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Technical Transformation of Comprehensive Recovery of Magnetite Process from Molybdenum Tailings
In the molybdenum tailings of the Fuyang molybdenum mine in Henan Province, the total iron content is about 6%. The iron minerals are magnetite, silicate iron ore, red (brown) iron ore, siderite and pyrite. magnetite, iron metal which accounts for 50% of the total iron. The weak magnetic separation process is used to comprehensively recover the magnetite in the molybdenum tailings, which has high economic value. Beneficiation plant beginning of construction, the installation of a weak magnetic separator drum, molybdenum tailings recovery of magnetite float, but the income of low grade iron ore, molybdenum tailings recovery of magnetite float, but income The grade of iron concentrate is very low, only about 20%, even after many selections, the grade is difficult to improve. After preliminary research, the main reason for the low grade of iron concentrate is that the size of the magnetite inlay is extremely fine. In the case where the fineness of the molybdenum tailings is -200 mesh, 55%, the large iron concentrate is obtained. Some of the magnetite still exists as a wrapped continuum. Therefore, in order to improve the grade of iron concentrate, a fine grinding process must be implemented. On the basis of the test in 2006, the rough selection-coarse concentrate re-grinding-grade-selection-high-frequency vibration fine screening process was used to transform the original simple magnetic separation process, and the grade of the iron concentrate after the transformation was improved. Up to 45%, although the increase is large, but the ideal iron ore grade index is still far from 60%, the reason is mainly because a section of re-grinding still can not reach the complete dissociation of magnetite. The required -400 mesh accounts for more than 95% of the fineness requirements. In 2007, the iron production process was re-engineered, and a section of re-grinding was changed to two-stage re-grinding, and the second-stage re-grinding used a tube mill. The second-stage grading used two cyclones directly in series, while eliminating the high frequency. Vibrate fine screen to increase the number of selections. After re-engineering, the second-stage re-grinding grade reached -400 mesh, accounting for 99.8%, and the final iron concentrate grade reached more than 63%. The iron recovery rate was increased by more than 1% compared with that before the transformation, which created considerable profits for the company. Economic benefits.
   First, the nature of floating molybdenum tailings
The results of chemical multi-element analysis and iron phase analysis of molybdenum tailings are shown in Tables 1 and 2, respectively.
Table 1 Results of chemical multi-element analysis of molybdenum tailings
ingredient
TFe
FeO
Fe 2 O 3
Mo
Cu
Pb
Zn
content
6.05
3.95
4.26
0.018
0.013
0.015
0.016
ingredient
SiO 2
TiO 2
Al 2 O 3
CaO
MgO
MnO
Na 2 O
content
63.23
1.00
12.26
3.38
1.52
0.21
2.09
ingredient
K 2 O
P
As
S
CO 2
Ig
content
3.81
0.12
0.011
0.36
1.03
2.96
Table 2 Analysis results of iron phase of floating molybdenum tailings
Iron phase
magnetite
Red (brown) iron
Iron carbonate
Iron sulfide
Iron silicate
Full iron
Iron content
3.00
0.32
0.43
0.22
2.08
6.05
Iron distribution rate
49.59
5.29
7.11
3.64
34.37
100.00
It can be seen from Table 1 that the main components available for recovery in the molybdenum tailings are iron and molybdenum. It can be seen from Table 2 that the form of iron is more complicated, and the iron distributed in magnetite is only 49.59%. The rest is mainly in the form of red (brown) iron ore, or distributed in carbonates and silicates. In the class of minerals.
The monomer dissociation degree of the magnetite in the molybdenum tailings sample was measured, and the results are shown in Table 3.
Table 3 Determination of monomer dissociation degree of magnetite in molybdenum tailings
magnetite
State of existence
monomer
Magnetite and
Gangue
Magnetite and
Sulfide
magnetite
Wrapped gangue
Gangue package
magnetite
Meteorite package
magnetite
Relative content
32.10
0.93
0.07
1.15
58.62
7.13
It can be seen from Table 3 that most of the magnetite is in the form of a wrapped continuum, and the relative content of the monomer is only 32.10%, so fine grinding is required.
   Second, the first iron selection process transformation
Since the establishment of the iron-making workshop, a simple magnetic separation process has been adopted, and the grade of iron concentrate is only about 20%. In order to improve the grade of iron concentrate, after a series of experimental studies in 2006, the first transformation was carried out using the process shown in Figure 1.
Figure 1 The iron selection process after the first transformation
After the first transformation, the re-grinding degree is -200 mesh, accounting for 60% to 65%, the iron concentrate grade has been hovering around 45%, and the recovery rate is about 28%. Although the grade and recovery rate of iron concentrates have been greatly improved compared with the establishment of the factory, it is far from the ideal grade. For this purpose, the iron concentrate was subjected to particle size analysis, and the results are shown in Table 4.
Table 4 Results of particle size analysis of iron concentrate after the first transformation
Size/mm
Yield/%
Iron grade /%
Iron distribution rate /%
Granular grade
Grand total
+0.180
-0.180+0.150
-0.150+0.105
-0.105+0.074
-0.074+0.0385
-0.0385
Total
2.50
2.10
1.35
42.35
4.10
47.60
100.00
43.63
25.10
23.90
33.17
36.65
52.99
42.71
2.55
1.24
0.75
32.90
3.51
59.05
100.00
2.55
3.78
4.54
37.43
40.95
100.00
It can be seen from Table 4 that the iron grade of -0.0385mm grade can reach 52.99%; however, although the grade of +0.0385mm accounts for 40.95% of iron, and the yield is more than half, the iron grade is very low, indicating the iron therein. Mineral monomer dissociation is very poor. Therefore, in order to achieve the desired iron concentrate grade, it must be finely ground to a fineness of more than 95% of the -400 mesh required to completely dissociate the magnetite. To this end, the second transformation was carried out in 2007.
   Third, the second iron selection process transformation
(1) Process
According to the results of the particle size analysis of the iron concentrate after the first transformation, the second transformation is mainly based on the process after the first transformation, adding two stages of regrind classification to ensure the final regrind to reach -400 mesh. More than 95%, in order to obtain a better grade of iron concentrate. The process flow after the second transformation is shown in Figure 2.
Figure 2 The iron selection process after the second transformation
(2) Selection of two-stage mill
At present, there are many vertical grinding machines and tube mills. However, from the use of the Shizhuyuan Pheasant Tailings Factory, the vertical mill has the following disadvantages:
1. The spiral blade wears unevenly, the lower part wears faster, the maintenance is complicated and frequent, the wearing parts are expensive, and the production cost is high.
2. The factory building must have a certain height; when the power is shut down, the slurry should be emptied, and the slurry and steel balls should be emptied during the inspection. Therefore, an accident pool must be built.
3, the reducer lubrication is not off.
The tube mill belongs to the stereotyped product. Compared with the vertical mill, the wearing parts are slow to wear, the equipment failure rate is low, the maintenance and repair is convenient, and the equipment and the wearing parts are low in price, and the motor power consumption is small. Therefore, it is considered economical and reasonable to use a tube mill for the two-stage regrind equipment. According to the process conditions, a ø1500×6400 tube mill was selected.
(3) Configuration of the two-stage hierarchical cyclone
In order to meet the process requirements, the classification of the second stage after re-grinding has certain difficulties. According to the relevant information, the material of -400 mesh should be directly separated, the diameter of the cyclone must be ≤100mm, and the concentration of the ore should be <12%. However, if the water is directly discharged from the tube mill to a concentration of 12% and then fed into the ø100mm cyclone, a large amount of additional water is required, and the concentration of the grit is also small at this concentration, which easily affects the grinding. mine. Therefore, the second stage of the retrofitting uses a cyclone series two-stage classification, in which the primary classification cyclone is ø150mm and the secondary classification cyclone is ø100mm.
The series connection of the cyclone is generally in the manner of Figure 3, that is, the overflow of the primary cyclone is first introduced into the pumping tank, and then pumped into the secondary cyclone. In this modification, the overflow of the primary cyclone is directly fed into the secondary cyclone without passing through the pump pool, which reduces the number of pumps, saves costs, and makes the system easy to coordinate and stabilize.
Figure 3 The cyclone is generally connected in series
Figure 4 This transformation of the cyclone series
   Comparison of technical indicators for four or two transformations
The comparison results of the technical indicators of the two transformations are shown in Table 5.
Table 5 Comparison of technical indicators of two transformations %
Indicator
First renovation
Second renovation
September
October
November
December
Iron concentrate grade
44.92
64.99
63.56
64.23
64.86
Iron concentrate recovery rate
28.55
29.91
29.14
29.75
29.62
Iron concentrate
Impurity content
S≤0.1
P≤0.1
SiO 2 20～25
S ≤ 0.1, P ≤ 0.1, SiO 2 5 to 10
Grinding fineness
-200 mesh 60-65
One section -200 mesh 60-65, two segments-400 mesh 99.8
It can be seen from Table 5 that after the second transformation, the grade of iron concentrate is over 63%, the recovery rate is over 29%, and the impurity content is very low, which is in line with the first grade standard of iron concentrate.
   Fourth, the conclusion
(1) The second stage of the magnetite ore comprehensive recovery process was carried out by the two-stage re-grinding stage grinding process of the Xiangyang molybdenum mine. The iron concentrate grade reached over 63%, and the recovery rate exceeded 29%. It has brought considerable economic benefits.
(2) The tube mill is the key equipment for achieving the re-grinding of more than 95% of the -400 mesh in the stage grinding process of the comprehensive recovery of magnetite in the Xiangyang molybdenum mine. The device is stable and reliable, convenient for maintenance and repair, and cost-effective.
(III) In the stage grinding process of comprehensive recovery of magnetite from Fuyang Molybdenum Mine, the two-stage two-stage cyclone is directly connected in series, which not only obtains satisfactory grading index, but also makes the system easy to coordinate and stabilize. .