Mass transfer electrostatic precipitation

Semidry Scrubbers The advantage of semidry scrubbers is in that they remove contaminants by way of a solid waste that is easier to dispose of (less expensive). Initially, the scrubbing medium is wet (such as a lime or soda ash slurry). Then a spray dryer is used to atomize the slurry into the gas which evaporates the water in the droplets. As this takes place, the acid in the gas neutralizes the alkali material and forms a fine white solid. Most of the white solids are removed at the bottom of the scrubber while some are carried into the gas stream and have to be removed by a filter or electrostatic precipitator (discussed later). Although semidry systems cost 5-15% more than wet systems, when combined with a fabric filter, they can achieve 90-95% efficiencies. Dry scrubbers are sometimes used in a very similar fashion, but without the help of gas-liquid-solid mass transfer, these systems use much higher amounts of the solid alkali materials. 

The MIS consists of a 16-foot rotary kiln with a dual refractory lining. This is connected to an 18-foot by 50-inch-diameter cyclone, which feeds into a secondary chamber (42 feet long by 52 inches i.d.) and quench sump. The exhaust then enters a wet electrostatic precipitator which is 40 feet high with a cross section that is 84 inches by 84 inches. The final unit is a mass transfer scrubber 8 feet long by 5 feet high. 

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