Using ultrasound for characterizing overflowing froth

Flotation is a separation process in which hydrophobic particles inside a liquid bath
attach to uprising bubbles, which subsequently form a froth layer on the liquid
surface. This froth phase, which consist of foam with particles, has a large impact on
the transport of separated materials and therefore the overall process efficiency.
Despite the importance for process control, a notable lack of suitable techniques for
on-line characterization of the froth’s properties such as the liquid fraction or particle
content can be found. An potential approach to gain information on the different
phase fractions in froth is the application of low-frequency ultrasound measurement
techniques. In this contribution an overflowing froth containing varying mass fractions
of Quartz particles and liquid is analyzed using combined optical and ultrasonic
measurements. The measured intensity of the ultrasonic reflections sent from above
the froth’s surface correlate to the fraction of solids inside the froth (Figure 1).
Therefore it is shown, that current optical froth characterization techniques can be
improved by incorporating ultrasonic measurements, which can be seen as a first
step towards advanced process control in industrial flotation processes.