Abstract:

The metal hydride (MH) method is viewed as one of the promising methods for hydrogen purification. The properties of MH materials will be significantly degenerated by the poisoning effect of impurity gases, especially for CO with strong effect. However, the present work in MH reactor level mainly focuses on some impurities with relatively insignificant effect yet, such as CH₄, CO₂, N₂, etc. To gain further insight into the reaction-separation behaviours of MH reactor running in by-product mixture, a flow-through type MH reactor filled with LaNi_4.3Al_0.7 is designed to separate hydrogen from mixture containing 0.1%CO and 39.9%CO₂. The effects of operating parameters such as temperature and pressure are systematically investigated for performance optimization. The optimum temperature of heat transfer fluids during hydrogen absorption process is found to be about 120℃, which keeps a balance between better anti-poisoning ability in high temperature and greater reaction driving force in low temperature. The experimental results also indicate that the optimum hydrogen partial pressure in the mixture gas should be about 0.84 MPa, due to the insignificant improvement of higher pressure. In addition, self-produce hydrogen purging is conducted to remove the impurity. The results of the experiment found clear support for the superiority of self-produce hydrogen purging for the MH reactor running in by-product mixture. Unexpectedly, purging the MH reactor with pure hydrogen for impurity replacement only leads to negligible improvement for impurity remove. A possible explanation is that molecular diffusion and desorption of impurities on the MH surface play a more important role for impurity transport and separation in MH reactor, rather than the viscous flow. The final hydrogen purity can reach 99.999% through self-produced hydrogen purge, and the hydrogen recovery rate can reach 77.6%, which shows the broad application prospects of metal hydride absorption separation method in the field of hydrogen separation and purification.

Key words: metal hydride, hydrogen purification, poisoning effect, performance optimization

摘要：

设计了一种填充LaNi_4.3Al_0.7的流通式金属氢化物反应器，用于从含0.1%CO和39.9%CO₂的混合气中分离提纯高纯氢，并系统实验研究了温度、压力等参数对装置分离纯化性能的影响。结果表明，吸氢过程中换热介质最佳温度约为120℃，旨在平衡高温下强抗中毒性和低温下强反应驱动力；混合气氢分压0.84 MPa被确定为较优工况。此外提出自产氢气吹扫以去除杂质并通过实验测试其性能，相比外加纯氢吹扫（主要通过黏性流促进杂质分离），自产氢气吹扫去除杂质效果更佳，其机理在于强化杂质表面脱附及分子扩散。通过自产氢气吹扫最终氢气纯度可达99.999%，氢气回收率达77.6%，展示了金属氢化物吸收分离法在氢分离提纯领域的广阔应用前景。

关键词: 金属氢化物, 氢气纯化, 中毒效应, 优化设计