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Limonite ore nature, the great majority of 2Fe 2 O 3 · 3H 2 O exists in the form, amorphous form, or a colloid aphanitic appearance color was brown, dark brown to brown-black, to the weak magnetic. Limonite has very few rich ore, iron content is lower than magnetite and hematite, and most of them contain a large amount of slime, which cannot be directly used for smelting without beneficiation , and is a refractory ore. However, as the market demand for steel increases and prices rise, it is increasingly important to conduct a siting study on limonite. At present, the limonite beneficiation process mainly includes: 1 single re-election process, because the density of limonite minerals changes greatly, resulting in low iron recovery rate and serious waste of resources. 2 Single wet strong magnetic separation process, the effect of fine-grain grade slime selection is poor. 3 Single flotation process, including positive flotation and reverse flotation, the key problem to be solved is the effect of fine-grained slime. 4 Selective flocculation flotation, selective flocculation of limonite by means of starch, humate, etc., and removal of silicate minerals by desliming or reverse flotation. With the development of the iron ore beneficiation process research, many types of joint processes have emerged, including strong magnetic separation-positive flotation-strong magnetic separation process, strong magnetic separation-amine reverse flotation process, reduction roasting-magnetic separation-leaching Process, etc. According to the characteristics of limonite ore in a certain area, an iron concentrate with a grade of 54.12% and a recovery rate of 62.16% was obtained by enhanced dispersion-strong magnetic separation process.
First, the nature of the ore
Process ore mineralogy analysis showed that iron-containing ore minerals are hematite and limonite; gangue minerals are kaolinite, illite, mica, calcite and small amounts of calcium and magnesium minerals. The results of multi-element chemical analysis and iron phase analysis of the ore are shown in Tables 1 and 2, respectively.
Table 1 Results of multi-element chemical analysis of ore
element
TFe
SiO 2
Al 2 O 3
CaO
MgO
P 2 O 5
S
Loss on ignition
content
36.26
18.23
17.58
5.89
3.61
0.036
0.14
17.44
Table 2 Phase analysis of iron in ore
Iron phase
Red, limonite
Iron sulfide
Iron silicate
All iron
Iron content
Iron share
35.76
98.59
0.42
1.16
0.09
0.25
36.27
100.00
Second, the selection scheme test
(1) Re-election process test
The density and hardness of silicate minerals and iron-bearing minerals in the ore are quite different, and should have good gravity sorting conditions. Therefore, the re-election test was carried out. The raw ore is ground to 75% to 0.074 mm, and the grooved shaker is used for sorting, and the stroke, the stroke, the bed inclination, the water amount and the ore supply amount are adjusted, and the test results are shown in Table 3.
Table 3 Shake test results
product name
Yield
Iron grade
Iron recovery rate
Coarse concentrate
Middle mine
Tailings
Raw ore
42.25
22.13
35.62
100.00
49.96
35.01
23.43
37.20
56.74
20.83
22.43
100.00
It can be seen from Table 3 that the iron concentrate grade and recovery rate obtained by the re-election process are both low, indicating that it is difficult to achieve better sorting index after re-election of ore. The reason is that after the ore is ground, the grain size polarization of iron minerals is serious, and some fine-grained iron minerals are lost in the tailings.
(2) Single flotation test
The silicon-bearing minerals in the ore are mainly kaolinite and ill mica which are difficult to float, which are easy to muddy and have a great influence on the subsequent flotation. Therefore, they need to be removed by pre-screening. In this test, a pre-screening-grinding-cation reverse flotation and pre-screening-grinding-anion positive flotation process was developed.
The test results show that the pre-screening-grinding-anion positive flotation process yields a higher grade iron concentrate. The test results are shown in Table 4, and the flow is shown in Figure 1 and Figure 2.
Figure 1 Anion positive flotation test process and conditions
Figure 2 Cationic reverse flotation test process and conditions
Table 4 Single flotation test results
Program
product name
Yield
Iron grade
Iron recovery rate
Figure 1 scheme
Concentrate
Tailings
Mud
Raw ore
37.44
33.30
29.26
100.0
52.00
31.12
26.68
37.64
51.73
27.53
20.74
100.0
Figure 2 scheme
Concentrate
Tailings
Mud
Raw ore
37.57
33.27
29.16
100.00
46.52
36.71
28.27
36.90
47.27
30.40
22.33
100.00
It can be seen from Table 4 that the consumption of the anion and cation collectors in both processes is large, which fully demonstrates that the ore is easily muddy. After pre-screening and de-mudging, some of the slime still enters the flotation operation, increasing the consumption of the medicament. In comparison, the pre-screening-grinding-anion positive flotation test has reached an ideal index, but the process is complicated, the consumption of the agent is too large, the iron recovery rate is low, and the fine-grained iron ore is pre-screened with Sludge loss is more serious. However, the cationic drug dodecamine has poor collection ability and sorting property, and can not effectively separate silicate minerals, which may be affected by slime. All in all, the test results show that it is difficult to obtain an ideal comprehensive index for a single flotation scheme.
(3) Selective flocculation test
In order to reduce the impact of silicate slime on subsequent tests, and to examine the feasibility of the flocculation and desiccant process, a selective flocculation test was carried out. Through the preliminary determination of the fineness of grinding and the amount of sodium carbonate, the amount of water glass and PD were changed one by one, and the optimum conditions of the mud removal test were finally determined. The best test results are shown in Table 5. The optimum process conditions are shown in Flowchart 3.
Table 5 Results of selective flocculation test
product name
Yield
grade
Recovery rate
Iron concentrate
Mud
Feed mine
87.17
12.83
100.00
39.31
20.03
36.84
93.02
6.98
100.00
Figure 3 Selective flocculation test process and conditions
The grinding fineness is 75% to 0.074 mm. When 3000 g/t sodium carbonate and 2000 g/t water glass are added during the grinding process, the slurry can be well dispersed. According to the research literature, the zero point of limonite is about 6, while the zero point of silicate mineral is 2~4. When the pH is between 4-6, limonite and vein Vision aggregation will occur between stone minerals. When 3000 g/t sodium carbonate is added, the pH of the slurry can be adjusted to between 8.5 and 10, resulting in negative charge on the surface of different minerals, so that it is well dispersed. PD is an anionic starch, which preferentially adsorbs on the surface of iron minerals with relatively lower surface electronegativity to form selective floc, thereby achieving the purpose of separating iron minerals. However, as can be seen from Table 5, it is still difficult to significantly improve the grade of concentrate iron by selective flocculation, which is only about 3 percentage points higher.
(4) Selective flocculation-strong magnetic separation process test
Under the conditions of grinding fineness of 75%~0.074mm, sodium carbonate 3000g/t, water glass 2000g/t, PD flocculant 200g/t, selective flocculation-strong magnetic separation rough selection-strong magnetic separation Selective and selective flocculation-strong magnetic separation-reverse flotation test scheme, the test results are shown in Table 6, and the test flow is shown in Figure 4, Figure 5 and Figure 6.
Figure 4 Selective flocculation-strong magnetic separation test process and conditions
Figure 5 Selective flocculation-strong magnetic separation-reverse flotation test process and conditions
Figure 6 Selective flocculation-strong magnetic separation-reverse flotation test process and conditions
Table 6 Selective flocculation - strong magnetic separation - strong magnetic separation (reverse flotation) test results
Program
product name
Yield
Iron grade
Iron recovery rate
Figure 4 scheme
Coarse concentrate
Middle mine
Tailings
Mud
Raw ore
46.04
8.28
36.81
8.87
100.00
53.43
37.99
19.45
20.21
36.72
66.99
8.57
17.91
6.53
100.00
Figure 5 scheme
Coarse concentrate