Oolite hematite fine dissemination size, and is often associated with siderite, chamosite and phosphorus-containing mineral association or another package, so Oolitic hematite is widely recognized as the most difficult selected from iron ore One of the types, but its reserves are abundant, 1/9 of China's iron ore resource reserves are braided hematite. The main reason for the poor selectivity of the 鲕-shaped hematite is that the particle size of the monomer dissociation is too small. When the dissociation particle size is reached, the conventional selection of the stellite hematite often fails to achieve the desired effect, so people Under the current conditions, a new process for processing fine-grained hematite is sought. In this experiment, a beneficiation magnetic separation process was used to conduct a beneficiation test on a braided hematite in Hebei. The test results show that under the optimal dispersion and flocculation conditions, 55.51% iron is obtained by strong magnetic separation. The recovery rate is 76.02% iron concentrate.
First, the nature of the ore
(1) Multi-element analysis of raw ore chemistry
Chemical multi-element analysis was performed on the ore samples, and the results are shown in Table 1.
Table 1 Multi-element analysis results of ore chemistry
ingredient | TFe | FeO | S | P | SiO 2 | Al 2 O 3 | CaO | MgO |
content | 47.41 | 9.81 | 0.22 | 0.24 | 15.08 | 4.85 | 2.78 | 3.12 |
From the analysis results in Table 1, it can be seen that the total iron grade of the ore is 47.41%: the main impurity in the ore is SiO 2 , followed by A1 2 O 3 ,
Mg0 and CaO; the content of harmful elements S and p is slightly higher; W(CaO+MgO) / w(SiO 2 +A1 2 O 3 )=0.296, indicating that the ore is an acidic ore.
(II) Analysis of ore phase of iron ore
The iron ore phase analysis was performed on the ore samples, and the results are shown in Table 2.
Table 2 % of ore iron phase analysis results
Name | magnetite | Red, limonite | Iron carbonate | Iron sulfide | Iron silicate | total |
Iron content | 0.58 | 43.45 | 2.97 | 0.49 | 0.17 | 47.66 |
Iron distribution rate | 1.22 | 91.17 | 6.23 | 1.03 | 0.35 | 100.00 |
From the results of Table 2, it can be seen that the useful iron minerals in the ore are mainly red limonite, which has an iron fraction of 91.17%, followed by iron carbonate and magnetite, and contains a small amount of iron sulfide and iron silicate. Iron ore iron content only accounts for 1.22%.
(3) Ore structure
The ore structure is mainly composed of a gel-like structure, and a small amount of disseminated structure is also seen. The colloidal structure is mainly cryptocrystalline and amorphous, with complex morphology, spherical or knob-like protrusions on the surface, and curved concentric annular bands. The interface of each ring is unclear and often has a gradual relationship. According to the shape of the outer shape, the gelatinous structure is further divided into a braided structure, a kidney-like structure, and a bean-like structure, which is dominated by a braided structure (see Fig. 1). The composition of the disseminated ore is mainly composed of gangue minerals such as quartz, and the hematite and limonite are scattered in the matrix of gangue minerals such as quartz.
Figure 1 Braided hematite
In the braided structure, the cement between the granules is a gangue mineral such as quartz, chlorite or carbonate. The internal structure of the granules is complex, and the hematite is concentric with the gangue (see Figure 2). The core is a single gangue mineral such as hematite or quartz, and the particle size of the core particles is not uniform.
Figure 2 Distribution of hematite and gangue
Process mineralogical studies have shown that gangue minerals are dispersed in fine pores (3 to 9 μm) in fine voids and between the hematite or limonite, or in a concentric layer with hematite, almost no separate existence. . Therefore, it is very difficult to greatly improve the grade of concentrate, and the recovery rate can only be guaranteed under the condition of increasing the grade of iron concentrate as much as possible.
Second, the test plan
According to the nature of the ore, it is known that the gangue minerals account for about 15% of the total minerals, and are dispersed in fine pores and between the grains of hematite or limonite by fine particles (3 to 9 μm), or are concentric with hematite. Distribution, almost no separate existence. Therefore, if the anti-flotation method is used to reduce the impurity, the collector can actually reach less gangue minerals, which will result in higher flotation tailings grade and lower concentrate grade; and a large amount of red iron in the ore. Mines and limonite are extremely muddy and will worsen the flotation process. Exploring the test results also indicates that the ore is not suitable for the flotation process.
On the other hand, the results of process mineralogical studies show that the more the fine-grained gangue is distributed, the lower the iron grade, the smaller the specific magnetization coefficient. Conversely, the smaller the fine-grained impurities, the higher the iron grade. Minerals, the greater the specific magnetic susceptibility. Therefore, it is reasonable to use a strong magnetic separation method to recover higher quality iron concentrates. In the exploratory experiment, it was found that a considerable part of the fine iron concentrate (mainly -30μm fine particles) derived from limonite was lost in the magnetic selection. Therefore, after fully dispersing the slurry, the flocculant added with iron minerals was considered. The particle size of the fine-grained iron mineral is increased, and then the strong magnetic separation is performed, so that the fine-grained iron mineral is more fully recovered and the iron recovery rate is improved.
In summary, the determination test was carried out according to the flocculation-strong magnetic separation scheme.
Third, test equipment and pharmacy
(1) Test equipment. XMB-φ240×300 rod mill, XCSQ-50×70 wet magnetic separator, HH.W21.600 meter constant temperature water bath, IKARW20 digital high speed mixer, 1000mL beaker.
(2) Test agents. NaOH, water glass, sodium hexametaphosphate, sodium tripolyphosphate, corn starch, sodium oleate, polypropylene decylamine.
Fourth, conditional test
(1) Dispersing conditions. Due to the extremely fine grain size of the helium-like hematite in the ore, in order to maximize the monomer dissociation degree of the mineral, the ore is finely ground to -500 mesh and 98%. Under such fineness of grinding, the ore that is easily muddy will produce a large amount of slime. The slime will form a cover on the surface of the fine-grained minerals, affecting the flocculation and sorting effects. Therefore, the slime must be sufficiently dispersed before flocculation. The specific operation of the dispersion test is as follows: the fine grinding product with dry mass of Wo is made into a certain concentration of 800 mL of pulp in a 1000 mL beaker, placed in a water bath, the temperature is controlled, and NaOH is used under the stirring of the IKARW20 digital high-speed stirrer. Adjust the pH of the slurry, then add the dispersant water glass and stir for 4 minutes. The dispersed slurry is settled for 1 min, and the upper suspension is sucked by the siphon method from the beaker scale to 650 mL. The remaining slurry is filtered and dried, and the mass is defined. The ratio of w to Wo is the sedimentation rate Es, that is,
The dispersion effect of fine particles in aqueous medium is measured by Es: the smaller the sedimentation rate Es, the better the dispersion effect of the particles, and the worse the dispersion effect of the particles.
The test results show that the pulp can achieve a better dispersion effect under the conditions of slurry concentration of 18%, pulp pH=11, pulp temperature of 18 °C, water glass dosage of 800g/t and impeller rotation speed of 750r/min. .
(2) Flocculation conditions. After the slurry is dispersed according to the determined dispersion conditions, the stirring speed is decreased, the flocculant of different kinds and different amounts is added, and the mixture is stirred for 5 minutes, and the flocculation condition is determined according to the agglomeration effect of the fine iron mineral. The results showed that the three flocculants of sodium oleate, polyacrylamide and corn starch were compared. The results showed that the corn starch had the best flocculation ability, and the suitable addition amount was 200g/t. In addition, through experiments, it was determined that the stirring speed should be controlled at 150 r/min during flocculation. Under the above conditions, the fine-grained iron mineral can be agglomerated to about 50 μm from about 7.6 μm to a particle size range suitable for strong magnetic separation.
(3) Strong magnetic selection conditions. Conditional tests were carried out on the field strength, tooth plate clearance and flushing water flow of strong magnetic separation. The results show that the grade and recovery rate of iron concentrate are ideal under the condition that the gap between the magnetic separator plates is 0.15mm, the flushing water flow is 150 mL/s, and the field strength is 1194kA/m.
V. Process test
According to the condition test results, one roughing and one sweeping flocculation one strong magnetic separation process test was carried out. When rough selection, the pulp concentration is 18%, the pulp pH=11, the pulp temperature is 18°C, the dispersant water glass dosage is 800g/t, the flocculant starch dosage is 200g/t, and the dispersed and flocculated impeller speeds are respectively The magnetic field strength of the strong magnetic separator is 1194 kA/m at 750 r/min and 150 r/min. When sweeping, the amount of dispersant and flocculant is halved, and other conditions remain unchanged. The test procedure and results are shown in Figure 3.
Figure 3 test number quality process
It can be seen from Fig. 3 that under the optimal test conditions, after one roughing and one sweeping, the concentrate iron grade is 55.51% and the iron recovery rate is 76.02%. Mineral processing indicators.
Sixth, the mechanism of sorting
During the beneficiation process, any sorting method and equipment is only applicable to a certain sorting size range. In order to achieve the maximum effect of each type of equipment in the beneficiation process and achieve the best selection index, when selecting the beneficiation process and mineral processing equipment, the ore dressing method and the effective sorting particle size range of the equipment must be fully considered. The sorting force is proportional to the cube of the grain size of the ore. Therefore, as the particle size of the mineral particles decreases, the sorting force acting on the mineral particles is greatly attenuated. At the same time, the resistance of the medium to the mineral particles is proportional to the primary of the particle size of the mineral particles. Therefore, as the particle size of the mineral particles decreases, the attenuation of the resistance of the medium to the mineral particles is slower. The above mechanism makes the difference between the sorting force and the resistance acting on the mineral particles greatly decrease with the decrease of the particle size of the mineral particles, thereby increasing the difficulty of separating the useful minerals from the gangue minerals, and selecting the fine-grained minerals. Don't get worse. This phenomenon can be improved by using a dispersion-flocculation process to agglomerate the fine-grained iron minerals to form a larger floc and then magnetically electrify.
When the dispersion-flocculation process is adopted, the dispersion-flocculation effect must be effectively grasped. The test found that good dispersion is the premise of flocculation, and the dispersion should be carried out under the premise that the dispersion method and the added dispersant do not have harmful effects on the agglomeration of the subsequent additives. Under this premise, the pulp is realized as much as possible. Fully efficient dispersion of all components or gangue components, the higher the dispersion efficiency, the better the sorting index. The pH value, concentration, temperature and stirring speed of the slurry have a great influence on the dispersion and flocculation, and the mode of action of the agent also has a certain influence on the selection.
Seven, conclusion
(1) According to the process mineralogy of a mantle-like hematite, the occurrence of iron minerals in the ore is diverse, and the mineral symbiosis is complicated, especially the iron mineral inlay is very fine, when the ore is When the fineness of grinding is 7.6 μm, the cleavage degree of the useful mineral hematite is only 85%. Through analysis, it is feasible to select the hematite by flocculation-strong magnetic separation process.
(2) Dispersion and flocculation test results show that the slurry concentration is 18%, the pulp pH=11, the pulp temperature is 18°C, the dispersant water glass dosage is 800g/t, the flocculant starch dosage is 200g/t, dispersion and flocculation. Under the conditions of impeller rotation speed of 750r/min and 150r/min, a good coarse magnetic selection index can be achieved.
(3) The results of strong magnetic separation test show that the magnetic field strength of strong magnetic separation has a great influence on the recovery rate of concentrate. The flow rate of flushing water also plays an important role in improving the grade of concentrate. The field strength was selected to be 1194 kA/m by field strength test.
(4) Under the selected test conditions, by dispersing a flocculation, one coarse and one sweep, the magnetic separation is selected, so that the final concentrate index can reach 55.51% of iron grade and 76.02% of iron recovery rate.
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