The use of coal for ilmenite reduction to produce synthetic rutile is widespread in industry. However, the carbon dioxide emissions associated with coal combustion pose significant environmental concerns. Alternative reductants such as hydrogen have the potential to promote environmentally friendly production of green rutile. This study aimed to assess the technical feasibility of reducing an Australian secondary (weathered) ilmenite using hydrogen, focusing on the effects of reduction temperature and time. The ilmenite was composed of 65 % titanium dioxide, 29 % iron oxide, and 6 % impurities. Samples at each stage of the processing were analysed using X-ray fluorescence spectrometry (XRF) and scanning electron microscopy (SEM). The results revealed that both temperature and time impacted ilmenite reduction, with increasing values of both parameters leading to higher reduction percentages. The maximum reduction percentages were obtained for a reduction time of 240 min at all temperatures, and there was an increase from 62 % at 973 K to 99 % at 1273 K for this reduction time. A reduction percentage of 90 % was obtained at 1273 K with a holding time of 60 min. This study indicates that a minimum temperature of 1073 K is required to achieve a reduction exceeding 90 % for secondary ilmenite. The SEM analysis showed that fine, discrete, metallised iron particles were present on the surface of the reduced secondary ilmenite. The investigation into hydrogen as an alternative reductant demonstrated improved iron–titanium separation in acid leaching compared with the conventional reduction method using coal and resulted in green rutile products with titanium dioxide grades exceeding 96 %, and iron oxide content below 1 %.

中文翻译：

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通过氢还原从再生钛铁矿生产绿色金红石


使用煤还原钛铁矿以生产合成金红石在工业中很普遍。然而，与煤炭燃烧相关的二氧化碳排放会带来严重的环境问题。氢等替代还原剂有可能促进绿色金红石的环保生产。本研究旨在评估使用氢还原澳大利亚次生（风化）钛铁矿的技术可行性，重点关注还原温度和时间的影响。钛铁矿由 65% 的二氧化钛、29% 的氧化铁和 6% 的杂质组成。使用 X 射线荧光光谱法 （XRF） 和扫描电子显微镜 （SEM） 分析加工每个阶段的样品。结果表明，温度和时间都会影响钛铁矿的还原，这两个参数的值增加会导致更高的还原百分比。在所有温度下，当 240 min 的还原时间时，获得的最大还原百分比，在此还原时间内，从 973 K 时的 62 % 增加到 1273 K 时的 99 %。在 1273 K 下，保持时间为 60 分钟，获得 90% 的还原百分比。这项研究表明，对于次生钛铁矿，需要最低温度为 1073 K，才能实现超过 90% 的还原。SEM 分析表明，还原的次钛铁矿表面存在细小、离散的金属化铁颗粒。对氢作为替代还原剂的研究表明，与使用煤的传统还原方法相比，酸浸法中的铁-钛分离得到改善，并导致二氧化钛品位超过 96% 且氧化铁含量低于 1% 的绿色金红石产品。