Abstract
One of the main challenges imposed by the climate crisis is to reduce the greenhouse gases emissions while keeping high levels of social and economic development. Therefore, the deployment of process alternatives that use residues as raw materials and integrate the conversion of by-products in added value products of interest is mandatory and integrated biorefineries play a major role in this context. In this work, thermodynamic analyses were performed to assess the conversion of a residual CO2 stream captured from the flue gases of a biomethane-based thermal power plant into syngas or methane. Results showed that the syngas production from CO2 is favored at high temperatures (>700 °C), low pressures (1 bar) and low H2/CO2 ratios (e.g. 1). Conversely, methane formation is favored at lower temperatures and higher H2/CO2 ratios. Simulations were also carried out considering the conversion of an off-gas stream from a biomethane plant, with different concentrations of CH4. Considering the syngas formation, the presence of CH4 in the feed stream enhances the CO2 conversion and increases the production of CO and H2 (desired products), while decreasing H2O formation (unwanted side product), possibly due to the simultaneous occurrence of the methane bi-reforming, RWGS and methanation reactions. Therefore, from the thermodynamic point of view, the use of the off-gas from a biomethane plant for syngas production could be a potential alternative for the destination of this residual stream, converting it into interesting chemical platforms and intermediates for fuels and chemicals production.
