Endress delivers a two-channel four-wire device Prosonic S system for floatation cell recovery. John Immelman writes.
The process of ‘flotation’ in gold, copper, lead, zinc, and coal mining is used to recover fine mineral particles.
The technique uses the surface tension of mineral particles to separate them from ore slurry.
The mineral particles to be ‘floated’ are made hydrophobic in each flotation cell with the addition of flocculant chemicals.
Air is then pumped through the slurry mixture and the targeted mineral particles attach themselves to the bubbles and rise to the surface. This forms a concentrated mineral froth.
The mineral froth is then extracted and the concentrated mineral is further refined.
Waste rock particles drop to the flotation tank’s bottom as tailings.
The flotation cell process makes the mining of mixed ore bodies efficient and economically viable.
In a typical flotation cell, various parameters need to be controlled. These include surface level and interface measurement, slurry pH, flow-meters for flocculent agent dosing, slurry flow, compressed air flow, and valve control using electromagnetic flow-meters.
Accurate and reliable measurement is crucial during the process, as there needs to be a balance between the amount of base slurry and the amount of froth produced.
Excess slurry and not enough froth leads to an under recovery of minerals. Excess injected flocculent costs money, but is also expensive to remove from the process later down the line.
The most common way to optimise the process is to measure the relative ‘thickness’ of the froth in relation to the level of the slurry in each flotation cell.
Since the density of the froth is high enough to reflect ultrasonic pulses from a continuous ultrasonic level sensor, this is an ideal technology for monitoring the level of the foam floating on the slurry.
The new two-channel four-wire device Prosonic S system, measures the distance to froth on one ultrasonic sensor, and the distance to the interface on another, complete with float, rod, and reflecting disk.
The float on the second sensor drifts on the slurry interface with the reflecting disk protruding through the foam.
When the Prosonic S system measures the distance to the disk, it measures the actual interface level.
The measurements can be used to determine if operating conditions are optimal, or if further adjustments to the chemical dosing, slurry, or bubbles need to be made.