Experimental investigation of CO2 solubility and its absorption rate into promoted aqueous potassium carbonate solutions at elevated temperatures

Abstract

Aqueous potassium carbonate solutions are suitable for capturing CO2 from flue gases and process gases with a low heat duty for regeneration. However, their absorption rate and capacity can be further improved by promoters. In this study, an experimental investigation of CO2 solubility and absorption rate into pure and promoted potassium carbonate solutions in a batch stirred reactor at elevated temperatures is presented. Measurements for pure K2CO3 solvents were carried out at 80 °C, 100 °C and 120 °C for 1.81 M and 2.53 M potassium carbonate concentrations. Solubility results were successfully validated against electrolyte-NRTL model predictions. The experiments were also used to provide a reference for evaluating the effect of promoter addition on CO2 solubility and absorption rate. Subsequently, four additives, namely Methyl diethanolamine (MDEA), Monoethanolamine (MEA), Piperazine (PZ) and Glycine were tested at various concentrations in a 1.81 M potassium carbonate solution at a temperature range of 100–120 °C. Results indicated an increase in solvent capacity and absorption rate for PZ- and MEA-promoted K2CO3 solutions. Glycine addition benefits the absorption rate mostly at low loadings, although the solvent capacity is not affected positively. MDEA has a detrimental effect on solvent capacity at higher concentrations, while no positive effect on absorption rate was found.