Thermodynamic, economic, and emissions assessment of integrated power to methanol concept with membrane-based biogas up-gradation and plasma electrolysis

Abstract

The utilization of carbon dioxide to create valuable products such as methanol shows promise for addressing the issue of carbon emissions and global warming. Concurrently, it provides a solution to the intermittency and security of renewable energy supply via the water-splitting hydrogen production process. This power-to-methanol concept has gained increased attention because methanol is a liquid that can be conveniently stored and transported under ambient conditions. While direct air capture is an expensive solution, the carbon dioxide readily available from biogas can serve as a win-win situation. Similarly, water electrolysis technologies have modular, operational, and production challenges. In the present study, carbon dioxide was sourced from biogas via membrane separation, whereas H-2 was produced using plasma electrolysis. The entire power-to-methanol scenario was simulated using Aspen Plus v11. High purity and recovery of carbon dioxide and methane (99.51 mol.% and 98.29% and 98.88 mol.% and 99.68%, respectively) were achieved via membrane separation. The plasma reactor supplied H-2 with a mass yield of similar to 50%. Pure methanol (99.97%) was produced with a perpass conversion of 19.91% (15.7% higher than the base case). A detailed exergy analysis was performed on the process, highlighting the losses in heaters, separators, and reactors. Subsequent heat integration resulted in energy savings of 6.6%, while wind power as an energy source yielded carbon-neutral emissions. This conceptual study showcases the tremendous potential of the concept of zero-carbon-emission methanol production.