Optimization of K₂CO₃ exposure conditions using response surface methodology for CO₂ capture with 2-methylpiperazine...

In this study, the optimization of potassium carbonate (K₂CO₃) exposure conditions for CO₂ capture with the use of 2-methypiperazine (2MPz) and monoethanolamine (MEA) as promoters was investigated. The tested operating conditions for the CO₂ capture process included the pH, temperature, K₂CO₃ dose, gas flow rate, and pressure, and their effect on the CO₂ absorption/desorption rate and CO₂ absorption efficiency was assessed. Response surface methodology (RSM) was also employed to determine the equations for the optimal long-term operating conditions. The results showed that the CO₂ absorption rate and efficiency increased under K₂CO₃ exposure with an increase in the pressure and loading rate. Moreover, for the temperature the absorption efficiency first increase and then decreases with increase in temperature, however, the with increase in temperature the faster absorption were observed with lower absorption loading rate. Furthermore, pH had a more complex effect due to its variable effects on the speciation of bicarbonate ions (HCO₃^-) and carbonate ions (CO₃^2-). Under higher pH conditions, there was an increase in the concentration of HCO₃^-, which has a higher CO₂ loading capacity than CO₃^2-. Contouring maps were also used to visualize the effect of different exposure conditions on the CO₂ absorption rate and efficiency and the role of 2MPz and MEA as promoters in the K₂CO₃ solution for CO₂ absorption. The results showed that the mean CO₂ absorption rate was 6.76 × 10^-4 M/L/s with an R² of 0.9693 for the K₂CO₃ solution containing 2MPz. The highest absorption rate (6.56-7.20 × 10^-4 M/L/s) was observed at a temperature of 298-313 K, a pressure of >2 bar, a pH of 8-9, and a loading rate of 80-120 L/h for a concentration of 1-3 M K₂CO₃ and 0.05-1.5 M 2MPz. The CO₂ absorption efficiency exhibited a variation of 56-70% under the same conditions.