Optimizing Mineral Flotation Processes

Flotation Cells and Circuits

Functions of Flotation Machines

Flotation machines must fulfill a wide variety of functions, which need to be met consistently in each cell throughout a cell bank. These functions include:

1. Maintain all particles, even the thicker or denser ones, in suspension.
2. Aerate the pulp, implying the efficient dispersion of fine air bubbles throughout the cell.
3. Promote optimal particle-bubble contact conditions, facilitating selective adhesion and transport.
4. Maintain quiescent conditions immediately below the froth column.
5. Ensure efficient transport of feed pulp to and from the cell.
6. Control the pulp level, froth level, and ideally, the degree of agitation.

Classification of Flotation Cells

Flotation cells are classified according to their size, capacity, energy consumption, froth area ratio, cell volume, and type of aeration.

Flotation Cell Classification by Volume

Flotation cells can be arbitrarily categorized by volume:

1. Small cells: Up to 60 cubic feet.
2. Medium-sized cells: From 60 to 200 cubic feet.
3. Large cells: From 200 to 1000 cubic feet.

Sub-Aeration Flotation Machines

These machines employ an impeller to keep the pulp dispersed and an air inlet that introduces air above atmospheric pressure in the vicinity of the impeller.

Pneumatic Flotation Cells

Pneumatic cells involve the introduction of gas from a blower under slight pressure near the bottom of the cell, typically using porous tubes or other dispersion systems.

Vacuum Flotation Machines

In vacuum flotation, pulp saturated with air at atmospheric pressure is subjected to a vacuum to induce the formation of bubbles.

Flotation Circuits and Stages

Flotation circuits are designed to achieve high recovery in conjunction with a high-grade concentrate.

Primary (Rougher) Flotation Stage

In this stage, the feed material to the flotation plant is processed.

Cleaner Flotation Stage

The cleaner stage aims to upgrade the primary concentrate to achieve the required quality specifications for downstream processes or foundries.

Scavenger Flotation Stage

The scavenger stage processes the tailings from the cleaner circuit to recover valuable particles that did not float in the previous stages.

Regrind Stage in Flotation

The regrind stage is crucial for achieving the primary metallurgical objective of recovering valuable species, as it liberates minerals for more effective flotation, rather than directly focusing on the grade of the concentrate at this point.

Second Cleaner Flotation Stage

The aim of this stage is to further increase the grade of the concentrate, representing the final concentrated valuable species.