Technology of using rough concentrate as carrier minerals

Abstract

Introduction. The work is aimed at the development and justification of flotation technology of microdispersions of minerals, including gold. At traditional approach to a problem of effective extraction of particles which size does not exceed 10-30 microns, formation of flotation complex is investigated using the apparatus of thermodynamics. Such approach is rational for solving technological problems, when the completeness of collective extraction of all solids present in the aqueous phase is a necessary and sufficient condition. At flotation of ores the requirement of completeness of extraction of valuable components is supplemented by a condition of selective separation of minerals. Materials and methods. The main method of research is a theoretical analysis of the hydrodynamic interaction of polydisperse particles, laboratory scale flotation experiments performed on a sample of gold-bearing ores with high content of gold microdispersions using carrier minerals. Results. It is shown that the hydrodynamic resistance force acting on a solid particle from the side of unrestricted liquid flow is composed of two components. The first one is the pressure force directed along the normal to the surface of the particle, and the second one is the friction force directed along the tangent to the surface of the particle. The influence of hydrodynamic force acting on the particle from the side of liquid bounded by the wall can be accounted for by correction, in the form of the ratio of particle size to its distance to the wall, which is less than unity. Discussion. It is shown that the hydrodynamic resistance force acting on a solid particle from the side of unrestricted liquid flow is composed of two components. The first one is the pressure force directed along the normal to the surface of the particle, and the second one is the friction force directed along the tangent to the surface of the particle. The influence of hydrodynamic force acting on the particle from the side of liquid bounded by the wall can be accounted for by correction, in the form of the ratio of particle size to its distance to the wall, which is less than unity. Conclusion. In flotation with the use of carrier minerals, it is necessary to take into account the influence of a large particle – the wall – on the motion of the liquid phase and small particles. The effect of the wall on the motion of a single fine solid particle in the case of the flowing of an arbitrarily shaped particle moving parallel to the wall has been evaluated. The results obtained can also be used to assess the effect of a group of particles in a fluid, provided that the interaction between the particles can be neglected. The hydrodynamic drag force acting on a solid particle from the unrestricted fluid flow is composed of two components. The first one is the pressure force, which is directed along the normal to the surface of the particle, and the second one is the friction force, which is directed along the tangent to the surface of the particle. The effect of the hydrodynamic force acting on the particle from the side of the fluid bounded by the wall can be accounted for by a correction, in the form of the ratio of the particle size to its distance to the wall, which is less than unity. Therefore, the presence of the wall leads to an increase in the rate at which the unsteady fluid flow between the wall and the particle approaches the steady state regime and, consequently, a decrease in the magnitude of the hydrodynamic drag force acting on the particle from the side of the fluid bounded by the wall. Results of theoretical analysis and experimental studies of kinetics of thinning and breakthrough of symmetric and wetting films prove efficiency of flotation mode of particle microdispersions by introduction of carrier minerals into flotation system. It is advisable to use rough concentrate extracted from ores as a carrier material. The main flotation front in this case can be considered as an ideal displacement apparatus, in which at mixing of mineral streams the influence of the distribution of extracted particles on the flotation rate on the technological indicators of the separation process is minimal. In terms of the structure and properties of its boundary layer of water, the surface of air bubbles in water is similar to the near-surface layers of water near solid hydrophobic surfaces. Therefore, the interaction of bubble and particles during flotation is determined by the forces of hydrophobic attraction (in the case of hydrophobic particles) and hydrophilic repulsion (in the case of hydrophilic particles).The temperature dependence of these forces allows to intensify the flotation process by the effect of heat flow on the boundary layers of air bubbles. For this purpose, aeration of the pulp during flotation is carried out by a mixture of air with hot water steam. The results of flotation of gold-bearing ores according to the technological scheme with the use of rough concentrate as a carrier material and the mode of flotation with a steam-air mixture are given. Resume. The analysis of hydrodynamic interaction of polydisperse particles revealed that the presence of the wall leads to an increase in the rate of approaching the unsteady fluid flow between the wall and the particle to a steady mode and, consequently, a decrease in the value of the hydrodynamic resistance force acting on the particle from the liquid bounded by the wall. The role of identity of structure and properties of water in the boundary layers of air bubbles and in the near-surface layers of water near solid hydrophobic surfaces in flotation processes is substantiated. It was shown that the connection between the structure and properties of water in the boundary layers of water and the mechanism of flotation complex formation is that in the case of hydrophobic particles their interaction with the bubble is determined by the forces of structural hydrophobic attraction, and in the case of hydrophilic particles by the forces of structural hydrophilic repulsion. Temperature dependence of these forces makes it possible to intensify the flotation process by the effect of heat flow on water in the boundary layers of air bubbles. For this purpose, aeration of pulp is carried out by a mixture of air with hot water steam. It is shown that it is advisable to use rough concentrate extracted from ores as a carrier material. The main flotation front in this case can be considered as an ideal displacement apparatus, in which at mixing of mineral streams the influence of the distribution of extracted particles on the flotation rate on the technological indicators of the separation process is minimal. The field experiment on flotation of gold-bearing ores proved the technological efficiency of using the rough concentrate as a carrier material and the mode of flotation with a steam-air mixture. Proposals for practical application and direction of future research. The results obtained can be used in the development of technological solutions aimed at improving the performance of flotation of ores with a higher content of micro-dispersions of minerals lost with the tailings of ore dressing. Technical and economic evaluation of the efficiency of flotation technology with carrier minerals may be one of the directions of further research.