Oil assisted flotation

Foams and emulsions may also be encountered simultaneously [114]. Figure 1.5 shows an example of an aqueous foam with oil droplets residing in its Plateau borders (see Section 5.6.7). In addition to containing gas, an aqueous phase, and an oleic phase, foams can also contain dispersed solid particles. Oil-assisted flotation of mineral particles provides one example (Chapter 10). Oil-sand flotation of bitumen provides another (Chapter 11). In the case of oil-sands flotation, an emulsion of oil dispersed in water is created and then further separated by a flotation process, the products of which are bituminous froths that may be either air (and water) dispersed in oil (from primary flotation) or air (and oil) dispersed in water (from secondary flotation). In either case, the froths must be broken and de-aerated before the bitumen can be upgraded to synthetic crude oil. (See Section 11.3.2). 

When separating low-density solid particles or oil droplets from water, the most common method used is dissolved-air flotation. A typical arrangement is shown in Figure 8.12b. This shows some of the effluent water from the unit being recycled, and air being dissolved in the recycle under pressure. The pressure of the recycle is then reduced, releasing the air from solution as a mist of fine bubbles. This is then mixed with the incoming feed that enters the cell. Low-density material floats to the surface with the assistance of the air bubbles and is removed. 

Use Synthesis of pharmaceuticals, dyestuffs, rubber chemicals, flotation agents, insecticides, fungicides, plasticizers, textile assistants, herbicides, oil additives, rust preventives, and pickling inhibitors. 

If a bubble carrying air-avid mineral particles reaches the surface of the flotation unit and then bursts, the raised mineral particles will sink again. Bubble stability is maximized by addition of a foam stabilizer or frother, which assists in generating a sufficiently stable foam layer on the flotation unit to enable the foam plus associated mineral to be skimmed from the water phase. The frother also puts an oily phase on the surface of each bubble as it forms, which helps the mineral-gangue differentiation function of the collector. Typical frothers are oily materials of no more than slight water solubility such as pine oil (a mixture of terpenes) or a long chain (C5 or higher) alcohol such as 1-pentanol, and are used at the rate of 20-45 g/tonne of ore. 

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