mechanical flocculatorsReading time:
paddle type flocculators
Paddle type agitators are the best suited to large flocculators (high cross flow rate) of the type found in drinking water treatment systems.
The mobile comprises a series of diametrically-mounted paddles, offset at regular intervals and attached to a vertical or horizontal shaft (photo 3). The whole is driven by a reduction gear, with or without speed regulator. The mobile can be driven either via a drive chain or direct. The latter system eliminates any restrictions associated with corrosion and chain maintenance. However, in the case of horizontal axis paddles, it does require a sealed passage through the wall.
The mobile comprises a turbine, a vertical shaft, three or four blades, driven direct by a reduction gear unit and, more often than not, a speed regulator.
This is the type of equipment featured in figure 1. However, in this case, the type of turbine and the speed of rotation will be different in order to satisfy the conditions detailed above (energy gradient, absence of any local overspeed. For instance, mobile peripheral velocities must not exceed 50 cm · s–1 in metal hydroxide floc.
In order to preserve floc integrity, it is advisable to select streamlined turbines with a strong axial component, generating higher peripheral velocities and pumping outputs with a minimum of local turbulence.