Biogas to H_2 conversion with CO_2 capture using chemical looping technology: Process simulation and comparison to conventional reforming processes

摘要

H-2 is a clean fuel and crucial industrial substance with rapidly increasing global demand. Although the combustion and utilization of H-2 does not emit CO2, the production of H-2 from fossil fuels is associated with heavy CO2 emissions. Biogas is a renewable, carbon neutral energy source that can be potentially used as a substitute for fossil fuels for H-2 production. Furthermore, with CO2 capture, H-2 production from biogas can become CO 2 negative. However, the energy efficiency of the conversion from biogas to H-2 is usually significantly lower than natural gas-based H-2 production processes due to the energy consumption associated with CO2 separation. This study presents an iron-based chemical looping technology as an alternative pathway to convert biogas into H-2. This chemical looping process requires neither upstream biogas compression and purification, nor downstream CO2 removal and H-2 purification, hence achieving a great level of process intensification. The chemical looping process, as well as the conventional steam methane reforming and mixed reforming processes for biogas to H conversion, are simulated in ASPEN to compare their performance. This simulation study shows that the chemical looping process can directly use biogas with CO2 volume ratio ranging from 0 to 50% to achieve 13-14% (relative percentage) increase in cold gas efficiency and 15-20% (relative percentage) increase in effective thermal efficiency over conventional reforming processes.