Column flotation

Column flotation is special technique that has been developed fairly recently as an alternative to conventional flotation. It is mainly used in the cleaning applications of sulphide flotation, where its ability to wash the froth off entrained gangue particles results in a higher grade product. In addition to this distinct advantage over conventional technology column flotation possesses significantly lower capital and operation costs and permits a superior process control.

Column flotation is carried out in tower like flotation cells. The cells are usually round and can measure over 10m in height and over 3m in diameter. Instead of an impeller that agitates the pulp and disperses the air, air is introduced at the bottom of the cell either by an internal sparger or an external bubble generator. The ore pulp is fed in the upper part of the column. As the bubbles rise up through the pulp they get in contact with the descending solids and contact is made in the collection zone. After attaching to the bubbles the ore minerals rise into the cleaning zone, where the mineralised froth is cleaned by a downward flowing stream of wash water. The wash water removes the rest of undesired hydrophilic gangue particles that may have got to the cleaning zone. It is essential that sufficient wash water is added to ensure that the flotation process is performed under a positive bias, i.e. the tailings stream flow that leaves the cell at the bottom is greater than the inflow of feed material.