Process optimization and mechanism study of ionic liquid-based mixed amine biphasic solvents for CO2 capture in biogas upgrading procedure

Abstract

This study focused on enhancing the efficiency of methane upgrading and reducing energy consumption in the biogas upgrading process through the use of biphasic solvents. An aqueous-based biphasic solvent, comprising methyl monoethanolamine (MMEA), N-methyldiethanolamine (MDEA), and 1-butyl-3-methylimidazolium tetrafluoroborate (ItFB), was meticulously prepared. The biogas upgrading effect, regeneration efficiency, regeneration energy consumption, economic viability, selectivity, and phase separation characteristics of this absorbent were systematically analyzed. Various parameters, including different inlet flow rates, stirring rate, methane inlet concentrations, reaction temperatures, and amine mixing ratios, were adjusted to investigate their impact. A comprehensive evaluation was conducted on the biogas upgrading effect and substance migration trends of the biphasic solvent. Optimal process parameters were determined, demonstrating the favorable impact of the biphasic solvent on biogas upgrading. The upgraded gas achieved a methane purity exceeding 96%, and the regeneration energy consumption decreased by 44.27% compared to 30 wt.% MEA, resulting in a more than 50% improvement in economic efficiency. The interaction between the ionic liquid and carbamate facilitated the phase separation process, with carbon enrichment after separation exceeding 95%. This enhancement significantly contributed to the improvement of regeneration energy consumption. The study thus concludes that biphasic solvents, exemplified by the described aqueous-based solution, offer a promising avenue for effective biogas upgrading with notable advancements in economic and energy efficiency.