Mathematical modeling for cryogenic upgrading of biogas and carbon capture

Biogas is used for various energetic purposes: Electricity generation, thermal purposes, replacement of fossil fuels in vehicles, injection into natural gas distribution networks and injection into blast furnaces to replace coke and pulverized coal. However, for the various uses, it is necessary to purify the biogas. The purification of biogas essentially involves the removal of CO2. When the CO2 is removed, the relative density of the gas decreases and the calorific value increases. Technologies for purifying biogas are commercially available, such as: Amine scrubbing, water scrubbing, pressure swing adsorption (PSA), membrane separation, and organic solvent washing. The use of cryogenics for biogas purification is still an emerging technology. In this context, the mathematical modeling of a cryogenic upgrading plant for the production of biomethane using Aspen Plus was carried out in this paper. The final results of the mathematical modeling show that it is possible to produce biomethane with a purity of 99.6% and to store CO2 with a purity of 92.3%, which could be used for the production of microalgae in photobioreactors and in MAG welding processes.