F), with a pressure drop of approximately 50-53 cm (19.5-21 inches) water column. Initial tests showed inlet and outlet size distributions to be identical with a mass mean diameter of 0.82 micrometers A and a geometric standard deviation of 3.9. The data analysis indicates that particle penetration is relatively independent of particle diameter. Further tests revealed that particle growth occurs prior to the CHEAF system. Simultaneous heated and unheated impactor runs provided dried particle size distribution and actual (or wet) size distribution existing inside the scrubber, respectively. Particle growth was then determined, showing that particles grew as much as three times their original size in the submicron range, and less for larger sizes. This particle growth to a more uniform size can explain why penetration is relatively independent of inlet dry particle size.

Prepared by Air Pollution Technology, Inc., San Diego, California, under contract no. 68-02-1496, ROAP no. 21ADL-004, program element no. 1AB-12. Includes appendices. "EPA/650-2-75-058a." "July 1975."