Demonstration of water-lean 30 wt% MEA + 15 wt% MEG with rich solvent recycle for biogas upgrading

This study investigates the potential of a water-lean 30 wt% monoethanolamine (MEA) solvent for biogas upgrading. The solvent consists of 30 wt% MEA, 15 wt% monoethyleneglycol (MEG), and 55 wt% water at zero loading. The solvent is investigated using a mobile pilot scale amine scrubbing unit, with a capacity of 1 ton CO per day, with the option to utilize a rich solvent recycle (RSR) configuration. Without the RSR configuration, the water-lean solvent obtains a low rich loading of 0.46 mol/mol resulting in a specific reboiler duty (SRD) of 3.92 MJ per kg CO, which is 6 % higher compared to aqueous 30 wt% MEA. Combining the RSR configuration with cooling enables a higher rich loading of 0.49 mol/mol and decreases the SRD to 3.48 MJ per kg CO, which is 6% lower than for aqueous 30 wt% MEA. It is found that 30 wt% MEA + 15 wt% MEG only achieves lower SRD than aqueous 30 wt% MEA if similar rich loading can be achieved. By measuring emissions from the absorber and stripper columns, it was found that MEG and MEA form 2-methyl-dioxolane resulting in increased emissions when utilizing this water-lean solvent.