Venturi scrubber

A venturi scrubber is designed to effectively use the energy from a high-velocity inlet gas stream to atomize the liquid being used to scrub the gas stream. This type of technology is a part of the group of air pollution controls collectively referred to as wet scrubbers. Venturis can be used to collect both particulate and gaseous pollutants, but although the liquid surface area provided is quite large they are more effective in removing particles since particles can be trapped by contact, but gases must be trapped by absorption during the relatively short exposure time. Venturi devices have also been used for over 100 years to measure fluid flow (Venturi tubes derived their name from Giovanni Battista Venturi, an Italian physicist). In the late 1940s, H.F. Johnstone, William Jones, and other researchers found that they could effectively use the venturi configuration to remove particles from gas streams. Figure 1 illustrates the classic venturi configuration. An ejector or jet venturi scrubber is an industrial pollution control device, usually installed on the exhaust flue gas stacks of large furnaces, but may also be used on any number of other air exhaust systems. They differ from other venturi scrubbers energy is derived from the high-pressure spray of liquid from a nozzle rather than the flow of process gas, allowing the scrubber to also act as a vacuum ejector and draw process gas through the device without external assistance. A venturi scrubber consists of three sections: a converging section, a throat section, and a diverging section. The inlet gas stream enters the converging section and, as the area decreases, gas velocity increases. Liquid is introduced either at the throat or at the entrance to the converging section. The inlet gas, forced to move at extremely high velocities in the small throat section, turbulently mixes with the liquid, producing an enormous number of very tiny droplets. Particle and gas removal occur in the diverging section as the inlet gas stream mixes with the fog of tiny liquid droplets.