Grinding regularity of iron ore (3)

In coarse grinding, both of these fractions are coarse-grained and have a less-too concave particle size characteristic curve, i.e., which contains a relatively small amount of very fine fraction (e.g., 0.02 to 0 mm or less). As the particle size of the honing is reduced, the fine-grained content of the ground mineral material increases, and thus the characteristic curve of the particle size composition obtains a concave shape. Experimental research on some of the same grain size in order to evaluate the size distribution obtained under various grinding conditions of particle sizes, is carried out to identify separated from the ground to a particle size of various iron-containing quartzite 0.074 ~ The content curve of 0.05~0 mm grain size in 0 mm grain size (Fig. 2). All kinds of quartz rock, the particle size decreases as grinding, 0 mm grain size from 0.074 to 0.05 to 0 mm size fraction content increased. This added feature varies with mineral composition. For the red iron-magnetite quartzite, it is the most obvious and uniform. At the same time, the 0.05~0 mm grain size is also very different in terms of its particle size composition, which depends on the particle size of the ground material from which the grain size is separated. Figure 3 shows the relationship between the specific surface of the 0.05~0 mm grain size and the grain size of the material. As the grinding size decreases, the specific surface area of ​​the 0.05~0 mm fraction increases sharply, because the fine fraction and fine fraction are increased; in the ground material, the 0.05~0 mm fraction exceeds 70. This range is particularly noticeable in the range of %. For some types of iron-bearing quartzite, this relationship curve has almost linear properties (Fig. 3 Magnetite quartzite from Southern Mining Company).

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The degree of grinding studied has an effect on the particle size composition of the same grade of grinding products, mainly because the total and actual unit production capacity of the qualified products decreases as the grinding size decreases. From a kinetic point of view, this situation clearly illustrates the law of the law, which proves that the increase in surface area is proportional to the increase in grinding power. According to this principle, it should be pointed out that under the same power consumption conditions, the unit production capacity of the mill according to the qualified product of the specified particle size decreases with the decrease of the product rate in the ground material, which means that the granularity of the qualified product. The characteristics are not constant. In terms of particle size, the quality characteristics of the ground product no longer conform to the evaluation of the grinding process by particle size, and to a large extent everything shows the evaluation of the grinding factor by the increase in the surface area of ​​the ground material.
For this reason, it is reasonable to regard the grinding process as a process of changing the specific surface area of ​​the material to be ground. This is also necessary because of the use of the pelletizing method for the agglomeration of the concentrate. When the ball is formed, the specific surface of the concentrate is the main parameter determining the normal progress of the pellet production process.
In order to identify the main regularity of the new surface of the material produced during grinding, the grinding power equation for the grinding material according to the particle size obtained above can be utilized. The actual unit production capacity of the grinding machine according to the qualified grain size is changed to the unit production capacity value of the grinding machine according to the newly generated surface meter, so that the newly generated total surface during grinding can be expressed by the following equation:

S=bVt

Total surface of ground material

S ₀₆ =bVt+S _и

Where S ₀₆ - the total surface of the newly generated ground material, m ² ;
B——the unit production capacity of the mill according to the newly generated surface meter, m ² /m ³ •hour;
T——grinding time, hour;
Sи - the total surface of the original material, m ² . [next]
The specific surface of the ground material:

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It is not difficult to see from the mathematical formula of closed-circuit grinding that the qualified grinding products are discharged from the process due to the formation of qualified grinding products and the increase of raw materials in the ore feeding machine. The grinding machine production capacity in the mining process is always higher than in the open grinding process. This increase depends in part on the efficiency of the grading equipment and the magnitude of the cyclic load, which also depends on the specified efficiency.
Under normal circumstances, the calculation of multi-component iron ore grinding regularity is a problem with many algorithms. The solution to this problem is bound to use differential to study the grinding rate of the components that make up the ore. The amount of material that has been ground can be calculated as a weighted average of the individual grindings of the individual components having different grinding rates. Assume that the ore does not contain qualified grinding products and [next]

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Comparison of the data calculated from the derived formula with the experimental data proves that they are extremely similar. In this case, it is actually completely similar in the rough grinding range. In the experimental study, there was some reduction in the grinding rate in the fine grinding range. Obviously, on the one hand, this has a close relationship with the particles to be ground, and on the other hand, the particles are ground. It is closely related to the improvement of particle strength. Obviously, the interaction of the particles is manifested in the effect of the coarse particles being protected by the contact of the impact surface by the coarse particles. According to the modern concept of solid physics, as the particle size shrinks, the increase in particle strength is closely related to the presence of natural defects in the microfracture shape of the material to be ground. The rupture process during grinding is usually started mainly in the above-mentioned defective places. As the grinding progresses, a new source of artificial micro-fracture is formed in the weakest part of the material, and these fracture sources are later developed to form the main fracture. As the defects in the material structure and the weakness are reduced, the grindability deteriorates, and under certain grinding conditions, the acceptable grain size or the newly formed surface actually stops increasing when a certain particle size is reached. The experimental study of the magnetite quartz rock thousand-way open grinding in the Krivorog mining area proves that the increase of the newly generated surface is slowed down when the surface of the ground material reaches 6000~8000 cm ² /g, reaching 6000~ When 8000 cm ² /g, it actually stops.
The particle size or specific surface of the ground material may be referred to as a limit value for the grinding method and conditions.
Taking into account the above situation and using the basic principles of formulating differential equation (3), the regularity of the grinding dynamics in the form of differentials according to the newly generated surface can be written as: [next]

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