Hematite is widely distributed in nature iron minerals, iron is an important raw material, also used as a red pigment. Oolitic hematite ore disseminated in fine granularity, and is often associated with siderite, chamosite or phosphorus-containing mineral association or another wrap, it is difficult to achieve a phosphorus-containing ore to iron and steel industry requires [ 1 ] Therefore, the braided hematite ore is one of the most difficult types of iron ore recognized at home and abroad, and such resources are basically not effectively utilized. About 1/9 of China's iron ore reserves are braided hematite, so it is important to study how to effectively use braided hematite in China [ 2 ] . A lot of research work has been carried out on this kind of ore at home and abroad [ 3 -7 ] , but the effect is not satisfactory. Studies have shown that the use of dephosphorization agent for the direct reduction roasting-magnetic separation method can obtain better indicators. Therefore, the effects of direct reduction roasting-magnetic separation process factors are studied, and the direct reduction roasting-magnetic separation of ore is determined. The best conditions provide a new way for the effective use of this type of ore. I. Ore properties and test methods The ore (original ore) used in the research is high-phosphorus-like hematite ore in western Hubei, and the grades of iron and phosphorus are 43.65% and 0.83%, respectively. The main useful minerals are hematite and a small amount of limonite, and the iron point of the red limonite is 97.82%. The reduction roasting uses coal as a reducing agent, and is added with a dephosphorization agent NCP, and is placed in a covered crucible, and then calcined at a certain temperature in a muff furnace for a fixed time, and after cooling, two turbulent grinding and magnetic are performed. selected. The main factors to be investigated include the amount of coal, the amount of dephosphorization agent, the reduction roasting temperature, the reduction roasting time, the grinding fineness and the like. The product obtained by direct reduction roasting-magnetic separation has a grade of iron greater than 90%. To avoid confusion with conventional iron concentrates, the product is named a reduced iron product. Test large changes in the total mass of the product after firing as compared with prior to firing, so that the ratio of the absolute amount of the metal with the absolute amount of gold metal iron in the reduced iron product with added test firing ore recovery calculated. The amount of coal and NCP refers to the ratio of coal or NCP to ore quality, expressed as a percentage. Second, the test results and discussion (1) Two-stage grinding time test The test results of the previous stage show that the improvement of iron grade and the reduction of phosphorus grade are achieved by fine grinding. Therefore, the influence of the second-stage grinding fineness in the seed roasting process is first investigated. The fixed conditions are: 40% coal, 20% NCP, 1000°C roasting temperature, 60min roasting time, 70% grinding concentration, and the first grinding fineness is -0.074mm55%, magnetic separation, magnetic field strength 87.6kA/m, concentrate regrind. The test results are shown in Figure 1. It can be seen from Fig. 1 that with the increase of the two-stage grinding time, the grade and recovery rate of iron are increasing, but the grade of phosphorus is greatly reduced when the grinding time is 20min, which should be embedded. The fine-grained gangue mineral can be sufficiently dissociated from the iron mineral at this time, and no agglomeration occurs. Therefore, it is determined that the second grinding time is 20 min, and the grinding particle size is 100% less than 16 μm. (2) Coal consumption test The other conditions were fixed, and the influence of the amount of coal in the roasting process was examined. The results are shown in Fig. 2. It can be seen from Fig. 2 that as the amount of coal increases, the grade and recovery of iron increase, and the grade of phosphorus decreases. In this process, coal can fully react with the ore to reduce Fe 2 O 3 in the ore, but when When the dosage exceeds 40%, the coal is excessive in the reaction. Although the recovery rate of iron is still somewhat increased, it will affect the effect of the phosphorus dephosphorization agent phosphorus, and the iron grade is slightly reduced. Therefore, the optimum amount of coal is determined to be 40%. (3) NCP dosage test The amount of fixed coal is 40%, other conditions are unchanged, and the amount of NCP is changed to test. The results are shown in Fig. 3. It can be seen from Fig. 3 that before the NCP dosage reaches 15%, the iron grade and recovery rate are obviously improved, and the phosphorus grade is obviously decreased. When the NCP dosage exceeds 20%, the influence on the result becomes small, so the NCP is determined. The optimum dosage is 20%. The main function of NCP is to react with the ore during the roasting process, thereby removing phosphorus during the magnetic separation process, and at the same time reducing the temperature of reduction of iron during roasting, which has a certain promoting effect on reduction. (4) Calcination temperature test The amount of fixed NCP was 20%, and other conditions were unchanged. The calcination temperature was changed and the test was carried out. The results are shown in Fig. 4. It can be seen from Fig. 4 that when the temperature is lower than 1000 °C, the recovery of iron increases with the increase of temperature, and the grade of phosphorus decreases, indicating that at this temperature, raising the temperature is conducive to the reduction of iron. And the removal of phosphorus, when the temperature continues to rise above 1000 ° C, the grade of phosphorus is obviously increased, and the recovery rate of iron is decreased, thereby knowing that within this range, the temperature has an adverse effect on the dephosphorization agent. influences. When the temperature is higher than 1000 °C in the test, the product after calcination is agglomerated seriously, and large iron particles are formed, and the grade of phosphorus in the reduced iron product is increased. It is inferred that some of the iron is melted and combined with phosphorus during the calcination process, making dephosphorization more difficult to achieve. Therefore, it was determined that the optimum temperature was 1000 °C. (5) Roasting time test The fixed temperature was 1000 ° C, other conditions were unchanged, and the baking time was changed to test. The results are shown in Fig. 5. It can be seen from Fig. 5 that as the roasting time is prolonged, the grade and recovery rate of iron increase, and the grade of phosphorus decreases. However, when the time exceeds 60 min, the influence of time becomes smaller, and it can be determined that when the time is 60 min. The reduction reaction was basically completed, so the calcination time was determined to be 60 min. The optimum conditions for the determination of high-phosphorus-like hematite roasting reduction in western Hubei were as follows: reducing agent dosage 40%, NCP dosage 20%, calcination temperature 1000 °C, roasting time 60 min, and a grinding fineness of -0.074 mm55. %, the second-stage grinding fineness is -16μm, and the magnetic separation field strength is 87.6kA/m. After repeated tests, the average indexes of the reduced iron products were as follows: iron grade 90.09%, iron recovery rate 88.91%, and phosphorus grade 0.07%. Third, the conclusion (1) Adding a dephosphorization agent during the reduction roasting process of the braided high-phosphorus hematite ore can achieve high-grade reduced iron products while reducing the phosphorus content to 0.07%. It provides a new way to make rational use of refractory high-phosphorus hematite. (2) In the process of reduction roasting, NCP plays the role of dephosphorization, and at the same time can reduce the temperature during roasting; (3) The reduction roasting temperature should be controlled at 1000 °C. If the temperature is too high, the iron mineral will recombine with phosphorus, and when the temperature is too low, the reduction effect will not be achieved. (4) Since the size of the inlaid hematite itself is extremely fine, the products subjected to reduction and roasting require sufficient fine grinding to be effectively sorted. references [1] Yao Jingwei. Re-planning and development of Ningxiang-type iron ore, Land and Resources Technology Management, 2005 (5): 13-16. [2] Tong Xiong, Li Yingshu, Zhou Qinghua, et al. Experimental study on new mineral processing techniques for difficult-to-select hematite hematite ore, China Engineering Science, 20057(9): 323-325. [3] Xiao Qiaobin, Ge Baoliang, Yang Bo, et al. Experimental study on the ore dressing of a braided hematite in Yunnan. Metal Mine, 2005, 8 (Supplement): 153-155. [4] Zhou Jicheng, Xue Zhengliang, Zhang Haifeng, et al. Study on dephosphorization technology of high phosphorus bismuth hematite. Ironmaking 2007, 26(2): 40~43. [5] Ji Jun. Research on dephosphorization technology of high-phosphorus iron ore. Mining and Metallurgy, 2003 (2): 33-37. [6] Liu Yahui, Sun Bingquan. Research on positive-reverse flotation of hematite, Metal Mine, 2004(1): 39~41. [7] Zhu Jiang, Xiao Gan, Wang Guiping, Research on mineral processing technology of a high-phosphorus hematite in Yichang, Hubei, Metal Mine, 2006 (8): 189-191.
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