This study evaluates the carbothermal microwave reduction of low-grade banded hematite jasper iron ore for the preparation of potential feedstock for the alternative iron-making process. The coal sample act as transparent material to microwave irradiation at low temperature, however, above 600 °C, an exponential rise in temperature with a heating rate of ~ 220 °C/min was achieved. In contrast, charcoal showed an excellent response to microwaves at low temperatures. It was found that the iron-oxide reduction with coal is lean, resulting in lower metallization; however, the higher magnetite content in the concentrate improves the iron separation efficiency compared to charcoal. The separation efficiency of 67.3 pct is achieved at 6 pct C using coking coal compared to 44.9 pct with charcoal. It is inferred that the coal can be employed as a reductant for microwave carbothermal reduction. The ferrite balls with a yield of ~ 5 pct having 95 pct purity and iron-rich concentrate with ~ 87 emu/g magnetization and ~ 37 pct metallization with 73 pct yield are achieved with 18 pct charcoal in 15 minutes. The chemically bonded hematite and quartz phase enhances the electrical resistance and thus leading to efficient heating compared to the unbonded synthetic mixture. The fayalite formation creates localized melt zones that form’ hot-spots’ for microwaves and enhances the heating rate and, consequently, the reduction kinetics.

中文翻译：

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低品位铁矿石的微波碳热还原

本研究评估了低品位带状赤铁矿碧玉铁矿石的碳热微波还原，以制备替代炼铁工艺的潜在原料。煤样在低温下充当微波辐射的透明材料，然而，在 600 °C 以上，温度呈指数上升，加热速率约为 220 °C/min。相比之下，木炭在低温下对微波表现出极好的响应。发现用煤还原氧化铁是贫的，导致金属化程度较低；然而，与木炭相比，精矿中较高的磁铁矿含量提高了铁的分离效率。使用焦煤在 6% C 下实现 67.3% 的分离效率，而使用木炭则为 44.9%。据推测，煤可用作微波碳热还原的还原剂。使用 18% 的木炭在 15 分钟内获得产量为 ~5%、纯度为 95% 的铁氧体球和具有 ~87emu/g 磁化强度和 ~37% 金属化的富铁精矿，产量为 73%。与未结合的合成混合物相比，化学结合的赤铁矿和石英相增强了电阻，从而导致有效加热。铁橄榄石的形成产生了局部熔融区，形成了微波的“热点”，并提高了加热速率，从而提高了还原动力学。使用 18% 的木炭在 15 分钟内获得产量为 ~5%、纯度为 95% 的铁氧体球和具有 ~87emu/g 磁化强度和 ~37% 金属化的富铁精矿，产量为 73%。与未结合的合成混合物相比，化学结合的赤铁矿和石英相增强了电阻，从而导致有效加热。铁橄榄石的形成产生了局部熔融区，形成了微波的“热点”，并提高了加热速率，从而提高了还原动力学。使用 18% 的木炭在 15 分钟内获得产量为 ~5%、纯度为 95% 的铁氧体球和具有 ~87emu/g 磁化强度和 ~37% 金属化的富铁精矿，产量为 73%。与未结合的合成混合物相比，化学结合的赤铁矿和石英相增强了电阻，从而导致有效加热。铁橄榄石的形成产生了局部熔融区，形成了微波的“热点”，并提高了加热速率，从而提高了还原动力学。