Production of hydrogen through the carbonation–calcination reaction applied to CH4/CO2 mixtures

The production of hydrogen combined with carbon capture represents a possible option for reducing CO2 emissions in atmosphere and anthropogenic greenhouse effect. Nowadays the worldwide hydrogen production is based mainly on natural gas reforming, but the attention of the scientific community is focused also on other gas mixtures with significant methane content. In particular mixtures constituted mainly by methane and carbon dioxide are extensively used in energy conversion applications, as they include land-fill gas, digester gas and natural gas. The present paper addresses the development of an innovative system for hydrogen production and CO2 capture starting from these mixtures. The plant is based on steam methane reforming, coupled with the carbonation and calcination reactions for CO2 absorption and desorption, respectively. A thermodynamic approach is proposed to investigate the plant performance in relation to the CH4 content in the feeding gas. The results suggest that, in order to optimize the hydrogen purity and the efficiency, two different methodologies can be adopted involving both the system layout and operating parameters. In particular such methodologies are suitable for a methane content, respectively, higher and lower than 65%.