In order to improve the quality of sinter produced by Baiyunebo iron ore concentrate,the effects of compound silicate gangue containing kalium and natrium on formation of complex calcium ferrite were studied using mini-sintering test device,optical microscope（OM） analysis and scanning electron microscope（SEM）/energy dispersive X-ray spectroscopy（EDX） analysis.The results show that with the increasing of K2O and Na2O content in sintering samples,K2O and Na2O highly enriched in the glassy phases,the contents of complex calcium ferrite and hematite in sinter decreased and the porosity increased;the mineral microstructure exhibited large cavities and thin framework and became inhomogeneous.The compound silicate gangue containing kalium and natrium significantly inhibited the generation of complex calcium ferrite（SFCA）.When the content of K2O and Na2O was higher in samples,a part of K2O and Na2O entered into complex calcium ferrite,which caused the fine grains of SFCA with acicular and columnar to agglomerate into coarse grains,and its bonding effect to iron oxides reduced.The content of K2O and Na2O in sinter had effects on quantity,composition and morphology of complex calcium ferrite.
In order to explore synthetic method of pure sodium pyroxene,the pure chemical reagents of Na2CO3,Fe（OH）3 and H2SiO3were used as raw materials,and the possible solid phase reactions for Na2CO3-Fe（OH）3-H2SiO3system in heating process had been studied by means of differential thermal analysis（DTA）and X-ray diffraction（XRD）. The influencing factors of sodium pyroxene（NaFeSi2O6）synthetic reaction,such as sintering temperature and holding time,had also been studied.The results show that sodium pyroxene can be largely synthesized at 737℃;it is helpful for synthesis of sodium pyroxene to increase sintering temperature appropriately,and the best temperature should be controlled at 900℃or so,because it will melt and decompose at temperatures higher than 900℃.In those influencing factors of sodium pyroxene synthesis the most important is temperature.The results will be helpful for providing pure NaFeSi2O6for further research on the formation of SFCA for NaFeSi2O6-KAlSi2O3-CaO-Fe2O3-CaF2 system in the sintering process of Bayan-obo iron ore.
WANG Yi-ciZHANG Jian-liangWANG Yue-congLUO Guo-ping
Influence of sintering temperature, basicity and MgO content on the formation characteristics of calcium ferrite in low silicon sinter of Baotou Iron and Steel Company was studied by means of mini-sintering test and mineralographic microscope analysis. In addition, the suitable sintering parameters such as temperature and basicity were explored. The results found that optimum temperature for the formation of calcium ferrite is 1 280℃, the basicity of 2.5-2.8 is helpful to the development of acicular or columnar calcium ferrite, and MgO content in the low silicon sintering raw materials should be lower than 2.8 % because MgO can intensively inhibit the formation of calcium ferrite. And calcium ferrite in the sinter belongs to calcium ferrite with low calcium, which is different from that in ordinary sinter at home and abroad. So, it provided theoretical basis for promoting formation of calcium ferrite in low silicon sinter and improving properties of sinter.
