ROTARY SCRUBBERS

Description

Rotary scrubbers are designed to separate particulate contamination from a gas stream and provide the gas stream with some forward momentum. The gas is drawn through the unit by a high-speed rotor onto which scrubbing liquor is fed. Particulate material is removed through inertial impaction either with the wetted rotor or a fine spray of scrubbing liquor.

There are two different designs of rotary scrubber - those with rigid rotors and those with flexible mop-like rotors. Rigid-rotor scrubbers are constructed from a series of rigid vanes, rather like a fan. Scrubbing liquor enters the rotor at the centre and is atomised by the vortex into a fine conical spray. Particles in the gas impact upon this conical spray and the resulting slurry collects in a chamber.

Mop scrubbers consist of a whorl of stiff fibres, like a traditional chimney sweep's brush. This rotates at high speed in the gas stream and is irrigated from the centre. Particles impinge on the wetted fibres as the mop drives the gas forward through the volute. The slurry formed is washed off the mop centrifugally to impact on the casing and collect in a chamber.

Application

Rotary scrubbers have high collection efficiencies (98%) of particles sized 3-4 µm. They can operate with high throughput volumes and can also operate as trace gas absorbers.

Sizing

Rotary scrubbers may have high operating collection efficiencies but they also have high operating costs. However, it must be remembered that they are designed to work without the need for additional fan power and, as well as acting as particulate scrubbers, they are able to drive the gas forward with an efficiency of approximately 40 % that of a fan.

A typical mop scrubber treating an air flow of 3500 m3/hour may require a 4 kW motor.