February 23, 2020

Beneficiation test of a poor iron ore in Shaanxi

A low-iron metal ore minerals Shaanxi mainly magnetite, titanium ore, followed by red limonite, pyrite, iron chromium aluminum and the like. Non-metallic minerals are mainly serpentine, followed by pyroxene, in addition to a small amount of quartz and carbonate minerals. Magnetite is the main purpose mineral for recycling, and the particle size is mainly -0.08mm. Some magnetites are in the form of a semi-self-shaped aggregate with a particle size ranging from 0.01 to 0.03 mm, which is finer and enveloped with gangue minerals; some magnetites and gangue minerals form lean organisms, while gangue minerals Mostly flake-like, fibrous serpentine, difficult to grind. In order to dissociate the magnetite from sufficient monomer, the ore must be finely ground. In this paper, the ore dressing experiment was carried out on the mine using the “weak magnetic separation process of coarse grinding weak magnetic tailing-magnetic product stage grinding stage” and “weak magnetic separation process of one stage grinding stage of raw ore pre-weak magnetic tailing”. Recommend the latter process to select the ore.

First, the nature of the ore

Multi-element analysis, iron phase analysis and mineral composition analysis were performed on the beneficiation samples. The results are shown in Tables 1 to 3.

It can be seen from Tables 1 to 3 that the natural type of the ore is serpentine type iron ore, and the industrial type is mixed ore. The metal minerals in the ore are magnetite and ilmenite, followed by red limonite, pyrite, and aluminum chromite. Non-metallic minerals are mainly serpentine, followed by pyroxene, in addition to quartz and carbonate minerals. The most important useful mineral in the ore is iron ore. The magnetite grade is mainly -0.08mm, accounting for 57.99%.

Table 1 Analysis results of ore bismuth (quality score) /%

TFe

Au 1)

Ag 1)

Cu

Pb

Zn

S

19.70

0.27

4.50

0.0058

0.0097

0.015

0.078

As

Mo

Cr

K 2 0

Na 2 0

Ti0 2

Ni

0.019

0.003

0.56

0.157

0.185

1.38

0.152

Co

V 2 0 5

Si0 2

A1 2 0 3

CaO

Mg0

LOI

0.014

0.14

28.60

2.44

2.09

26.96

7.35

1) The unit is g/t.

Table 2 Results of ore phase analysis

Name

content/%

Occupancy rate /%

Magnetic iron in iron

15.10

75.01

Iron in red brown iron ore

2.05

10.18

Carbonate in carbonate

0.43

2.14

Iron in silicate

2.35

11.68

Iron in iron sulfide

0.20

0.99

total

20.13

100.00

Table 3 Ore mineral composition (mass fraction) /%

magnetite

Ilmenite

Hematite

Aluminum chromite

Pyrite

20~25

1 to 3

1 to 2

8~10

Rare

Serpentine

pyroxene

quartz

Carbonate mineral

50~60

Rare

1

less

Part of the magnetite is a shape-semi-self-shaped granular aggregate with a particle size of less than 0.01-0.03 mm. This part of the magnetite is finely grained and encapsulated with gangue minerals. In order to improve the quality of the iron concentrate, it must be finely ground to fully dissociate the gangue.

Some magnetite and gangue minerals form a poor life, while gangue minerals are mostly flaky, fibrous serpentine, serpentine is not easy to grind. Therefore, it is predicted that multiple sections of grinding and multi-stage sorting are required.

Most magnetites contain a certain amount of Ti. This part of the magnetite contains about 65% iron. Another part of the magnetite is chrome magnetite, with an average iron content of about 53%, and chrome magnetite. It is a granular and fine-grained aggregate with a particle size of 0.01 to 0.3 mm. It is partially encapsulated in aluminous chromite ore in fine granules and needs to be finely ground to dissociate.

Second, the beneficiation test

(1) rough grinding weak magnetic tailing-magnetic product phase grinding phase weak magnetic separation process

1. Grinding particle size test

Grinding particle size is a key factor in determining the selection criteria. Only by grinding the ore, so that the iron mineral can be dissociated from the sufficient monomer, it can be separated from the gangue mineral by the sorting process. The test was carried out by a wet weak magnetic separator, and the grinding particle size test was carried out under a magnetic induction intensity of 100 mT, and the additional water flow rate was 100 mL/s (the same applies hereinafter), and the results are shown in Table 4.

Table 4 Effect of coarse grinding grain size on iron coarse concentrate index

-0.074mm fraction content /%

Yield/%

grade/%

Recovery rate/%

50

36.24

45.40

81.91

60

37.55

43.66

82.03

70

36.57

46.30

82.96

80

36.22

46.30

82.96

90

34.98

47.73

82.62

It can be seen from Table 4 that as the material is ground and the TFe grade of the iron concentrate is slightly increased, the recovery rate is slightly increased. Considering that the coarse concentrate needs to be reground, the coarse grinding grain size can be appropriately thickened. Considering comprehensively, the coarse selection is preferably -0.074mm, which is 60%. The test results also show that when the grinding particle size is coarse, the tailings yield is large and the iron loss rate is low. Therefore, it is considered that the particle size at the time of tailing can be further coarsened, and a pre-tailing test before grinding is performed in the subsequent test.

2, magnetic induction test

The magnetic induction strength test was carried out by grinding the material to -0.074 mm and the particle size was 60%. The results are shown in Table 5.

Table 5 Effect of rough magnetic induction on the index of iron concentrate

Magnetic induction intensity / mT

Yield/%

grade/%

Recovery rate/%

80

33.42

47.20

79.40

100

33.84

47.60

81.30

120

35.85

45.80

82.31

140

37.11

45.00

82.84

It can be seen from Table 5 that with the increase of magnetic induction intensity, the TFe grade of iron concentrate has a slight downward trend, and the recovery rate is increasing. Considering the grade and recovery rate, the selection of 100mT for rough magnetic induction is appropriate.

3. Select regrind particle size and number of segments

After a period of re-grinding, the coarse concentrate was subjected to a selective and selective comparison test with a magnetic induction strength of 100 mT. The results are shown in Tables 6 and 7.

Table 6 Effect of re-grinding particle size on iron concentrate index

-0.037mm fraction content /%

Yield/%

grade/%

Recovery rate/%

60

28.16

56.80

78.61

70

26.96

58.03

77.52

80

26.30

59.98

78.06

90

26.39

59.37

77.50

Table 7 Effect of re-grinding particle size on iron concentrate index

Grinding particle size

Yield/%

grade/%

Recovery rate/%

-0.037mm60%

24.50

58.90

67.38

-0.037mm70%

22.31

59.50

61.74

-0.037mm80%

18.43

61.30

52.82

-0.037mm90%

21.17

60.70

59.61

-0.030mm85%

24.68

62.00

75.07

-0.030mm90%

24.10

62.23

74.19

-0.030mm98%

23.31

62.60

71.89

From the results of Table 6 and Table 7, it can be seen that as the material is ground, the grade of iron concentrate TFe is on the rise. When the grinding particle size reaches -0.037mm and the grain size accounts for 90%, whether it is selected once or twice, the iron concentrate TFe grade is still difficult to reach 62%; when grinding to -0.037mm grain size accounts for more than 85% , two selected, iron concentrate TFe grade is greater than 62%. The test results also show that when a regrind particle size is -0.037mm, the grain size is 70%, and after one selection, about 12% of the tailings can be discarded. Considering the grade, recovery rate and grinding cost, the regrind particle size selection is -0.037mm, which accounts for 70% of the grain size.

4, selected magnetic induction strength test

The fixed regrind particle size was -0.037mm, and the grain size was 70%. Once selected, the magnetic induction strength test was carried out. The test results are shown in Table 8.

From the results of Table 8, it can be seen that with the increase of magnetic induction intensity, the TFe grade of iron concentrate shows a downward trend and the recovery rate is increasing. Considering the grade and recovery rate, it is better to select a magnetic induction intensity of 70mT.

Table 8 Effect of selected magnetic induction on iron concentrate index

Magnetic induction intensity / mT

Yield/%

grade/%

Recovery rate/%

50

25.98

58.20

73.99

70

28.17

57.20

79.22

90

28.76

56.60

79.93

5. Selected two-stage regrind particle size test To determine the selected two-stage regrind particle size, a selective two-stage test was carried out under the condition of magnetic induction intensity of 50 mT. The results are shown in Table 9.

Table 9 Effect of selected two-stage regrind particle size on iron concentrate index

-0.030mm fraction content /%

Yield/%

grade/%

Recovery rate/%

80

24.74

61.40

73.34

85

25.33

61.80

76.44

90

24.71

62.20

74.76

98.34

19.98

64.00

61.64

It can be seen from Table 9 that as the material is ground, the grade of iron concentrate TFe is on the rise. And when the grinding particle size reaches -0.030mm and the grain size accounts for 90%, the iron concentrate TFe grade reaches 62%. Therefore, to obtain iron concentrate products with a grade of more than 62%, the regrind particle size -0.030mm should be above 90%.

6, magnetic induction strength test

The fixed two-stage grinding grain size is -0.030mm, and the grain size is 90%. The selected two-stage magnetic induction strength test is carried out. The results are shown in Table 10.

Table 10 Effect of selected two-stage magnetic induction on iron concentrate index

Magnetic induction intensity / mT

Yield/%

grade/%

Recovery rate/%

40

18.94

62.60

58.78

50

24.20

62.20

74.40

60

25.05

61.80

75.89

It can be seen from Table 10 that as the magnetic induction intensity increases, the iron concentrate TFe grade shows a downward trend. The recovery rate is on the rise. Under the premise of ensuring that the iron concentrate TFe grade is greater than 62%, it is advisable to select 50mT for the selected two-stage magnetic induction.

7. Comprehensive conditional parallel test

The coarse-grained grinding grain size is -0.074mm, the grain size is 60%, the magnetic induction intensity is 100mT, the length of regrind is -0.037mm, the grain size is 70%, the magnetic induction is 70mT, and the second-stage regrind is -0.030mm. %, magnetic induction strength 50 mT, a comprehensive parallel test was carried out, and the results are shown in Table 11.

The results in Table 11 show that the rough grinding weak magnetic tailing-two-stage re-grinding-two-stage re-selection process is suitable for the selected conditions, and the test results are stable.

(II) Pre-weak magnetic tailing of raw ore-weak magnetic separation process in stage grinding stage

Since the useful iron mineral content in the ore is only 20% to 25%, if some waste rock is discarded before grinding, and the selected grade is appropriately increased, the ore processing cost can be reduced. Due to the quality limitation of the sample, the pre-weak magnetic tailing test was carried out on the two ore grades of -2mm and -12mm respectively, and the magnetic products after the tailing were further subjected to stage grinding magnetic separation.

Table 11 Comprehensive conditions parallel process test results

Test number

product name

Yield/%

TFe grade /%

TFe recovery rate /%

l

Concentrate

24.44

62.80

74.73

Tailings

75.56

6.87

25.27

Raw ore

100.00

20.54

100.00

2

Concentrate

24.14

62.40

74.44

Tailings

75.86

6.82

25.56

Raw ore

100.00

20.23

100.00

3

Concentrate

24.66

62.80

74.90

Tailings

75.34

6.89

25.10

Raw ore

100.00

20.68

100.00

average

Concentrate

24.41

62.68

74.69

Tailings

75.59

6.86

25.31

Raw ore

100.00

20.48

100.00

According to the flow shown in Figure 1, the pre-tailing-stage grinding-stage magnetic separation full-flow test was carried out on the -2mm and -12mm ore, respectively. The results are shown in Table 12.

Table 12 Raw ore tailing-stage grinding stage magnetic separation full process test results

Raw ore size / mm

product name

Yield/%

TFe grade /%

TFe recovery rate /%

2

Concentrate

24.24

62.06

72.76

Tailings

75.76

7.44

27.24

Raw ore

100.00

20.68

100.00

12

Concentrate

23.41

62.95

72.09

Tailings

76.59

7.45

27.91

Raw ore

100.00

20.44

100.00

-2mm and -12mm weak magnetic pre-spinning-stage grinding stage magnetic separation two processes throwing tails were 45.35% and 22.67%, respectively, the obtained iron concentrate index is not much difference. This test determined that the ore tailing particle size was -12 mm.

(3) Recommended process

The final recommended principle flow is: the raw ore crushed to -12mm is pre-thrown by magnetic pulley, and the quality process of wet weak magnetic selection in the stage of grinding of magnetic product is shown in Fig. 2. An iron concentrate having a yield of 23.41%, a TFe grade of 62.95%, and a recovery of 72.09% can be obtained by a pre-tailing-stage grinding-stage magnetic separation process.

Third, the conclusion

(1) A certain type of iron ore in Shaanxi is serpentinite type iron ore, and magnetic iron accounts for 75.01%. The industrial type is mixed ore. The magnetite has a large particle size variation range, but mainly consists of -0.08mm fine particles, accounting for 57.99%. The fine-grained magnetite assembly having a partial particle size of less than 0.01 to 0.03 mm not only wraps the gangue but is also poorly associated with the gangue. The main gangue mineral serpentine itself is fibrous and flake-shaped, which is not easy to be ground during the grinding process. Therefore, multi-stage re-grinding is required to fully dissociate the magnetite. Some chrome magnetites contain Ti, Cr, Al, Mg, and Mn, and the average iron content is only about 53%. Most of the magnetite contains Ti, and the average iron content is about 65%. This is the main reason for the low grade of iron concentrate.

(II) The final recommended procedure is: -12mm original ore magnetic pulley pre-tailing-stage grinding-stage selection, the obtained iron concentrate yield is 23.41%, the TFe grade is 62.95%, and the TFe recovery rate is 72.09%, of which MFe recovery rate It is 94.26%.

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