Flotation as a method for separating valuable substances from waste was patented in 1906. It is a very efficient and thus popular method, especially in mining industry, but it is also used in other processes, for example for separating the ink from the recycled waste paper. Before flotation the mined ore rocks are mechanically ground to powder of desired grain size, typically 50-100 µm. The powder is mixed with water and chemicals and the resulting pulp is fed to a series of flotation cells. In the flotation cell air is fed into the pulp to produce bubbles that naturally move upwards and produce froth on top of the pulp. The grains, depending on their mineral contents, tend either to float and stick to the bubbles or to sink in the liquid. Due to variation in grain properties (size, shape, mineral content, etc.) the separation is far from ideal. Both the froth and pulp still contain grains having various mineral contents. Consequently the separated grains in the froth and in the remaining pulp are usually fed to the next flotation cells to continue the separation process and, for example, suitable chemicals are used to strengthen the separation. The main parts of a typical flotation cell used in mineral processing industry are represented in the following figure.
mineral notation, machine vision, classification, control
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