At present, domestic iron tin ore beneficiation method has re-election, weak magnetic separation, re-election - flocculation - low intensity magnetic separation, flotation, flocculation - electrostatic separation, the general stage grinding, stage separation, weak magnetic separation - Shake The bed re-election combined process to treat this type of ore can achieve better sorting indicators. In an iron ore plant in Sichuan, in addition to iron, the ore is accompanied by valuable components such as tin and sulfur. In the original plant, only the iron selection process was carried out, and the tin in the ore entered the tailings pond with the tailings, resulting in waste of resources. Therefore, it is necessary to add tin-selecting operations to maximize the comprehensive recovery of valuable elements in the ore and improve resource utilization. Entrusted by the plant, the iron ore mine was studied for mineral processing technology, in order to provide technical basis for the comprehensive development and utilization of the mine.
First, the nature of the ore
The main valuable elements in the ore are tin, iron and sulfur. Tin is mainly in the form of cassiterite, which is the main iron mineral. Gangue minerals are quartz, tremolite, serpentine, mica, chlorite.
(1) Multi-element analysis of raw ore. The results of multi-element analysis of raw ore are shown in Table 1.
It can be seen from Table 1 that the SiO 2 content in the ore is 40.98%, which belongs to the high silicon lean iron type tin-containing magnetite. The harmful elements sulfur and phosphorus will affect the quality of the concentrate and the phosphorus content is low.
Table 1 Multi-element chemical analysis results of ore
(2) Analysis of the original mineral phase. The results of analysis of the original ore and iron phases are shown in Tables 2 and 3, respectively.
Table 2 Results of raw ore tin phase analysis
Table 3 Analysis results of ore phase of iron ore
(3) The state of occurrence of valuable elements and mineral characteristics. Magnetite is the most important metal mineral. It is mainly composed of crystals with fine particle size, generally 0.02-0.15mm, maximum 0.25mm, and minimum of 0.005mm. Magnetite is mainly intercalated with silicate minerals, and a small number of scattered stars are scattered between gangue minerals or grains, and closely embedded with gangue.
The amount of hematite is small, and the crystal grain size is 0.02 to 0.05 mm. The main associated mineral is quartz, and a small amount is tremolite, serpentine and the like. The limonite is in the shape of granules or flakes. The former is composed of pyrite, and the latter is formed by mirror iron ore. The pyrite is in the form of a granular shape with a particle size of 0.01 to 0.045 mm.
Tin is mainly found in iron ore and gangue minerals in the cassiterite state. Associated minerals mainly magnetite, tremolite, phlogopite, serpentine, and the like; Ci magnesium chlorite, arsenopyrite, copper ore pyrite.
Second, the beneficiation process research
The minerals with recyclable value in the ore are mainly magnetite and cassiterite, which can be recovered by magnetic separation and re-election, respectively. Considering the high content of iron minerals, and the processing capability of the device is larger than the magnetic reselection apparatus, thus pressing the first magnetic reselection test procedure test.
(1) Magnetic separation test
In order to fully improve the iron recovery rate, the experiment considers two weak magnetic separation and strong magnetic separation processes. In the grinding fineness condition test, the selected grinding fineness -200 mesh accounts for 65%, and the second grinding fineness -200 mesh accounts for 90%. In the magnetic field strength condition test, the weak magnetic selective magnetic induction intensity is 0.12T, and the strong magnetic selective magnetic induction intensity is 1.24T (the same below). The magnetic separation process and results are shown in Figure 1.
Figure 1 Magnetic separation test number quality process
It can be seen from Figure 1 that the grade of a weak magnetic separation iron concentrate is 58.91%, the recovery rate can reach 74.78%; the grade of a strong magnetic iron ore concentrate is 15.83%, and the grade of secondary strong magnetic iron ore concentrate is 14.71%, both of which are much lower than The original ore grade has no meaning for the introduction of strong magnetic separation in this sample. The subsequent optimization test uses two weak magnetic separations, and the tailings enter the re-election system to select tin.
(2) Re-election test
The cassiterite is brittle and avoids over-grinding during the beneficiation process to prevent tin from being lost in the tailings during the re-election process. Therefore, in the process of sorting, it is advisable to follow the stage grinding and stage selection process, try to get the early take, lose early, and compare the test through multiple schemes. Finally, use a shaker - medium mine re-grinding - second shake The flow of the bed. The re-election experiment focused on the influence of the fineness of the grinding of the second-stage grinding of the selected tin on the tin selection index. The regrind fineness of the ore in the shaker was taken as -200 mesh, accounting for 85%, 94%, and 98% respectively. The test procedure is shown in Figure 2, and the results are shown in Table 4.
Figure 2 Weak magnetic separation - shaker reselection test process
Table 4 Weak magnetic separation - shaker test results %
It can be seen from Table 4 that when the grinding fineness -200 mesh accounts for 85%, the comprehensive recovery rate of tin is low, and the occupation rate of tin in the middle ore reaches 13.57%, indicating that the tin ore contains a large number of continuous organisms, and the tin is selected. The fineness of the section grinding is not enough; when the grinding fineness -200 mesh accounts for 94%, the comprehensive recovery rate of tin is higher, up to 63.40%; when the fineness of grinding -200 mesh accounts for 98%, the tin is in the tailings The occupation rate is 27.52%, indicating that it cannot be excessively finely ground, otherwise the fine-grained cassiterite is easily lost in the tailings.
In summary, the selected fineness of the second stage of the selected tin is preferably from -200 mesh to 90% to 95%.
(III) Flotation desulfurization test
The ore contains a certain amount of pyrite. Due to the high density of pyrite, it is 4.9-5.2g/cm 3 . It is easy to be concentrated at the concentrate end when re-selecting the shaker. In order to obtain high-quality tin concentrate, Re-elected tin concentrates can be desulfurized by reverse flotation to obtain qualified tin concentrates and sulfur concentrates. Flotation agent system: Dinghuang medicine 200g / t, pine oil 60g / t.
(4) Full process expansion test
Based on the above-mentioned laboratory small-scale test, an industrial shaker was used to carry out the full-flow expansion test. The process of stage grinding, phase selection, weak magnetic separation-primary shaker-middle mine re-grinding-secondary shaker-tin-sulfur separation flotation is adopted. The quality of the test number is shown in Figure 3.
Figure 3 The whole process of expanding the number of trials
It can be seen from Fig. 3 that the whole process expansion test can obtain iron concentrate with a grade of 64.47% and a recovery rate of 75.09%; a tin concentrate with a grade of 31.07% and a recovery rate of 62.94%; a sulfur concentrate with a grade of 40.86% and a recovery rate of 32.03%.
The results of multi-element chemical analysis of tin concentrate are shown in Table 5.
Table 5 Results of multi-element chemical analysis of tin concentrates %
It can be seen from Table 5 that the grade and impurity content of tin concentrates reach a class of eight grade standards.
Third, the conclusion
(1) The magnetite occupation rate in the ore is 74.14%, and the content of red and limonite is very small. Only weak magnetic separation operation can produce qualified iron concentrate. The useful mineral magnetite and the cassiterite are finely sized, and the fineness of the second-stage grinding of the tin is preferably from -200 mesh to 90% to 95%.
(2) The test uses the stage of grinding, stage selection, weak magnetic separation-re-selection shaker-tin-sulfur separation flotation combined process to treat the ore, and obtains better selection index, which can obtain grade 64.47%, recovery rate. 75.09% iron concentrate; grade 31.07%, recovery rate 62.94% tin concentrate; grade 40.86%, recovery rate 32.03% sulfur concentrate.
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