The High Phosphorus Sulfur Siderite Xuanye Joint New Technical And Theoretical Research

China has abundant reserves of iron ore in the world. However, the available iron ore resources tend to be poor-graded, fine-disseminated and mixed with impurity. With the continuous and rapid development of iron and steel industry, the contradiction between supply and demand of domestic iron ore has become more and more serious. At present, the domestic supply of iron ore is no more than 50%. For heavy shortage of iron ore reserves in China, exploiting new iron reserves is needed timely. On this background, the exploitation and utilization of approximately 10 billion tons of refractory high-phosphorus iron ore is proposed.Huimin primary iron ore was used as materials in the present study. Based on the investigation on properties of mineralogy and extensive experimental research, a novel dressing-metallurgy combination flowsheet consisting of removing sulfur and phorsphors by reverse flotation--odium-salt-added catalyst reductive roasting—magnetic flocculation was adopted for treating this ore, in order that the extreme difficulties might be overcome of exploitation of this iron ore. What's more, the application of this creative technology would play an important role in the beneficiation and exploitation of similar refractory iron ore.Mineralogy analysis of run-of-mine indicated that it contains about 30% iron. The contents of P and S in the ore reached 1% and 1.4% respectively. The iron minerals were mainly siderite and small amounts of magnetite, additional 23.40% of iron minerals occurs as silicate.The phosphorous mainly occured as collophanite, while the sulfur occurs as pyrite. Because of its complex minerals composition, poor iron-content, fine-grained dissemination and high content of phosphorous and sulfur, the research on dressing and metallurgy process of this iron ore should be faced with considerable difficulties.Following tentative experiment was conducted, which indicated that a single mineral processing or a single metallurgy methods was never effective in dealing with the iron ore, and removal of sulphur and phosphorous impurities effectively would be key to exploitation and utilization of the ore. Therefore, a novel process of desulfurization and dephosphorization by reverse flotation was creatively put forward in this paper, which aimed at removal of the sulphur and phosphorous as much as possible on condition of guarantee of iron recovery. Through a great deal of laboratory experiment, a product with 0.27% phosphorous and 0.34% sulfur and iron recovery 80.93% was obtained by the combined process of desulfurization-dep hosphorization. Basing on the bench-scale test, a continuous test at 1d/t scale was carried out, which resulted a consistent technical indexes compared with those of bench-scale test. Satisfactory separation indexes were obtained by the novel process of desulfurization and dephosphorization by reverse flotation. However, large dosage and numerous types of reagents were the characteristic of the flotation system.Therefore, optimization experiments were carried out for simplification of the reagent system in reserve flotation. As a result, Dephosphorization agent was greatly reduced through decreasing the desorption rate of phosphorus by 19.77 percents(doseage of pulp pH adjustment agent was reduced from 9000g/t to 2500g/t, and 25.68% of starch and 54.08% of collectors were saved), meanwhile, the regulator SIS and sodium silicate were no longer used. Considering the mutual disruption of reagents used in desulphurization and dephosphorization, an asynchronous process of desulphurization and dephosphorizatio, with alkaline desulphurization preference was applied creatively. The process yielded a product of 0.48% for phosphorus content,0.38% for sulphur content and 80.06% for iron recovery.In this papar, the effects of altering parameters on indexes of the iron concentrate during the reduction roasting were studied. The optimized parameters were identified, that was 1050℃for reduction temperature,150min for reduction duration,1:5 for Mcoal:More and 1:20 for MNa2CO3:More 1:20. In order to identify the pattern of phase transitions of iron minerals with altering the reduction temperatures and reduction durations, SEM and EDAX analyses were employed. The results indicated the siderite was deoxidized according to the theory of Gradual Dcoxidizing, with the order of siderite-magnetite-metallic iron accompanied by the production of fayalite. Both increasing reduction temperature and extenting reduction duration were benefit for enhancement of the metallic iron phase.Fowlling the magnetic separation research of sodium-salt-added catalyst reductive roasting, a concentrate with 65.85% Fe, at a recovery of 74.21% and phosphorous content 0.21% was obtained on the condition of 90.45% below -45μm of grinding fineness and 232kA/m of magnetic field intensity. But only 68.55% of iron recovery could be obtained by wet drum type weak magnetic separation. Therefore, enhancement of the recovery of fine particles of magnetic minerals effectively would be principal to improve the indexes of low intensity magnetic separation.Study on mechanism of sodium-salt-added catalyst reductive roasting was conducted, in which the kinetics of thermodynamic calculations and metallurgical analysis were performed. Thermodynamic calculations showed that the magnetic roasting process of siderite is endothermic process. Speciafically, when the reduce temperature was 1050℃, the isobaric thermal effect of siderite was 68856.67J/mol. In order to observe morphology appearance and analyse mineral composition, SEM and EDAX analyses of sodium-salt-added catalyst reductive roasting sample were employed. The results showed that addition of Na2CO3 would promote reconstruction and development of metallic iron. What's more, the more Na2CO3 was added, the larger iron particless sizes assembled. The results of XRD pattern of reductive roasting sample indicated it was hopeful to promote the reduction of siderite and magnetite when appropriate ratio of Na2CO3(MNa2CO3:More 1:20～1:10) was added to the test samples before reductive roasting. It was observed obviously in the XRD pattern that diffraction peak of metallic iron is increased markedly and diffraction peak of fayalite was significantly reduced. While no addition of Na2CO3 or excess addition of Na2CO3 would be harmful to reductive of siderite and magnetite. At the same time, thermodynamic calculations of collophanite morphological changes showed that the collophanite had not transformed to P2 during reductive roasting. Consequently, improving the degree of dissociation of iron and apatite would be an efficient way to acquire qualified concentrate.As traditional equipments were not good at recovering fine particles of magnetic iron minerals, a novel separation technology was applied in the present study, involving fine-grinding and then magnetic flocculation. The effects of parameters of flocculation on indexes of the iron concentrate were investigated through a self-made separation column and the optimum parameters were identified (grinding fineness was 88.7% below -45μm, tangential flow was 3L/min, stirring intensity was 250r/min,). Under the optimum conditions, the grade and recovery rate of the iron concentrate produced by single flocculation reached 66.32% and 74.26% respectively. Meanwhile, the contents of phosphorus and sulphur substantially declined to 0.21% and 0.28% separately. Compared to separation indexes by wet drum type weak magnetic separation, nearly 6% increase of iron recovery rate was obtained. It implied that the magnetic flocculation was capable to effectively recover fine particles of magnetic iron minerals.In summary, an innovative technology was conducted for processing the Huimin raw ores which were characterized of high contents of phosphorus and sulphur but a deficiency of iron. The technology consisted of reserve flotation for the desorptions of phosphorus and sulphur, sodium salt reduction roasting and magnetic flocculation in sequence, yielding a concentrate of 67% for iron grade,0.21% for phosphorus content,0.28% for sulphur content with a comprehensive recovery rate of about 60%. Undoubtedly, the progress made in this dissertation might supply a good base for exploitation of Huimin primary iron ore resources.