ABSTRACT

A novel setup of fluidized bed was developed to study the reduction of iron oxides by pure hydrogen. The setup enabled the introduction of powder directly to pure hydrogen atmosphere at experimental temperature. The arrangement was to minimize the experimental uncertainties due to gas switching. Hematite and magnetite powders were studied in the temperature range of 768-888 K. Reduction rates of the two powders were found to be similar. For both powders, the reduction rates were very high before the O/Fe ratio reached 0.5. Thereafter, the reduction was sluggish. SEM analyses revealed that the later stages of reaction was controlled by diffusion through the product layer on bigger particles, irrespective of the type of oxide powder. The results have indicated that both hematite and magnetite powder could be employed in fluidized bed. The results have also suggested that process optimization is essential regarding the sluggish reaction below 0.5 O/Fe ratio.

摘要

开发了一种新的流化床装置来研究纯氢对氧化铁的还原。该设置能够在实验温度下将粉末直接引入纯氢气氛中。这种安排是为了最大限度地减少由于气体切换引起的实验不确定性。在 768-888 K 的温度范围内研究了赤铁矿和磁铁矿粉末。发现两种粉末的还原率相似。对于这两种粉末，在 O/Fe 比达到 0.5 之前，还原率非常高。此后，减持缓慢。SEM 分析表明，无论氧化物粉末的类型如何，反应的后期阶段都是通过较大颗粒上的产物层扩散来控制的。结果表明，赤铁矿和磁铁矿粉均可用于流化床。