China is one of the few countries in the world with rich iron ore resources, complete minerals and high supporting level. It is also one of the oldest mining producing countries and major mineral consumption countries in the development and utilization of iron mineral resources. There are advantages in the quantity of ore, but the high content of harmful impurities such as sulfur, phosphorus and silica, and the fine grain size of the inlay make the ore dressing difficult and inefficient, and the quality and variety are at a disadvantage, especially the sulfur content in the iron concentrate. Higher, lacking competitiveness in the international market. In recent years, a large number of high-quality imported iron ore for the sustainable development of China's iron mines caused serious impact, reducing the sulfur content of iron ore has become an urgent task of research, development and utilization of pyrite containing ore to China The development of the national economy has an important role to play.
1 Associated iron ore desulfurization iron selection process technology
1.1 Stage grinding, stage selection and desulfurization iron selection process
Grinding fineness has a great influence on the beneficiation index. Different grinding fineness products have different particle size composition, which affects the mineral dissociation degree and optionality. Fine-grained iron ore needs Fine grinding can dissociate mineral monomers. For single iron ore with fine grain size and sulfur type (pyrite and pyrrhotite), stage grinding and stage selection process are usually adopted to achieve the purpose of iron reduction and sulfur reduction.
The iron minerals in an iron ore in Anhui mainly exist in the form of magnetite. The sulfur mainly exists in the form of pyrite. The iron concentrate with a grade of 65.25% and a recovery rate of 80.33% can be obtained by stage grinding and weak magnetic separation. Xu Kai et al. used an iron ore containing 42.86% TFE and 1.69% sulfur as the research object, and successfully obtained the whole magnetic separation process through stage grinding, stage selection, reasonable control of magnetic field strength and selection times. The iron grade is 66.97% iron concentrate, and the iron recovery rate is 80.3l%.
Zhang Yanming carried out systematic experimental research using stage grinding and stage selection process. The results showed that the iron recovery rate increased from 86.43% to 90.38%, and the sulfur content in iron decreased significantly. The iron ore in an iron ore in Yunnan has a fine grain size and a low iron grade of 20.18%. The harmful elemental sulfur exceeds the standard and is difficult to select ore. The ore was treated by stage grinding and stage selection process to obtain iron concentrate with a grade of 63.98%, a recovery of 71.55% and a sulfur content of 0.48%.
1.2 Magnetic separation - flotation combined desulfurization iron selection process
The magnetite currently selected in China has a fine grain size and contains a large amount of pyrrhotite and pyrite, which makes the negative influence of magnetic agglomeration in the selection very obvious. It is more and more difficult to improve the concentrate grade by a single magnetic separation method. Combining the magnetic separation method with the anion reverse flotation to achieve complementary advantages in the magnet ore sorting process is conducive to improving the grade of the concentrate of magnetite ore. Magnetic separation-flotation combined process is one of the more effective processes for reducing sulfur in high-sulfur iron ore in China.
Wang Ju is directed to an imported high-sulfur magnetite ore (including sulfide ore mainly pyrrhotite and pyrite). The ore is subjected to sulfur reduction and iron ore dressing test after the first reverse flotation magnetic separation process. The grade was reduced from 6.14% of the ore in the ore to less than 0.30%, and a good test index was obtained. Shao Weihua et al. conducted a study on a mine in Yunnan. Under the conditions of 5.71% sulfur and 31.52% iron, the iron ore concentrate was 65.36% and sulfur was 0.171%. The iron recovery rate is a satisfactory indicator of 81.67%. Guo Lingmin et al. comprehensively recovered the sulfur and iron resources in a tailings. The ore contained refractory pyrrhotite, and the flotation-magnetic separation-flotation combined recovery process successfully obtained the sulfur grade of 38.77%. The high-quality sulfur concentrate and qualified iron concentrate containing 58.04% of iron and 0.547% of sulfur.
Yang Guofeng et al. studied the Baiyinbao high-sulfur magnetite. The ore contained 1.98% sulfur, some of which existed in the form of pyrrhotite. The magnetic separation-flotation combined process effectively reduced the sulfur in the iron concentrate. The content of the product has finally obtained a high-quality iron concentrate with a total iron grade of 65.20% and a sulfur content of 0.22%, which provides a new idea for the development and utilization of difficult-to-treat iron ore resources. The nature of the Kellykke iron ore in Golmud, Qinghai Province is complex. The presence of pyrrhotite interferes with the selection of useful minerals in iron ore and affects the final selection index. Du Yuyan removes most of the gangue by magnetic separation first. A part of the sulfur (pyrite) is then used to remove the sulfur (maghemite) from the magnetic concentrate by flotation, which gives a better index. Li Bing et al. carried out an analysis of the ore material composition of an iron ore mine in Huanren. The iron ore has high sulfur content. The iron minerals mainly exist in the form of magnetite and pyrrhotite in the ore, and magnetic separation is adopted. The flotation joint sorting process was carried out for experimental research. The results show that the process of flotation after magnetic separation can obtain 64.97% TFE grade and 0.16% sulfur qualified iron concentrate, and the total iron recovery rate can reach 71.21%.
1.3 roasting - magnetic separation - flotation combined desulfurization process
At present, the reduction and roasting magnetic separation process of domestic iron ore is not widely used due to its high cost and low grade of iron concentrate. The process is mainly suitable for iron ore with large burning loss such as limonite and siderite. For weak magnetic iron ore with low theoretical grade and various sulfur types, iron concentrate with low impurity content can be obtained by roasting-magnetic separation-flotation combined process, which greatly improves product quality.
Yu Jun, who for the copper industry in western Bayannaoer high sulfur content iron ore to determine the roasting programs and roasting conditions, the roasted ore magnetic separation - reverse flotation tests cation. The experiment shows that the reverse flotation can obtain iron concentrate with a TFe grade of 63.67% and a recovery of 50.82%. The sulfur content is reduced from 2.74% to 0.31%, achieving the goal of upgrading and reducing impurities.
Wang Xuesong et al. used a magnetization roasting test of roasting pyrite cinders in a rotary kiln to effectively reduce the weak magnetic Fe2O3 in the slag into ferromagnetic Fe3O4 with a magnetic susceptibility of 2.38%. By ball milling, magnetic separation process, can greatly improve the concentrate grade and metal recovery, slag desulfurization effect is obvious at the same time in the rotary kiln, the desulfurization rate can be as high as 85%.
Liu Zhanhua et al. used a direct reduction roasting-magnetic separation method for high-sulfur iron tailings with an iron grade of 17.75% and a sulfur content of 5.87%. The iron grade was 93.57% and the sulfur content was 0.39%. The direct reduced iron product with a weak magnetic concentrate recovery rate of 82.01% provides a new way to effectively improve the comprehensive utilization rate of resources.
2 Research and application of new agents
The progress of mineral processing pharmacy has played an important role in the development of China's sulphur-containing iron ore beneficiation process, especially the development of iron and sulfur reduction. The domestically developed flotation reagents mainly include activators and collectors .
2.1 Research and application of new activator of pyrite
Wang Ju is aiming at an imported high-sulfur magnet ore (including sulfide ore mainly pyrrhotite and pyrite), using a new high-efficiency floating sulfur MHH-1 activator for desulfurization test research. The iron concentrate grade is composed of ore containing sulfur 6.14. % fell below 0.30% and achieved good test results. The iron ore desulfurization special activator MHH-1 has obvious effects on the removal of sulfide ore in iron concentrate, especially pyrrhotite with strong magnetic properties and poor floatability. Compared with other activators, MHH-1 has a small dosage, low cost and obvious desulfurization effect. The development of this product provides a new way for iron concentrate to reduce iron and reduce sulfur.
Hu Dingbao used HH-1 high-efficiency activator for desulfurization test for the high content of pyrrhotite in the sulfur-containing magnetite of Xinqiao Mining Co., Ltd., and obtained iron concentrate with sulfur content of 0.319%, TFe grade of 66.99%, and TFe recovery. The rate of 47.68% and the sulfur concentrate sulfur 34.59%, sulfur content recovery rate of 99.23% of the selection indicators, all indicators have met the requirements.
Yin Zhaoyang has a high sulphur content in the ore body of the lower part of the Yeshan Iron Mine, especially the large content of pyrrhotite, which causes the actual content of sulfur in the magnet concentrate to exceed the standard. By strengthening the flotation process, increasing the amount of yellow medicinal application, application The composite activator MS-1 and other means reduced the sulfur content of the iron concentrate from 0.8% to 0.4%, which met the sales requirements.
2.2 Research and application of new collectors for pyrite
The gangue entrainment in the magnetic separation concentrate of Anqing Copper Mine is serious, which affects the improvement of iron concentrate grade; the production water uses a large amount of backwater, and the high pH backwater inhibits the pyrrhotite, which seriously reduces the desulfurization rate of flotation; The pyrrhotite is poorly floatable, and a strong collector must be used to obtain satisfactory results. Anqing Copper Mine Huang Heping adopted improved grinding fineness, improved water quality of iron production, and adjusted the type of collector chemicals (from the previous single yellow medicine to diesel and yellow medicine combination), the desulfurization effect was obvious, and it was greatly Economic benefits.
Chen Dianzhuo and others used QY-309 mixed collector for high-sulfur iron resources in a tailings of a plant to directly de-sulfurize and deplete the weak magnetic concentrate. The iron grade of flotation concentrate was 67.56% and sulfur. The content is only 0.13%. Yang Liuyi et al. [21] conducted a sulfur extraction test on a low-grade carbonaceous sulfur-bearing magnetite ore in Yunnan. The test results showed that the new chemical agent 402 was used as a sulfur-collecting collector, and the sulfur grade was 42.25%. It is 92.96% of sulfur concentrate.
The sulfide in the ore of Panzhihua Concentrator is mainly pyrrhotite. Jiang Fangqi et al. proposed to use high-grade xanthate under acidic conditions by analyzing the process mineralogy and ore properties of sulfide in the secondary iron concentrate of Panzhihua Concentrator. The purpose of the collection of pyrrhotite is to achieve the purpose of reducing sulfur in the iron concentrate. Finally, the sulfur content in the iron concentrate is reduced by 0.2% to 0.3%, and the grade is also improved to some extent.
3 Theoretical research and development of the mechanism of desulfurization agent and pyrite
3.1 Research status of pyrite ore crystal structure
Through the magnetic separation process, the pyrrhotite of different crystal systems is effectively enriched, most of the pyrite enters the tailings, and a small amount of pyrite that is not completely decomposed by the monomer enters the flotation with the pyrrhotite; In the flotation process, the palatability of pyrrhotite of different crystal systems is quite different, and the floatability of pyrite with different crystal structures is not significantly different. Therefore, the research status of the crystal structure of pyrrhotite is as follows. Pyrrhotite (Fe1-xS, 0 < x < 0.223) is often symbiotic with various sulfide minerals, and has three homogeneities: monoclinic, hexagonal and orthorhombic. Multi-image variants, commonly known as monoclinic and hexagonal pyrrhotite.
The study of the floatability of pyrrhotite with different crystal structures (monoclinic and hexagonal) shows that there is a clear distinction between monoclinic and hexagonal floatability [24]. Cai Congguang et al. and Liang Dongyun and others demonstrated that the floatability of single crystal pyrrhotite is better than that of hexagonal pyrrhotite. The ratio of S content to Fe content increases, pyrrhotite The crystal structure changes from a hexagonal system to a monoclinic system, and the magnetic properties are weakened from strong to weak, and the floatability is improved from poor.
Liu Zhineng et al. carried out the flotation test and surface potential ε of unactivated and activated hexagonal pyrrhotite by the amount of butyl ammonium black medicinal agent. The flotation behavior of Liufang magnetic pyrite was studied under the butyl ammonium black drug system. And its surface adsorption mechanism, the results show that the surface of the hexagonal pyrrhotite is the best under neutral conditions. Li Wenjuan et al. studied the flotation behavior of monoclinic pyrrhotite by single mineral test. The results show that the buoyancy of monoclinic pyrrhotite in Dinghuang or Ethylsulfide system is basically the same, and the slurry potential is the same. Its flotation behavior has little effect; under alkaline conditions, the ability of ethyl sulphide to collect monoclinic pyrrhotite is stronger than that of butyl sulphate.
The chemical composition, physical properties and crystal structure of pyrrhotite determine its floatability, surface oxidization and brittleness. X-ray diffraction, electron probe and flotation test were used to investigate the structural components and floatability of single-angled pyrrhotite and hexagonal pyrrhotite. The results show that the monoclinic ratio of hexagonal pyrrhotite is rich in sulfur. The flotation recovery of monoclinic and hexagonal pyrrhotite is similar to that of pulp pH, but the recovery rate of monoclinic pyrrhotite is higher than that of hexagonal pyrrhotite, and the floatability is better than that of hexagonal pyrrhotite. Under acidic conditions, hexagonal pyrrhotite is more susceptible to Cu2+ activation than monoclinic pyrrhotite.
3.2 Research Status of the Mechanism of Action of Pyrite and Chemicals
In recent years, domestic and foreign mineral processing workers have carried out a lot of research on the reaction mechanism of sulfur-selecting chemicals and pyrite, and applied the research results to guide the production practice of mines, and achieved considerable economic benefits.
Qi Wulin et al. studied the activation effect and activation mechanism of sulfuric acid and oxalic acid on pyrrhotite after being inhibited by lime. The experiment confirmed that the activation mechanism of pyrrhotite by sulphuric acid and oxalic acid is manifested in two aspects: one is to increase the surface oxidation potential of pyrrhotite and hinder the further generation of hydrophilic substances; the other is to remove the hydrophilicity adsorbed on the surface of pyrrhotite. The substance is exposed to a fresh surface. At present, the electrochemical research of pyrrhotite mainly includes surface oxidation of pyrrhotite, electrochemical study of collector and mineral action, and activation of pyrrhotite by copper ions.
Yan Wenqing detected the presence of hydrophobic double xanthate on the surface of pyrrhotite after the action of butyl xanthate by UV spectroscopy. Zhang Qin passed the infrared spectrum detection of pyrrhotite to infer that xanthate produced double xanthate on the surface of pyrrhotite. Bozkutr et al. examined the infrared spectrum of pyrrhotite adsorbed with isobutyl xanthate and also proved that it formed a double xanthate on its surface. Rao et al. observed that the pyrrhotite adsorbed a small amount of xanthate under a nitrogen atmosphere, which may be due to the fact that the oxidation of xanthate to a double xanthate requires a higher potential, and the potential of the nitrogen atmosphere is significantly too low. It can be seen that the flotation behavior of pyrrhotite and the oxidation of pulp
The original environment is closely related, that is, the slurry potential is one of the determinants of the flotation recovery and flotation rate of pyrrhotite.
ZHANG Qin et al. obtained the buoyancy and pH value of pyrrhotite and the existence of pulp potential by studying the mechanism of action of xanthate and pyrrhotite when the concentration of ethyl xanthate was 1×10-4 mol/L. Matching relationship, at a certain pH value, the pyrrhotite can only float in the appropriate pulp potential area. Khant reported that by increasing the slurry potential by pre-inflating into the slurry, the pyrrhotite can be effectively inhibited, and conversely, without pre-inflation, it has a certain activation effect. Under acidic conditions, copper ions exchange with iron ions on the surface of the pyrrhotite to activate the mineral surface. The pyrrhotite surface has a fast oxidation rate. It is reported that under the same conditions, the pyrrhotite is oxidized at a rate of 20 to 100 times that of pyrite. When pyrrhotite is oxidized to a certain extent to form FeSO4 and Fe2(SO)3, elemental sulfur is produced, but after sulphide, its specific surface area is large, it is easy to be severely oxidized, and Fe(OH)3 and FeO(OH) are formed on the surface. Hydrophilic layer, the floatability is reduced.
Huang Erjun et al. showed that ammonium sulfate and ammonium bicarbonate have good activation of lime-reduced pyrite by experiments on single minerals and on-site slurry samples, and can be made at high alkalinity (pH 11 ~ 12). Pyrite activates floating. The mechanism of activation of pyrite by ammonium sulfate includes:
(1) Precipitating Ca2+ in the slurry and appropriately lowering the pH value;
(2) Desorption of Ca2+ on the mineral surface, and more thorough;
(3) The activation of ammonia and the adsorption of a small amount of ammonium sulfate on the surface of the mineral, it is possible to complex Cu2+ through it;
(4) When ammonium sulfate is used to activate pyrite, the concentrate grade is high, which is related to its ability to keep the slime flocculation from entering the concentrate.
4 Conclusion
(1) In summary, in recent years, in the field of desulfurization of sulfur-containing magnetite ore, domestic and foreign scholars have done a lot of research, whether it is process flow, anti-flotation agent or theoretically, there is a large amount of literature reports, currently in magnetic flotation Research on process technology has made good progress and achieved significant economic benefits in production. It can be said that in today's increasingly exhausted resources, strengthening theoretical research, developing efficient new desulfurization technology and new anti-flotation agents are still the focus and development direction of pyrite ore dressing research.
(2) Research on new desulfurization technology has always been a topic of concern for mineral processing workers: 1 Consider using a full magnetic separation process. On the basis of the current stage of grinding, weak magnetic separation, fine screening and re-grinding, the high-efficiency fine screening and high-efficiency magnetic separation equipment are used for selection. Compared with the reverse flotation process, the process is simple, the process is reliable, the investment is saved, the construction period is short, and the operation is easy; 2 considering the weak magnetic separation-reverse flotation-weak magnetic separation combined process. The process first removes the pyrite and gangue minerals without magnetic, and then selects the pyrrhotite by reverse flotation. Finally, the magnetic separation ensures the grade of the iron concentrate, and removes as much as possible from the sulfur-containing magnetite ore. Sulfur makes iron ore the most valuable for exploitation.
(3) The research direction of reverse flotation technology is to develop new anti-flotation agents, processes and equipment with high efficiency, low consumption and low toxicity to improve the beneficiation efficiency, reduce the cost of ore dressing and environmental pollution. The application research of reverse flotation reagents includes the development of excellent collectors with strong collection ability, high selectivity and low temperature resistance, and new activators without sulfuric acid, high efficiency, low cost, energy saving and energy saving, in order to improve work efficiency, reduce economic costs and avoid Corrosion of equipment reduces environmental pollution.
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