Renewable hydrogen production from biogas using iron-based chemical looping technology

Abstract

An integrated recycling waste bioenergy and manufacturing low-carbon hydrogen by a method to convert biogas to hydrogen based on the chemical looping concepts was proposed in this study. Biogas from biomass anaerobic digestion and pyrolysis was employed in the reduction step as the feedstock of fuel gas. Simulated marsh gas (CH4 and CO2) and pyrolysis gas (CO and H2) were used to validate the feasibility of the reduction performance with iron (III) oxide at different reaction temperatures. The experiments were conducted by using a thermogravimetric analyzer and a tandem packed-bed reactor. As for marsh gas, the reaction behavior was completely different under different CO2 concentrations and converting temperatures. The reduction reaction with CH4 would be divided into three stages, including complete combustion, competition reaction, and partial oxidation stage. Furthermore, the syngas with a tailored ratio of 1:1 can be produced without CH4 breakthrough by adjusting CO2 concentration. Besides, the total H2 production achieved 241.9 mL per gram of oxygen carrier with a purity of 98.29%. Regarding the pyrolysis gas, the solid conversion and CO breakthrough curve were investigated. Compared to a single reactor, seven reactors were required to increase the average solid conversion from 34.1% to 42% and reduced the total redox time from 705.6 min to 437.7 min. Overall, this study provided a link between waste bioenergy recycling and H2 generation with a novel chemical looping hydrogen generation (CLHG) system and supplied theoretical support for scaling up the packed-bed reactor to improve H2 production efficiency.