Scrubbers are most commonly used for removal of particulate and gaseous pollutants, undesirable liquid mists and also for elimination of odour.

Depending on the method adopted wet dust collection scrubbers are of various types.

# Wet Cyclone (Centrifugal Scrubber) : Dust laden gas stream impinges upon the wetted surfaces of a dust collector sprayed by a liquid. Dust particles are captured by a liquid film and are thus removed from gas stream. The basic principle of dust collection is combination of centrifugal action with impact by liquid particles. The unit provides efficient low pressure drop scrubbing for particles 10 microns and above and works on a low pressure drop.

# Venturi Scrubber : the most commonly used high efficiency wet device for particulate matter separation is venturi scrubber. The contaminated gas after acceleration in the converging section enters the throat section. The scrubbing liquid fed uniformly at the top of the converging section cascades by gravity towards throat where they get mixed up with the gas at high energy and extreme turbulence. The scrubbed gas and entrained droplets with dust particles entrapped, enter the diverging section where further collisions and agglomeration take place. The gases then enter the cyclone separator where all liquid drops with entrained particles are removed from the gas stream and pass out through a drain connection to a settling tank. The clean gas leaves at the top. On most installations the filtered liquid is recirculated back to the sprays. The venture pressure drop is fixed based on the require scrubbing efficiency for a given application. Venturi can be offered either with fixed or variable throat with leaf dampers or centre cone. Depending on the need and degree of sophistication required, adjustable throat can be operated with manual or automatic device. These are used for removal of gaseous pollutants also.

# Packed Bed Scrubber : This is an efficient and well accepted method for removal of noxious and corrosive contaminants from gases by absorption and chemical reaction and also for separation of particulate matter from air/gas stream. The contaminated gas flows upward through a tortuous path over the packing media on which scrubbing liquid is uniformly sprayed. The movement of gas and liquid is counter-current. Demister located above spray manifold prevents liquid entrainment. The scrubbing liquid collected may be recirculated or disposed off. The material of construction of scrubbers can be MS/MSRL/SS/FRP or MS with anti-corrosive painting depending on application. Packing media may be either ceramic or plastic depending on temperature of gas to be scrubbed.

This is also an effective device for removal of odour. Depending on requirement of efficiency, multiple packing media may be adopted.

# Odour Control : A specially designed odour control system comprising of cross-flow packed bed scrubber followed by an adsorption tower are offered for typical applications including animal feed, food processing, sewage treatment, leather tanning etc.