At the end of the “Twelfth Five-Year Plan”, the iron production of the Jiugang plan headquarters will reach 10 million tons. The annual processing scale of the ore dressing will reach 14 million tons, and the annual output of iron concentrate will be about 7 million tons, all of which will be supplied to the wine steel headquarters for sintering and iron making. produce. In order to ensure the completion of iron production tasks and operating profit, on the one hand to improve the grade of iron materials into the furnace, to improve blast furnace utilization coefficient; on the other hand, to reduce the coke rate, to ease the shortage of coke coal resource company pressure, reducing their purchasing coke, cut costs. Therefore, it is necessary to improve the quality of the ore concentrate iron concentrate.

The Jiugang concentrator mainly deals with its own mines—the iron ore of the Bishangou and Hegou mining areas in Jingtieshan. Jing Tieshan iron ore is a typical refractory iron-poor ore, which has the characteristics of low ore grade, complex mineral composition and fine grain size. The iron minerals in the ore are mainly specular iron ore, magnesite and limonite, with a small amount of magnetite; the gangue minerals are mainly jasper, barite , iron dolomite and quartz ; the surrounding rock of the ore body is phyllite.

In the past, the Jiuquan concentrator used a shaft furnace to roast a weak magnetic separation process for the lump ore (100~15mm), and a strong magnetic separation process for the fine ore (15~0mm). The comprehensive concentrate iron grade is only about 52.5%, among which the strong magnetic selected, low iron grade magnetic concentrate were approximately 47.5% and 56.0%, Si0 2 content of approximately 10.0% and were 10.5%, metal recoveries were 67% and 81%. The low quality of iron concentrate has always affected the smelting coefficient and coke ratio of the blast furnace, while the low recovery rate has made the resources not fully utilized, which have become an important factor restricting the development of the wine steel.

At the end of 2005, Jiuquan cooperated with Changsha Research Institute of Mining and Metallurgy to complete the semi-industrial test for the improvement of the weak magnetic separation concentrate of Jiuquan Steel. The project was industrialized at the end of 2007. After the reverse flotation selection, the iron grade of the weak magnetic separation concentrate of Jiuquan Steel is increased to about 60%, and the Si0 2 content is reduced to about 6.5%. In this case, how to improve the concentrate quality of the powder ore system has become the key to solving the problem of concentrate quality in the entire concentrator. This study seeks to improve the quality of the concentrate quality of the Jiugang powder ore system through comparison of multiple schemes.

I. Current status of powder ore sorting process and indicators

The powder ore system of Jiugang Concentrator was put into operation in 1980. The original design was a two-stage continuous grinding one-to-one coarse-sweeping magnetic separation process. Because the ore was difficult to select, the recovery rate after commissioning was very low, only about 60%. After many process changes, the recovery rate reached about 67%. In recent years, with the gradual expansion of the ore dressing scale, the proportion of difficult ore dressing in the ore is gradually increasing, the ore size of the ore is becoming finer, and the ore property is seriously deteriorated.

At present, the production process of the powder mine system is shown in Figure 1. The iron grade of the concentrate is about 47.5%, the iron recovery rate is about 67%, the Si0 2 + A1 2 0 3 content is about 11.5%, and the tailings iron grade is as high as 20%. %about. The main problems in this process are as follows: (1) The grinding product has uneven grain size. On the one hand, the fineness does not meet the requirements, the iron mineral can not be completely dissociated, affecting the improvement of the concentrate iron grade and the impurity content; on the other hand, the crushing is serious, the magnetic separation process is difficult to recover -0.038mm fine iron Minerals range from 45% to 55%, which is the main reason for the metal recovery rate. 2 The process structure is not reasonable enough. Adopting a single strong magnetic separation process, the mechanical inclusions are severe, resulting in high impurity content of concentrate.

Third, the test ore sample

    The test ore samples were taken from the magnetic machine in the field. The results of chemical multi-element analysis and particle size analysis are shown in Table 1, Table 2.

Table 1 Results of multi-element analysis of mineral samples

ingredient

TFe

FeO

Si0 2

A1 2 0 3

CaO

MgO

MnO

content

31.53

7.90

27.33

3.96

1.45

2.09

1.24

ingredient

BaO

S

P

Ka 2 0

Na 2 0

Lg

content

4.72

1.12

0.053

0.087

0.054

10.14

Table 2 Results of particle size analysis of mineral samples

Size/mesh

Yield/%

grade/%

Distribution rate /%

TFe

SiO 2

TFe

SiO 2

+120

6.02

28.02

32.33

5.22

7.78

-120+150

2.01

28.99

32.89

1.80

2.64

-150+200

6.02

31.00

29.44

5.78

7.08

-200+300

13.84

32.07

18.90

13.74

10.46

-300+400

6.32

35.79

24.58

7.00

6.21

-400

65.79

32.62

25.02

66.46

65.83

total

100.00

32.30

25.01

100.00

100.00

From the results of Table 2, it can be seen that the on-site grinding product-200 mesh content is higher, reaching 85.95%, but the particle size distribution is uneven in thickness, and the phenomenon of over-grown and over-grinding is more serious. -120 mesh fraction content accounted for 6.02%, this part of the iron grade is low, Si0 2 content is high, most of them are continuous organisms, need further fine grinding; over-pulverized -400 mesh size content as high as 65.8%, which is partly due to mud Seriously, it is easy to cause metal loss when sorting, which affects the recovery rate.

Fourth, the test results

In the laboratory, the optimization of the powder ore sorting process was carried out. Grinding equipment for XMB 240×300 rod mill, magnetic separation equipment is SLon-100 periodic pulsation high gradient magnetic separator and 500 imitation Jones magnetic separator, the flotation equipment is XFDII-0.75L and XFDII-0.5L single tank flotation machine, the classification equipment is 50 cyclone. The reverse flotation collector is a cationic collector GE-609, the inhibitor is starch, and the regulator is NaOH.

(1) On-site production process simulation test

In order to facilitate the analysis and comparison, the simulation test of the on-site strong magnetic separation process was first carried out according to Figure 2. The high-gradient magnetic separation in Figure 2 is different from the on-site process because laboratory tests are limited by conditions and high-gradient magnetic separation cannot form closed circuits.

The selection criteria obtained by the simulation test are: concentrate iron grade 47.60%, Si0 2 content 9.86%, iron recovery rate 77.13%; tailings iron grade 14.43%.

(2) Optimized process test for strong magnetic rough selection

1. Full magnetic separation process for strong magnetic rough selection

On the basis of the flow of Figure 2, after the strong magnetic rough concentrate and the coarse-grained magnetic sweep concentrate are re-ground to -300 mesh 84%, a coarse gradient sweeper is used to perform a coarse three sweep and re-election. The level is unchanged. The test process is shown in Figure 3. The test results are: concentrate iron grade 49.74%, Si0 2 content 6.76%, iron recovery rate 74.41%; tailings iron grade 14.97%.

2, strong magnetic rough selection can not concentrate the magnetic-floating process 1

On the basis of the flow of Figure 3, 84% of the 235 regrind products and the fine-grained high-gradient mines are not subjected to high-gradient re-election, but a coarse-precision three-sweep and a coarse-two-three-sweep Reverse flotation. The test process is shown in Figure 4. The test results are: concentrate iron grade 51.31%, Si0 2 content 4.51%, iron recovery rate 73.80%; tailings iron grade 14.83%.

3, strong magnetic rough selection of non-concentrate magnetic-floating process 2

On the basis of the flow of Fig. 4, the fine-grained fraction is changed from a coarse-grained three-sweeping reverse flotation to a high-gradient mine to a coarse-grained three-sweeping reverse flotation . The test process is shown in Figure 5. The test results are: concentrate iron grade 51.44%, SiO 2 content 4.43%, iron recovery rate 73.45%; tailings iron grade 14.94%.

(III) Optimized process test of some concentrates selected by strong magnetics

1. Full magnetic separation process of some concentrates by strong magnetic rough selection

On the basis of the flow of Figure 3, reduce the strong magnetic rough field strength, so that the strong magnetic rough concentrate is first used as part of the final concentrate, but not with the coarse-grained magnetic sweep concentrate. The magnetic separator is re-selected. The test process is shown in Figure 6. The test results are: concentrate iron grade 49.82%, Si0 2 content 7.20%, iron recovery rate 74.50%; tailings iron grade 14.91%.

2, strong magnetic rough selection of some concentrates of the magnetic-floating process 1

On the basis of the flow of Figure 4, reduce the strong magnetic rough field strength, so that the strong magnetic rough concentrate is first produced as part of the final concentrate, and not re-grinded together with the coarse-grained magnetic sweep concentrate. selected. The test process is shown in Figure 7. The test results are: concentrate grade iron grade 50.66%, Si0 2 content 5.30%, iron recovery rate 74.38%; tailings iron grade 14.75%.

3, strong magnetic rough selection of some concentrates of the magnetic-floating process 2

On the basis of the flow of Figure 5, reduce the strong magnetic rough field strength, so that the strong magnetic rough concentrate is first produced as part of the final concentrate, and not re-grinded together with the coarse-grained magnetic sweep concentrate. selected. The test flow is shown in Figure 8. The test results are: concentrate grade 50.82%, Si0 2 content 5.02%, iron recovery rate 74.65%; tailings iron grade 14.60%.

V. Comparative analysis of various process indicators

The comparison of the test results of the six optimization processes and the on-site simulation process is shown in Table 3.

Table 3 Comparison of various process indicators

Process

Raw ore

Iron grade

Concentrate

Yield

Concentrate grade

Tailings

Iron grade

Concentrate iron recovery rate

TFe

TFE after burning

SiO 2

SiO 2 after burning

Ig

figure 2

31.20

50.56

47.60

9.86

14.43

77.13

image 3

31.20

46.68

49.74

57.91

6.76

7.87

14.11

14.97

74.41

Figure 4

31.20

44.87

51.31

60.36

4.51

5.36

14.99

14.83

73.80

Figure 5

31.20

44.55

51.44

60.58

4.43

5.22

15.09

14.94

73.45

Figure 6

31.20

46.66

49.82

58.18

7.20

8.41

14.37

14.91

74.50

Figure 7

31.20

45.80

50.66

59.47

5.30

6.22

14.81

14.75

74.38

Figure 8

31.20

45.83

50.82

59.22

5.02

5.92

15.19

14.60

74.65

It can be seen from Table 3:

(1) Compared with the simulation process (Fig. 2), the concentrate grades of the six optimization processes (Fig. 3 to Fig. 8) have been greatly improved, and the content of concentrate Si0 2 has been greatly reduced. The iron grade increased by 2.14 to 3.84 percentage points, and the Si0 2 content decreased by 2.66 to 5.43 percentage points, and the effect of improving quality and reducing impurities was remarkable.

(2) The selection criteria of the three kinds of strong magnetic rough selection non-concentration optimization process (Fig. 3 to Fig. 5) are better than the selection indexes of some concentrate optimization processes corresponding to the strong magnetic rough selection corresponding to the process structure. In the case of a similar recovery rate, the concentrate iron grade of the concentrate process is generally not high, especially the concentrate Si0 2 content is 0.44 to 0.79 percentage points lower. Therefore, the strong magnetic rough selection is not allowed to be concentrated in the concentrate process.

(3) Under the same strong magnetic rough selection concentrate treatment method, the magnetic-floating process is 1.57~1.70 and 0.84~1.00% higher than the whole magnetic separation process concentrate concentrate, and the concentrate Si0 2 content is 2.25~2.33 and 1.90~. 2.18 percentage points. Therefore, the magnetic-floating process is better than the full magnetic separation process.

(4) Under the same strong magnetic rough-choice concentrate treatment method, the two magnetic-floating process indexes are compared, and the magnetic-floating process 2 is more significant than the magnetic-floating process 1 in improving the quality and reducing the noise, and the magnetic-floating process 2 The structure is simpler.

(5) The magnetic-floating process of strong magnetic rough selection and non-concentration has the advantages of high grade of concentrate iron and low content of SiO 2 , but large flotation ore; strong magnetic coarse selection of magnetic concentrate of some concentrates Process 2 can obtain a part of qualified concentrate in advance, so that the flotation mine volume is greatly reduced, but the concentrate quality is worse than the former.

According to the above analysis and comparison, it is considered that the magnetic-floating process 2 of the non-concentrate of the strong magnetic rough selection and the magnetic-floating process of the partial concentrate of the strong magnetic concentrate should be used for the expansion test, and the laboratory test index is verified by expanding the test, and Conduct a technical and economic evaluation to determine a reasonable process for improving the quality of the concentrate in the Jiugang powder ore system.

V. Conclusion

(1) The iron grade of the concentrate of the Jiugang Powder Mine System is only about 47.5%, and the content of impurity Si0 2 + A1 2 0 3 is about 11.5%, which affects the further improvement of the smelting coefficient of the blast furnace and the further reduction of the coke ratio. There is a need to improve the quality of concentrates through process optimization.

(2) The 6 kinds of wine steel powder ore optimization and selection process studied in this experiment can obtain more significant effect of improving the quality of the concentrate, and compared with the results of the on-site simulation process, the recovery rate of concentrate iron is equivalent. Under the circumstances, the iron grade of concentrate can be increased by 2.14 to 3.84 percentage points, and the content of Si0 2 can be reduced by 2.66 to 5.43 percentage points.

(3) According to the comparison of the structure and indicators of the six optimized process flows, combined with the actual situation of the site, it is recommended to carry out the magnetic-floating process of the magnetic-free floating process in which the strong magnetic roughing is not allowed to concentrate and the coarse magnetic separation of some concentrates. 2 Conduct further expansion tests.

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