I. Overview
Fluorite, also known as fluorspar, is the most important fluorine-containing industrial minerals, widely used in metallurgy, chemicals, ceramics, building materials and other departments. Metallurgical grade fluorspar concentrate do block co-solvent in steel smelting, which was accounted for about 50% of world production of fluorite. The acid grade fluorite powder concentrate consumed by the chemical industry accounts for more than 40% of the world's fluorite production and is increasing year by year. The products of the fluorine chemical industry mainly include hydrofluoric acid, hydrochlorofluorocarbon refrigerants, fluorine plastics and fluorine fine chemical products. Among them, hydrofluoric acid is a key raw material for the production of various inorganic and organic fluorides.
SiO 2 and CaCO 3 are the main harmful components of acid grade fluorite powder. The presence of SiO 2 increases the raw material consumption of the hydrofluoric acid production, and the silicic acid formed by the siliceous acid contaminates the hydrofluoric acid. The presence of CaCO 3 causes segregation of carbon dioxide to cause the mixture to expand.
Located in Yongfeng County, Jiangxi Province, Yongfeng Fluorite Mine is rich in reserves and belongs to a single fluorite deposit. The fluorite is produced in the form of lumps, granules, clusters, strips and fine particles. The gangue mineral is mainly quartz , accompanied by a small amount of feldspar , calcite , kaolin and so on. The ore bodies are often interspersed with fine quartz veins into a grid.
Yongfeng Fluorite Selection Factory was established in 1987 with a designed production capacity of 300t/d. Since the start of production, it has been using a section of grinding, one coarse and one sweeping flotation process. Because the ore source is different, and some are rich ore and some are poor ore after hand-selected concentrate. The nature changes greatly and the inlay is complicated. Therefore, the original process is used for production, and the flotation effect is not good. The lower, generally less than 70%, the concentrate containing SiO 2 often exceeds the standard, causing export sales difficulties or being downgraded and reduced prices. Therefore, there is an urgent need for technical improvements in the production process. Entrusted by the factory, Changsha Industrial College has undertaken the task of testing new technologies. The test work achieved good results with the cooperation of the rectangular.
Second, flotation test
(1) Samples and test methods
After the sample is taken from the existing powder ore bin, the ball mill leaks and deposits the powder ore under the ore belt. Since the amount of leakage is small, the deposit is formed in a few days of production cycle, and the particle size is fine, so the sample is representatively good. After the sample was collected, it was wrapped in a plastic bag, and the particle size was visually observed to be -2 mm. The water content of the ore sample was determined to be 8.4%. The main components of the sample are shown in Table 1.
Grinding was carried out using a laboratory roller bar mill, and a 1 L and 0.75 L flotation machine was used for the flotation test.
(2) Relationship between grinding fineness and grinding time
After the sample, the wet weight of each sample was 327.5g, which was equivalent to 300g dry ore, and 100mL of water was added to the rod mill for grinding test. The result is shown in Figure 1.
(3) Influence of different grinding fineness on rough selection of fluorite
Imitate the variety and dosage of the chemicals used in the factory. The dosage of fixed Na 2 CO 3 is 1500g/t, NaSiO 3 200g/t, oxidized paraffin soap 700g/t, flotation weight concentration 30%, and 1L flotation machine for different grinding fines. The effect of the degree on the rough selection test, the results are shown in Figure 2.
(4) Relationship between regrind fineness and regrind time of flotation coarse concentrate
According to the flotation results of (3), the coarse grinding fineness is selected to be -0.074mm, accounting for 50%, and the remaining conditions are copper (III), and the flotation coarse concentrate is obtained. Speaking of flotation coarse concentrate into the rod mill re-grinding test, the results are shown in Figure 3.
(5) Crude concentrate re-grinding flotation process I closed circuit test
According to the expectation of the process transformation, considering the production practice of the original process, the refinement fineness need not be too fine, as long as the SiO 2 of the concentrate can not be exceeded, the recovery rate can be improved to reduce the re-grinding production cost. Considering comprehensively, the regrind fineness is selected to be -0.074mm, accounting for 78%.
Due to the high quality requirements of fluorite concentrate, the production process is long and the number of selections required is high. Therefore, if the whole process of open-circuit test is carried out in the test, it will be difficult to float if the fluorite is not added after several times of selection. And an open circuit test, in succession generation ore, the amount will be later refined mineral less, it is difficult to obtain stable results. In summary, open circuit tests should be avoided in the full flow test of fluorite flotation, but the results should be obtained directly using closed circuit tests.
The closed circuit flow I selected is shown in Fig. 4. According to the conventional method, after 5 consecutive samples of the ore sample, the weight of the 4 # and 5 # -like flotation products reached a stable equilibrium of leaching. They were weighed and quantified separately, and their weighted averages were calculated. The obtained indicators are shown in Table 2.
(6) Refining flotation process of coarse concentrates II closed circuit test
Considering that the concentrate index in (5) is 0.97% of SiO 2 , it is necessary to further improve the process in order to stably maintain SiO 2 <1% in production. And the recovery rate indicator may improve.
According to the comprehensive analysis, the number of selections increased to 7 times, and the middle 1 with higher mud content was returned to the sweeping to avoid the influence of rough selection of fluorite. According to this, the closed circuit test procedure of Process II is shown in Figure 5. After 6 consecutive samples of the ore sample, the weight of the 10 # and 11 # sample flotation products reached a stable balance of entry and exit. They were weighed and quantified separately, and their weighted averages were calculated. The obtained indicators are shown in Table 3.
Third, discussion
(1) Comparison of new technology and original technology
It can be seen from the results in Table 4 that the coarse concentrate re-grinding flotation process II is used to obtain better indexes. Compared with the original process (six-time selection of one-stage grinding), the quality of the new process concentrate reached the premium grade under the condition of the flotation reagent system, and the flotation recovery rate increased by more than 10%. Obviously, the new process has greater advantages than the original process, and can be used as the basis for the current process transformation of the production process.
(2) Rough grinding and regrind index
The coarse grinding size directly affects the production capacity of a section of grinding machine, which is the production capacity of the plant. If the coarse grinding degree is coarse, the mill production capacity will increase. At the same time, it also directly affects the size of the coarse recovery. From Figure 2, it can be seen that the coarse grinding fineness decreases and the coarse recovery rate increases. Therefore, it is important to choose a balanced coarse grinding fineness. Due to limited conditions, this test did not perform detailed closed-circuit tests on different rough grinding fineness. If the experimental work in this area is increased, the total recovery rate is expected to increase further.
Regrind is the key to determining the quality of the concentrate. A suitable range is to substantially dissociate the ore particles and is suitable for flotation. If it is too thick, the ore particles will not be dissociated and difficult to float. The fines will be muddy and deteriorate the flotation process. From the results of Table 4, the regrind fineness selected in the test is more suitable and can be determined.
(3) Selected times
Due to the high quality requirements of fluorite concentrates, increasing the number of selections on the basis of regrind can improve the quality of the concentrate and improve the operational stability of the production process. From the comparison of the data in Table 3 and Table 4, the amount of SiO 2 in the 7 selections compared with the 6 selected concentrates was reduced by half, exceeding the requirements of the special grades, and the recovery rate was not affected or even improved. Therefore, 7 selections are better.
(4) Return of the mine
The medium mine adopts the method of sequential return, which is simple and convenient, and easy to handle the connection. It is the most common and the most convenient for the factory to accept.
The middle 1 produced by the selection 1 process shall return to the rough selection in the order of return. However, considering that the medium 1 contains high mud, and the main part is the fine grain difficult to grind the ore body and gangue, in order to avoid the mud cover covering the rough fluorite floating, avoiding the fine grain ore continuation in the process in a vicious cycle, it will be taken early in a row manner back to scavenging. Tests have shown that this works better. Industrial piping connections are not complicated, as in practical applications.
Fourth, the conclusion
1. Using coarse concentrate and re-grinding 7 times of new technology to select Yongfeng fluorite-quartz ore, and obtain closed-circuit test index: concentrate contains CaF 2 98.63%, SiO 2 0.48%, and recovery rate is 80.64%.
2. Compared with the original process (six-time selection of one-stage grinding), the quality of fluorite concentrate is improved, reaching the standard of special grade, and the recovery rate is increased by more than 10%. The new process can be used as the basis for the transformation of the existing process.
3, coarse grinding flotation fineness can be further detailed screening.
4. The middle 1 in the selection 1 process returns to the sweeping operation, and the effect is better than the return to the rough selection operation.
Author unit
Changsha Industrial College: Deng Haibo
Yongfeng Fluorite Selection Factory: Yang Yunhai
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