The Bayer Process is the dominant industrial method to produce alumina from bauxite ore. Due to the generation of large amounts of Bauxite Residue (red mud), an alternative method, called the Pedersen Process, is of our interest. This process makes use of a combination of pyrometallurgical and hydrometallurgical techniques in order to prevent the Bauxite Residue generation. In the conventional Pedersen Process, iron in the bauxite is separated in the form of pig iron through a carbothermic smelting-reduction step which has a CO₂ emission similar to that during conventional iron production. In order to eliminate the CO₂ emission of this step, the focus of the present work is to reduce the iron oxides of bauxite ore by hydrogen gas (H₂) prior to smelting and minimizing the use of solid carbon materials for the reduction. The thermochemistry and the kinetics of reactions during calcination and direct reduction of a bauxite ore were studied by a thermogravimetric technique and in situ analysis of the gaseous products. The onset temperatures for the decomposition of bauxite components during calcination were determined. The kinetics of the reduction of hematite to metallic iron was studied and it is shown that the reduction of iron oxides to metallic iron starts at temperatures below 560 °C and it accelerates at higher temperatures. Moreover, it is indicated that the formation of hercynite (FeAl₂O₄) phase retards the complete reduction at temperatures higher than 760 °C.

中文翻译：

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H 2气体在固定床反应器中直接还原铝土矿的现象

拜耳法是从铝土矿中生产氧化铝的主要工业方法。由于产生了大量的铝土矿残留物（红泥），因此我们对另一种称为Pedersen工艺的方法感兴趣。为了防止铝土矿渣的产生，该方法利用了火法冶金技术和湿法冶金技术的结合。在常规的彼德森方法中，铝土矿中的铁通过碳热熔化-还原步骤以生铁的形式分离，该步骤具有类似于常规铁生产过程中的CO ₂排放。为了消除该步骤的CO ₂排放，本工作的重点是通过氢气（H _2）还原铝土矿矿石中的铁氧化物。），然后进行冶炼并尽量减少使用固态碳材料进行还原。通过热重技术和气态产物的原位分析研究了铝土矿煅烧和直接还原过程中的热化学和反应动力学。确定了煅烧期间铝土矿组分分解的起始温度。研究了赤铁矿还原为金属铁的动力学，结果表明，氧化铁还原为金属铁的过程始于低于560°C的温度，并在较高温度下加速。此外，表明在超过760℃的温度下，水杨铁矿（FeAl ₂ O ₄）相的形成阻碍了完全还原。