FILTER APPARATUS AND METHOD FOR COLLECTING FLY ASH AND FINE DUST

A-3374 IN THE UNITED STATES PATENT AND TRADEMARK OFFICE Inventors: Karim ZAHEDI and Jeffrey C. ALEXANDER Title: FILTER APPARATUS AND METHOD FOR COLLECTING FLY ASH AND FINE DUST Fly ash and fine dust in a gas stream from a coal combustor, for example, are efficiently collected in a 2-stage, tubular, granular bed filter. The stages of the filter are arranged one above the other so that the granules may move from the upper stage to the lower stage under the influence of gravity. Larger particulate in the gas stream is first collected by the lower stage, and then the remaining particulate is electrically charged and collected by the upper stage. Both stages are electrified sufficiently to rigidify the granular beds and adhere the particulate to the granules, so that the granules and the collected particulate move downwardly through the filters as a plug. Granules that exit from the lower stage are cleaned and returned to the upper stage. Non-porous granules may be used to prevent fine particulate from becoming embedded in the granules.