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Progress bauxite anti-flotation desilication research
Xiao Yuqin 1,2 , Cheng Xinchao 2 , Yang Taifen 1
(1. Beijing University of Science and Technology, 2. Beijing Research Institute of Mining and Metallurgy)
At present, most of the bauxite mines that have reached the industrial scale in China's basic reserves are bauxite bauxite. The outstanding characteristics of this kind of bauxite are high aluminum, high silicon, low iron and low aluminum to silicon ratio. The mineral composition is very complicated, the size of the inlay is fine, the inlay relationship is complicated, and the aluminum mineral and the aluminosilicate mineral can be ground. Sexual differences are large. In view of the special properties of the above ore, the production method of alumina mainly adopts the sintering method and the combined method. However, compared with the Bayer method, the sintering method and the combined method are obviously high in both direct energy consumption and indirect energy consumption, which seriously restricts the development of China's alumina industry.
In order for such bauxite to meet the needs of the Bayer process for the production of alumina, it is necessary to pre-desiliconize the bauxite. At present, pre-desiliconization of bauxite is mainly concentrated on beneficiation methods and can be divided into three categories, namely, physical beneficiation, bio-election and chemical beneficiation. Specifically, it includes washing, sieving, selective disintegration, sorting, flotation, selective flocculation, vulcanization sorting, bacterial beneficiation, magnetic filtration, carrier flotation, selective flotation flotation, chemical leaching and radiant beneficiation, etc. . Among them, the flotation method is the most widely used. It has the advantages of good desiliconization effect and simple process. The product after flotation desiliconization can fully meet the needs of the Bayer process, achieving the goal of reducing energy consumption and saving cost.
   
Flotation desiliconization is a method for separating useful minerals from gangue minerals based on the difference in surface properties between minerals. It can be divided into positive flotation desiliconization and reverse flotation desiliconization. Positive flotation desiliconization has been widely used in field production and has made certain progress. However, there are still the following problems:
(1) During the crushing and grinding process, the aluminosilicate mineral is brittle and easy to grind than the diaspore. In order to achieve the requirements of useful mineral flotation particle size, it is bound to cause mudstone mineralization, which inevitably enhances the mechanical entrainment of flotation, leading to deterioration of flotation indicators;
(2) The concentrate has a large floating amount, which means that the slurry has a large circulation, which is difficult to operate and control, and it will cause difficulty in filtration and dewatering of the concentrate. The water content in the concentrate must be evaporated during the smelting and dissolution stage. Removal, which undoubtedly increases unnecessary energy consumption;
 
(3) A large amount of chemicals are adsorbed on the surface of the concentrate, which makes it difficult to remove the concentrate before smelting;
(4) The concentration of tailings is low, which brings inconvenience to the treatment and utilization of tailings. Compared with positive flotation desiliconization, the use of reverse flotation desiliconization can completely overcome the above drawbacks, and easy to achieve coarse grinding, which is beneficial to reduce the energy consumption of grinding and reduce the water contained in the concentrate. From this point of view, de-flotation desiliconization should be a promising approach. This paper reviews the current status of de-siliconization in reverse flotation and looks forward to the anti-flotation desiliconization technology.
1 Research status of desiliconization in bauxite reverse flotation
The bauxite reverse flotation of aluminum-silicon separation is a suppression of diaspore, flotation aluminosilicate minerals. At present, a large number of experimental studies on de-flotation desiliconization have been made, and great progress has been made in theory and flotation reagents, and on the basis of small-scale experiments, the expansion and re-election experiments have been successfully carried out.
1.1 Crystallization and surface chemistry of major minerals in bauxite
   
The crystal structure of the mineral directly affects the polarity of the surface after mineral cleavage and the nature of the unsaturated bond, which in turn determines the nature of the mineral in aqueous solution. That is to say, the difference in flotation behavior between different minerals is essentially due to the difference in crystal structure between them. Therefore, studying the relationship between mineral crystal structure, surface properties and flotation behavior will help to understand the flotation behavior of minerals more clearly, and it has guiding significance for the development of mineral flotation separation process.
   
Cui Jirang et al. [ 1 ] of the Beijing Research Institute of Mining and Metallurgy first reviewed the crystal structure and surface properties of diaspore and kaolinite, and conducted experimental and theoretical calculations on the dispersion and agglomeration behavior of kaolinite particles. It is believed that the solution characteristics of kaolinite and the difference in charge properties between the end face and the bottom surface have an important influence on the dispersion and agglomeration of the particles. This part of the work is part of the national scientific and technological research in the "Ninth Five-Year Plan" and provides basic information for the selection of China's diaspore-type bauxite mines, laying a solid foundation for future research work. Subsequently, Central South University and Northeastern University conducted a deep research on this.
   
Feng Qiming et al. [ 2 ] applied a quantum chemical method of density functional-DFT-pseu-dopotential to simulate the atomic and electronic structures of a-AIOOH and its (010) surface, using generalized gradient approximation. (GGA-PBE) theoretically calculated the lattice parameters and atomic fraction coordinates, and selected the Slab model with the atomic layer number of 4 and the vacuum layer thickness of 7.5 to simulate the (010) plane of T a-AIOOH, and the atomic relaxation surface was obtained. The surface energy is 0.491 J / m2. According to surface state density analysis, surface atomic arrangement and frontier orbital theory, it is inferred that the anion collector is difficult to chemically interact with the atoms of A1 on the diaspore (010) surface, but it is easy to surface H. Atomic interactions. Subsequently, Hu Yuehua et al [3-6] analyzed the relationship between the crystal structure characteristics and wettability of diaspore, kaolinite, pyrophyllite and illite, and combined their flotation tests to obtain their hydrophilicity. The order of strength to weakness is: diaspore > kaolinite, illite > pyrophyllite . At the same time, the relationship between crystal structure, surface wettability, electrical properties and floatability, and the effect of crystal defects and grindability on the floatable behavior were analyzed. The number of cleavage bonds on the crystal plane of the four mineral crystals is calculated, and the order of the number of cleavage bonds per unit area of ​​the crystal faces on the three sides of the aluminosilicate mineral crystal is: Nsi-011101< Ns1-010101< Ns-011101, NAI-011101
1.2 Study on flotation reagent for desiliconization of bauxite by reverse flotation
In recent years, the research on de-solanation desiliconization has focused on the synthesis and action mechanism of strong collectors of aluminosilicate minerals and inhibitors of diaspora. The collectors used are mainly dodecylamine, tetradecylamine, octadecylamine, quaternary salt DTAL, lauric chloride, N-(2-aminoethyl) monolaurin, N-(3-aminopropyl ) January lauric acid, methylamine, N-alkyl-1,3-propylenediamine and fatty polyamines ["One'51. The regulators used are mainly cationic polypropylene amide, SA3, SFL, Sodium chloride, sodium fluoride, modified starch, phenylenedioxydiacetic acid, sodium oxalate, sodium citrate, sodium salicylate, lactic acid and ATNO [16-25] . [next]
Although the research on flotation reagents has made great progress, there are still many difficulties in realizing the industrialization of de-flotation desiliconization. The research and development of highly collectible, highly selective collectors and highly selective inhibitors is still one of the key tasks in the future research on de-semiconversion.
1.3 Development of selective grinding and grading technology
Selective grinding is based on the difference in hardness between useful minerals and gangue minerals. During grinding, selective pulverization is achieved through optimization and adjustment of process parameters, so that high-hardness and hard-to-grind minerals enter the coarse-grained grade, while low hardness The fragile minerals enter the fine-grained grade. Selective grading is based on the degree of pulverization and particle size after mineral grinding to achieve a preliminary separation of useful minerals from gangue minerals. The hardness of the main useful mineral in bauxite in China - diaspore has a hardness of 6.5-7, and the hardness of the main gangue minerals - kaolinite, illite and pyrophyllite are less than 3, indicating the existence of useful minerals and gangue minerals. With obvious hardness difference, it is completely possible to carry out selective separation in the coarse grinding, so that Al 2 O 3 is concentrated in the coarse fraction, and SiO 2 is enriched in the fine fraction. This not only achieves the goal of energy saving and less load, but also provides conditions for reverse flotation desiliconization of coarse-grained and fine-grained materials.
Beijing Research Institute of Mining and Metallurgy Renai Jun [26, 27] is performed for the characteristics of the mineral bauxite flotation cyclone research, particularly selective fractionation by examining the parameters of cyclone classifier, coarse grade mineral and It is treated separately with fine-grained minerals. Based on laboratory small experiments and expanded re-election, industrial applications have been obtained. It provides a valuable reference for the future selective flotation and classification of reverse flotation. Subsequently, Zhang Min [ 28 ] for Luoyang bauxite, from technical, economic and operational management, etc.
Wei Xinchao et al. [ 29 ] examined the effects of grinding media size, medium shape, filling rate, ball ratio and grinding concentration on the selective grinding of bauxite. It is believed that with the increase of particle size, each grade of aluminum The silicon ratio becomes larger, and the ratio of high aluminum to silicon in the coarse fraction is higher, indicating that selective grinding is feasible. In order to achieve "selective grinding is very selective", it has created favorable conditions for some coarse-grained products and flotation of narrow-level materials after de-sludge. Subsequently, Zhang Guofan et al. [ 30 ] examined the effects of three kinds of grinding media, spherical, short cylindrical and short cylindrical + spherical, on the selective grinding of bauxite. It is concluded that the large-diameter spherical medium is easy to cause over-grinding and small diameter. The spherical medium can improve the aluminum-to-silicon ratio of coarse-grained bauxite, and the short cylindrical medium has good selectivity. The short cylindrical + spherical medium can greatly improve the ratio of aluminum to silicon in coarse-grained grade, and is suitable for selective grinding of bauxite. Requirements. This paper makes a comprehensive comparison of selective grinding media selection, discusses the process of bauxite ore dressing and grinding, and drafts a “coarse-wet-grading-coarse-grain-ball milling process and a coarse-grained self-grinding-ball milling process. "Two technically feasible grinding process options for reference for selective grinding.
It provides a theoretical basis and has a guiding role in practice. Yuan Zhitao et al [ 31 ] strengthened the selective grinding process of bauxite by adding ZM-1 grinding aid, and improved the product yield of A / S > 9 in the coarse fraction, which reduced the amount of flotation material and reduced Mud, enhanced flotation, and improved dewatering efficiency. The research of ZM-1 grinding aid also provides a basis for the further development of the “selective grinding ten flotation” process.
1.4 Development of dispersion and selective flocculation
In the desiliconization process of bauxite reverse flotation, the intermixing of different minerals and the cover of the slime in the slurry suspension system have significant effects on the recovery of fine-grain diaspore and the ratio of concentrate to aluminum-silicon. influences. Therefore, it is important to study the dispersion between the ore particles and selective flocculation to achieve effective separation of various silicate minerals.
Luo Zhaojun et al [ 32 ] analyzed the adhesion of fine-grain diaspore to various silicate gangue minerals based on the classical DLVO theory, and pointed out the diaspore and gangue particles. The van der Waals force is always attracted, while the electrostatic effect is repellent under weak alkaline conditions; under weak acid conditions, the mechanical entrainment is more serious, which is not conducive to reverse flotation desiliconization. This theoretical study provides a theoretical basis for the design of dispersion conditions in the future.
Wang Yuhua et al. [ 33 ] showed that the addition of sodium carbonate in the grinding process can effectively disperse the slurry, achieve selective desilting, improve the anti-flotation index, and significantly reduce the drug consumption. Subsequently, Zhang Yunhai et al [ 34 . 35 ] Separation test of diaspore and illite with dispersant YF-1 and flocculant YX-1, the dispersant YF-1 has good dispersion effect on illite, and flocculant YX-1 is good. The selectivity. Under sufficient dispersion conditions, illite and boehmite can be effectively separated by selective flocculation. At the same time, the composite flotation YB-1, dispersant YF-2 and flocculant YX-3 were used to investigate the reverse flotation separation of the artificial mixed ore of diaspore and hard kaolinite, after one rough selection and one selection. , get good sorting indicators.
1.5 Research on other factors affecting reverse flotation
Factors affecting flotation In addition to flotation reagents, there are numerous physical parameters such as particle size and particle size composition, grinding fineness, slurry temperature, slurry concentration, stirring strength and aeration of flotation equipment .
Wang Yuhua [36, 37] by reverse flotation of bauxite many physical factors affect analysis, select pulp density, stirring intensity, and the amount of material size inflatable four factors were studied, basic rule is as follows: 1) In pharmaceutical dosage units ore Under constant conditions, as the concentration of the slurry increases, the ratio of aluminum to silicon in the concentrate and the recovery rate of A1 2 O 3 decrease. The main reason is that the mass flow rate of gangue minerals and water-hard aluminum increases with increasing concentration. Both increase, the slurry depth increases accordingly, and the diaspore also rises under the action of mechanical inclusions, which deteriorates the flotation index, and the suitable flotation concentration is between 16% and 22%; 2) when floating When the engine speed is low, the turbulence of the slurry is poor, the recovery rate of the concentrate is high, and the quality of the concentrate is relatively poor. When the rotation speed is too high (greater than 300 r/min), the pulp is turned over seriously, the mechanical inclusion effect is obvious, the recovery rate and quality of the concentrate are decreased, and the suitable flotation machine speed is about 250-300 r/min; 3) As the amount of aeration increases, the mass flow rate of gangue minerals increases correspondingly, which is conducive to the improvement of the ratio of aluminum to silicon in concentrate. However, the excessive inflation is not conducive to the improvement of recovery rate. The suitable aeration amount is about 25~ 45 mL/s. 4) The comparison between the ball mill and the rod mill test shows that by continuously grinding the grinding conditions, it is difficult to increase the content of the intermediate size (-0.15+0.043 mm) significantly, and the particle size composition of the ore discharge is adopted. It is relatively uniform, and the diaspore rich aggregate content is relatively high, and the excessive pulverization is relatively small. The flotation test under the same conditions shows that the rod mill is about 0.3-0.4 higher than the aluminum-silicon ratio of the ball mill flotation concentrate, and the recovery rate of Al 2 O 3 is about 2% to 6% higher.
1.6 Application of reverse flotation technology
After several years of efforts, small trials of bauxite reverse flotation have made great progress, and closed-circuit tests and expanded re-election tests have been carried out on the basis of small-scale tests.
The Beijing Research Institute of Mining and Metallurgy [38] proposed the process of “selective grinding + polymer flocculation and dephosphurization and ten reverse flotation” for the process mineralogy of Henan ore samples, and completed under acidic and alkaline conditions. The reverse flotation desiliconization closed circuit test. The main components of the test ore sample are diaspore (65.57%) and gibbsite (1.25%). The gangue minerals are kaolinite (10.8%), illite (6.9) and pyrophyllite (3.1%). ), chlorite (0.7%). The content of ore A1 2 O 3 is 64.55 %, A/S is 6.07. In the acidic medium, the recovery rate of concentrate A1 2 O 3 is 84.01%, A/S is the index of 10.04; in the alkaline medium, the concentrate is obtained. From the recovery rate of 87.15% and the A/S of 9.57, it basically meets the technical requirements of the “Tenth Five-Year” national scientific and technological research, and it can completely realize the industrialization of reverse flotation by optimizing the internal structure of the process and the combination of chemicals. It has pointed out the direction for further industrialization. [next]
Central South University [39] conducted separate trials for the "973" ore samples taken from Henan and the "National Five-Year" national research and mining samples. The main useful mineral of the "973" ore sample is diaspore, the main gangue. The minerals are illite and kaolinite, as well as a small amount of chlorite and pyrophyllite. The raw ore A1 2 O 3 is 63.97 %, A/S is 5.71, the recovery rate of concentrate A1 2 O 3 is 85.76 %, A/S is the index of 10.04; the main useful mineral of the “Ninth Five-Year Plan” is the one water. The dilatedite is followed by pyrophyllite, illite and a small amount of chlorite and kaolinite. The raw ore A1 2 O 3 is 64.69%, the A/S is 5.68, and the concentrate A1 2 O 3 content is 85.04 %. A/S The result is 10.52. The two consecutive elections have achieved success, showing the good adaptability of reverse flotation to different mineral samples and laying a solid foundation for the industrialization of reverse flotation.
2 Anti-flotation desiliconization technology outlook
1) The primary problem is the slime. During the grinding process, part of the diaspore was muddy, which seriously affected the flotation index. Selective dispersion and selective flocculation of pulp are still one of the research directions in the future. In addition, the development and research of selective crushing equipment, grinding equipment , high-efficiency desliming equipment and flotation equipment suitable for coarse and fine-grain bauxite are also necessary in the future.
2) Research and development of strong collectors with high selectivity. There are some differences in the planktonic properties between three silicate gangue minerals such as kaolinite, illite and pyrophyllite. In order to achieve de-flotation desiliconization, all three gangues must be floated. Therefore, it is important to develop and develop collectors with strong harvesting ability, high selectivity and less foaming.
3) Develop an effective selective inhibitor of diaspore. The diaspore has good flotation property, so it is necessary to develop and develop an inhibitor with high efficiency and high selectivity in order to effectively separate the aluminosilicate from the diaspore.
3 Conclusion
The anti-flotation desiliconization of bauxite has achieved many results in theory and has been recognized by many people in the industry. With the deepening of research, people will have a clearer understanding of the importance and necessity of bauxite reverse flotation desiliconization. From the current situation, the desiliconization of bauxite reverse flotation will be one of the main contents of current and future research on bauxite flotation desiliconization.
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4.2 Relationship between electrical and buoyancy of mineral surface
Zata potential relationship of pH in pure calcite and apatite and phosphate rock slurry supernatant in FIG. 3.
Figure 2 Zeta potential change and pH off TF.
··... pure water - clear liquid
1,2-Apatite 3,4 - Calcite
It can be seen from Fig. 2 that the Zata potential on the surface of the apatite in the online water is more negative than the Zata potential on the surface of the calcite, but it is opposite in the clear liquid. The reason for this phenomenon is due to inevitable ions such as Ca 2+ and PO 3 -4 in the clarified liquid. Since the solubility of Ca 3 (PO 4 ) 2 is much lower than that of CaCO 3 , the surface of the apatite with relatively negative potential preferentially adsorbs Ca 2+ ions at its anionic active sites, and the concentration of Ca 2+ in the clarified solution is PO 3 - 4 . The concentration is much higher, so the surface potential is reversed. Many scholars have also confirmed this phenomenon [ 2 , 4 ] . It should be pointed out that this surface potential reversal phenomenon is beneficial to the adsorption of [P m (OC 2 H 4 ) n O] 2 P(O)O - on the surface of apatite, which has practical significance for achieving preferential phosphorus release, but two minerals. The narrowing of the difference in surface properties will increase the difficulty of sorting. Therefore, in the phosphate flotation, adjusting the appropriate pulp pH value and selecting effective inhibitors are important technical measures to improve the sorting efficiency.
4.3 Effect of Ca 2+ concentration on AEP capture performance
The Ca 2+ and Mg 2+ ringing in the slurry has been confirmed by practice. The ability of AEP collectors to counteract the effects of Ca 2+ and Mg 2+ is much stronger than that of general fatty acid traps. It can be seen from Fig. 2 that when the concentration of Ca 2+ is more than 200 mg/L, the recovery rate of phosphate rock using sodium oleate as a collector is significantly decreased, and when the concentration of Ca 2+ is as high as 600 mg/L, the concentration of AEP is The ability to capture also has little effect. This indicates that AEP has strong resistance to hard water and is less interfered by Ca 2+ ions in the slurry. The reason is that the solubility is increased and the dispersing ability is improved, so that the effective component of the collector in the slurry is relatively increased, thereby improving the low temperature resistance of the agent. In addition, the ether-based oxygen atom has unpaired P electrons, which can be adsorbed by hydrogen bonds with metal ions on the surface of the mineral. Especially when there are multiple ethoxy groups in the molecule, the ether groups can be arranged into a structure similar to a crown ether. The mineral surface makes the hydrophobicity of the alkyl group still maintain good trapping properties, compensating for the trapping properties that are weakened by the increase in polarity. In addition, the introduction of P atoms in the polar group is advantageous for improving the selectivity of the agent.
5, the conclusion
Ether alkyl phosphate (AEP) has strong resistance to hard water, is insensitive to Ca 2+ and Mg 2+ ions, and has a certain low temperature resistance. As a phosphate rock collector in weak alkaline medium and low temperature pulp, it has better selective harvesting capacity. The alkali consumption is significantly lower than when the flotation is carried out using a conventional fatty acid collector. While saving heating with coal consumption plays a significant role in reducing phosphate rock beneficiation costs.
There are chemical adsorption and physical adsorption on the surface of ether alkyl phosphate and phosphorus lime and calcite. At pH=8, apatite and calcite are easier to sort. The active ingredient of the collector is [R m (OC 2 H 4 ) n O] 2 P(O)O - .
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