At present, iron ore resources in China in iron ore resources easily selected dwindling iron ore resources is characterized by lean ore more high-grade ore less, associated minerals much more complex component ore, ore mostly fine dissemination size, to cause some dressing Difficulties. Technically speaking, advanced technologies, advanced processes and advanced equipment are urgently needed to promote the efficient development and utilization of lean iron ore resources. In terms of economic benefits, the concentrator must expand the production scale for the production of lean iron ore, and must expand the processing capacity of the ore, save energy and reduce consumption, and reduce the cost of mineral processing, so that there will be better economic benefits. Before the ore enters the grinding operation, a part of the gangue minerals mixed into the ore are pre-selected and removed, so as to achieve the loss of the original ore grade.

The pre-selection process optimized by ultra-fine crushing and coarse-grain tailing is an effective method for increasing production capacity, saving energy and reducing consumption, and creating better economic benefits.

Hubei Valley County grade iron ore content of 14 to 15% TFe, associated with titanium ore, which TiO 2 content of 6-7% TFe mining total reserves of more than 1.9 millions of tons, TiO 2, more than 10 million tons, suitable for open-pit mining . Since the mine is a lean iron deposit, it has not been exploited. With the improvement of the domestic iron ore situation and the improvement of the mineral processing technology level, advanced mineral processing technology and equipment are urgently needed to promote the efficient development and utilization of lean iron ore resources. This is the current priority of the mine.

The iron ore mine in Gucheng County, Hubei Province, commissioned several research institutes to conduct multiple ore dressing tests on iron ore from 1980 to 2005, but has not obtained a suitable beneficiation process and better beneficiation index. Generally obtained mineral processing technical indicators: iron concentrate yield is 14.77% ~ 12.96%; iron concentrate grade TFe content is 58.45 ~ 63.35%; recovery rate is 57.12 ~ 54.32%. In order to obtain better mineral processing technology and mineral processing technical indicators, in order to discuss the best new iron ore pre-selection process and new equipment, in July 2009, the Changsha Separation Engineering New Technology Research Institute and Changsha Shenxiang General Machinery Co., Ltd. were commissioned. Mine construction 5 million tons / year of ore dressing plant to do iron ore beneficiation research and test, for the beneficiation process design, equipment selection to provide basic data.

In view of the characteristics of lean, fine and miscellaneous iron ore in Gucheng County, Hubei Province, in-depth and meticulous research has been carried out. If the ore is treated by conventional beneficiation process, the unit has high power consumption, high steel consumption, high water consumption and poor economic benefits. Therefore, we propose to optimize a preselected lean ore fine crushing process: super fine selection of energy-efficient equipment roll mill, using a process more crushing less grinding, reducing the particle size of the iron ore into the mill, a ball mill prior to the iron ore The coarse-grained tailings realize the early loss and fully recover, creating favorable conditions. This has far-reaching practical significance for improving the production capacity of the grinding system by using iron-poor ore, saving energy and reducing consumption, and creating better economic benefits.

The small-scale test of the project uses a roller mill ultra-fine crushing (0~5mm)-dry weak magnetic separator coarse-grain tailing-grinding-two-stage wet weak magnetic separator to select the open process. When the TFE content of the ore grade is 15.25%, the yield of iron concentrate is 14.49%; the content of iron concentrate grade TFe is 65.12%; the recovery rate is 61.90%, which provides a basis for design and construction.

First, the effect of ultra-fine crushing of roller mill on the fine-grained low-grade iron ore with embedded grain size

In the ultra-fine crushing operation of the fine-grained low-grade iron ore, due to the iron ore in the condition of the layer, the roller is repeatedly crushed and twisted by the rapidly rotating grinding roller, so that the ore is crushed into fine particles. And powdery. Therefore, fatigue bonding or microcracking and internal stress occur at the interface between the useful mineral and the gangue, and part of the bonding interface is completely separated. Such a large part of the useful minerals will obtain complete monomer dissociation, and the other part will not have complete monomer dissociation at the internal bonding interface of the particles, and microcracks or internal stress will also occur. When the particles with complete monomer dissociation or partial monomer dissociation are obtained, when the pre-selection operation is carried out, the coarse concentrate with higher grade and the tailing with lower grade can be obtained. When the coarse concentrate with less gangue minerals enters the ball mill, there is no internal bonding interface of the particles completely dissociated, and because of the large number of microcracks and internal stress, the useful minerals in this part of the ball mill It is easy to get better monomer dissociation with gangue. Such coarse concentrate grinding is beneficial to the magnetic separation selection operation to improve the grade of the final concentrate.

After the fine-grained low-grade iron ore is superfinely crushed by a roller mill, the pre-selection: dry weak magnetic separation can discard about 40% of the tailings with lower grade, and wet weak magnetic separation can discard about 50% of the lower grade. Tailings. The reason is that the ultra-fine crushed product of the roller mill has a small particle size and a wide particle size distribution range, wherein the particle size below -5 mm is more than 80%, the particle size below -1 mm is more than 50%, and the -200 mesh size is up to 20%. About about %, its ultra-fine crushed product is in powder form, so the iron ore of this size distribution is pre-selected, and a significant sorting effect is obtained when the coarse-grained tail is thrown.

2. Mineral processing technology for low-grade iron ore development and utilization in Gucheng County, Hubei Province

(1) Preparation of samples

400kg of representative core sample was taken from the iron ore mine in Gucheng County, Hubei Province. After being crushed to a particle size of 25mm or less by PE125×150 jaw crusher , it was ultra-finely crushed to 0~5mm by ZMJ900A roller mill. Take a representative ore sample for chemical analysis of raw ore and sieve analysis of ore size distribution characteristics. Then, the sieve is sieved with a 5 mm standard sieve, and the product is super-finely crushed by a back-rolling mill, and then combined with the sieved product, mixed by a pile cone method, and then separately sampled and weighed to prepare a sample. The test sample was taken out as a test sample for pre-selected coarse-grained tailing.

(II) Separation test of raw ore roll mill

Table 1 Raw material roller mill discharge 5.0mm sieve size distribution table

Size (mm)

+5

-5 to +3

-3～+2

-2~+1

-1 to +0.5

-0.5 to +0.2

-0.2 to +0.1

-0.1～+0.074

-0.074

total

content(%)

11.11

9.30

6.95

10.04

12.01

10.91

14.54

4.67

20.47

100.00

Cumulative content (%)

20.41

27.36

37.40

49.41

60.32

74.86

79.53

100.00

The results in Table 1 show that the superfine crushing of the original ore roller mill has obtained good results: the particle size below -5 mm accounts for 88.89%, and the particle size below -0.074 mm accounts for 20.47%. The fine-grained iron ore has a relatively uniform grain size distribution. The ore particle size is suitable for coarse-grained tailing. It can abandon a large amount of tailings before entering the ball mill, reduce the amount of coarse ore concentrate and reduce the particle size of the ball mill coarse concentrate. Improve the grade of coarse concentrate and create favorable conditions for the next magnetic separation process.

(III) Analysis of the occurrence state of iron minerals in ore

Table 2 Results of chemical phase analysis of iron

Iron mineral type

Titanium magnet

Iron carbonate

Iron sulfide

Iron silicate

Red brown iron

TFe

Iron content%

8.72

0.028

0.31

5.43

0.57

15.11

Distribution rate%

57.71

0.52

2.05

35.94

3.77

100

It can be seen from Table 2 that iron is mainly distributed in titanomagnetite and silicate minerals, and the distribution ratio of iron in magnetic iron is 54.27%. The distribution of iron in silicate minerals is 35.94%, and that in chernorite is 3.77%; magnetite can be recovered by weak magnetic process, and red iron iron ore can be recovered by strong magnetic process.

(4) Chemical analysis of multi-element of ore

Table 3 Multi-element chemical analysis results of ore (%)

element

TFe

Fe 2 O 3

SiO 2

Al 2 O 3

Na 2 O

MgO

content

14.68

18.27

35.87

5.30

0.54

12.25

element

CaO

K 2 O

TiO 2

MnO

SO 3

P 2 O 5

content

17.05

0.60

6.46

0.21

0.58

1.32

element

SrO

ZrO 2

CuO

ZnO

BaO

Cl

content

0.031

0.095

0.015

0.027

0.064

0.025

The chemical composition analysis of the ore samples in Table 3 shows that the content of ore TFe is only 14.68%, of which Fe 2 O 3 is 18.27%; TiO 2 is 6.46%. Iron and ilmenite are the main objects of mineral processing. . The impurity SO 3 content is 0.58%, the P 2 O 5 content is 1.32%, and the harmful elements sulfur and phosphorus are high, which needs to be removed for mineral separation.

(5) Inlay grain size characteristics of main minerals in ore

According to the statistical analysis of ore inlay size, when the grinding fineness reaches -0.074mm (-200 mesh), more than 90% of magnetite, ilmenite and pyrite can be dissociated, and the grinding fineness is up to When -0.037mm (-400 mesh), the dissociation degree of the three mineral monomers is above 98%. To completely dissociate the three minerals, the fineness of grinding should be 0.074mm~0.037mm.

Third, the original ore ultrafine crushing pre-selected coarse grain tailing test

(1) Dry-type weak magnetic separator coarse-grain tailing test

The ore is produced by the company's model ZMJ900A roller mill for ultra-fine crushing. The original ore feed size is 30mm, and the ore is crushed to 0~5mm at a time, and the production capacity is 20~30t/h. After the ultrafine crushed product is pre-screened to a particle size of -5 mm or less, the YCφ400-400 dry weak magnetic separator is used for the coarse grain tailing. It is determined by the condition test results: the test conditions of the dry weak magnetic separator are: fixed magnetic field strength is 1400 Oe, sorting roller speed is 56 rpm, and the processing amount is 3 t/h. Change the distance of the tailings baffle from the barrel and carry out the condition test of the tailings amount. The process flow chart is shown in Figure 1, and the test results are shown in Table 4.

Fig.1 Flow chart of coarse-grained tail-opening process of raw ore roll mill superfine-dry type weak magnetic separator

Table 4 Raw ore weak magnetic separator tailings baffle condition (-5mm) coarse grain tailing test results

Magnetic field strength (KA/m)

Baffle distance

(mm)

Granular grade

(mm)

product

Yield

%

grade%

Recovery rate%

TFe

TFe

111.4

40

0～-5

Coarse concentrate

66.91

18.01

83.62

Tailings

33.09

7.13

16.38

Raw ore

100.00

14.41

100.00

111.4

20

0～-5

Coarse concentrate

60.86

19.91

81.23

Tailings

39.14

7.16

18.77

Raw ore

100.00

14.92

100.00

111.4

10

0～-5

Coarse concentrate

56.65

20.63

78.61

Tailings

43.35

7.33

21.39

Raw ore

100.00

14.87

100.00

It can be seen from Table 4 that the ultrafine crushing 0~-5mm coarse grain tailing of the original ore roller mill obtains a good beneficiation index. With the closer the tailings baffle of the dry weak magnetic separator to the barrel, the more tailings are cut, the grade of tailings and the grade of coarse concentrate also increase, but the recovery rate decreases. It is suitable to determine that the distance between the tailings baffle and the barrel is 10 mm. The dry magnetic separation can abandon the yield of 43.35%; the grade TFe content is 7.33%; and the recovery rate is 21.39% of the tailings.

(2) Wet weak magnetic separator coarse grain tailing test

After the super-fine crushing of the original ore roller mill, DCφ400-300 wet electromagnetic weak magnetic cylinder magnetic separator is used. The fixed magnetic field strength is 1325Oe, the separation roller speed is 56YPM, the processing volume is 3t/h, and the ore size is changed. The particle tailing test, the process flow chart is shown in Figure 2, and the test results are shown in Table 5.

Fig. 2 Process diagram of coarse-grained tail-opening process of raw ore roller mill superfine-wet weak magnetic separator

Table 5 Results of coarse-grained tailing test of ore-bearing wet-type weak magnetic separator

Magnetic field strength (KA/m)

Feed concentration

(%)

Granular grade

(mm)

product

Yield

%

grade%

Recovery rate%

TFe

TFe

105.4

40

0～-5

Coarse concentrate

43.38

25.54

73.28

Tailings

56.62

7.14

26.72

Raw ore

100.00

15.12

100.00

105.4

40

0 to -3

Coarse concentrate

39.81

25.85

70.38

Tailings

60.19

7.19

29.62

Raw ore

100.00

14.62

100.00

105.4

40

0 to -2

Coarse concentrate

39.22

27.27

71.62

Tailings

60.78

6.98

28.38

Raw ore

100.00

14.94

100.00

It can be seen from Table 5 that the original ore roller mill is ultra-finely crushed, -5mm; -3mm; -2mm or less, and the wet type weak magnetic separator is used for coarse grain tailing, and a better beneficiation index is obtained. The particle size is reduced, the yield of tailings is increased, and the grade of tailings is not changed much, but the grade of coarse concentrate is obviously increased, and the recovery rate is reduced. The magnetic field strength is determined to be 1200~1325Oe, and the ore size is 3 A particle size of ~5 mm or less is suitable.

Fourth, the original mine roller mill ultra-fine crushing - coarse grain tailing - grinding - two-stage wet weak magnetic separation open circuit process test

After the original ore roller mill is ultra-finely crushed to 0~5mm, it is sieved to 0~-5mm, then the dry type weak magnetic separator is used for coarse grain tailing, and the obtained coarse concentrate is further ground, the fineness is -200 mesh accounted for 99.67%, and then two-stage wet weak magnetic separation, and finally obtained high-grade iron concentrate. The process flow chart is shown in Figure 3, and the test results are shown in Table 6.

Fig. 3 Flow chart of the ultra-fine crushing of the original ore roller mill - coarse grain tailing - grinding - two-stage wet weak magnetic separation open circuit

Table 6 Superfine crushing of raw ore - coarse grain tailing - grinding - two-stage weak magnetic selection open circuit test results

Dry weak magnetic separator

Baffle distance (mm)

Grinding fineness

-200 mesh (-0.074mm) %

product

Yield

%

grade%

Recovery rate%

TFe

TFe

20

99.67

Concentrate

14.49

65.12

61.90

Middle mine

1.33

18.78

1.64

Tailings 1

39.14

7.16

18.36

Tailings 2

45.04

6.14

18.10

Raw ore

100.00

15.25

100.00

10

99.67

Concentrate

13.30

64.49

57.05

Middle mine

0.61

20.67

0.86

Tailings 1

43.35

7.33

21.14

Tailings 2

42.74

7.38

20.95

Raw ore

100.00

15.04

100.00

From the test results in Table 6, it can be seen that the original mine roller mill superfine-dry-weak magnetic separator coarse-grain tailing-grinding-two-stage wet weak magnetic separator selects the open process, and obtains better beneficiation index. . The test conditions are suitable for selecting a dry weak magnetic separator baffle distance of 20 mm. The obtained mineral processing technical indicators are: iron concentrate production rate is 14.49%; iron concentrate grade TFe content is 65.12%; recovery rate is 61.90%,

V. Conclusion

(1) Research on the optimization process of ore dressing of low-grade ilmenite with very fine grain size in Gucheng County, Hubei Province, using roller mill technology to determine the ultra-fine crushing (0-5mm)-dry type of roller mill Weak magnetic separator coarse-grain tailing-grinding-two-stage wet weak magnetic separator selection process. By adopting this optimization process, the particle size of the iron ore into the ball mill can be reduced, and the coarse grain tailing can be carried out before the iron ore is put into the ball mill, thereby realizing "the early loss" and creating favorable conditions for improving the lean iron ore grinding. The production capacity of the mining system, saving energy and reducing consumption, and creating better economic benefits are of great significance.

(B) the lean primary magnetic ilmenite minerals recovered metal magnetite and ilmenite. Magnetite can be recovered by weak magnetic separation. Ilmenite can be recovered by a strong magnetic-flotation process. The final product must remove impurities, reduce sulfur and remove phosphorus.

(3) The grain size of magnetite and ilmenite in the ore is generally 0.105mm (140 mesh) to 0.052mm (300 mesh), the grain size of the inlay is very fine, and the grinding grain size is -0.074mm (-200 mesh). When the monomer dissociation is more than 90%; when the grinding particle size reaches -0.037mm (-400 mesh), the monomer dissociation degree is more than 98%. To completely dissociate the metal mineral, the grinding fineness should be 0.074mm ~ 0.037mm. Therefore, the ore must be finely ground to dissociate the iron ore monomer to improve the concentrate grade and recovery rate.

(4) The iron ore mine in Gucheng County, Hubei Province adopts the ultra-fine crushing of the roller mill--the dry weak magnetic separator, the coarse-grain tailing (0~-5mm) open-circuit process, when the ore grade is 14.41%~14.87%, it can be discarded. The yield is from 33.09 to 43.35%, the content of grade TFe is from 7.13 to 7.33%, and the recovery is from 16.38 to 21.39% of tailings. Dry weak magnetic separation coarse grain tailing has achieved good mineral processing indicators.

(5) The iron ore mine in Gucheng County, Hubei Province adopts the ultra-fine crushing of the roller mill-wet weak magnetic separation coarse-grain tailing (-5~-2mm) open circuit process. When the original ore grade is: 15.12~14.94%, the production can be abandoned. The ratio is 56.62~60.78%, the grade TFe content is 7.14~6.98%, and the recovery rate is 26.72~ 28.38% tailings. A better beneficiation technical index has been obtained than the dry weak magnetic separation coarse grain tailing.

(6) The iron ore mine in Gucheng County, Hubei Province adopts roller mill ultra-fine crushing (0~-5mm)-dry weak magnetic separator coarse-grain tailing-grinding-two-stage wet weak magnetic separator to select the open process. Better mineral processing technical indicators were obtained (see Table 6). The preferred index obtained is: iron concentrate yield 14.49%; iron concentrate grade TFe content 65.12%; recovery: 61.90%.

(7) Recommended procedure: super-fine crushing of raw ore roller mill (0~-5mm)-dry or wet weak magnetic separator coarse-grain tailing-grinding-two-stage wet weak magnetic separator selection process And equipment, with simple technology, advanced equipment, superior mineral processing index, and significant economic benefits, provide a basis for new plant selection.

(8) Hubei Lituo Investment Co., Ltd. decided to use the original mine roller mill ultra-fine crushing (0~-5mm) according to the results of the iron ore test in Gucheng County, Hubei Province. The dry weak magnetic separator is used for coarse-grain tailing-grinding- Two-stage wet weak magnetic separator selection process. Entrusted the design of Hubei Daye Nonferrous Design Institute and Mineral Processing Design Institute. The design plan has been confirmed, and the contract for the purchase of 6 ZMJ1600A roller mills has been signed with Changsha Shenxiang General Machinery Co., Ltd., and the beneficiation process design and equipment selection for the mine construction 5 million tons/year concentrator are being done. Ready to work.

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