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Figure 1 Selected fractions of molybdenum plant
Fig. 2 Effect of grinding time on floatability of molybdenum ore
Figure 3 Effect of grinding and grinding on the floatability
Figure 4 Mica surface after co-grinding with molybdenite
Figure 5 Mica surface X-ray diffraction pattern
It is absolutely necessary to ensure sufficient molybdenite monomer dissociation degree, the intermediate product of the molybdenum ore flotation regrinding modest, but and not "through the mill." Once the “over-grinding†is caused, the recovery rate and grade of molybdenum concentrate will decrease significantly.
Zhang Zheng, Lin Chun Yuan et al JINDUICHENG three fine foam products made by regrinding found: re-ground level, and then pulverized with a sample of an increase of between 65% -200 mesh to -400 mesh 96.7%, molybdenum concentrate grade And the recovery rate has also increased significantly. However, when the fineness of regrind continues to increase and the fineness reaches 100% - 400 mesh, the grade and recovery rate of molybdenum concentrate not only does not rise, but decreases (see Figure 1), and there is a clear "over-grinding".
The explanation of the mechanism of "over-grinding" mainly includes the following:
After research, Sutherland, Clark, Jerry Yajin, Shechin and others believed that the fine sulfide minerals produced by “over-grinding†were too small and light, and the collision energy was too small to break up the solid particles. The water layer between the bubbles and the adhesion occurs.
Lin and Samacin Darren (1972), Lin (1975), Gan Mickey and Glasson have shown that long-term grinding leads to important physicochemical changes on the solid surface, which gradually make the minerals amorphous. Surface lattice distortion can also cause crystal shape changes, resulting in solid oxidation or chemical reaction with liquid medium.
In the past, the traditional view of molybdenite over-grinding believed that over-grinding caused a decrease in the “face-to-face ratio†of molybdenum ore, and an increase in the proportion of “edges†increased the influence of Pe and Ph (“edge effectâ€), causing P (falling off). Pressure) changes, even reverse. Once P>0, according to the judgment formula, molybdenite will not float. This is similar to the results of the study by Samasin Daren and others. However, “over-grinding†only affects the mineral surface, while Samacin Daren believes that “over-grinding†affects the internal structure of the mineral. It seems that the two should be combined. When shallow over-grinding, it mainly affects the "face-to-edge ratio". When the depth is over-grinded, it causes lattice distortion, and the molybdenum amorphous change is dominant.
The adsorption and agglomeration of various slime affects the quality and recovery of molybdenum concentrate, which is another reliable explanation for “over-grindingâ€.
After the molybdenum ore is broken, there are two types of forces on the fracture surface: the "face" molecular bond fracture exhibits van der Waals force; the polar bond on the "rib" exhibits a polar force after fracture. They are attracted to the surrounding medium or other similar particles in order to achieve a balance of forces, resulting in agglomeration. As the "excessive wear", a large specific surface area mineral particles, greatly increased risk of inter-particle contact, between the solution of monomers has been away from molybdenite, or molybdenite minerals similar to other properties (typically talc, sericite, etc. Easy Floating, easy to muddy gangue) Adsorption, agglomeration, formation of "symbiotic" agglomerates into the molybdenum concentrate, or into the tailings.
Xing Yongqing believes that the “face-to-edge ratio†of molybdenum ore is not reduced, and the “over-grinding†of molybdenite is the result of agglomeration of molybdenum fine mud and a large number of gangue fine mud. He used the molybdenum deposit of the Yangjiazhangzi molybdenum ore, the talc of the Xinhua molybdenum ore, the quartz of the Jinduicheng molybdenum ore, and the samples were prepared in a ratio of 2:8. The samples were ground and aerated by agate . The effect of grinding time and sample on the grade and recovery of molybdenum concentrate is shown in Figure 2.
It can be seen from the figure that the grinding time is lengthened and the quality and recovery rate of molybdenum concentrate are continuously decreasing. The influence of several gangue minerals is also different. Mica and talc have greater interference than quartz, which may be similar to the layered structure of molybdenum ore, which is more likely to be related to the adsorption and agglomeration of molybdenite. [next]
Xing Yongqing also studied the effect of molybdenum ore mixed with gangue after grinding, or first separately grinding and mixing to reduce the flotation of molybdenum ore (see Figure 3).
Obviously, when the molybdenum ore and the gangue are finely ground together, the new surface between the ore particles is more likely to cause adsorption and agglomeration. Therefore, the fine grinding ratio of the fine grinding is more disturbing to the molybdenum ore.
To confirm the existence of adsorption and agglomeration. Xing Yongqing also made a surface analysis of the mica flakes mixed with molybdenite. The Auger spectrum measurement is shown in Figure 4; the X-ray diffraction analysis results are shown in Figure 5.
A—the moire energy spectrum of the mica before the measurement; b—the Auger spectrum after the sputtering of 3 mm
A-before surface treatment; b-surface after one treatment; c-surface after secondary treatment
As shown, the mica surface contains molybdenite. The molybdenite is also present only on the surface of the mica and can be eliminated by sputtering or surface treatment. It has been confirmed that molybdenum ore adsorbs or contaminates the surface of mica during mixed grinding.
As mentioned above, the reasons for “over-grinding†are different and are still under study. However, the serious impact of “over-grinding†on molybdenum beneficiation has been widely known and attracted everyone's attention.
In order to achieve sufficient monomer dissociation, the intermediates of molybdenum beneficiation must be finely ground. However, excessive fine grinding will cause "over-grinding". To this end, each molybdenum plant should be based on the characteristics of the ore, after research to determine the best sorting granularity, to obtain better production indicators.