Using water eliminates the possibility of explosions. Minimal fire and explosion hazards: Various dry dusts are flammable.Handles high-temperature, high-humidity gas streams: No temperature limits or condensation problems can occur as in baghouses or ESPs.No secondary dust sources: Once particulate matter is collected, it cannot escape from hoppers or during transport.Smaller sizes result in lower capital costs and more flexibility in site location of the scrubber. Therefore, vessel sizes, including fans and ducts downstream, are smaller than those of other control devices. Small space requirements: Scrubbers reduce the temperature and volume of the unsaturated exhaust stream.Relative advantages and disadvantages of wet scrubbers compared to other control devices Wet scrubbers have been used in a variety of industries such as acid plants, fertilizer plants, steel mills, asphalt plants, and large power plants. Some disadvantages of wet scrubbers include corrosion, the need for entrainment separation or mist removal to obtain high efficiencies and the need for treatment or reuse of spent liquid. Wet scrubbers are more appropriate for humid / sticky air streams.Wet scrubbers can neutralize corrosive gases.Wet scrubbers can remove both gases and particulate matter.In wet scrubbers, flue gases are cooled, resulting in smaller overall size of equipment.Wet scrubbers have the ability to handle high temperatures and moisture.Some advantages of wet scrubbers over these devices are as follows: In general, obtaining high simultaneous gas and particulate removal efficiencies requires that one of them be easily collected (i.e., that the gases are very soluble in the liquid or that the particles are large and readily captured), or by the use of a scrubbing reagent such as lime or sodium hydroxide.įor particulate control, wet scrubbers (also referred to as wet collectors) are evaluated against fabric filters and electrostatic precipitators (ESPs). However, in many cases, the best operating conditions for particles collection are the poorest for gas removal. Wet scrubbers can achieve high removal efficiencies for either particles or gases and, in some instances, can achieve a high removal efficiency for both pollutants in the same system. If the gas stream contains both particulate matter and gases, wet scrubbers are generally the only single air pollution control device that can remove both pollutants. Various wet-scrubber designs are used to remove gaseous pollutants, with the packed tower and the plate tower being the most common. Good gas-to-liquid contact is essential to obtain high removal efficiencies in absorbers. Wet scrubbers that remove gaseous pollutants are referred to as absorbers. The greater the number of liquid droplets that are not captured by the mist eliminator, the higher the potential emission levels. Additionally, a properly designed and operated entrainment separator or mist eliminator is important to achieve high removal efficiencies. To obtain high efficiency removal of 1 micrometer (or less) particles generally requires high-energy devices such as venturi scrubbers or augmented devices such as condensation scrubbers. Low energy devices such as spray towers are used to collect particles larger than 5 micrometers. Also, the resultant scrubbing liquid must be treated prior to any ultimate discharge or being reused in the plant.Ī wet scrubber's ability to collect small particles is often directly proportional to the power input into the scrubber. Any droplets that are in the scrubber inlet gas must be separated from the outlet gas stream by means of another device referred to as a mist eliminator or entrainment separator (these terms are interchangeable). The droplets are then collected, the liquid dissolving or absorbing the pollutant gases. Wet scrubbers remove dust particles by capturing them in liquid droplets. The versatility of wet scrubbers allow them to be built in numerous configurations, all designed to provide good contact between the liquid and polluted gas stream. Scrubbers can be designed to collect particulate matter and/or gaseous pollutants. Inlet gas characteristics and dust properties (if particles are present) are of primary importance. The design of wet scrubbers or any air pollution control device depends on the industrial process conditions and the nature of the air pollutants involved.

The mist eliminator for a venturi scrubber is often a separate device called a cyclonic separator A packed bed tower design where the mist eliminator is built into the top of the structure. See also: Particle collection in wet scrubbers A venturi scrubber design.

Smoke stack scrubber