With the development of steel industry and the chemical industry, the use of super iron concentrate more and more widely, research and development of super iron ore mining enterprises and become various research departments of a development direction. Super iron concentrate refers TF e≥71%, SiO 2 ≤1.5% of iron ore, it is both the mineral processing products, is a promising new functional materials development potential, mainly used in powder metallurgy, production Metallized pellets, magnetic materials, chemicals, environmental protection, food preservation and sewage treatment have great application value and market potential. Up to now, the raw materials of domestic powder metallurgy, magnetic materials and other industries mainly rely on iron scales, because the scale performance is unstable, the chemical composition is complex, and the supply is limited, it is difficult to meet the demand of high-grade powder metallurgy products. Due to the large scale of production, stable composition and less harmful impurities, many iron concentrates are used in many developed countries to produce powder metallurgy products and magnetic materials. With the continuous development of China's high-tech industry, the demand for high-grade reduced iron powder and ferrite will also increase.

Super iron concentrate powder is a high-purity magnetite powder obtained by fully purifying ordinary iron concentrate powder. Both the magnetite and the hematite in the iron ore can effectively extract the super iron concentrate, and the beneficiation process and method are generally determined according to the gangue type, the inlay size and the symbiotic relationship with the iron mineral of the ordinary concentrate of the concentrator. The main mineral processing methods include: flotation, magnetic separation, electro-election and fine screening. The production technology can utilize the original equipment of the mining enterprise, and the upgrading and upgrading of its products can realize the upgrading of its products and improve the economic value of the products.

The main process of the main plant of Banshi Mining Company is “stage grinding stage selection, fine screening and self-circulation process”. The grinding and dressing plant of the concentrator is separated from the filtration plant by about 200 meters, and the grinding concentrate is flowed into the filtration plant through the pipeline. It is concentrated and magnetically selected into a filter for dehydration. The grinding workshop is selected by the magnetic separation column as the final check to ensure the concentrate grade is over 67%. In the actual production process, since the magnetic separation column can effectively reduce the non-monomeric dissociated particles into the concentrate, the concentrates often produce more than 68% of the concentrate, and even more than 69% of the concentrates also occur.

First, the sample overview

The ore dressing plant produces iron concentrate as magnetite. The concentrate grade is 67.63%, the main impurity SiO 2 content is 4.05%, the S and P contents are relatively low, and the fineness is -200 mesh (-0.074mm) accounting for 87%. Under the microscope, the iron-bearing minerals have magnetite minerals and a small amount of hematite. The iron minerals that are not dissociated by the monomers are mostly self-shaped crystals and semi-automorphic crystals embedded in the gangue. The magnetite mainly Quartz continuous, large particles are often wrapped by quartz, there are also a very small amount of magnetite wrapped in small gangue. The magnet mineral is mainly in a dip-like structure with less veins. The full analysis of iron concentrate chemistry is shown in Table 1.

Second, the determination of the test plan

According to the workshop space and actual layout of the concentrator, the concentrator only removes a part of the concentrate from the filtration plant to achieve the purpose of purification by increasing the screening and magnetic separation process, and re-grinding or flotation of the concentrate. It is difficult to achieve for the concentrator. Therefore, the entire experimental scheme only considers the purification of concentrate by the combination of screening and weak magnetic.

Third, the test method

In order to further clarify the composition and bonding state of the test concentrate, it is judged whether the concentrate grade can be improved by magnetic separation under the existing particle size. First, the sample was subjected to a low field strength magnetic separation test using a magnetic separation tube. The test results are shown in Table 2. It can be seen from the test results that the concentrate grade cannot reach the target grade by the magnetic separation method under the existing particle size.

(1) Sifting fineness test

In order to further improve the concentrate grade, the concentrate is upgraded to the desired grade by sieving and magnetic separation without re-grinding. Screening tests were carried out using 200-mesh, 300-mesh, and 400-mesh inspection sieves, and the grades of sieve-level and sieve-level iron ore were as shown in Table 3.

It can be seen from the results of the screening test that as the particle size under the sieve becomes thinner, the grade of the concentrate under the sieve is also significantly improved. Under the microscope, the basic monomer of the sieve is dissociated.

(2) Magnetic separation test under different conditions

In order to further reduce the impurity SiO 2 content and increase the iron grade, three low-field magnetic separation tests were performed on the three undersize products. The test results are shown in Table 4. It can be seen from the test results that the low field strength magnetic selection is increased by about 0.5% on average, and the field strength has little effect on the grade. Through the above test, it can be determined that when the particle size under the sieve reaches -400 mesh or less, the concentrate grade can reach the requirements of the super iron concentrate, and the magnetic separation concentrate grade can be increased by about 0.5%. Therefore, the best test condition is that the sieve size reaches -400 mesh, and magnetic separation is performed to improve the concentrate grade.

Fourth, the proposed transformation plan

(1) Proposal of the program

According to the analysis of multi-condition test results and the actual situation of the concentrator, it is considered that a diverter valve can be added from the concentrating magnetic separation part to distill a small part of the concentrate for purification, and a Derrck high-frequency fine screen and a magnetic piece are added in the filter plant. The column is selected and sieved into the concentrate pool. Because the grade is still about 65%, it can be directly returned to the concentrated magnetic separation by pump and mixed with ordinary concentrate. Because the amount is relatively small, the influence on the grade of ordinary concentrate can still be small. Ensure the concentrate grade of more than 67% of the ordinary concentrate, sieve into the magnetic separation column, the magnetic separation column concentrate as the final super concentrate into the filtration system, the intermediate mine return concentrate pool and the sieve concentrate to return the concentrated magnetic selected. The proposed process flow is as follows:

(2) Equipment selection

In the fine particle grading equipment , the Derrck high-frequency fine screen produced by American company Derrick and its 0.05mm polyester screen have achieved good grading effect in other mines at home and abroad, and can effectively control the screen. Particle size -0.038mm reached more than 90%. Therefore, it is highly recommended to use the Derrck high-frequency fine sieve as a classification device for extremely fine particles.

In the weak magnetic separation equipment, the conventional magnetic separation equipment (cylinder magnetic separator) has a strong "magnetic agglomeration" effect on the magnetite sorting process due to the large magnetic field force. Magnetic agglomeration reduces the selectivity of the magnetic separation process, resulting in "magnetic inclusions" and "non-magnetic inclusions." The magnetic inclusions cause the continuum to enter the magnetic separation concentrate, and the non-magnetic inclusions cause the monomer gangue to enter the magnetic separation concentrate. Therefore, it is difficult to obtain a high-grade magnetite concentrate by a single magnetic separation method. The magnetic separation column is an electromagnetic low-viscosity magnetic field high-efficiency magnetic weight separation equipment which can fully disperse magnetic agglomeration and fully utilize magnetic agglomeration. In the Anshan Design and Research Institute using magnetic separation column to purify the super iron concentrate test, through the reasonable control of the rising water flow, magnetic field strength, magnetic field change cycle and the size of the discharge valve of the magnetic separation column, more than 72% of the super iron concentrate is effectively produced. mine. The magnetic separation column is the best sorting device for magnetite purification of super iron concentrate.

The filter plant has a total of 5 filters, and now it is used in two and three standby. The retrofit process can utilize an alternate filter that not only saves investment costs, but also makes full use of existing equipment without affecting existing production.

V. Conclusion

(1) The magnetite in the original iron concentrate is mainly composed of fine-grained disseminated structure, which belongs to fine-grained inlay, and its crystal structure is complete. The fine-grained useful minerals and gangue minerals are easily dissociated completely. The magnetic particles are relatively pure and are ideal magnetic raw materials.

(2) Due to the mineral processing technology and the location restrictions of the plant, the test can only be purified by screening and magnetic separation process without increasing the grinding equipment .

(3) After the original concentrate is screened, the -400 mesh grade grade can reach the required grade of the super iron concentrate, and then the magnetic separation column with good magnetic separation effect can throw a part of the middle ore to obtain the TFe71.76. %, super iron concentrate with SiO 2 ≤0.50%, can guarantee the grade of ordinary concentrate more than 67%, no tailings thrown, no metal loss.

(IV) The key to this process is to select the graded particle size. In order to meet the classification requirements, the Derrck high-frequency fine sieve with good fine-grained screening effect is selected for the screening and magnetic separation column with good magnetic separation effect.

(V) The proposed transformation plan is based on the actual situation of the ore dressing plant, which avoids the improvement of concentrate grade through the grinding and flotation process.

(6) The scheme is easy to be reformed and basically does not affect the existing production process. The new equipment cited has the advantages of advanced technology, low energy consumption, and a large increase in the grade of concentrate.

references:

(1) Zhang Jinrui on the research status and direction of super iron concentrate (M) Mining and Metallurgy Project 2000-12.

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