Dust Control Handbook for Industrial Minerals Mining and Processing

Spray Tower ScrubbersFigure 1.23. Typical design of an impingement plate scrubber.Gravity spray tower scrubbers employ atomized water, which falls counter-current through arising dust-laden airstream, to remove dust particles. These scrubbers are generally of lowerefficiency and operate at pressures of 1 to 2 inches wg. They are approximately 70 percentefficient on 10-μm particles and above with poor efficiency on particles smaller than 10 μm.However, they are capable of treating high dust concentrations without becoming plugged.Wet Cyclone ScrubbersSimilar to a dry cyclone, wet cyclone scrubbers use centrifugal forces to throw particles on thecollector's wetted walls. Water is introduced from the top of the scrubber to wet the walls andwash the particles away. Pressure drops for these collectors range from 2 to 8 inches wg with agood efficiency for removing particles 5 μm and larger.Electrostatic Precipitators (ESPs)Electrostatic Precipitators (ESPs) are particulate control devices that use electrical forces tomove particles from the airstream to collection plates. Particles passing through the precipitatorare given a negative electrical charge by being forced to pass through a region, called a corona,in which gas ions flow. Once the particle has been negatively charged, it is forced to thepositively charged plate. Particles are removed from the plate by knocking action.42 Fundamentals of Dust Collection Systems