Effect of slurry concentration on flotation

In the floating beneficiation process, the size of the pulp density affect not only concentrate grade and recovery, but also affects the pharmaceutical consumption, water and electricity consumption. Now let's analyze the relationship between slurry concentration and the following factors.

(1) The concentration of slurry affects the flotation time. In the flotation mine, when the processing capacity of the ball mill is constant, the slurry flow rate is also certain under a certain pulp concentration. Since the number of flotation machines in each operation is constant, the flotation time of each operation is also constant. However, when the concentration of the slurry increases or decreases, the ore flow rate also decreases or increases. The time the slurry stays in the flotation machine (flotation time) is prolonged or shortened, as shown in Figure 6-33. Curve 3 is shown. The length of flotation time directly affects the recovery rate and grade.

(2) The concentration of pulp affects the volume concentration of the agent

Flotation mines generally calculate the dosage in grams per ton. If the dosage of the agent in this unit is constant, the volume concentration of the agent increases as the concentration of the slurry increases, or decreases as the concentration of the slurry decreases, as shown by curve 2 in Fig. 6-33. In the flotation process, if the mineral concentration of the flotation concentrate is just a better condition in a certain volume concentration of the medicament, then the increase or decrease of the concentration of the pulp will cause the dosage of the medicament to be "excessive" or "by volume". Insufficient, causing adverse conditions affecting the flotation mine index.

(3) The influence of slurry concentration on the aeration degree of pulp agglomeration, as shown in curve 1 of Figure 6-33, if the concentration of pulp is too large or too small, the aeration of the slurry will be reduced, and the strength of the aeration will directly affect Flotation time. In general, a larger amount of aeration can increase the production capacity of the flotation separator and obtain a better flotation index.

The concentration of the slurry is determined by the nature of the ore and the conditions of the flotation. The general principle is that when the relative density of the ore is relatively large and the particle size of the material is coarse, the flotation concentration should be used for rough selection and sweeping operations. Conversely, when the ore has a relatively low relative density and a fine particle size, a lower concentration should be used for the separation operation during the selection operation or the mixed concentrate. In the production practice, the rough selection is 25% to 45%, the majority is 28% to 30%; the selection is 10% to 20%; the sweep is 20% to 40%.

The pH of the slurry is also called the pH of the slurry. It refers to the concentration of hydrogen ions [H+] or the concentration of alkali ions [0H-] in the slurry. In aqueous solution, when the temperature is 20 ° C, the product of their concentration is 10-14 mol / liter, ie

CH2O=[H+][OH-]=10-14 mol/L

If the aqueous solution is neutral, the hydrogen ion concentration [H+] is equal to the alkali ion concentration [OH-], that is,

[H+]=[OH-]=10-7 mol/L

For the sake of convenience, the negative value of the logarithm of the hydrogen ion concentration [H+] is used to indicate the concentration of hydrogen ions in the solution, which is often referred to as the pH value. which is

pH=-lg[H+]

Therefore, the pH indicates the concentration of hydrogen ions in the solution, which indicates the pH. Neutral when pH=7, alkaline when pH>7, and acidic when pH<7.

In the flotation process, the effect of pH on mineral flotation is multifaceted, which is an important factor affecting the flotation ore index.

(1) The effect of pH on the hydrophilicity and electrical properties of the surface of the ore. Under the condition of large pH value, due to the large amount of OH- ions in the slurry, the surface of the ore particles adsorbs a large amount of OH-, which will cause the ore. The hydrophilicity of the grain surface increases and hinders the adsorption of the collector anion. The pH also affects the electrical properties of the surface of the ore. The pH value directly affects the zeta potential of the surface of the ore. Especially for flotation mines of certain oxidized ores, the flotation minerals used are different due to the different pH values.

(2) The dissociation of flotation minerals into effective ions is directly related to the pH value. Most of the flotation oreing agents act in an ionic manner with the surface of the ore surface. That is to say, after the agent is dissociated into ions, it can interact with the mineral surface. The amount of dissociation of the agent into effective ions is strongly dependent on the pH. If the effective ion of the agent is off-X-, it is necessary to produce more effective ions X- under alkaline pulp (pH>7). because

The above reaction is reversible, and the reaction proceeds to the left only when the concentration of [OH-] is increased, resulting in more X-. For example, in the case where the pulp is alkaline, the xanthate can dissociate more anionic ROCSS-, the fatty acid dissociates into RCOO-, and the oxide dissociates into CN-.

When the active ion of the agent is a cation, more cations can be resolved only in the slurry of low pH. If the effective ion of the amine collector is a cation, the hydrolysis reaction is:

In the above formula, the reaction is carried out to the right under a small pH condition.

(3) Flotation of various minerals Under certain conditions, there is a suitable pH value. Under different chemical conditions, various minerals have a critical pH that can be floated and not floated. Because the pH of the pulp often directly or indirectly affects the floatability of the mineral, the critical pH is a function of the flotation condition. If different collectors are used or the concentration is changed, the critical pH of the mineral is also Will change. For example, when xanthate is used as a collector, the adsorption density of xanthate anion on the mineral surface has a certain relationship with the ratio of xanthate as a collector and hydroxide ion concentration ([X-]/[OH-]). The higher the pH value, the lower the amount of xanthate adsorbed on the mineral surface.

According to the study, in the flotation ore of some insoluble oxides and silicate minerals, the pH value affects which kind of complex is produced after the chemical adsorption of the collector on the mineral surface. the pH is conducive to form hydroxyl complex (first oxyhydroxide) metals, is advantageous to increase the recovery rate. Test example oleic floating soft manganese ore beneficiation, can be obtained at pH = 8.5 when a relatively high recovery rate, this time generated more hydroxy metal complex + MnOH mineral surfaces.

According to the above, it can be known that any mineral flotation mine has a suitable pH value under certain flotation conditions, and only a suitable sorting index can be obtained under the condition of suitable pulp pH. .

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