C OMBINATION D EVICES - L IQUID -P HASE AND G AS -P HASE C ONTACTING S CRUBBERS Sven Stolle

C OMBINATION D EVICES Wet-collector scrubbers that use energy from both the gas stream and liquid stream to collect pollutants E.g. Cyclonic spray Mobile bed Baffle spray Mechanically aided scrubbers

C YCLONIC SPRAY combination of dry cyclone and spray chamber capable of effectively removing some gases (but only for very soluble gases) Rarely chosen when gaseous pollutant removal is the only concern Not useful for removing submicrometer particles Maintenance problems: erosion (high velocities) and nozzle plugging Low-medium energy device Applications: Mining operations, Drying operations, Food processing, Foundries

M OBILE -B ED / M OVING - BED S CRUBBERS similar to packed towers, but bed is in constant motion gas stream keeps the packing in motion, while liquid is sprayed over the packing good collection efficiency for particulate and gaseous pollutants packing is made of polypropylene or polyethylene plastic balls particles as small as 2 to 3 μm can be removed but not submicrometer particles high gaseous-pollutant removal efficiencies Maintenance problems: nozzle plugging, deterioration of the spheres (e.g. in high temperatures) Applications: Mining operations, Pulp mills, Utility boilers, Food industry

B AFFLE S PRAY S CRUBBERS similar to spray towers, but additionally gas streams atomize the liquids by passing the baffles Liquid sprays capture pollutants and also remove collected particles from the baffles Particles larger than 10 μm can be removed Not specifically used for gas collection Low efficiencies Low Maintenance problems Applications: Mining operations, Incineration, Chemical process industries

M ECHANICALLY A IDED S CRUBBERS Motors to supply energy Less space required than other scrubbers Higher power requirements high collection efficiencies for particles with diameters >1 μm not used for gas absorption Maintenance problems: moving parts Applications: Mining operations, Food product industries, Chemical industry, Foundries and steel mills centrifugal-fan scrubbers mechanically induced spray scrubbers