In the ironmaking processes via the carbothermic reduction with the tall-bed reactor, the composite pellets are rapidly reduced to highly metallized direct reduced iron (DRI) with high productivity under high temperature. Without coke making and ore sintering process, carbothermic reduction are not only help broaden the selection of raw materials but an environmentally friendly approach for the ironmaking process. In this study, experiments were conducted for iron ore-coal composite pellets under four heating rates. During the reduction, the reaction was quenched at different temperatures by quickly moving the specimens to room temperature. After the experiments, we performed phase analysis by X-ray diffraction, chemical composition analysis by wet method, and microstructure observation and element distribution analysis by scanning electron microscopy with energy dispersive spectrum. The pellet morphology during the experiments was also recorded. The pellets under fast heating rates (80°C/min and 40°C/min) collapsed over 1300°C. The pellets under the slow heating rate (20°C/min) maintained their spherical morphology until 1400°C. We found that the formation and melting of fayalite (2FeO–SiO₂ or Fe₂SiO₄) played a key role in the collapsing behavior of pellets, which can be classified into three different stages, (a) between 1000°C and 1200°C, a large amount of fayalite compound (melting point at 1178°C) was formed. (b) above 1178°C, the fayalite compound started to melt and became a liquid phase. (c) between 1178°C and 1400°C, the pellets lost their strength, and collapsed due to the excess amount of liquid phase present.

在高床反应器碳热还原炼铁过程中，复合球团矿在高温下以高生产率快速还原为高度金属化的直接还原铁（DRI）。没有焦炭和矿石烧结过程，碳热还原不仅有助于拓宽原材料的选择，而且是炼铁过程的一种环保方法。本研究在四种加热速率下对铁矿-煤复合球团进行了实验。在还原过程中，通过将样品快速移至室温，在不同温度下淬灭反应。实验结束后，我们进行了 X 射线衍射的物相分析，湿法化学成分分析，用能谱扫描电子显微镜观察微观结构和元素分布分析。还记录了实验过程中的颗粒形态。在快速加热速率（80°C/min 和 40°C/min）下的颗粒会在 1300°C 以上坍塌。在缓慢加热速率 (20°C/min) 下的丸粒保持其球形形态直到 1400°C。我们发现铁橄榄石 (2FeO-SiO₂或 Fe ₂ SiO ₄ ) 在球团的崩塌行为中起关键作用，可分为三个不同阶段，(a) 在 1000°C 和 1200°C 之间，大量铁橄榄石化合物（熔点在 1178 °C) 形成。(b) 在 1178°C 以上，铁橄榄石化合物开始熔化并变成液相。(c) 在 1178°C 和 1400°C 之间，颗粒失去强度，并由于存在过量的液相而坍塌。