十字路口的绿色钢铁：铁矿石的混合氢基还原
Green steel at its crossroads: hybrid hydrogen-based reduction of iron ores
摘要：
钢铁和炼钢产生了全球约7%的二氧化碳排放量，这是由于使用碳来还原铁矿石。用氢代替碳作为还原剂提供了减少排放的途径。然而，使用可再生能源生产氢气仍然是一个瓶颈，因为要使每年18亿吨的粗钢产量可持续发展，每年至少需要约9700万吨绿色氢气。使炼铁行业更具可持续性的另一个基本方面在于绿色氢气和能源的最佳利用，从而减少成本高昂的过程中氢气回收工作。因此，我们在这里展示了如何通过两种技术的知识组合来显着提高铁矿石还原过程中的氢气和能源消耗效率：在低温下通过固态直接还原（DR）将矿石部分还原到动力学定义的程度，随后在还原等离子体下将其熔化并完全转化为铁（即通过氢等离子体还原，HPR）。结果表明，这两种技术之间的最佳过渡点发生在它们的氢利用效率相等的地方。我们发现，经由DR通过磁铁矿将赤铁矿还原成方铁矿是清洁且有效的，但是当铁在铁矿石球团的最外层形成时，其变得缓慢且低效。相反，HPR开始暴力和不稳定的电弧离域，但顺利和有效地处理半还原氧化物时。我们进行了混合还原实验，通过在700°C下通过DR将赤铁矿球团部分还原至38%的整体还原（使用标准热重分析系统），随后将它们转移至HPR，在电弧熔炼炉中用Ar-10%H2的气体混合物进行，以实现转化为液态铁。
英文摘要：
Iron- and steelmaking cause ~7% of the global CO2 emissions, due to the use of carbon for the reduction of iron ores. Replacing carbon by hydrogen as the reductant offers a pathway to reduce emissions. However, production of hydrogen using renewable energy will remain a bottlenecks, because making the annual crude steel production of 1.8 billion tons sustainable requires a minimum amount of ~97 million tons of green hydrogen per year. Another fundamental aspect to make ironmaking sector more sustainable lies in an optimal utilization of green hydrogen and energy, thus reducing efforts for costly in-process hydrogen recycling. We therefore demonstrate here how the efficiency in hydrogen and energy consumption during iron ore reduction can be dramatically improved by the knowledge-based combination of two technologies: partially reducing the ore at low temperature via solid-state direct reduction (DR) to a kinetically defined degree, and subsequently melting and completely transforming it to iron under a reducing plasma (i.e. via hydrogen plasma reduction, HPR). Results suggest that an optimal transition point between these two technologies occurs where their efficiency in hydrogen utilization is equal. We found that the reduction of hematite through magnetite into wustite via DR is clean and efficient, but it gets sluggish and inefficient when iron forms at the outermost layers of the iron ore pellets. Conversely, HPR starts violent and unstable with arc delocalization, but proceeds smoothly and efficiently when processing semi-reduced oxides. We performed hybrid reduction experiments by partially reducing hematite pellets via DR at 700°C to 38% global reduction (using a standard thermogravimetry system) and subsequently transferring them to HPR, conducted with a gas mixture of Ar-10%H2 in an arc-melting furnace, to achieve conversion into liquid iron.
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