Super concentrate selection process
Effective super concentrate extracted from natural iron ore magnetite and hematite only. In addition to the rich ore (such as Brazil's hematite containing only about 0.5% SiO 2 ) can be directly extracted from the super concentrate, generally from the commercial concentrate. Super concentrates have different quality requirements depending on their use. For example, in terms of SiO 2 content, it is required to produce sponge iron as a steelmaking raw material of less than 2%; for advanced magnetic materials, it is required to be 0.2% or less. The requirements between them vary by more than 10 times, so the process of selecting super concentrates is varied. The main processes include flotation, magnetic separation, electro-selection and fine screening.
First, flotation flotation can be divided into positive flotation and reverse flotation. For high-rich hematite (or specular iron ore), both high-quality super concentrates can be obtained by both positive flotation and reverse flotation.
From the research and production situation at home and abroad, the current desiliconization from magnetic separation concentrate by cationic reverse flotation is one of the effective methods to improve the grade of iron concentrate. The desiliconization float uses a cationic collector for reverse flotation, and can be floated in a neutral or alkaline slurry without adding an iron mineral inhibitor.
US Pili Qi beneficiation plant with an annual part of magnetic concentrate production 3-6 million t super concentrate for the manufacture of magnets. The magnetically selected concentrate containing 69% of iron and 2% of SiO 2 is used as a collector for the quaternary ammonium salt, and the gangue and the continuum are selected from the flotation, and a super iron concentrate containing 71.5% of iron and 0.15% of SiO 2 is obtained.
Federal Republic of Germany uses an alkyl hydroxyacetate amine flotation iron ore magnetic separation concentrate. The amount of amine salt was 110g/t. Under the condition of natural pH, a super concentrate with 71.3% iron and 1.01% SiO 2 was obtained by one rough selection and two sweeps.
In the United States, the Mersby region uses a cationic reverse flotation process to treat a magnetically selected concentrate containing 4% SiO 2 to produce a super concentrate containing less than 2% SiO 2 . The process is characterized by the elimination of the return of intermediate products as much as possible, emphasizing the separate treatment (including flotation, magnetic separation, fine screening, etc.) to ensure the quality of the concentrate. It can also be seen from the figure that at the same time as obtaining the super concentrate, a common concentrate suitable for smelting of the blast furnace can be obtained.
The US Mines Bureau conducted small and continuous tests on some magnetites in the Lake Superior Lakes, Figure 1.
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China Northeast Institute of Technology began this research in the early 1980s. They started from the investigation of the genesis of the deposit and the type of ore. The cationic surfactant was used as the collector of quartz . The desiliconization flotation of the magnetic separation concentrate was studied. The super SiO 2 content was less than 0.5%. Concentrate. The raw materials they have tested include Anshan Iron and Steel Sintering Plant and Qi Dashan two kinds of roasting magnetic separation concentrates, Qidashan magnetic separation concentrate, Shantoushan magnetic separation concentrate, Nanfen magnetic separation concentrate, Baoguo magnetic separation concentrate. , Yuanjiagou magnetic separation concentrate, Pandishan magnetic Yi concentrate, Zhoujia magnetic separation concentrate and Dashihe magnetic separation concentrate. Among them, Nanfen's magnetic separation iron concentrate has the best desiliconization flotation effect, and the obtained super concentrate TFe is greater than 72%, and SiO 2 is between 0.24 and 0.17%.
On this basis, from October to November 1982, the Northeast Institute of Technology cooperated with the Yingkou Pandishan Iron Mine to carry out industrial experiments with Nanfen magnetic separation concentrate, and obtained 72.17% of iron and 0.24% of SiO 2 . Super Concentrate. In 1984, the Northeastern Institute of Technology further studied the magnetic separation concentrate of Nanfen in the laboratory, reducing the SiO 2 content to below 0.1%.
The Northeast Institute of Technology conducted two experiments on the desiliconization flotation of several magnetic separation concentrates in the Benxi area of ​​Anshan. The first step is the conditional test. The test uses a 100ml M•S type (XFG-63 type) small flotation machine. Under the condition of stirring speed of 1600r/min, the amount of mineral sample used in each test is 25g to find the appropriate grinding size. Flotation process and flotation conditions (such as pH value, type and amount of collector and foaming agent, desliming effect, etc.). The second step is to check the test. After the test, a homogenous flotation machine with a tank capacity of 1000 ml was used, and the amount of the ore sample used was 300 g each time, and the test was carried out according to the suitable conditions found in the first step. The results obtained from the inspection test are similar to those of the conditional test.
The synthetic dodecylamine RNH 2 (R=C 1 l～C 1 3) used in the test is a product of Dalian Grease Chemical Factory, and is added with hydrochloric acid when used.
According to the nature of the magnetic separation concentrate, the test procedure is basically divided into two types as shown in Fig. 2 and Fig. 3, and the flotation is carried out under a suitable grinding grain size.
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The above tests were carried out without any adjusting agent, and the flotation was carried out under natural pH conditions. The flotation slurry temperature is 20 ° C. If it can further finely grind and raise the flotation pulp temperature, it is also possible to improve the flotation index.
Recently, Angang Dagushan Concentrator used the original production process to intercept a fine sieved screened product for reverse flotation, and obtained ultra-pure concentrate with 71.5% iron content and 0.5% silicon content. For the production of magnetic materials.
The flotation adopts 10 sets of 3A flotation machine, and the medicament is made of dodecylamine prepared by hydrochloric acid for acid reverse flotation. After a period of reverse flotation, the concentrate is the final product and its tailings are returned to the original process.
The product size of ultra-pure concentrate is -200 mesh, accounting for more than 95%. A fine sieve is added after the reverse flotation operation to ensure the quality of the product when the production is fluctuating.
The plant is currently only in small batches of intermittent production according to user needs.
Second, magnetic separation
For some magnetites, a high purity super concentrate can be obtained using a dry or wet weak magnetic field separator, or a combination of the two. The Nanfen Concentrator has used a cylindrical weak magnetic field magnetic separator to process the rich ore for the production of sponge iron. In recent years, many units have used the weak magnetic separation or re-election to obtain high-quality concentrates with a TFE of about 71% in the laboratory.
Benxi Iron and Steel Company Iron and Steel Research Institute uses the grinding-dewatering tank-magnetic separation process for Nanfen magnet concentrate to obtain TFe71.9%, SiO 2 less than 0.6%, phosphorus and sulfur content less than 0.02% high purity super fine mine. The small test and batch production test process is shown in Figure 4.
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The tests were carried out by magnetic separation at various grinding sizes.
For hematite ore, the wet magnetic field magnetic separator has a good effect. In 1965, the Canadian Presti Steel Company purchased the specular iron concentrate selected by the spiral concentrator from the Cartier Mining Company and grinded it to -35. As a feed to the Jones magnetic separator, the content of SiO 2 by strong magnetic separation decreased from 6% to less than 0.3%, and the insoluble content decreased to about 0.4%. The plant produces approximately 20 tons of high-priced iron oxide per day for the manufacture of barium ferrite. Further, Montreal, Canada metal powder produced by a method similar to the insoluble material is less than 0.2% iron oxide product, yield 100t / d.
The first large-scale super concentrate plant in Canada, built in 1976, Sedek-Dorsco, used a Jones magnetic separator to process the specular iron ore concentrate (-14 mesh) produced by the spiral concentrator, producing 3 million tons per year. Super concentrate, made into pellets for direct reduction. The ore grade is TFe66.5%, SiO 2 5%; super concentrate grade TFe68.7%, SiO 2 1.5%.
The Dorsey Company of Brazil treated the hematite (-100 mesh) with a Jones Strong Magnetic Separator to obtain a super concentrate containing 1.5% SiO 2 .
Under the condition of reducing the current intensity, the strong magnetic field magnetic separator can also treat the magnetite to obtain the super concentrate by the strong flushing action of the water flow, reaching 70.8% TFe and 1.5% SiO 2 .
The Soviet ferrous metal beneficiation research and design institute conducted laboratory tests and semi-industrial tests on the process of producing high-quality concentrates from the magnetite of the Dzerzhinsky Mining Bureau.
The original design was to select the concentrate from the central concentrator of the Dzerzhinsky Mining Authority and then temper it by hot pressing to produce a super concentrate. According to the plan, it is necessary to produce 65,000 tons of super concentrate miners with a SiO 2 content of 0.15 to 0.4%, and complete the design of an industrial test plant with an annual output of 5000 tons.
In 1983, the concentrator researched and developed a process to produce super concentrate with a SiO 2 content of less than 1% using magnetite quartzite as a raw material. To this end, in the existing process of the Central Concentrator, a classifier overflow pre-de-sludge, hydraulic grading, magnetic separation and a final selection of concentrates using a magnetic-hydraulic sorting machine were added. In the grinding section, the processing capacity and grinding concentration of the mill are reduced, so that the grinding grain size is maintained at -0.044 mm 95 to 99%. The ore sample of the process test is the ore (magnetite quartzite) currently produced by the Paris Commune member and this A magnetic product of dry ore magnetic separation. The average iron grade of the selected ore is TFe32.7% and magnetic iron 23%.
The process flow for the production of super concentrates by the central selection plant of the Dzerzhinsky Mining Bureau is shown in Figure 5.
Brief description of the process: The crushed material is fed into the MLLIP-36×40 ball mill for three-stage grinding. The volume ratio of each section of the mill is 1:1:1. The first stage is classified by IKCH-30 single spiral classifier, the second stage and the third stage using ф360mm hydrocyclone. During the test, the production capacity of the first stage mill was 60-84.5t/h. Under the condition of average production capacity of 79.2t/h, the overflow of the classifier was -0.071mm, which was 73.4%, and the new generation was -0.07. The unit production capacity of the lmm class is 1.44t/m 3 •h. The grinding capacity of the hydrocyclone is 86.2～90.9%-0.044mm when the grinding capacity of the second stage is 25.3～36.1t/h. The unit production capacity according to the particle size is 0.29-0.5t/m 3 •h. The particle size of the third-stage grinding is 92.3-gg.1%-0.044mm. The unit production capacity according to the particle size is 0.04. ~0.10t/m 3 •h. Under this grinding condition, the concentrate in the V-stage beneficiation contains 69.7-70.3% iron and 2.8-2.4% SiO 2 . The hydrocyclone with diameter 250mm and 150mm The classification of the fine-grained product and subsequent magnetic separation (paragraph VI) can increase the concentrate grade to 70.5 to 70.9% and reduce the SiO2 content to 1.1 to 1.5%. This is done by a magnetic-hydraulic sorting machine. The concentrate is further refined to increase the concentrate grade to 71.2% and the SiO 2 content to 0.9%.
The central concentrator of the Dzerzhinsky Mining Bureau produces 5,000 tons of super concentrate with a SiO 2 content of 0.9% per year. The estimated annual economic benefit is 287,400 roubles. It is currently being explored whether it is possible to mechanically produce super concentrates with a SiO 2 content of at least 0.4%. [next]
Third, the electric selection Ф150mm stainless steel friction electric cyclone sorting machine one electrode grounding, one connected with the high-voltage pulsating power supply, under the condition that the electric field strength is maintained at 1.5kV/cm, the separation of the dried hematite and quartz is tested. Received good results. The schematic diagram of the test process is shown in Figure 6.
The overflow product R 2 of the cyclone separator is mainly a clay portion in the ore, which is characterized by a very fine particle size. If the product C 1, M 1 and M 2 together, resulting in a yield of 83.63, while the SiO 2 content is less than 0.17%, suitable for the production of hard ferrite .C 1 second choice available SiO 2 content It is a 0.1% super concentrate with a yield of about 70%, suitable for the production of soft ferrite, and the remainder containing SiO 2 0.24% can be returned or combined with M 1 and M 2 for the manufacture of hard ferrite.
4. Fine sieve The fine mesh is used to screen out the continuous body and coarse gangue in the magnetic separation concentrate, and the super concentrate can also be obtained under certain conditions. For example, the first magnetic separation concentrate of the Piric concentrator in the United States is sieved by two narrow sieves with a sieve opening of 0.1 mm, and the second sieve fine mesh is combined with the magnetically selected concentrate to obtain TFe69. %, SiO 2 2% super concentrate.
In summary, the methods for producing super concentrates are various, and which ones are used depends on the use of super concentrates and the nature of the ore. At present, for hematite, only the hematite (mirrorite) rich or re-elected concentrate with coarser grain size can be obtained by strong magnetic or positive flotation. For magnetite, the cationic desiliconization reverse flotation method works best.
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