Biogas upgrading by adsorption processes: Mathematical modeling, simulation and optimization approach - A review

Biogas is attracting more attention as a viable energy carrier and enabler for sustainable developments. Upon rapid increase in the size and number of biogas plants around the world, the associated technologies are also in transformation. Adsorption processes have played a prominent role in widespread utilization of biogas and its economical viability. Beside undeniable contribution of experimental activities in the progress of adsorption based processes for biogas upgrading, mathematical modeling and simulation methods have evolved to support further growth. This is also beholden to the considerable advancements in the capabilities of computational methods for handling complex phenomena. The present manuscript aims to review the progresses made in implementation of mathematical modeling, simulation and optimization methods for biogas upgrading with emphasis on adsorption based processes. Firstly, the significance of biogas upgrading and the role of computational methods are explained. Then, strategies and methodologies for development of mathematical models and process simulations based on the governing transport mechanisms are described considering pressure swing adsorption, vacuum pressure swing adsorption, temperature swing adsorption and fixed adsorption beds for trace removal. Based on the studies so far, these processes have offered methane purity and recovery within tunable range of 50-99% and 75-99.4%, respectively. In addition to highlighting the applications of molecular computational methods for design and analysis of various adsorbents, experiences and benefits gained from hybridization and intensification strategies are elaborated. Finally, various aspects of the techno-economical assessment of the processes are presented. The ultimate objective was to set a platform based on the achievements in the past for identification of existing gaps and providing recommendations on the potential avenues for future activities.