SEPARATION OF FINE PARTICLES FROM GAS STREAMS BY CONDENSATIONAL GROWTH

A NUMBER OF INDUSTRIAL PROCESSES, INCLUDING INCINERATORS AND METALLURGICAL PROCESSES, TYPICALLY EMIT LARGE NUMBERS OF FINE PARTICLES. MEASUREMENTS AT AN OPERATING SEWAGE SLUDGE INCINERATOR HAVE SHOWN THAT HEAVY METALS (INCLUDING CADMIUM, CHROMIUM, NICKEL, LEAD, AND ZINC) ARE CONCENTRATED IN THE FINE PARTICULATE (APPROXIMATELY 0.25 MUM) LEAVING THE INCINERATORS. VENTURI SCRUBBERS HAVE BEEN TYPICALLY INSTALLED TO REMOVE PARTICULATE FROM THESE FLUE GAS SOURCES. THESE SCRUBBERS, BY THEMSELVES, ARE NOT CAPABLE OF REMOVING PARTICLES SMALLER THAN ABOUT 0.5 MUM. ABOVE 1.0 MUM, VENTURI SCRUBBERS CAN HAVE A HIGH COLLECTION EFFICIENCY. RESEARCHERS ARE STUDYING THE USE OF THE SUBMICRON PARTICULATE PENETRATING THE VENTURI SCRUBBER AS CONDENSATION NUCLEI FOR STEAM INJECTED INTO THE FLUE GAS TO SUPERSATURATE IT WITH WATER VAPOR. THEORETICAL ANALYSES SHOW THAT WATER DROPLETS AS LARGE AS 1.0 MUM CAN BE PRODUCED WITH REASONABLE STEAM RATES AND CONTACT TIMES. THESE WATER DROPLETS (A DILUTE SUSPENSION OF THE FINE PARTICULATE) ARE REMOVED FROM THE FLUE GAS STREAM WITH A HIGH EFFICIENCY MIST ELIMINATOR AND DRAINED TO THE SCRUBBER SUMP. PRELIMINARY ANALYSES HAVE SHOWN THAT HEAVY METALS IN THE FINE PARTICULATE LEAVING THE VENTURI SCRUBBER CAN BE REDUCED BY 90 PERCENT USING THIS PROCESS.