Factors affecting flotation dynamics
Flotation is a complex process involving many sub-processes, which generally include:
1 introduction of feedstock, introduction of slurry, introduction of air;
2 the adhesion of the ore particles and bubbles, the colloidal particles and bubbles collide, the ore particles adhere to the bubbles, and the ore particles fall off the bubbles;
3 The transfer of the ore particles between the pulp and the foam, the mineralized bubbles enter the foam, the ore particles are directly brought into the foam, and the ore particles are returned to the slurry from the foam;
4 elimination of flotation products, elimination of foam, elimination of tailings.
Each of the above sub-processes will have an impact on the flotation rate. On the Other hand, mineral flotation is a complex phenomenon. In addition to mechanical, process and operating conditions, physical and chemical factors also have an important impact on the rate. In summary, the factors affecting the flotation rate can be divided into four categories:
1 properties of ore and minerals, such as the type and composition of minerals, particle size distribution, ore shape, monomer dissociation, mineral surface properties, etc.;
â‘¡ flotation chemistry factors, such as the selective collector, collector capacity strength, activators, inhibitors, kind and amount of foaming agent, pH value, water and the like;
3 flotation machine characteristics, such as flotation machine structure and performance, aeration amount, bubble size distribution and dispersion degree, agitation degree, thickness and stability of foam layer, foaming speed, etc.;
4 operating factors, such as pulp concentration, temperature, etc.
People have conducted a lot of explorations for different purposes from different angles. The research on the influence of these factors on the flotation rate shows that the problems involved are actually very complicated, and it is difficult to draw a consistent result of the influence of each factor on the flotation rate, which also brings great difficulties to the flotation dynamics.
(2) Flotation rate equation and series
The attachment of the ore particles to the bubbles is the basic behavior of the flotation process. This process is analogous to chemical reactions. Collisions and adhesions of ore particles to bubbles correspond to interactions between molecules such as molecules, atoms, ions, etc. in chemical processes. When a first-order reaction in a chemical process is used to describe the behavior of mineral flotation At the time of narrow-grain pure mineral flotation conditions, the fitting is good; while for the actual ore flotation process, it is disappointing, and generally no satisfactory results are obtained. The flotation process carried out in the flotation cell is much more complicated than the chemical reaction between relatively homogeneous molecules, atoms and ions.
First order reaction
The laboratory pure mineral test and the results of the screening studies on industrial flotation products show that for a narrow grade single mineral, the flotation rate is proportional to the concentration of the ore in the slurry in the flotation tank, following the first grade. Reaction rate equation:
(Maximum recovery rate, pure minerals take 100%). Since the flotation rate is proportional to the rate constant and the n-th power of the recovery, when comparing the speed of the flotation process, the magnitude of the rate constant can be directly compared for the same reaction order. If the rate constant is large, the flotation rate is fast. If the number of reaction stages is different, you must directly calculate the flotation rate at a certain moment to compare.
(3) Flotation rate constant distribution characteristics
Flotation practice shows that when the floatability of the particles constituting the flotation material is more and more similar (for example, the pure mineral fraction is getting narrower and narrower) until the floatability of each of them is the same, this The flotation rate of the material is consistent with the first order reaction. At this time, the rate constants of the respective ore particles should be equal. At this time, we refer to these ore particles which have the same buoyancy and have the same first-order reaction rate constant as a species. In actual ore, particles of different composition, different particle size, dissociation degree and surface properties may exist in the same grain group. Therefore, if the first-order kinetic equation is used to describe the flotation of the actual ore, it can be considered that the k value is not constant but varies with time. In the actual ore flotation, since the flotation material is composed of different k-value varieties, the varieties with larger rate constants will be floated at a faster rate, while the lower rate constants will be floated at a slower rate. As the varieties with larger rate constants continue to float, the average k value of the remaining materials in the flotation machine gradually decreases as the flotation time increases, that is, the k value is a function of time.
Since the flotation material is composed of different k-value varieties, the proportion of the varieties with different k values ​​and how to distribute them is a research topic, which also determines the use effect of the actual flotation kinetic model. Because the composition of flotation materials is actually very complicated, the distribution of k values ​​also has a variety of expressions, which can be divided into two categories, namely continuous distribution and discrete distribution.
Studies on the distribution function of reaction series and rate constants are all within the scope of empirical equations. It can be considered that the problem of the number of flotation reaction stages is actually a macroscopic representation of the flotation rate. The problem of k-value distribution is a microscopic analysis of the composition of minerals at different rates in the material.
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