Process technology for recovering fine-grained iron oxide by wet high gradient and strong magnetic separation

BMO ditch iron ore beneficiation plant production scale of 800 000 t / a, since the operation, the basic production targets to meet the design requirements. However, since the iron ore is hematite, it is easily muddy, and the grinding process is two-stage continuous grinding, and the grinding products are graded by a hydrocyclone (ie, strong magnetic magnetic separation to feed) - The 500 mesh size is over 50% and the grade is 40.00%. Due to the fine particle size, this part of the ore cannot be effectively recovered during the sorting process, resulting in low iron recovery rate, iron grade of tailings, and improved recovery rate of the iron ore. This has become an urgent problem for the concentrator. .

First, the nature of the ore

Manyingou Mine is divided into three medium-sized hematite ore sections of Mangyingou, Yangjiacun and Shuangshuijing. The deposit belongs to the medium-sedimentary metamorphic hematite deposit, and the ore body is present in the former Sinian Limahe Formation sandstone and the Jinyun phyllite. Hematite iron minerals, followed by limonite, siderite, martite, occasionally magnetite, titanium, iron and the like; gangue minerals dominated by quartz, sericite, dolomite, Calcite is second. The ore structure is mainly composed of phosphorous crystal transformation structure, image-like structure, metasomatic structure and cementation structure. The structure is mainly composed of massive structures, followed by powdery and strip-like structures. The particle size of iron minerals is generally between 0.0025 and 0.04 mm. Sometimes hematite is changed into phenocrysts, the particle size can reach 0.15-1.4 mm, and the particle size of gangue mineral quartz is generally between 0.0025 and 0.15 mm, which is often filled by hematite. , dissolution, ore hardness is small. The results of multi-element chemical analysis of iron ore are shown in Table 1, and the results of iron phase analysis are shown in Table 2.

Table 1 Multi-element analysis results of iron ore

element	TFe	S	P	SiO ₂	Al ₂ O ₃	CaO	MgO
content	47.92	0.016	0.103	20.94	5.28	0.46	0.48
element	FeO	Mn	Na ₂ O	K ₂ O	TiO ₂	Burning down	Alkali ratio
content	0.18	0.32	0.030	1.34	0.294	1.53	0.036

Table 2 Iron phase analysis results of iron ore

Iron phase	Red, limonite	magnetite	Iron carbonate	Pyrite	Iron silicate	total
Iron content	46.57	0.10	0.30	0.11	0.84	47.92
Distribution rate	97.18	0.21	0.63	0.23	1.75	100.00

It can be seen from Table 1 and Table 2 that the iron content in the ore is 47.92%, and the iron in hematite and limonite accounts for 97.18%. The content of silica in the ore is 20.94%, the content of alumina is 5.28%, the content of sulfur is 0.016%, and the content of phosphorus is 0.103%. It belongs to low sulfur, phosphorus, high silicon, aluminum, acid weak magnetic iron ore.

Second, the current process flow problems

The mine commissioned the Maanshan Iron and Steel Group Design and Research Institute to carry out the design of the Mangangou Mining Group's 800,000 t/a concentrator. According to the results of the ore dressing test and its recommendations, the ore dressing process is determined to be two-stage continuous grinding, wet high gradient strong magnetic separation process. One section of grinding fineness - 200 mesh accounted for 55%, and the second section of grinding fineness - 200 mesh accounted for 85%. The second-stage grinding products are subjected to strong magnetic rough selection and tailing, and the coarsely-selected concentrate is selected by high-gradient magnetic separator to obtain high-gradient strong magnet concentrate with iron grade above 66.00%; The mine is then subjected to a high-gradient magnetic sweep to obtain an iron concentrate with an iron grade above 50.00%. The process flow is shown in Figure 1.

Figure 1 Man Yinou iron ore beneficiation number quality process

With the reduction of iron ore resources and the increase of mining volume, the ore grade is reduced to 40.00%, the iron concentrate grade is about 58.00%, and the iron concentrate grade is about 47.00%. In actual production, the high gradient magnetic separator is stronger Ganzhou magnetic rings of gold Equipment Co Slon type of vertical ring pulsating high gradient magnetic separator strong magnetic substance is a divalent rod Ñ„2mm medium thick box infeed slurry ( That is, the iron ore grade of the selected and rough-selected tailings is about 35.00%, and the concentration is about 16.00%. After concentration, the grit is put into the sweeping. The sand iron grade is about 30.00%, the concentration is about 20%, and the iron concentrate is about 47.00%. The thick box overflow particle size is very fine, almost all -500 mesh (-0.037mm), of which -20Î¼m is as high as 73.02%, its concentration is very small, about 6% to 8%, the yield is 20 of the ball milled ore. %. This part of the ore grade is close to the grinding grade, which is more than 40.00%, and the concentration tank overflow is directly discharged into the tailings, which is the main reason for the high tailings. How to recover this part of fine-grained minerals, reduce the grade of tailings, and improve the recovery rate of sweeping operations is an urgent problem to be solved.

Third, laboratory magnetic media test

According to the production site, no chemicals are added to the thick tank feeding, grit and overflow. Under the condition of the same current intensity 400A and magnetic induction intensity 0.6T of the high gradient magnetic separator, the magnetic mediums of different diameters are used for sorting. Table 3, Table 4 and Table 5 are shown.

Table 3 Test results of thick box feeding high gradient magnetic separator

Test conditions		sample name	grade/%	Yield/%	Recovery rate/%
Magnetic medium / mm	Magnetic induction / T	sample name	grade/%	Yield/%	Recovery rate/%
Î¦2	0.6	Concentrate Tailings Raw ore	47.38 28.27 34.56	32.91 67.09 100.00	45.12 54.88 100.00
Î¦1	0.6	Concentrate Tailings Raw ore	51.35 27.33 34.56	30.10 69.90 100.00	44.72 55.28 100.00

Table 4 Test results of thick box grit high gradient magnetic separator

Test conditions		sample name	grade/%	Yield/%	Recovery rate/%
Magnetic medium / mm	Magnetic induction / T	sample name	grade/%	Yield/%	Recovery rate/%
Î¦2	0.6	Concentrate Tailings Raw ore	39.79 21.04 27.75	35.79 64.21 38.19	51.31 48.69 100.00
Î¦1	0.6	Concentrate Tailings Raw ore	44.48 21.36 27.75	38.19 61.81 100.00	61.22 100.00 100.00

Table 5 Test results of thick box overflow high gradient magnetic separator

Test conditions		sample name	grade/%	Yield/%	Recovery rate/%
Magnetic medium / mm	Magnetic induction / T	sample name	grade/%	Yield/%	Recovery rate/%
Î¦2	0.6	Concentrate Tailings Raw ore	51.22 37.22 40.09	20.50 79.50 100.00	22.20 77.80 100.00
Î¦1	0.6	Concentrate Tailings Raw ore	51.28 35.79 40.09	27.76 62.24 100.00	35.51 64.49 100.00

It can be seen from Table 3, Table 4 and Table 5 that for the thick tank feeding, grit and overflow, the diameter of the rod medium of the high gradient magnetic separator has an influence on the three kinds of samples. Under the condition of the same magnetic induction intensity of 0.6T, the magnetic separation concentrate grade of Ñ„2mm rod medium is 3 percentage points higher, and the recovery rate and the tailings grade are not much different. For the thick box grit, the magnetic separation concentrate of Ñ„2mm rod medium is used. The recovery rate is about 10% lower, and the recovery rate is about 10% lower. The magnetic separation concentrate grade of the Ñ„1mm rod medium in the thick box overflow is similar to the magnetic separation concentrate grade 51.00% using the Ñ„2mm rod medium. The Ñ„2mm rod medium is about 15% higher. It is indicated that the Ñ„1mm rod medium can effectively recover a part of the fine-grained iron ore with higher grade.

IV. Industrial test of Ñ„1mm and Ñ„2mm magnetic media

(1) Test conditions

Two Slon-1750 high-gradient magnetic separators in the smelting and dressing operation of Man Yinou Iron Ore Group Company were selected by Ñ„2mm rod media, which has poor recovery effect on fine-grained hematite. Therefore, the concentrator used the Ñ„1mm rod medium test in the laboratory to dismantle the original Ñ„4mm rod quality using a company's idle Slon-1250 high-gradient magnetic separator. The installation was provided by Zhangzhou Jinhuan Company. Ð¤1mm rod medium, the machine is placed next to a Slon-1750 high-gradient magnetic separator in the sweeping operation, and one feeding box is used to feed the two different types of high-gradient magnetic separators at the same time, for Ñ„1mm Contrast industrial test with Ñ„2mm rod medium.

(2) Test results

The test was carried out under the same conditions of the same ore and the same magnetic induction intensity, wherein the sweep was selected for the sweep, and the sweep was selected for the Slon-1250mm high gradient magnetic separator to sweep the concentrate; the sweep 1 to the tail was the Slon-1750mm high gradient. The magnetic separator was used to sweep the tailings; the 2-tail was Slon-1750mm high-gradient magnetic separator to sweep the tailings. The test results are shown in Table 6, Table 7, and Table 8. The magnetic separation concentrate grades and recovery rates of Ï†1mm and Ï†2mm magnetic media of Slon type high gradient magnetic separator under different magnetic induction conditions are shown in Fig. 2 and Fig. 3 respectively.

Table 6 Test results of magnetic induction strength 0.7T

Sample serial number	sample name	grade/%	Yield/%	Recovery rate/%	Magnetic induction / T
Sweep 1 - fine	Sweeping concentrate	51.94	17.05	28.59	0.7
Sweep 1-tail	Sweeping tailings	26.66
Sweep 2 - fine	Sweeping concentrate	47.73	17.96	27.69	0.7
Sweep 2-tail	Sweeping tailings	27.30
Sweep	Sweeping to mine	30.97	100.00	100.00

Table 7 Test results under magnetic induction of 0.6T

Sample serial number	sample name	grade/%	Yield/%	Recovery rate/%	Magnetic induction / T
Sweep 1 - fine	Sweeping concentrate	50.21	25.03	38.52	0.6
Sweep 1-tail	Sweeping tailings	26.76
Sweep 2 - fine	Sweeping concentrate	48.99	23.44	35.19	0.6
Sweep 2-tail	Sweeping tailings	27.62
Sweep	Sweeping to mine	32.63	100.00	100.00

Table 8 Test results of magnetic induction at 0.5T

Sample serial number	sample name	grade/%	Yield/%	Recovery rate/%	Magnetic induction / T
Sweep 1 - fine	Sweeping concentrate	53.20	9.66	14.35	0.5
Sweep 1-tail	Sweeping tailings	33.94
Sweep 2 - fine	Sweeping concentrate	52.92	19.96	29.51	0.5
Sweep 2-tail	Sweeping tailings	31.53
Sweep	Sweeping to mine	35.8	100.00	100.00

Figure 2 Slon type high gradient magnetic separator under different magnetic induction conditions

Grade distribution of magnetically selected iron concentrates in Ï†1mm and Ï†2mm magnetic media

â– A magnetic medium Ï†1mm; â— A magnetic medium Ï†2mm

Figure 3 Slon type high gradient magnetic separation under different magnetic induction conditions

Distribution of magnetic separation iron concentrate recovery rate of Ï†1mm and Ï†2mm magnetic media

â– A magnetic medium Ï†1mm; â— A magnetic medium Ï†2mm

From the test results, it can be seen that in the same feeding condition, the magnetic induction intensity is 0.6T, and the magnetic separation concentrate of the SLon-1250 type high gradient magnetic separator using Ï†1mm rod medium is higher than that of the Slon-1750 type high gradient magnetic separator of Ï†2mm rod medium. The grade of magnetic separation concentrate is about 2% higher, and the recovery rate is about 3 percentage points higher. The tailings are about 1% lower than the magnetic separation tailings of the Slon-1750 high-gradient magnetic separator with Ï†2mm rod medium. With the decrease of the magnetic induction intensity, the selection results of the high-gradient magnetic separators with different diameters of the rod medium are small.

V. Conclusion

(1) By testing the test results of different magnetic media, it can be known that for the thick tank feeding, grit and overflow, the diameter of the rod medium of the magnetic separator has an influence on the three kinds of samples. Under the same magnetic induction intensity of 0.6T, using Ï†1mm rod medium, the magnetic separation concentrate grade of the thick tank feeding and overflowing is about 51.00%, and the tailings are not much different; the recovery rate of overflow is Ï†1mm using Ï†1mm The rod medium is about 15 percentage points higher. The density of the Ï†2mm rod medium in the thick box is 4% lower than that of the Ï†1mm rod medium. The grade of the tailings is not much different, and the recovery rate is 10% lower. It is indicated that the Ï†1mm rod medium can effectively recover a part of the fine-grained iron ore with higher grade.

(II) Contrast test of Ï†1mm rod medium and Ï†2mm rod medium in the sweeping operation of Manyingou Iron Ore Dressing Plant shows that when the magnetic induction intensity is â‰¥0.6T, the Ï†1mm rod medium is better than the Ï†2mm rod medium, and its concentrate grade is good. It can be increased by 2% on average, the tailings are reduced by 1% on average, and the recovery rate is increased by 3% on average. It is indicated that the use of Ï†1mm rod media requires a large magnetic induction.

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