Green may g de mine located in the southern edge of the western part of the Qaidam Basin Qinghai Golmud, is an iron-based mining and gold were (with) cobalt, bismuth, silver, lead, zinc, copper, molybdenum, nickel Comprehensive deposits of ten minerals such as cadmium . Its biggest feature is that a variety of metallogenic elements can form an ore body separately, and can also be symbiotic and associated with each other. The types of deposits are unique and very complex. There are many ore bodies in the mining area. There are 88 iron and polymetallic ore bodies in the north and south. It is a rare iron-gold polymetallic deposit in China.

Among them, the ferrite, lead and zinc ore are low in grade, and the copper and molybdenum ore are less available due to the small amount of minerals. The gold, cobalt and antimony ore resources are difficult to select due to the complex nature of the ore. Points have been commissioned by a number of research units for experimental research. The iron ore body belongs to the skarn type ore. The ore nature is not very complicated. The proven reserves of iron ore approved by the Qinghai Provincial Reserve Committee reached 71.079 million tons. With the further deepening of geological exploration work, the resource reserves are expected to reach About 300 million tons, it is the main value of the mining area.

In 2004, Golmud City Government signed a project agreement with Inner Mongolia Qinghua Group Qinghua Mining Co., Ltd. to explore and develop Kendrick iron ore resources through investment promotion. Lanzhou Nonferrous Metallurgy Design and Research Institute was commissioned by Qinghai Qinghua Mining Co., Ltd. in 2005 to design the mining and mining project of Kendake Iron Mine in Golmud City, Qinghai Province. However, the ore dressing test research of iron ore is very limited, and it is still impossible to obtain representative ore samples for detailed experimental research, which poses challenges for our design work. Based on the analysis and research of limited experimental data, this paper proposes a reasonable and feasible solution to the problem of pyrrhotite in removing ore effects and indicators in ore by reference to the production practice experience of similar ore properties at home and abroad. The selection process is more than one case.

1. Kendrick iron ore properties

The iron ore in the Kendrick Mine is a skarn-type ore. The most important metal minerals in the ore are magnetite, pyrrhotite and pyrite, sphalerite, galena, chalcopyrite, pyrite, hematite and so on. The gangue minerals are mainly diopside , calcite , followed by chlorite.

Among them, the main useful component of ore is magnetite, which is about 50%. The largest particle size is 1.35mm, the smallest is 0.005mm, and generally 0.074mm. The semi-automorphic or granular granules of these fine particles are gathered together to form a block of different sizes, and the block is more than 1 mm; in addition, a small amount of magnetite is mixed in different degrees. In sulfides and gangue minerals; there are also vein magnetites filled in the gangue minerals; and some of the larger magnetites contain some irregularly shaped fine gangue mineral residues, possibly Affect the further improvement of the quality of magnetite concentrate.

Pyrrhotite and pyrite are the main harmful impurities of iron, and the content is about 5%. However, it may also become a useful component for comprehensive recovery, in which pyrrhotite is mainly (about 80%), and the two are often aggregated in a vein or agglomerate, and the particle size is generally large (0.1 to 0.5 mm). And often in the form of aggregates, the aggregates are mostly between 0.2 and 3 mm; a few are irregularly filled with magnetite particles, the contact limit is very irregular; secondly, occasionally pyrrhotite and magnetite The text is like a pattern, or magnetite is filled in the pyrrhotite fissure, but this part is very small, about 5%.

Second, the optional test results

For the iron ore of the Kendok mining area, the Central Laboratory of the Qinghai Geological Bureau conducted a preliminary optional test in 1979. The ore dressing test sample was taken by the First Geological Team of Qinghai Geological Bureau in 1979 as a secondary sample of chemical analysis.

The process flow and conditions recommended by the test unit are shown in Figure 1. The test indicators are shown in Table 1.

Figure 1 Test process and conditions

Table 1 Results of mineral processing test

It can be seen from Fig. 1 and Table 1 that for the iron ore in the Kendok mining area, the flotation desulfurization and regrind re-election process can obtain iron concentrate with a grade of 64.49% and a recovery rate of 86.92%. The process is basically suitable for the ore nature. However, the purpose of the test at that time was mainly for the geological evaluation of the deposit, and the comprehensive utilization of resources played a leading role. From the perspective of investment development, on the basis of making full use of mineral resources, enterprises hope to obtain the maximum economic benefits. The sulfur concentrate and high-sulfur iron concentrate obtained in the test process are too long for the Kendrick iron ore mine because the vehicle transportation distance is too long (approximately 200km of unmanned smoke, 385km away from the emerging industrial high-tech base Golmud) No economic benefits. In addition, the setting of flotation desulfurization operation in the test process is also worthy of analysis and research. For the 2.5 million t/a scale selection plant, it will directly affect the investment and benefit of the enterprise. Therefore, the design process should be optimized according to the specific conditions of the project and on the basis of the test process.

Third, the selection and determination of the selection process plan

According to the nature of the ore, the design should adopt the stage grinding stage selection process. The grinding fineness of a section is -0.074mm 65%~70%. The second-stage grinding fineness is -0.074mm 95%.

Considering that the harmful mineral pyrrhotite and pyrite in the ore are coarser in grain size, the pyrrhotite has both a certain floatability and a certain magnetic property. For this reason, the sulfur is desulfurized under rough grinding conditions. There are two possible options for a post-grinding sorting process. Scheme I: Flotation desulfurization after magnetic separation. That is, magnetic separation is used to remove most of the gangue and a part of sulfur (pyrite), and then the sulfur in the magnetic separation coarse concentrate (magnesia) is removed by flotation; scheme II: magnetic separation after flotation and desulfurization . That is, first remove the sulfur (pyrite and pyrrhotite) by flotation, and then remove most of the gangue by magnetic separation. The two process schemes are applied in practice. The characteristics of the scheme workers are: the process is relatively simple, the flotation operation deals with less minerals, the flotation reagents are used less, and the application school is extensive. The characteristic of Scheme II is that if sulfur is used as the object of recovery, the recovery rate is high. The process flow of the two schemes is shown in Figure 2 and Figure 3. The detailed comparison results of the two schemes are shown in Table 2.

Table 2 Comparison of two selection process plans

It can be seen from Table 2 that the scheme I is obviously superior to the scheme II in economy, and the design should adopt the scheme I, that is, the sorting process of the flotation desulfurization after the magnetic separation. The specific process structure is secondary magnetic separation, and the magnetic separation coarse concentrate flotation desulfurization adopts one rough selection, two sweep selection, and one selection. The crude concentrate after desulfurization enters the second stage of grinding and grading operation, and the cyclone overflows to obtain iron concentrate by secondary magnetic separation.

Figure 2 Scheme I process

Figure 3 Scheme II process

Fourth, the conclusion

From a design perspective, the process should be determined based on test data for the corresponding depth of a representative ore sample. However, under the conditions of market economy, some private entrepreneurs dare to take risks. Under the condition that the basic data is very limited, the technicians need to try to determine a technically feasible and economically reasonable process plan. From a certain perspective, this puts higher demands on our mineral processing work.

Based on the preliminary optional test data, the design process is optimized and improved as described above. 1 Unproduced sulfur concentrate and high-sulfur iron concentrate, the product scheme only has 61.5% iron concentrate of TFe grade; 2 will change the first magnetic process to float and then float, saving many flotation machine slots and flotation Pharmacy consumption.

The optimization and improvement of the above design process is theoretically feasible, but it still needs to be verified by experiments. The author has suggested that investment companies conduct verification tests when possible representative mineral samples, so that the design work is based on a sound scientific basis. At the same time, through the content of this article, we also hope that peer experts and scholars will give us guidance and guidance, and provide constructive opinions for our program.

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