Effect of Na2O on the enrichment behavior of phosphorus in the slag system CaO-SiO2-Fe2O3-P2O5
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摘要: 通过MoSi2高温箱式炉试验和FactSage、扫描电镜及XRD等分析方法，对渣中Na2O对含磷渣中磷的赋存形式、物相析出规律以及含磷渣中磷的富集行为的影响规律进行系统研究。结果表明：对于CaO-SiO2-Fe2O3-P2O5渣系，Na2O的加入会取代nC2S-C3P固溶体中部分钙，形成Na2Ca4(PO4)2SiO4固溶体，随着Na2O进一步增加直至过量时，前述反应生成的高磷固溶体(Na2Ca4(PO4)2SiO4)中Ca和Si组分的比例进一步降低，逐渐富集成为更高磷固溶体Na3PO4，富磷相中磷的品位得以提高。随着渣中Na2O含量的增加，炉渣熔点明显降低，富磷相中磷含量明显增加，P2O5含量超过30%，完全满足钢渣磷肥对磷含量的要求。因此在炼钢过程加入适量的Na2O（低于6%）代替CaF2作助熔剂造渣，可以促进渣中磷富集，进而改善含磷渣中磷资源回收作磷肥的效果。Abstract: In this paper, the effects of Na2O in slag on the existing forms, the law of phase precipitation and the phosphorus enrichment behavior of phosphorus-containing slag are systematically studied by high-temperature experiments in MoSi2 furnace and analyzed by FactSage, SEM and XRD. The research results show that: for the CaO-SiO2-Fe2O3-P2O5 slag system, the addition of Na2O will replace solid solution calcium of nC2S-C3P, forming Na2Ca4 (PO4)2SiO4 solid solution. As the content of Na2O increases to excess, the content of Ca and Si in P-solid solution (Na2Ca4(PO4)2SiO4) reduces, and the Na3PO4 phase produces the grade of phosphorus in the P-rich phase increases. With the increase of the content of Na2O in slag, the melting point of the slag decreases significantly, the content of phosphorus in the P-rich phase increases significantly, and the content of P2O5 exceeds 30%, which ultimately meets the requirement of phosphorus content in the steel slag phosphate fertilizer. Therefore, adding an appropriate amount of Na2O (less than 6%) in the steel making process instead of CaF2 as the fluxing agent can promote the phosphorus enrichment effect in the slag, and the converter slag can be used as a phosphate fertilizer.
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图 1 CaO-SiO2-Fe2O3三元渣中试验渣系成分
Figure 1. Observed slag composition in the ternary phase diagram of the CaO–SiO2–Fe2O3 system
图 3 A、D和G方案熔渣凝固过程中析出相的析出过程
Figure 3. The precipitation process of precipitates during the solidification of A、D and G slag in schemes
图 4 合成渣熔点随Na2O成分变化趋势
Figure 4. The tendency of the melting point of synthetic slag with different Na2O content
图 5 不同Na2O含量合成渣的背散射电子图
1-富磷相；2-RO相；3-基体相
Figure 5. SEM-BSE image of experimental samples A, D, G slag
表 1 试验渣化学成分
Table 1. Composition of the synthetic slag samples %
渣样 CaO SiO2 Fe2O3 P2O5 Na2O A 42.86 17.14 30 10 0 B 42.15 16.85 30 10 1 C 41.43 16.57 30 10 2 D 40.71 16.29 30 10 3 E 40.00 16.00 30 10 4 F 39.29 15.71 30 10 5 G 38.57 15.43 30 10 6 H 37.86 15.14 30 10 7 I 37.15 14.85 30 10 8 J 36.43 14.57 30 10 9 K 35.72 14.28 30 10 10 
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表 2 相应合成渣终样EDS结果分析
Table 2. Chemical composition of each phase from the sample in Fig.5 by EDS
% 序号 物相 Na2O MgO SiO2 P2O5 CaO Fe2O3 A 富磷相 0.00 2.95 15.24 20.75 58.90 2.16 RO相 0.00 5.30 0.07 0.17 0.61 93.85 基体相 0.00 11.46 31.29 3.56 53.68 0.00 D 富磷相 2.16 0 14.58 23.63 59.61 0.00 RO相 0.00 10.48 0.00 0.00 0.00 89.52 基体相 1.53 0.00 25.32 3.32 68.80 1.03 G 富磷相 12.31 0.00 8.63 31.74 47.01 0.31 RO相 4.36 0.00 0.38 1.55 0.00 93.71 基体相 3.70 0.00 22.51 2.95 68.31 2.53
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