A model of iron ore sintering was built with consideration of fuel combustion,catalysis of sinter mixture as well as formation of melt and mineral,which was verified via sintering pot tests and showed a good fit to the experimental results.The effect of bed depth on temperature was reflected by the residence time in high-temperature zone,rather than the top value of the temperature,which was weakened by melt formation as well as hematite decomposition.Moreover,the effect of bed depth,fuel content and distribution on sintering process was different,which was reflected by temperature profiles and the rule of calcium ferrite formation.The formation of melt as well as magnetite was a process which was decided by kinetic factors,while the formation of calcium ferrite was related to fuel blending conditions,which is determined by thermodynamics when the fuel ratio inside sinter granules is low or fuel content is high,otherwise,it is determined by kinetics.
The relationship of time to minerals composition in sinters is investigated by mineragraphy are claritied observation and component analysis, and the effects of temperature and atmosphere on mineralization process. Results are obtained as follows. The initial melt forms below the eutectic temperature of CaO·Fe2O3 and CaO·2Fe2O3, which is complex substance containing Ca, Fe, Si and Al, rather than the binary calcium ferrite melt. Minerals composition of binding phase is related to local content of silica in melt, which is influenced by temperature. Appearance of the melt promotes the transition from hematite to magnetite, which then alters the mechanism of calcium ferrite formation. Before the formation of magnetite, the contents of Fe and Ca within the multiple calcium ferrite decrease with temperature, but in the case of magnetite presence, the content of Fe increases solely with increase of temperature and decrease of oxygen potential. Temperature and atmosphere determine minerals composition together, and bring influence on sintering process in different ways. It can be deduced that temperature affects kinetics of the mineralization process, but atmosphere just plays a role in thermodynamics.
ZHANG Jun, GUO Xing-min, HUANG Xue-jun (State Key Laboratory of Advanced Metallurgy and School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China)
ZrOCl2·8H2O and ZrO(NO3)2·2H2O were used respectively to synthesize a NASICON solid electrolyte by a sol-gel method. The structure and properties of two samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS). The crystal structure was investigated by the Rietveld refinement. It is found that both the samples contain a monoclinic C2/c phase as the main conductive phase with the lattice parameters of a=1.56312 nm, b=0.90784 nm and c=0.92203 nm, though a small amount of rhombohedral phase is also detected in the final product. The sample synthesized by ZrO(NO 3 ) 2 ·2H 2 O contains more monoclinic phase (89.48wt%) than that synthesized by ZrOCl 2 ·8H 2 O (74.91wt%). As expected, the ionic conductivity of the latter is higher than that of the former; however, the activation energy of the latter (0.37 eV) is slightly higher than that of the former (0.35 eV).
Heng-yao DangXing-min GuoYong-ping HuangJiang-qi Rong
采用溶胶-凝胶法制备Y0.06Sr0.94Ti1-xFexO3-δ（x为原子分数。x=0.2，0.3，0.4，0.5）混合导体材料，用X射线衍射（XRD）分析该材料的物相，采用交流阻抗法和电子阻塞电极法分别测定其总电导率与离子电导率，研究铁含量对Y0.06Sr0.94TiO3混合导体材料的结构及电性能的影响。结果表明该材料属于单一立方相钙钛矿结构；在测试温度范围内，Y0.06Sr0.94Ti1-xFexO3-δ的总电导率和离子电导率都随温度升高而增大；随 Fe 掺杂量增加，总电导率和离子电导率都增大。在800℃下Y0.06Sr0.94Ti1-xFexO3-δ（x=0.2，0.3，0.4，0.5）的总电导率为0.019～0.12 S/cm，离子电导率为0.0106～0.0153 S/cm。根据传导活化能可以看出，x从0.3增加到0.4时材料的传导机制发生改变。
