Dust Control Handbook for Industrial Minerals Mining and Processing

Wet scrubbers are particularly advantageous when handling moist hot gases. Problems such asbag blinding and condensation can arise when fabric collectors are used to clean moist hot gases.These problems are eliminated when using scrubbers. However, wet scrubbers dischargecontaminated water, which requires further treatment in a settling pond or sewage system.Venturi ScrubbersVenturi scrubbers are a type of wet scrubber and consist of a venturi-shaped inlet and a separator(Figure 1.22). Dust-laden air is accelerated to velocities between 12,000 and 36,000 feet perminute in the throat of the venturi. These high velocities atomize the coarse water spray andcreate pressure drops ranging from 5 to over 15 inches wg. The venturi can be ceramic-lined forabrasive applications. The extreme turbulence promotes collision between water droplets anddust particles in the throat of the venturi. An inertial separator then removes these agglomerates.Impingement Plate ScrubbersFigure 1.22. Typical designs of a venturi scrubber.In another type of wet scrubber—an impingement plate scrubber (see Figure 1.23)—the exhaustpasses upward through openings in perforated plates, which hold a layer of water. Animpingement baffle is located above each hole, resulting in the formation of small droplets.Intimate gas/liquid contact results in efficient particle collection. A pressure drop of 4 inches wgis typical.Fundamentals of Dust Collection Systems 41