The selection of the working position of the fine screening equipment in the beneficiation process is directly related to the production technical indicators and economic benefits of the concentrator. Different types of concentrating plants should use different fine sieving and regrind processes according to different requirements. The principle of fine screening and regrind principle is shown in Figure 1. The fine sieving and regrinding process can be generally classified into three categories: fine sieving, self-recycling and re-grinding, fine sieving, separate regrinding, and fine sieving, self-recycling, and re-grinding. The fine screening and self-circulating re-grinding process is actually a combination of the first two types of processes, and there are few applications at home and abroad. Therefore, only two types of processes are described below. The ore processed by the Dashihe Concentrator belongs to the Anshan-type lean magnetite and is a strip-like and patch-like structure. The main gangues are quartz , hornblende, pyroxene and the like. Ƒ mineral hardness of 10 to 12, a density of 3.3t / m 3, bulk density of 2.2t / m 3. 98% of the iron mineral magnetite was ore TFe is 25 to 27%, 37 to 42.8% rate of the magnetic . The mineral inlay has a particle size of 0.5 to 0.062 mm, that is, 32 to 250 mesh, of which -200 mesh accounts for about 85%. In general, the ore is of the type that is easy to grind and good. [next] The plant uses a fine screening process and production indicators that do not require a fine screening process. The fluctuations of the concentrate grades in the two production processes are shown in Figure 4. The fine iron grade of the fine screening process is as high as 66.19%, the probability of grade 65~68% is 86.67%, and the lower than 64% is only 1.49%. The concentrate grade is high and stable, mainly due to fine screening. It can ensure that the final selected particle size of the under-sand products is steadily maintained at -150 mesh 90-95%. The concentrate grade without the fine screening process averaged 64.31%, and fluctuated within a large range of 62 to 67%, and even 8.33% of the concentrate grade was less than 62%. From the change of the secondary cyclone grading overflow particle size (150 mesh) without the fine screening process (the figure shown in Fig. 5), the -150 mesh content is a large fluctuation of 50 to 90%, and the pattern and the fine sieve are not used. The variation curve of the iron ore grade of the process concentrate (Fig. 4) is similar, which indicates that the cyclone without the fine screening process fails to ensure the final inclusion of the particle size, resulting in a low grade of concentrate iron and a large change. Example 2: The Nanfen Concentrator completed a fine screening self-recycling process in May 1979 (Figure 6). In December of the same year, the plant conducted several quality inspections on the production process of the four-selection workshop. See Figure 7. After the fine-screen self-recycling and re-grinding process, the plant improved the grade of concentrate by 2.61 under the condition that the recovery rate was not reduced. ~2.71%, the average iron concentrate grade of the whole plant reached 68.08% in 1979, and the mill processing capacity increased by 1.5~2.69t/(tai · h), which achieved good results.
Specification:
1) Main machine dimension: 9.65m*2.23m*2.4m
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For the old selection plant, the fine sieve is used for re-grinding, and only the fine sieve and the original are set.
The ball mill of the production system constitutes a closed circuit, which constitutes a fine screening and re-grinding process. This fine screen regrind process, which is based on the original system ball mill, is what we call the fine screen self-circulation regrind process. Because the fine screen self-circulating and re-grinding process is relatively easy to transform the old plant, it is the most widely used fine-screen regrind process in China. Especially magnet dissemination size coarse ore processing plant, the flow separating effect is particularly significant.
According to the original ball mill load, the return amount of the fine sieve is generally controlled at 20 to 40%. Too large will destroy the grinding effect and create a vicious circle.
A few typical columns are listed below.
Example 1: Flow chart of fine screening and re-grinding of Dashihe Concentrator.
In May 1977, the initial mass application process of fine screening was shown in Figure 3. [next]
After years of production practice, the following improvements have been made:
(1) The upper sieve material is changed from the return cyclone to the direct return to the secondary ball mill to reduce the load on the glue pump and the cyclone.
(2) The fine mesh screen hole is changed from 0.3mm to 0.2mm.
(3) It is transformed from a section of 400×1524mm fine sieve into a two-stage fine sieve (0.2mm for one fine sieve mesh and 0.15mm for two fine sieve mesh), one angle of inclination 50°～51°, and the second section inclination angle 55°～ 56°.
After the improvement, the classification efficiency of the fine sieve is increased by 15.04%, and the return per hour of each two-stage ball mill is reduced by about 8 tons. After entering the 1980s, the iron concentrate grade of the plant has exceeded 68%.
2) Bending machine dimension; 3.8m*2.23m*2.4m
3) Suitable material: galvanized steel, colored steel, etc
4) Coil thickness: 0.6 –1.5mm
5) Roller stands:16
6) Roller diameter:80mm
7) Totally power:18.5kw
8) Main Power:7.5kw; Hydraulic power:4.0kw; side bending power:1.5kw*2
Curving power:4.0kw
9) Roller material: 40Cr
10) Shaft material: high grade #45 steel
11) Cutting Blade material:Cr12 steel
12) Machine speed: forming speed 13m/min Seaming speed:6m/min
13) Span : ≤45m
14) Power supply: AC380V±10%, 50Hz, or as per your requirement
