A Technical Analysis of the H₂ Purification Trains Downstream of Alkaline Electrolyzers

In view of achieving decarbonization targets, green hydrogen has emerged as a promising low-emission alternative. Typically, green hydrogen is produced by splitting water using various electrolysis technologies powered by renewable energy. Among these, alkaline electrolyzers have been proven as suitable for large-scale applications, operating effectively in alkaline environments under near-atmospheric pressure levels and temperatures. Once produced, H₂ must undergo purification for use in industrial and mobility sectors, with particularly stringent purification requirements for fuel applications. Despite the relevance of H₂ purification due to its usage as an energy carrier, no comprehensive analyses of H₂ purification trains downstream of H₂ production are available in the literature. To fill this gap, the aim of this work is to perform a detailed technical assessment of purification trains downstream of alkaline water electrolyzers, considering KOH removal, oxygen removal, compression and dehydration. Different case studies are discussed, focusing on the alkaline electrolyzer operating pressure (i.e., atmospheric or higher) and considering the application of H₂ in both the industrial and mobility sectors. The design and methodology of the process were developed within the Aspen Plus^® simulation environment, to support the electrolyzers’ integration in industrial settings.