Direct Reduction Behaviors of Composite Binder Magnetite Pellets in Coal-based Grate-rotary Kiln Process
Direct Reduction Behaviors of Composite Binder Magnetite Pellets in Coal-based Grate-rotary Kiln Process
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DOI：
10.2355/isijinternational.51.214
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发表时间：
2011-02
影响因子：
1.8
通讯作者：
De‐qing Zhu;Vinicius Mendes;Vinicius Mendes;T. Chun;Jian Pan;L. Qihou;Jian Li;G. Qiu
中科院分区：
文献类型：
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作者：
De‐qing Zhu;Vinicius Mendes;Vinicius Mendes;T. Chun;Jian Pan;L. Qihou;Jian Li;G. Qiu
直接还原铁是电弧炉冶炼优质特殊钢的必要炉料。作为直接还原工艺的替代方案，中南大学创新性地开发了链篦机-回转窑煤基复合粘结剂磁铁矿球团直接还原工艺，并投入生产。在模拟煤基链篦机-回转窑工艺条件下，研究了复合粘结剂磁铁矿球团的直接还原行为。在管式炉中，以非炼焦煤为还原剂，直接还原磁铁精矿和复合粘结剂组成的预热球团和以膨润土为粘结剂组成的氧化物球团，通过测定还原度、抗压强度变化、气孔率、物相变化和显微结构，研究了球团的还原行为。结果表明，预热球团的还原性明显好于焙烧球团。预热球团的上级还原性应归因于其较高的有效扩散率，由于较高的孔隙率。预热球团还原30 min后抗压强度迅速上升，还原结束时达到较高值，金属化球团表面光滑完整，而焙烧球团还原金属化球团抗压强度较低，裂纹和断口较多。由于复合粘结剂的多重作用，预热后的球团具有自固化功能，消除了球团在还原过程中的裂纹和断裂，保持了球团的完整性，抑制了还原粉化，防止了回转窑内的结瘤。
Directly reduced iron is an imperative burden for EAF (electric arc furnace) to make good quality and special steel. As an alternative of direct reduction processes, an innovative coal-based direct reduction of composite binder magnetite pellets in grate-rotary kiln has been developed at Central South University and put into operation. A study of the direct reduction behaviors of composite binder magnetite pellets was carried out in a simulating coal-based grate-rotary kiln process in this paper. Preheated pellets made of magnetite concentrate and composite binder and fired oxide pellets containing bentonite as binder were directly reduced using non-coking coal as reductant in a tube furnace, and their reduction behaviors have been demonstrated by measuring reducibility, variations of compress strength, porosity, phases changes and micro structure under XRD, SEM and optical microscopy. It is shown that preheated pellets possess much better reducibility than fired oxide pellets. Superior reducibility of preheated pellets should be ascribed to their higher effective diffusivity due to higher porosity. The compressive strength of preheated pellets climbs quickly after reducing for 30 min and achieve a high value at the end of reduction, leading to smooth and intact metallized pellets whereas the compressive strength of metalized pellets from reducing of fired pellets is much lower, more cracks and fractures being formed. The preheated pellets possess self-curing function because of the multiple functions of composite binder, eliminate cracks and fractures and keep pellets intact during reducing, depressing reduction degradation and preventing accretion in rotary kiln.