New Design of a Separator Unit with Metal Hydride and an Analysis of Its Potential Application in the Process of Hydrogen Separation from a Binary Mixture of Gases

Abstract

Synthesis gases produced in the processes of the high-temperature gasification of otherwise unusable waste, with the use of technologically efficient and cost-effective separation methods, may represent a reliable source of hydrogen intended for applications in the industry and the transport segments. One of the possible solutions to the separation of hydrogen from a mixture of gases is the use of metal hydride (MH) alloys, which are capable of binding hydrogen into their structure. This is the subject of the present article, in which a new design is presented for a fully functional system and a hydrogen separator unit, and the potential application of a commonly available metal hydride alloy in the separation of hydrogen from a binary mixture containing carbon dioxide and hydrogen is discussed. Load testing of the selected type of metal hydride alloy with a high concentration of carbon dioxide in the mixture, representing 40 vol. % and 4 vol. %, was performed. In addition, testing the alloy’s ability to separate hydrogen from a mixture containing H2 and CO2 was conducted using small alloy samples and a newly designed hydrogen separator unit. The resulting higher purity of hydrogen after the separation was confirmed by an experiment, in which the hydrogen concentration in the resulting mixture increased by 2.7 vol. %. The purity of the desorbed hydrogen amounted to 99.4 vol. %. The testing also confirmed a high degree of degradation of the alloy, caused by the poisoning effect of CO2 on the selected alloy type. There was also a significant decrease in the absorption ability of the alloy—from 1.7 wt. % to 1.2 wt. %—and a significant extension of the absorption time caused by the slower kinetics of the hydrogen storage, which occurred as early as after ten absorption–desorption cycles.