工程科学学报，第40卷，第6期：679689,2018年6月 Chinese Journal of Engineering,Vol.40,No.6:679-689,June 2018 DOI:10.13374/j.issn2095-9389.2018.06.005:http://journals.ustb.edu.cn 某低品位铁矿回转窑还原结圈物特性及其形成机制 黄柱成，沈雪华，易凌云四，朱顺伟，钟荣海 中南大学资源加工与生物工程学院，长沙410083 ☒通信作者，E-mail:ylycsuc@126.com 摘要回转窑结圈一直以来是制约煤基回转窑直接还原工艺发展的重要因素，以某低品位铁矿回转窑还原结圈物为研究 对象，深入研究回转窑结圈物的特性及其形成机制.从结圈物的宏观形貌、物化性能、软熔特性和微观结构入手对某低品位铁 矿球团回转窑结圈物的特性进行分析，并结合热力学相图、化学物相及能谱分析研究了结圈物的形成机制.结果表明：结圈物 由熔融物包裹球团形成，接近窑壁，其熔融包裹物增多，结圈物中MFe、CO含量明显增大，软熔温度越低：由球团粉末中Fe0 与Si0,形成的铁橄榄石及煤灰带入的C0而形成的钙铁辉石低熔点相是造成结圈的主要原因：低熔点相的存在同时也促进 了金属化球团间铁晶粒的相互扩散与迁移，从而加剧了结圈现象。 关键词回转窑结圈：软熔温度：低熔点物质：铁晶粒迁移：结圈机制 分类号TF046.2 Properties and formation mechanism of rings during rotary kiln reduction of low-grade iron ore HUANG Zhu-cheng,SHEN Xue-hua,YI Ling-yun,ZHU Shun-wei,ZHONG Rong-hai School of Minerals Processing and Bioengineering,Central South University,Changsha 410083,China Corresponding author,E-mail:ylycsu@126.com ABSTRACT To ease the imbalance between the supply and demand for iron ore in the ferrous industry of China,a low-temperature reduction process via an ore-coal composite method was developed to recover iron from low-grade iron-ore resources (about 30%).In addition,industrial tests on this new reduction process were performed using a rotary kiln (l.5 mx 15 m).However,rings were formed in the rotary kiln after some days of operation,and these rings affected normal operation.Ring formation during rotary kiln re- duction has become a restraining factor for development of coal direct reduction processes using rotary kilns.Previous studies have mainly focused on the reduction process of high-grade ore (>60%)for direct-reduced iron production.The manner in which high- grade ore reduction differs from low-grade ore reduction is unclear.So,the characteristics of the ring samples need to be studied prima- rily.Then,the characteristics that affect the formation mechanisms of the rings need to be investigated.Accordingly,relative operation may be developed and ring formation may be prevented.In this paper,ring samples formed in a rotary kiln during a low-grade iron-ore reduction process were studied.The characteristics and formation mechanisms of the ring samples were investigated in detail.The char- acteristics for ring samples collected from different positions in the rotary kiln were analyzed from the aspects of macro morphological, physical,and chemical compositions,softening and melting properties,and microstructural properties.Thermodynamic phase dia- grams,scanning electron microscopy coupled with energy dispersive X-tay spectroscopy,X-ray diffraction,and chemical phase analy- ses were applied to reveal the ring formation mechanism during the rotary kiln reduction process.Results show that rings mainly com- prise pellets and molten wrappage surroundings.The amount of molten wrappages and the proportions of MFe and CaO increase in the ring samples that are next to the kiln wall.The results also show that the ring samples exhibit lower softening and melting temperatures 收稿日期：2017-08-08 基金项目：国家自然科学基金资助项目(51504230)工程科学学报，第 40 卷，第 6 期: 679--689，2018 年 6 月 Chinese Journal of Engineering，Vol． 40，No． 6: 679--689，June 2018 DOI: 10． 13374 /j． issn2095--9389． 2018． 06． 005; http: / /journals． ustb． edu． cn 某低品位铁矿回转窑还原结圈物特性及其形成机制 黄柱成，沈雪华，易凌云，朱顺伟，钟荣海 中南大学资源加工与生物工程学院，长沙 410083  通信作者，E-mail: ylycsu@ 126． com 摘 要 回转窑结圈一直以来是制约煤基回转窑直接还原工艺发展的重要因素，以某低品位铁矿回转窑还原结圈物为研究 对象，深入研究回转窑结圈物的特性及其形成机制． 从结圈物的宏观形貌、物化性能、软熔特性和微观结构入手对某低品位铁 矿球团回转窑结圈物的特性进行分析，并结合热力学相图、化学物相及能谱分析研究了结圈物的形成机制． 结果表明: 结圈物 由熔融物包裹球团形成，接近窑壁，其熔融包裹物增多，结圈物中 MFe、CaO 含量明显增大，软熔温度越低; 由球团粉末中 FeO 与 SiO2形成的铁橄榄石及煤灰带入的 CaO 而形成的钙铁辉石低熔点相是造成结圈的主要原因; 低熔点相的存在同时也促进 了金属化球团间铁晶粒的相互扩散与迁移，从而加剧了结圈现象． 关键词 回转窑结圈; 软熔温度; 低熔点物质; 铁晶粒迁移; 结圈机制 分类号 TF046. 2 收稿日期: 2017--08--08 基金项目: 国家自然科学基金资助项目( 51504230) Properties and formation mechanism of rings during rotary kiln reduction of low-grade iron ore HUANG Zhu-cheng，SHEN Xue-hua，YI Ling-yun ，ZHU Shun-wei，ZHONG Ｒong-hai School of Minerals Processing and Bioengineering，Central South University，Changsha 410083，China  Corresponding author，E-mail: ylycsu@ 126． com ABSTＲACT To ease the imbalance between the supply and demand for iron ore in the ferrous industry of China，a low-temperature reduction process via an ore-coal composite method was developed to recover iron from low-grade iron-ore resources ( about 30% ) ． In addition，industrial tests on this new reduction process were performed using a rotary kiln ( 1. 5 m × 15 m) ． However，rings were formed in the rotary kiln after some days of operation，and these rings affected normal operation． Ｒing formation during rotary kiln re￾duction has become a restraining factor for development of coal direct reduction processes using rotary kilns． Previous studies have mainly focused on the reduction process of high-grade ore ( ＞ 60% ) for direct-reduced iron production． The manner in which high￾grade ore reduction differs from low-grade ore reduction is unclear． So，the characteristics of the ring samples need to be studied prima￾rily． Then，the characteristics that affect the formation mechanisms of the rings need to be investigated． Accordingly，relative operation may be developed and ring formation may be prevented． In this paper，ring samples formed in a rotary kiln during a low-grade iron-ore reduction process were studied． The characteristics and formation mechanisms of the ring samples were investigated in detail． The char￾acteristics for ring samples collected from different positions in the rotary kiln were analyzed from the aspects of macro morphological， physical，and chemical compositions，softening and melting properties，and microstructural properties． Thermodynamic phase dia￾grams，scanning electron microscopy coupled with energy dispersive X-ray spectroscopy，X-ray diffraction，and chemical phase analy￾ses were applied to reveal the ring formation mechanism during the rotary kiln reduction process． Ｒesults show that rings mainly com￾prise pellets and molten wrappage surroundings． The amount of molten wrappages and the proportions of MFe and CaO increase in the ring samples that are next to the kiln wall． The results also show that the ring samples exhibit lower softening and melting temperatures