Iron ore as the main raw material for the steel industry is an important strategic resource of a country, in recent years, with the rapid development of the steel metallurgical industry, the demand for iron ore raw materials is also growing. However, the limited iron-rich ore and easy-choice iron ore resources on the earth will gradually dry up, and it is very important to study the high-efficiency sorting technology of high- phosphorus iron ore. The beneficiation of high-phosphorus iron ore has always been a major problem in the mineral processing industry. China's high-phosphorus iron ore reserves account for 14.86% of the total reserves, reaching 7.45 billion tons. Therefore, it is imperative to increase the research on high-phosphorus iron ore beneficiation and phosphorus reduction, and to develop effective, economical and practical new methods and technologies [1 , 2] . The reserves of a high-phosphorus iron ore in Yunnan are large. The ore contains about 42% iron. The iron minerals are mainly in the form of hematite and limonite. The phosphorus content of harmful impurities is 0.586%, and the phosphorus minerals and iron minerals are mutually contaminated. The size of the inlay is extremely fine, and it is a high-phosphorus refractory iron ore. Through a large number of experiments, it was determined that the ore was treated by reduction roasting-magnetic separation-reverse flotation process, and the iron grade of iron concentrate was 61.72%, the recovery rate of iron was 67.48%, and the phosphorus content of iron concentrate was 0.20%.
First, the nature of the ore
The main minerals in a high-phosphorus iron ore in Yunnan are hematite and limonite, and a small amount of magnetite. The gangue minerals are mainly calcite , chlorite, quartz and the like. The main element analysis results and phase analysis results are shown in Tables 1 and 2.
Table 1 Main chemical composition of raw ore (mass fraction) /%
Table 2 copper phase analysis results
It can be seen from Table 1 and Table 2 that the main target element of the iron mineral is iron, the ore grade iron grade reaches 42.66%; the harmful element sulfur and arsenic content is lower, and the harmful element phosphorus content is higher, 0.586%; the iron ore belongs to Iron-bearing iron ore, iron mainly exists in the form of red limonite, which is a high-phosphorus red-brown iron ore, and the phosphorus mineral and iron mineral are mutually contaminated, mainly distributed in hematite and limonite. The size of the inlay is extremely fine and is very difficult to select iron ore.
Second, the test plan
A single process test (strong magnetic separation, re-election, direct flotation) and joint process tests (gradient magnetic separation, grading re-election, magnetic flotation/floating, magnetic combined sorting, and magnetic weight/heavy one) were performed on the ore samples. The iron combined concentrates have not obtained iron concentrates with better indicators, and the phosphorus content in the concentrates cannot be reduced to less than 0.2%. To this end, change the train of thought, decided to first reduce the ore by using the method of reduction roasting to magnetite, and then use the magnetic separation method to select the iron concentrate with higher iron grade, and then use the method of reverse flotation to iron concentrate. Phosphorus is reduced to less than 0.2%, and an iron concentrate with acceptable grade and impurity phosphorus is not exceeded.
Third, the test results
(1) Reduction roasting test
The calcination temperature, the amount of reducing agent and the calcination time are the main influencing factors of the calcination test. The temperature is too low and the reaction proceeds too slowly; if the temperature is too high, weak magnetic Fe-Iron or iron silicate is formed, which affects the concentrate index. The calcination time is too short, the reaction is not completely carried out, the concentrate grade and recovery rate are lowered; the calcination time is too long, and a large amount of heat energy is consumed, and the magnetic properties of the reaction product are greatly reduced, which affects the effect of magnetic separation later [3] .
After the ore is crushed to -2mm, it is mixed with coke with a particle size of -1mm and a dosage of 5%, and then calcined for 20min, then ground to -0.074mm, and 100%, and magnetic separation is performed under the condition of magnetic separation current of 2A. The effect of the calcination temperature on the test results is shown in Figure 1.
Figure 1 Calcination temperature test results
It can be seen from Figure 1 that as the calcination temperature increases, both the iron grade and the recovery rate increase. When the calcination temperature reached 1000 ° C, both the iron grade and the recovery rate decreased. A suitable calcination temperature of 1000 ° C can be seen.
The ore is crushed to -2mm and mixed with -1mm of coke powder. The calcination temperature is 1000°C, the reduction is calcined for 20min, then the grinding to -0.074mm is 100%, and the magnetic separation is 2A. The effect of the amount of coke used on the test results is shown in Figure 2.
Figure 2 Reductant dosage test results
It can be seen from Fig. 2 that with the increase of coke consumption, the iron grade and iron recovery rate both increase first and then decrease, and the extreme value occurs when the coke consumption is 8%. It can be seen that the appropriate amount of coke is 8%.
The ore is crushed to -2mm and mixed with -1mm coke. The amount of coke is 8%. It is reduced and calcined at 1000oC, then ground to -0.074mill, which is 100%, and magnetically selected under magnetic separation current of 2A. The effect of baking time on the test results is shown in Figure 3.
Figure 3 reduction roasting time test results
It can be seen from Fig. 3 that with the prolongation of the reduction roasting time, both the iron grade and the iron recovery tend to rise first and then decrease. When the reduction roasting time is 30 min, the iron grade and recovery rate reach the maximum. It can be seen that a suitable reduction roasting time is 30 min.
(2) Magnetic separation test
1. Magnetic field strength test After the ore is crushed to -2mm, 8% of -1mm coke is added, calcined at 1000 °C for 30min, then ground to -0.074mm, which is 100%, magnetic separation, and the effect of magnetic separation current on the test results The results are shown in Figure 4.
Figure 4 Magnetic separation current test results
It can be seen from Fig. 4 that when the magnetic separation current is too high, the concentrate iron grade is less than 60%, and the magnetic separation current is too low, the iron concentrate recovery rate is less than 50%. When the magnetic current is 2.5A, the selection index is more suitable. At this time, the concentrate grade is 61.77%, and the recovery rate is 68.25%.
2. Grinding particle size test After crushing the ore to -2mm, add -1mm coke 8%, calcined at 1000 °C for 30min, then grind, and perform weak magnetic separation under the condition of magnetic separation current of 2.5A. The effect of the effect is shown in Figure 5.
Figure 5 Grinding particle size test results
It can be seen from Fig. 5 that the finer the material, the more complete the dissociation of the iron mineral monomer, and the higher the grade of the concentrate iron, but the material is too fine, resulting in serious loss of iron during magnetic separation. According to the test results, it is determined that the suitable grinding grain size is -0.054 mm and the grain size is 90%.
3. The comprehensive test passed the condition test to determine the various process parameters and then carried out a comprehensive test. After the ore is crushed to -2mm, 8% of -1mm coke is added, calcined at 1000 °C for 30min, then ground to -0.054mm, 90%, and weak magnetic separation under magnetic separation current of 2.5A. The iron grade is 60.86%, the phosphorus content is 0.42%, and the recovery rate is 70.68% iron concentrate.
(III) Phosphorus reduction test of iron concentrate
Because the phosphorus mineral contained in the iron ore is closely symbiotic with iron ore, it is impregnated on the edge of iron oxide mineral particles, and a small amount of phosphorus is present in the crystal lattice of iron ore and iron clay , and some phosphorus minerals are calcined. During the process, it was separated from the iron minerals, and the phosphorus content was reduced from 0.59% to 0.42%. However, some of the phosphorus minerals remained in the magnetic separation concentrate, causing the phosphorus content of the iron concentrate to exceed the standard, so the iron was carried out. Concentrate anti-flotation phosphorus reduction test [4] .
Sodium carbonate was used as the pH adjuster, starch was used as the inhibitor, RP was used as the collector, and 2 oil was used as the foaming agent. The weak magnetic separation concentrate was subjected to a coarse and a fine reverse flotation dephosphorization. The test flow is shown in Fig. 6. The test results are shown in Table 3.
Figure 6 Reverse flotation process
Table 3 Results of reverse flotation test
It can be seen from the results in Table 3 that the reverse flotation process can obtain an iron concentrate with an iron grade of 61.68% and a recovery rate of 91.87% (compared to 65.93% of the ore), and the phosphorus in the iron concentrate is reduced to 0.21%.
(4) Full process test
The whole process test was carried out on the basis of the above conditions test. The test process is shown in Figure 7, and the test results are shown in Table 4.
Figure 7 Reduction roasting - magnetic separation - reverse flotation process
Table 4 Full process test results
It can be seen from the results in Table 4 that the red brown iron ore is treated by reduction roasting, magnetic separation and reverse flotation, and the iron concentrate grade is 61.72%, the iron recovery rate is 67.48%, and the iron concentrate phosphorus content is 0.20. % of mineral processing indicators.
Fourth, the conclusion
1. An iron ore iron mineral in Yunnan is mainly in the form of red limonite. The phosphorus content is 0.586%, and the mineral inlay size is fine. It is difficult to obtain iron concentrate which meets the smelting requirements by conventional physical beneficiation method. Through a large number of experiments, it was determined that the ore was treated by the reduction roasting-magnetic separation-reverse flotation process, and a good selection index of 61.72% concentrate grade, 0.20% phosphorus content and 67.48% iron recovery rate was obtained.
2. With the increasing tension of iron ore resources and the increasing demand for raw materials for smelting, the roasting-magnetic separation-reverse flotation process proposed in this study is similar to the development and utilization of refractory fine-grained high-phosphorus red limonite. Provide new ideas.
references:
[1] Lin Xianghui, Luo Renmei. New Progress in Mineral Processing and Pharmaceutics Research of Difficult-Selected Iron Ore in Western Hubei[J]. Mining and Metallurgical Engineering, 2007(3): 28-29.
[2] Sun Bingquan. Progress of China's complex refractory iron ore beneficiation technology in recent years [J]. Metal Mines, 2006 (3): 11-13.
[3] Xiao Junhui. Industrial experiment of new technology for iron and phosphorus reduction in a fine grain refractory red brown iron ore [J]. Metal Mines, 2007 (1): 44-46.
[4] Li Guangtao, Zhang Zonghua. Experimental study on the beneficiation of a high-phosphorus red-brown iron ore in Sichuan[J]. 金属矿.2008(4):43-46.
Author unit
Jiangxi University of Science and Technology (Ai Guanghua, Yu Xinyang)
Guangxi University (Wei Zongwu)
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