(西安建筑科技大学 冶金工程学院，西安 710055)
摘 要: 煤基直接还原-磁选技术是实现镍渣中铁资源回收的重要方法。通过预氧化改善镍渣还原特性，控制还原过程中铁颗粒的生长是该工艺的关键环节。本文以氧化率和金属化率为评价指标，研究镍渣氧化行为及氧化条件对还原效果的影响。结合XRD、SEM-EDS及Image-ProPlus图像分析，探究预氧化镍渣还原过程铁颗粒生长特性并建立铁颗粒的生长动力学模型。结果表明：预氧化技术能改变镍渣含铁物相类型，有利于提高还原产物金属化率。延长还原时间及升高还原温度能够加快还原产物中金属铁颗粒的聚集和生长速度。还原温度1373 K还原时间从30 min延长至60 min时，铁颗粒的平均尺寸由8.32 μm增加到29.44 μm。预氧化镍渣还原过程中铁颗粒生长活化能和指前因子分别为14.591 kJ/mol和3.341，控制因素为表面扩散及铁颗粒迁移。
关键字: 预氧化；镍渣；直接还原；金属铁颗粒；生长动力学
（School of Metallurgical Engineering, Xi’an University of Architecture and Technology, Xi’an 710055, China）
Abstract:The coal-based direct reduction-magnetic separation is an important process to recover iron from nickel slag. Improving the reduction characteristics of nickel slag by pre-oxidation and controlling the growth characteristics of iron particles during the reduction process are the key points of the process. In this paper, the pre-oxidation behavior of nickel slag and the influence of pre-oxidation conditions on the reduction process were investigated using the oxidation degree and the degree of metallization as the evaluation index. The growth characteristics of metallic iron particles during the reduction of pre-oxidized nickel slag were investigated by XRD, SEM-EDS and Image-Pro Plus image analysis, and the growth kinetic model of metallic iron particles was also developed. The results show that the phase containing iron in nickel slag can be changed by the pre-oxidation technique which is benefit for improving the metallization ratio of the reduced products. The aggregation and growth of metallic iron particles in the reduction products of pre-oxidized nickel slag can be accelerated as the reduction time prolonging and the reduction temperature increasing. The average sizes of the metallic iron particles increase from 8.32 μm to 29.44 μm when the reduction time is extended from 30 to 60 min at the reduction temperature of 1100 ℃. The activation energy and prefactor of iron particle growth in the reduction process of pre-oxidized nickel slag are controlled by surface diffusion and iron particle migration are 14.591 kJ/mol and 3.341, respectively.
Key words: pre-oxidation; nickel slag; direct reduction; metallic iron particles; growth kinetics
