Flotation to music

In Kazakhstan, the share of finely disseminated ores requiring deep grinding to liberate extractable minerals is gradually increasing. At the same time, a significant portion of the ore is ground to sizes less than 10 microns, with a considerable fraction of nanoparticles that can only be effectively floated by gases released from the aqueous phase of the flotation pulp. This method marked the beginning of flotation as a process (Germany patent No. 39369, 1986). However, despite the purposeful efforts of scientists and industrialists, it has not yet been applied in industrial flotation practice. The staff of the beneficiation laboratory of the NC CPMI RK noted at the end of the last century that no more than 25 mg/L of air gases dissolve in water.

Experiments showed that this amount of gas is insufficient to recover all ore particles present in the flotation pulp. A search for a solution to this problem began. Experiments revealed that in an acoustic field, when floatable hydrophobic mineral particles are present in the pulp, their flotation process does not depend on the limited solubility of air gases in water and continues until all hydrophobic particles pass into the froth concentrate.

The acoustic flotation process is physically effective in the frequency range from units to thousands of kilohertz (kHz), but currently profitable only at frequencies of a few kilohertz, which can be generated in the pulp by mechano-hydroacoustic devices, such as the developed acoustic rotary aerator. The advantage of using gases released from the aqueous phase of the pulp is especially significant in the flotation of micro- and nanodispersions that cannot be floated by other methods. Technological studies have shown that if the efficiency of the method is evaluated for particle size below 10 micrometers, then with 50% of this size fraction, during flotation of sulfide minerals from finely disseminated complex ores, the extraction of galena in the lead cycle using the acoustic method is 16% higher than with traditional flotation. At the same time, the lead content in the concentrate is 14% higher, and contaminating zinc is 7% lower. The extraction of sphalerite in the zinc cycle using the acoustic aerator is 11% higher, the zinc content in the concentrate is 9% higher, and contaminating lead is 5% lower. Even if these results are halved when transferred to an industrial scale, the effect of implementing the method would still be impressive, as beneficiation plants compete for every percent of extraction.

Currently, simultaneous work is underway on an in-depth study of the discovered phenomenon and on the creation and testing of a semi-industrial version of the apparatus for comparative testing at a pilot plant. Detailed research is being conducted on the hydrodynamic and acoustic aspects of the flotation process in a sound field, which allows rapid progress toward developing an industrial version. For example, it was established that the transition from pre-acoustic to acoustic oscillations occurs in water at frequencies of 1.47 kHz, and in flotation pulp at 2.90 kHz. This is preliminarily associated with the water structural factor, but requires further study, without which the process will not be fully controllable. Another significant factor is that with increasing acoustic frequency, the efficiency of ultrasonic absorption by the pulp increases, but the depth of penetration of acoustic vibrations into the pulp decreases, and it is necessary to determine the boundaries of this phenomenon.

Eremin Yu.P.

Academician of the Academy of Mineral Resources of the Republic of Kazakhstan, Doctor of Technical Sciences,

Chief Researcher of the RSE "NC CPMI RK"