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Venturi Scrubbers

CFW supplies venturi scrubbers to a range of industries. These units are effective for the high-efficiency removal of small-diameter particulates and for reducing gaseous emissions. Custom units can be made if required.

While cyclonic scrubbers offer a low-cost particulate removal solution that is fairly effective, higher efficiencies are sometimes required. Venturi scrubbers can be used for this purpose. Like cyclonic scrubbers, venturi scrubbers can remove some gaseous pollutants, though they are not as efficient for this purpose. While gas removal efficiency is relatively low (up to 60% for very soluble gases), there are many situations where venturis are ideal for removing dusts and gaseous pollutants simultaneously, for example where potential scaling or plugging problems exist.

Venturi scrubbers have a narrowed "throat" through which the air moves. Water is injected into the scrubber and forms fine droplets that remove pollutants. High-efficiency venturi scrubbers can be more effective for particle removal than any other wet scrubbing systems, especially for very small particles. Efficiencies may reach 99%. They can also handle combustible and explosive dusts, particles that are moist or sticky with the potential to cause plugging, and large inlet volumes. They are suitable for use in cement kilns or to remove fly ash.

There are many designs on the market. The main division is between the “wetted throat” and the “non-wetted throat” approach. In the former design, liquid coats the throat, making it less susceptible to particle caking and abrasion. It is also suitable for hot inlet gases because of the cooling effect of the liquid. The latter type is suitable mostly for moist, cool airstreams.

Some venturi models have adjustable throats for greater versatility. They can also be equipped with evaporative cooling “quench sections” for improved handling of high-temperature gases. The absorption of gaseous pollutants can be improved by optimising venturis to operate with lower gas velocities so as to increase contact time between the gas and liquid. However, there is a trade-off, as particle collection efficiency will be lower for small particles. Overall contaminant removal efficiency may be enhanced by designing the scrubber to contain several venturis in series.

All venturi scrubbers require an entrainment separator to effectively remove particles. The most common separator device is a cyclone.