| Yuanjiacun iron ore belongs to a large iron ore deposit, proven reserves of 1.26 billion tons. The mineral composition of ore deposits is very complicated, along with the micro-fine crystal size and various minerals. In terms of 11th five-year national science and technology support plan project and national development and reform commission (NDRC) major industry technology development projects, name as "High Efficient Separation Research of Micro-fine Maghemite" and "Development and Application of Taigang Yuanjiacun Micro-fine Hematite Ore", the quartz-type hematite has been utilized at its large extent. However, the amphibole hematite is stored as a goaf due to Ihe non-effective separation technology. Therefore, the development of novel separation technology for the amphibole hematite is very important and urgent.In this thesis, the magnetic separation, flotation separation and deep-reduction magntic separation were used to dispose the Yuanjiacun iron ore, respectively. The separaction rules of amphibole hematite were revealed under different conditions. The depth reduction-magntic techology was certified to be the appropriate method to separate the amphibole hematite, and the iron resource can be recycled effectively. The main results are obtained as follows.(1) The study of mineralogy shows that the mean iron grade of Yuanjiacun amphibole-type hematite is 37.06%. The useful mineral was hematite and gangues mainly consisted of quartz and amphibole. The gangue minerals and iron mineral are embedded closely each other, for example, the quartz and amphibole are embedded in the iron ore stripes and the iron ore with a fine size below 0.01 mm are embedded in the stripes of quartz and amphibole. The crystal grain size of hematite is very fine, consisting of -0.02 mm (63.96%) and -0.01mm (25.78%). Quartz crystal grain size is rougher than hematite, and amphibole crystal grain size is extremely fine, consisting of -0.02 mm (59.96%),-0.01 mm (24.08%). Yuanjiacun amphibole-type iron ore is named as a difficult separation mineral due to the fine and mixed feature.(2) The results of magnetic separation show that the grade of iron concentrate is 44.12%, tailings grade is 21.74% and the iron recovery rate is 81.66% when the grinding fineness is-0.074 mm85% and magnetic field intensity is 796 kA/m. Studies have shown amphibole displayed low magnetism and easily gathered in the process of HIMS (high intensity magnetic separation), which was 1.15. Low monomer dissociation degree and inclusion in the process of magnetic separation caused the low efficiency in HIMS.(3) The research results of single mineral and artificial mixed mineral flotability show that in the sodium oleate anionic collector reverse flotation system, starch can inhibit not only hematite but also amphibole, and Ca2+ can activate quartz and amphibole. The active role of Ca2+ aimed at amphibole is weaker than quartz which causes the difficult separation between amphibole and hematite. In the lauryl amine cationic collector reverse flotation system, lauryl amine shows the flotability aimed to quartz, amphibole and hematite, but the difference is tiny. Comparision the flotability of quartz, amphibole and hematite in anionic collector reverse flotation system with that in cationic system, the separation rules are drawn as following:the flotability difference of hematite and quartz in anionic reverse flotation system (91.65 percentage points)> the flotability difference of hematite and quartz in cationic reverse flotation(86.52 percentage points)> the flotability difference of hematite and amphibole in cationic reverse flotation system (59.52 percentage points)> the flotability difference of hematite and amphibole in anionic reverse flotation system (16.89 percentage points).(4) The results of zeta potential and infrared spectrum analysis show that CaCL2 can occur adsorption on the surface of quartz and amphibole, which lead to the activate amphibole and quarz. The hydroxyl groups contained in the starch can show chemical adsorption on the surface of hematite and amphibole, which shows strong defference aimed to quarz. Thus, the hematite and amphibole are suppressed in the CaCl2 system. Lauryl amine can produce physical adsorption on the surface of hematite, quartz and hornblende, which caused the poor selectivity in the cation flotation system. The analysis result is consistent with the rule of single mineral flotability study.(5) The anionic reverse flotation and cationic reverse flotation results for the HIMS (high intensity magnetic separation) concentrate show that they have the same rule with single mineral flotation. Both the flotation separation efficiency and the grade of iron concentrate are low. The results show that it is difficult to realize separation of silica and iron through the conventional mineral separation methods. The main reasons of the mineral separation difficulty is:first, mineral crystallization is difficult to realize the monomer dissociation of minerals due to the fine particle size; Second, the unselective adsorption and reunion of micro-fine mineral in the process of separation aggravate the difficulty of the separation; Third, the double property of amphibole containing silica and iron limit the mineral separation.(6) The results of deep reduction and magnetic separation experiments show that the reduction process is accelerated with increasing temperature, which lead to the high metallization rate. The more amount of blending coal, the more of ? (CO) in the atmosphere, the thermodynamic driving force of iron oxide to metallic iron is then improved. However, the residual carbon will restrain the combination and growth between the iron droplets, and is easy to form the cementite of Fe3C, which reduces the metallization rate of reduction product. CaO as additives, can neutralize acids in the mineral, inhibit the formation of low melting point, reduce liquid phase blocking ore internal micro-pores, and reduce the transfer resistance of gas. After deep reduction and magnetic separation, the metallization rate, the grade of iron and the iron recovery ratio reach maximum values of 91.20%,92.94% and 89.85%, respectively. The high-purity iron powder with iron grade of 96.18% is then obtained with a screning treatment.(7) The low-cost coal is applied as reductant to produce the high-grade iron powder using the method of depth reduction and magnetic separation, which is a novel technology to dispose the refractory iron ore. The depth reduction and magnetic separation lead to the high iron grade (>90%), low content of the harmful elements. It can be used as raw materials in electric furnace steelmaking.The research results in this paper will be significant for the development and utilization of Yuanjiacun amphibole-type iron ore. |
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