Cryogenic technology for biogas upgrading combined with carbon capture - a review of systems and property impacts

CO2 makes a major contribution to the climate change, and biomass renewable energy and carbon capture and storage (CCS) can be deployed to mitigate the CO2 emission. Cryogenic process for biogas upgrading combined with carbon capture is one of the most promising technologies. This paper reviewed the state-of-the-art of cryogenic systems for biogas upgrading combined with carbon capture, and introduced the status and progress of property impacts on the cryogenic systems with emphasize on phase equilibrium. The existing cryogenic systems can be classified as flash liquefaction system, distillation system, and liquefaction combined with desublimation system. The flash liquefaction system produces biomethane and CO2 in lower purity than the other two systems. Thermodynamic optimization on the flash liquefaction system and liquefaction combined with desublimation system should be done further, and comprehensive comparison between three cryogenic systems needs to be carried out. As to the phase equilibrium, PR EOS is safe to be used in predicting VLE and SVLE with an independent thermodynamic model describing the fugacity of the solid phase. However, the impacts of binary mixing parameter, different EOS models and mixing rules, on the performance of the cryogenic system need to be identified in the future. (C) 2017 The Authors. Published by Elsevier Ltd.