A sample of limonitic nickel ore was characterized by XRD, SEM-EDS, and ICP-OES techniques. The Rietveld refinement method showed that the main mineral constituent of this sample is goethite (55.8 pct). Thermal analysis experiments were performed and the determination of the goethite content in the sample could be confirmed by the mass loss associated to the dehydroxylation of this mineral at temperature of ≈ 150 °C. After thermal decomposition, the sample was reduced in a rotary kiln using hydrogen and subsequent characterization showed that for low temperatures (400 °C ≤ T < 550 °C) the main chemical reaction is the reduction of hematite to magnetite. At high temperatures (500 °C ≤ T < 800 °C), metallic iron could be identified in the solid product of the reaction by XRD technique and reduction of hematite to metallic iron was the main chemical reaction identified at this temperature. In addition to metallic iron, tetrataenite was identified and quantified in the reduced sample at high temperature (T > 600 °C) and the results suggest that most of the nickel is in this mineral phase. The shrinking core model was used for the kinetic studies of the reduction process and for the reduction of hematite to magnetite at low temperature (T ≤ 550 °C). The slow step was diffusion of reagent (H2) or product (H2O) through the reduced solid product layer on the particle surface, the apparent activation energy calculated for the reaction was 46.2 kJ. For the reduction of hematite to metallic iron at high temperature (T ≥ 550 °C), the slow step was the reaction of hydrogen with hematite at the reaction surface of the particle, and the apparent activation energy achieved by the chemical reaction was 29.5 kJ.

中文翻译：

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氢还原褐铁矿镍矿的动力学研究

褐铁矿镍矿样品通过 XRD、SEM-EDS 和 ICP-OES 技术进行了表征。Rietveld 精炼方法表明该样品的主要矿物成分是针铁矿 (55.8 pct)。进行了热分析实验，样品中针铁矿含量的测定可以通过与该矿物在 ≈ 150 °C 温度下脱羟基相关的质量损失来确认。热分解后，样品在回转窑中使用氢气还原，随后的表征表明，对于低温（400 °C ≤ T < 550 °C），主要的化学反应是赤铁矿还原为磁铁矿。在高温下（500 °C ≤ T < 800 °C），通过XRD技术可以在反应的固体产物中鉴定出金属铁，赤铁矿还原为金属铁是在该温度下鉴定的主要化学反应。除了金属铁，在高温 (T > 600 °C) 还原的样品中还鉴定并量化了四砟石，结果表明大部分镍都在这种矿物相中。收缩核心模型用于还原过程的动力学研究以及赤铁矿在低温（T ≤ 550 °C）下还原为磁铁矿的过程。缓慢的步骤是试剂 (H2) 或产物 (H2O) 通过颗粒表面的还原固体产物层扩散，计算的反应表观活化能为 46.2 kJ。用于在高温下（T≥550℃）将赤铁矿还原成金属铁，