Optimization of K2CO3 exposure conditions using response surface methodology for CO2 capture with 2-methylpiperazine and monoethanolamine as promoters

Abstract

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 (CO32−). Under higher pH conditions, there was an increase in the concentration of HCO3−, which has a higher CO2 loading capacity than CO32−. 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.