31 FILTERS AND FILTERING APPARATUS, PARTICULARLY FOR THE PURPOSE OF REMOVING DUST, FUMES, NOXIOUS GASES AND FOR THE PURPOSE OF REMOVING AND/OR TRANSFERRING HEAT TO AND FROM THE FILTERED LIQUID OR GAS, AND OTHER MECHANICAL DUST AND GAS SCRUBBERS AND HEAT EXCHANGERS FOR INDUSTRIAL AND PYROMETALLURGICAL APPLICATIONS, AND PARTS AND ACCESSORIES THEREFOR