Study on Removal Process of Wear Iron in Metal Mill in Non-Metallic Mineral Grinding

Non-metallic ore is an important industrial mineral, widely used in various industries. Non-metallic minerals (such as feldspar , quartz , kaolin, etc.) are multi-component symbiosis, and the impurity content, especially the content of Fe in it, determines the quality grade of the product. In practical applications, the purity of non-metallic mineral materials is relatively high. In order to reduce the content of iron impurities in non-metallic minerals, iron removal treatment is usually required in the processing.

At present, magnetic separation is the most extensive and effective method for removing iron from non-metallic ore. Generally, minerals are ground before iron removal to improve the separation and purification effects. However, in the entire grinding and conveying process of non-metallic minerals, mechanical iron is mixed, resulting in secondary pollution of raw materials by external Fe elements. Nowadays, the use of PP or PE material conveying pipes and ceramic flow troughs can well solve the iron pollution in the transportation process, and there is little research on the iron pollution generated during the grinding process.

Thus, the quarry paper as examples, non-metallic mill (stone mill, ball mill and other high aluminum) and wear metals (rod mill, ball mill, etc.) for grinding, sorting index difference comparative analysis under two conditions And optimize the separation and purification process of feldspar.

1 Indicator requirements for feldspar in various industries

At present, the iron content in China's feldspar ore is generally 0.2% to 2.0%. Table 1-3 lists the classification standards and quality requirements for feldspar materials in various industries.

2 The effect of grinding in different ways on the sorting index

With the increasing demand for non-metallic minerals, mineral processing plants each need to increase production, thus gradually grinding stone mill and other non-metal rod by a greater production grinding mill and the like conventionally used alternatively. The rod mill has a certain reduction in power consumption compared with the stone mill, the site occupancy has also dropped significantly, and its maintenance and maintenance volume is small, which is a good choice in terms of expanding production. However, since the grinding medium is metal, a large amount of mechanical wear iron is generated in the grinding process and mixed into the raw material, so that the iron content of the raw material is increased, and the difficulty of removing iron in the subsequent order is increased. Take a feldspar as an example, and carry out iron removal and purification according to the general sorting process (as shown in Figure 1).

Before and after grinding with different media, the content of each component in feldspar is shown in Table 5.

Table 4 Changes in composition of feldspar before and after grinding

It can be seen from Table 4 that Fe2O3 compared with stone grinding after feldspar grinding increased by 0.08%, and the increased Fe element should be derived from rod wear-wearing iron. The 13 000 Gs background field sorting test was carried out on the two materials after grinding by LGS-EX (lab-specific strong magnetic separator). The results are shown in Table 5.

Table 5 Magnetic separation results of feldspar materials

It can be seen from the results in Table 5 that even the material after the rod grinding and grinding can not completely select the mechanical iron generated during the grinding even with the strong magnetic separation equipment of the background field of 13 000 Gs.

Figure 2 shows the fine sand after feldspar warp grinding and strong magnetic purification.

It can be seen from Fig. 2 that there are still small black particles in the material after sorting.

3 Analysis of wear iron characteristics of metal mill

The main sources of analysis of mill wear iron are abrasive rods and liners. The grinding rod of the mill used in the test was 45# steel, and the liner was a commonly used Mn13. Among them, Mn13 is an austenitic structure and is a weakly magnetic material. It cannot be completely selected by magnetic selection alone.

The mill was run at no load and the particle size of the worn iron was analyzed. The distribution is shown in Figure 3.

As can be seen from Fig. 3, the particle size of the worn iron is mostly 1 to 10 μm, and 10 μm or less is 99% of the total amount, and the particle size is very fine. Therefore, the iron powder is mostly suspended in the liquid.

To aspirate particles from the liquid, the conditions are met: F sorption > mg + F surface

Where: F is the magnetic field suction, F is suction = k · Χ · B · V · dH / dl (where k is the custom suction constant, Х is the specific magnetic susceptibility, B is the separation magnetic field strength, dH / dl is Select the magnetic field gradient, V is the material volume), that is, the suction force of the same material under the same magnetic field and gradient is proportional to the material volume V; m is the mass of the material, m=ρ·V (where ρ is the material density), ie The mass of the same material particle is proportional to the material volume V; the F surface is the surface tension of the water to be overcome when the material leaves the liquid surface, F surface = σ·d (where σ is the surface tension coefficient of water, and d is the material effluent) Side length), that is, the surface tension of the same material is proportional to the length d of the water outlet. For the same material, the relationship between suction, resistance (mass plus surface tension) and particle size is shown in Figure 4.

It can be seen from Fig. 4 that in the case of a small particle size, the resistance will be significantly greater than the suction force, and the material cannot be sucked out; as the particle size increases, the resistance increases under the condition that the magnetic field strength and gradient are constant. Smaller, when the particle size reaches a certain size, the suction will be greater than the resistance, and the material will be sucked out of the liquid.

4 wear iron removal program

From the above analysis, it is known that the magnetic separation alone cannot completely remove the mechanical iron that the metal mill wears into the material. Since the wear iron is in the micro-grain grade, in order to better eliminate the interference caused by the subsequent process, this test adds multiple de-sludge equipment before the strong magnetic separation, in order to make these before the strong magnetic separation process. The fine fraction is removed.

The improved sorting process is shown in Figure 5.

It can be seen from Tables 7 and 8 that after the rod grinding and de-muding and then after strong magnetic separation, the sorting result of the material is relatively close to the result of strong magnetic separation after stone grinding.

5 Conclusion

The use of metal mills such as rod mills for the processing of non-metallic minerals is undoubtedly a good way to improve processing capacity and yield, but the mechanical wear iron produced during the processing is not completely sortable by magnetic separation alone. In this paper, the improvement and purification process of non-metallic minerals added to the desiccant equipment after grinding with a metal mill for this problem can reduce the influence of mechanical wear iron on the quality of the final fine sand, which is of great significance in actual production.