Dewatering flotation concentrates

Figure 7.16. Delkor horizontal belt filter dewatering copper flotation concentrate (filter area 21 m2)...

A recently developed KDF filter Figure 12.15) from Amafilter is based on a similar principle to that of a disc filter. It was developed mainly for the treatment of mineral raw materials like coal flotation concentrates or cement slurries. It can produce a filter cake of low moisture content, at very high capacities of up to 1750kgm h The pressure gradient is produced by pressurized air above the slurry level which, besides providing the necessary driving force for the filtration, is also used for displacement dewatering of the cake. 

Whatever the size of coal being processed, there will always be a need to separate residual coal from the washings, for which the decanter is a standard separating device (as well as for the final dewatering of waste liquids — the coal tailings). Fine coal may also be separated by means of froth flotation, and the dewatering of flotation concentrates is another good application for decanters. 

In the dewatering of flotation concentrate slurries, produced during mineral dressing operations, and in similar processes, the objectives are to recover the maximum amount of solids, produce saleable products where possible, and thus increase plant capacity at the most economic cost. There has been a significant improvement in process efficiency in this application by the use of belt discharge drum filters in place of disc vacuum filters and string/scraper drums. 

The lead concentrate from rougher flotation ceUs is upgraded by additional flotation steps. The final concentrate is dewatered by settling in thickeners to a moisture content of 50%. Vacuum filtering further decreases the moisture level to 15%. 

Mining and ore processing Setting slimes, flocculation of flotation waste, clarification of waste water from gravel wash, coal washeries, concentration and dewatering of sludges... 

The phosphate concentration in the tailings is upgraded to a level adequate for commercial exploitation through removal of the nonphosphate sand particles by flotation [32], in which the silica solids are selectively coated with an amine and floated off following a slurry dewatering and sulfuric acid treatment step. The commercial quality, kiln-dried phosphate rock product is sold directly as fertilizer, processed to normal superphosphate or triple superphosphate, or burned in electric furnaces to produce elemental phosphorus or phosphoric acid, as described in Section 9.2. 

Zinc and lead usually occur together in nature as sulfides. Earlier separation processes involved the fine grinding of the combined sulfides and then treating the particles with chemical reagents to cause one sulfide to be preferentially wetted and rhns the two sulfides separated by the froth flotation process. In a first stage, the lead sulfide is floated while the zinc sulfide sinks to the bottom of the tank. In the second stage, the process is reversed and the zinc sulfide is floated. Gangue and other nonmetals collect at the bottom of the tank. The separated sulfides are dewatered to a 6-7% moisture content and are referred to as the zinc concentrate and the lead concentrate. 

Dewatering and filtration are the most important processes in flotation. It is shown in [161] that the settling rate of iron ore fines can be enhanced 25 to 30-fold at optimum concentrations of... 

At Mount Weld, Australia, physical concentration of the REE minerals is performed as follows the run of mine material is subjected to crushing, grinding and flotation to produce a concentrate with a grade of 40 % REO. The obtained concentrate is sent to a thickener, where the resulting pulp is dewatered by applying... 

In ROM coal, a large portion of both coal and shale is already liberated sufficiently to permit immediate concentration. Because dewatering of coarse coal is much more efficient and cheaper than that of fines, and because many users prefer larger size fractions for their particular processes, the preparation of feed before cleaning has traditionally consisted of as little crushing as possible. Therefore, coal preparation consists mostly of gravity concentration and to some extent flotation, complemented by screening and solid/liquid separation auxiliary processes. 

In the flotation section, classification units may be used to split the minus 1.0 mm plus 0.1 mm feed into two size fractions for separate treatment. The coarser fraction (minus 1.0 mm to approximately plus 0.4 mm) can be concentrated by gravity (spirals) and froth flotation methods. The finer, minus 0.4 mm plus 0.10 mm, fraction is dewatered to 60%-75% solids. After being condi-... 

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