Evolution of mineral facies in magnetic field enhanced reduction of Bayan Obo ore
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摘要: 以低温直接还原工艺为基础，在1 223 K，B=1.02 T条件下，对白云鄂博含碳球团进行磁场强化还原试验，通过考察铁矿物的还原效率和稀土矿物的矿相演变规律，来研究磁场对白云鄂博矿中铁氧化物还原以及稀土相转变的作用。结果表明：磁场可以促进铁氧化物的还原，还原进行到60 min时，试样金属化率可以达到90.23%，与无磁条件相比，金属化率增加了52.82个百分点；磁场加快了氟碳铈矿以及独居石的分解，同时可以促进CaO·2RE2O3·3SiO2和RE2O3·2SiO2的生成。Abstract: Based on the low-temperature direct reduction process, the magnetic field enhanced reduction experiment of Bayan Obo carbon bearing pellets was carried out at 1 223 K, B = 1.02 T. The effect of magnetic field on iron oxide reduction and rare earth phase transformation of Bayan Obo ore was studied by investigating the reduction efficiency of iron minerals and the ore phase evolution of rare earth minerals. The results show that the magnetic field can promote the reduction of iron oxide, and the metallization rate of the sample can reach 90.23% after 60 min reduction, increased by 52.82% compared with that under the non-magnetic condition. The magnetic field can accelerate the decomposition of bastnaesite and monazite, and promote the formation of CaO·2RE2O3·3SiO2 and RE2O3·2SiO2 (RE = rare earth elements).
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图 3 不同还原时间X射线衍射分析
Figure 3. X-ray diffraction analysis of samples with different reduction time
图 5 还原时间30 min时试样微观形貌
Figure 5. Microscopic morphology of sample with 30 min reduction time
图 6 稀土矿相转变过程
Figure 6. Phase transformation process of rare earth ore
1-RECO3F；2-REOF；3-CaO·2RE2O3；3SiO2； 4-RE2O3·2SiO2；5-CaO·SiO2；6-REPO4；7-SiO2；8-CaF2；9-CaCO3；10-Ca3(PO4)2
表 1 白云鄂博原矿主要化学成分
Table 1. Main composition of raw ore in Bayan Obo
% TFe FeO SiO2 P2O5 S F 37.17 12.17 16.30 1.48 0.86 8.42 Na2O CaO Al2O3 TiO2 BaO Fe2O3 0.35 14.22 0.28 1.02 2.90 39.58 Nb2O5 ThO2 RE2O3 MgO 0.31 0.038 5.84 0.94 
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表 3 还原后物料的铁相组成
Table 3. Iron phase composition of reduced materials
时间/ min 磁场条件 常规条件 主相 副相 主相 副相 0 Fe2O3、Fe3O4 Fe2O3、Fe3O4 5 Fe2O3、Fe3O4 FeO Fe2O3、Fe3O4 20 FeO Fe FeO Fe3O4 45 Fe FeO Fe 60 Fe FeO Fe
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表 4 扫描电镜图片中各点能谱分析结果
Table 4. Energy spectrum analysis results of dots in the scanning electron microscope images
% 序号 Fe C O Ca Si F 1 56.60 6.04 33.57 0.17 0.24 0 2 86.48 6.02 2.89 0.46 0.30 0 3 0 0 0 37.47 0 62.53 4 3.34 81.79 10.58 0.53 0 0 5 61.31 0 36.85 0 0 0 6 14.39 30.70 29.10 8.15 11.80 0 7 0 0 0 38.83 0 60.59 8 0 83.12 12.15 3.14 0 0
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表 5 不同还原时间内产物中稀土相的组成
Table 5. Composition of rare earth phase in the product with different reduction time
时间/min 常规条件 磁场条件 0 RECO3F、REPO4、CaF2、SiO2、CaCO3 RECO3F、REPO4、CaF2、SiO2、CaCO3 5 RECO3F、REPO4、REOF 、CaO·2RE2O3·3SiO2、CaF2、SiO2、Ca3(PO4)2、Ca2SiO4 RECO3F、REPO4、REOF 、CaO·2RE2O3·3SiO2、CaF2、SiO2、Ca3(PO4)2、Ca2SiO4 20 RECO3F、REPO4、REOF 、CaO·2RE2O3·3SiO2、CaF2、SiO2、Ca3(PO4)2、Ca2SiO4 CaO·2RE2O3·3SiO2、CaF2、Ca3(PO4)2、Ca2SiO4 45 RECO3F、CaO·2RE2O3·3SiO2 、CaF2 、Ca2SiO4、Ca3(PO4)2 CaO·2RE2O3·3SiO2 、RE2O3·2SiO2、CaF2 、Ca2SiO4、Ca3(PO4)2 60 CaO·2RE2O3·3SiO2 、RE2O3·2SiO2、CaF2 、Ca2SiO4、Ca3(PO4)2 CaO·2RE2O3·3SiO2 、RE2O3·2SiO2、CaF2 、Ca2SiO4、Ca3(PO4)2
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