Orifice scrubbers

This type of technology is a part of the group of controls collectively referred to as wet scrubbers. Orifice scrubbers are also known as self-induced spray scrubbers, gas-induced spray scrubbers, and entrainment scrubbers. The operating 

Orifice scrubbers are primarily used to control particulate matter, including particulate matter less than or equal to 10 pm in aerodynamic diameter, particulate matter less than or equal to 2.5 pm in aerodynamic diameter, down to particles with an aerodynamic diameter of approximately 2 pm. 

Orifice scrubber collection efficiencies range from 80 to 99%, depending upon the application and scrubber design. This type of scrubber relies on inertial and diffusional interception for PM collection. Some orifice scrubbers are designed with adjustable orifices to control the velocity of the gas stream. 

Orifice scrubbers are used in industrial applications including food processing and packaging (cereal, flour, rice, salt, sugar) pharmaceutical processing and packaging and the manufacture of chemicals, rubber and plastics, ceramics, and fertilizer. Processes controlled include dryers, cookers, 

Typical gas flow rates for an orifice scrubber unit are 0.47 to 24 sm3/sec (1,000 to 50,000 scfm). In general, orifice scrubbers can treat waste gases up to approximately 150°C (300°F). 

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FIG. 17-47 Performance curve for orifice scrubber collecting ammonium flii-orescin aerosol, Semrau et at, EFA 600/2-77-237, 1977.)... 

Temperature In general, orifice scrubbers can treat waste gases up to approximately 150 C (300 F). 

Pollutant Loading Orifice scrubbers can accept waste flows with PM loadings up to 23 grams per standard cubic meter (g/sm ) or 10 grains per standard cubic foot (gr/scf), or higher, depending upon the nature of the PM being controlled. 

Orifice scrubbers generally do not require precleaning, unless the waste gas contains large pieces of debris. Precooling may be necessary for high temperature waste gas flows which increase the evaporation of the scrubbing liquid. 

Orifice scrubbers are relatively simple in design and usually have few moving parts, aside from a fan and possibly an automatic sludge ejector. 

References 68 through 72 provide additional information on orifice scrubbers, design and scale-up principles, as well as operational guidance. 

Venturi and orifice scrubbers are simple forms of wet scrubbers. The turbulence created by the venturi or orifice is used to atomise water sprays and promote contact between the liquid droplets and dust particles. The agglomerated particles of dust and liquid are then collected in a centrifugal separator, usually a cyclone. 

Orifice scrubbers usually have low liquid demands, since they use the same scrubbing liquid for extended periods of time. Because orifice scrubbers are relatively simple in design... 

Figure 20.6. Wet scrubbers, (a) Wet cyclone scrubber, (b) Spray scrubber, (c) Venturi scrubber, (d) Orifice scrubber.

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