Separation technology of micro-fine weak magnetic iron ore selective flocculation process

After 50 years of development and utilization of iron ore resources easily selected gradually growing shortage situation, obviously insufficient reserve mines, many easy to choose the iron mines have entered the underground mining period. The substantial increase in the cost of mining ore has made the company's production and operation status and the competitiveness of foreign iron ore producers in an unfavorable situation. Contrary to this, China still has a considerable amount of reserves of weak magnetic iron ore, but because of the fine grain size of the ore, it is within the range of fineness of the existing equipment process (-200 mesh accounts for 70% to 90%). The dissociation degree of the useful mineral is only 30% to 60%, and when the monomer dissociation degree is 80% to 90%, the particle size of the iron ore particles tends to be about -500 mesh (10 to 20 μm). At present, the mineral selection in this range of grades has exceeded the limits of existing equipment processes, and fine iron mineral particles cannot be recycled, resulting in a large loss of useful minerals. This is also a difficult problem in the world that the weak magnetic iron ore has been unable to be effectively solved. Therefore, under the existing conditions, people began to seek new processes for processing fine-grained weak magnetic iron ore. In many new beneficiation processes, the selective flocculation method is applied to the treatment of fine-grained weak magnetic iron ore, which has strong vitality and develops rapidly from theory to practice.

I. Research progress on selective flocculation process of fine weak magnetic iron ore

The selective flocculation process of fine-grained weak magnetic iron ore is mainly based on the addition of a certain amount of flocculant in a mineral suspension containing two or more kinds. The flocculant is selectively adsorbed weakly due to the different surface properties of the mineral. The surface of the magnetic iron mineral is agglomerated by the molecular action of the flocculant, and other minerals in the suspension are still present in a dispersed state. The floccules and suspensions are further separated, and the separation of weak magnetic iron minerals and gangue minerals can be achieved. At present, according to the mechanism of agglomeration of fine ore particles, selective flocculation can be further divided into: polymer flocculation, hydrophobic flocculation, and magnetic composite flocculation.

(1) Polymer flocculation process

This process is a "bridge" effect of high molecular weight polymers. The high-molecular flocculant has a large molecular weight, a chain length, and a large number of reactive functional groups along the length of the chain. It can adsorb several or several tens or more solid particles and join them together by bridging to form a large porous body. Floc. The interaction between the flocculated reactive functional group and the surface ions of the particles is achieved by hydrogen bonding, chemical strengthening or chemical reaction. In the solid-liquid separation and water treatment technology, it has been widely used to deal with fine-grained infiltrated weak magnetic iron ore and successful industrial practice.

Changing the surface potential or electrical properties of the particles causes a large difference in the potential of the different particles, so that for a certain polymer flocculant, the difference in the number of active particles on the surface of different particles is increased to achieve the selective purpose. Early success reports on selective flocculation and many of today's industrial applications for selective flocculation have been carried out using this method, and the application of this method has mature experience. Read has done a more detailed study of the hematite- quartz system. Hematite - quartz system, the previously added sodium hexametaphosphate and sodium phosphate, and the potential difference between the silica of large hematite, hematite was added strongly anionic polyacrylamide flocculant - Quartz system. Since the potential of quartz is relatively negative, the possibility of adsorption by strong anionic flocculant is inhibited, thereby achieving effective separation of hematite and quartz.

In recent years, people have made a lot of meaningful interest in the selective flocculation of minerals or selective de-sludge by high-molecular flocculants, followed by conventional re-election, flotation and magnetic separation methods for sorting fine-grained weak magnetic iron ore. jobs. He Yanshu and Song Quanyuan conducted selective flocculation-de-sludge studies on 100%-400 mesh siderite and limonite for the refractory characteristics of fine-grained weak magnetic iron ore. Studies have shown that the process of selective flocculation of siderite and limonite is deeply affected by water quality (Ca ^{2 +} , Mg ^{2 +} ion content), and sodium hexametaphosphate is used to eliminate Ca ^{2 +} and Mg ^{2 + in} tap water to soften The purpose of water quality. After quartz adsorbs high modulus water glass (modulus is 3.1), the surface hydration is strengthened and the negative charge is increased. Therefore, high modulus water glass can effectively inhibit the flocculation of anionic polyacrylamide on quartz, and UV-visible is applied. The selective flocculation mechanism of siderite and limonite was studied in detail by means of spectrophotometer and infrared spectrometer. Under the condition of high pH, ​​the anionic polyacrylamide is mainly adsorbed on the surface of the iron oxide ore by the action of hydrogen bonds and chemical bonds, and is a monomolecular layer adsorption mainly composed of chemical adsorption. The bridging mode is mineral/polymer-mineral.

(2) Hydrophobic flocculation process

Hydrophobic flocculation is a behavior based on the selective hydrophobization of mineral particles. An essential feature of the hydrophobic agglomeration sorting process. It is a medium or strong agitation that takes a long time. The strong turbulent conditions give the ore sufficient kinetic energy to overcome the intergranular repulsion energy barrier and increase the agglomeration rate. The emulsified non-polar oil is added to strengthen the floc during the mixing process. . At present, the existing hydrophobic flocculation separation process includes: shear flocculation flotation, hydrophobic flocculation magnetic separation, emulsion flotation, carrier flotation, oil agglomeration sorting and emulsion extraction.

S Song et al. studied the flocculation magnetic separation (PMS) method, magnetically selecting fine-grained weak magnetic iron ore in the form of floc, instead of strong magnetic separator or high gradient magnetic separator to treat fine-grained weak magnetic iron ore. We carried out with finely ground to micron sized hematite and limonite studied, addition of the oil and coal oil, sodium hydrophobic cause flocculation, the formation of large flocs. The test results show that compared with the conventional magnetic separation under the same conditions, the FMS method can effectively recover fine-grained hematite and limonite with a medium-field strong magnetic separator, and obtain high sorting efficiency. When the FMS method is used to treat hematite ore with an iron grade of 30.5%, the refined iron grade obtained is 64% and the recovery rate is 82%. The study found that the sorting efficiency of FMS method is closely related to the main parameters of hydrophobic flocculation (sodium oleate, stirring time and kerosene dosage). This indicates that the FMS method has high sorting efficiency, which can be attributed to the formation of hydrophobic flocs, so that the magnetic force of the magnetic field acts on the fine-grained iron minerals, and the fine-grained iron minerals are more likely to adhere to the teeth in the magnetic separator. On the board, thus entering the magnetic concentrate.

British RD Pasco et al. used sodium oleate as a selective flocculant to separate fine (<10 μm) hematite from quartz. The results show that the main factors affecting the particle size of hematite flocs are oleic acid concentration, pH value, shear rate and stirring time. Flocculation occurs only when the solubility of oleic acid in the solution is supersaturated. If oleic acid droplets are produced around the mineral particles, an increase in flocculation speed and floc size is observed. The produced hematite flocs have an anti-fracture effect in the shear rate range of 300/s to 2200/s. Its strength is attributed to the gravitational pull created by the interaction of hydrocarbon chain connections and hydrophobicity. Hydrophobic floes formed with sodium oleate are easily recovered by flotation. The hematite and quartz containing 15% of TFe are mixed and fed. The recovery rate by rough selection is 94%, and the grade of iron concentrate is 46%. The fine weak magnetic iron mineral is subjected to shear flocculation before flotation, which can significantly improve the recovery rate.

(3) Magnetic composite flocculation

Magnetic composite flocculation separation process is a new process of fine-grained weak magnetic iron ore sorting developed in recent years. It refers to the addition of magnetic species and placed in the external magnetic field on the basis of polymer flocculation and hydrophobic flocculation. Enhanced flocculation while maintaining good selectivity.

Based on the conditions of pH adjuster, various dispersants, various collectors and non-polar oils, Song Shaoxian found a better chemical condition for selective hydrophobic flocculation magnetic separation of fine-grain Daye. Then, based on this, the magnetic composite flocculation was studied. The magnetic species were taken from Chengchao iron ore with Fe68.40% (particle size <10μm) and field strength of 0.08T. The results show that the addition of micron magnetite is The superposition of magnetic flocculation greatly increases the recovery rate of the concentrate, but the Fe content of the concentrate decreases. When the amount of magnetic species is low, the Fe content of the concentrate decreases by only 0.3%, but the recovery rate increases by 5%. Therefore, the addition of a small amount of magnetic species can significantly improve the beneficiation recovery rate.

Zhang Defei discussed the role of magnetic species in the selective flocculation-de-sludge process for sorting Tierden iron ore. The applied magnetic field is a permanent magnet block made of Nd-Fe-B material as the magnetic field source. The magnetic species is a magnetically selected iron concentrate with less than 10 μm and 84%, containing 70.12% of TFe. Studies have shown that with the increase of the amount of magnetic species, the iron recovery rate of demineralized concentrates is gradually increased. For hematite pure minerals, there is a very obvious upward trend. Increasing the amount of magnetic seeds is conducive to increasing the iron recovery rate of de-sludge concentrates. However, the amount of magnetic species should be appropriate and the dosage should not be large, otherwise the concentrate grade will be lowered. . External magnetic field to improve job desliming desliming grade iron ore, iron recovery Advantageously, the external magnetic field than that applied external magnetic field is not applied, the concentrate can be improved desliming iron grade of 1.5% to 2%, 2% increase metal recovery.

Second, the research trend of micro-weak magnetic iron ore selective flocculation process

According to the research status of micro-weak magnetic iron ore selective flocculation process, combined with the characteristics of weak magnetic iron ore beneficiation process research, the research on the selective flocculation process of fine-grained weak magnetic iron ore in the future mainly includes the following aspects:

(1) extending from artificially mixed components to natural ore systems. Observed in a single component test due to one or more reasons such as heteroaggregation, electrical neutralization, dissolved ion interference, slime cover, physical capture, inclusions, and flocculation, as well as cross-contamination during the grinding process The selectivity to this often loses selectivity in mixed components or natural ore systems. Therefore, it is necessary to ensure that the selectivity in natural complex systems can be further extended to industrial applications.

(2) Research and development of highly efficient selective dispersants and flocculants. This is another problem in ore sorting. It is a fine iron mineral, easy to lose, high-efficiency flocculation-de-sludge, flocculation-flotation, flocculation-magnetic separation is an effective means. In combination with this need, we will develop corresponding flocculating and dispersing agents, such as the molecular design and development of high-efficiency series of fine hematite flocculants, the mechanism of action between flocculants and minerals, and the interaction and agglomeration between hematite and gangue minerals. And the mechanism of dispersion.

(III) Numerical simulation of ore process mineralogy. Based on the existing research, the structure, structure, mineral composition, inlay relationship and monomer dissociation of this type of ore are studied in detail. Through the means of numerical simulation, the suitable beneficiation process and its ore dressing theoretical indicators are predicted to provide a basis for the effective treatment of such complex and difficult hematite.

(4) Development of high-efficiency selective flocculation separation equipment. Aiming at the phenomenon that fine-grained ore is easily muddy in the fine ore, the combination of heavy, floating and magnetic force fields is designed to achieve high dispersion of the mud mineral in the ultra-fine state. At the same time of flocculation, the pulsating water oscillating sieve is used to remove the slime, and the single-particle iron is discharged from the discharge port by a fixed sedimentation line in the gravity and strong magnetic composite field to realize multi-field compounding of weak magnetic particles of about -20 μm. sorting.

Third, the conclusion

The fine floc weak magnetic iron ore selective flocculation technology has made great progress, and various sorting processes and theories are becoming more and more mature. Compared with other conventional beneficiation processes, the selective flocculation process has shown significant advantages in terms of selectivity and separation efficiency in the treatment of fine-grained weak magnetic iron ore. It is foreseeable that the selective flocculation process will have broad development and application prospects in the field of sorting and processing of fine-grained magnetic ore.

In summary, the selective flocculation process opens up a new way to effectively treat micro-fine weak magnetic iron ore. Conducting basic research on selective flocculation of fine weak magnetic iron ore, looking for technically and economically reasonable beneficiation process, not only can fully exploit and utilize China's existing iron ore resources, further increase the self-sufficiency of state-owned iron ore, and reduce iron in China. The import volume of ore, saving foreign exchange expenditure, is also very important for promoting the development of mineral processing technology worldwide.