Biogas upgrading technologies: Energetic analysis and environmental impact assessment

Biogas upgrading for removing CO2 and other trace components from raw biogas is a necessary step before the biogas to be used as a vehicle fuel or supplied to the natural gas grid. In this work, three technologies for biogas upgrading, i.e., pressured water scrubbing (PWS), monoethanolamine aqueous scrubbing (MAS) and ionic liquid scrubbing (ILS), are studied and assessed in terms of their energy consumption and environmental impacts with the process simulation and green degree method. A non-random-two-liquid and Henry's law property method for a CO2 separation system with ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([bmim][Tf2N]) is established and verified with experimental data. The assessment results indicate that the specific energy consumption of ILS and PWS is almost the same and much less than that of MAS. High purity CO2 product can be obtained by MAS and ILS methods, whereas no pure CO2 is recovered with the PWS. For the environmental aspect, ILS has the highest green degree production value, while MAS and PWS produce serious environmental impacts.

Upgrading process for removing CO2 from biogas is necessary. In this work, three upgrading technologies, i.e., pressured water scrubbing (PWS), monoethanolamine aqueous scrubbing (MAS) and ionic liquid scrubbing (ILS), are assessed. Process simulation and green degree method are adopted to evaluate the energy consumption and environmental impacts, respectively. Thermodynamic model is established for CO2 separation system with ionic liquid. The results indicate that the specific energy consumption of ILS and PWS is almost same but much lower than that of MAS. ILS presents the highest green degree production value, while MAS and PWS produce serious environmental impacts.Figure optionsDownload as PowerPoint slide