CO2 absorption into potassium hydroxide aqueous solution: experimental and modeling

In this work, the CO2 absorption by potassium hydroxide aqueous solution was studied. The response surface methodology (RSM) based on central composite design (CCD) was used to design experiments, make models, and find the optimum operating conditions for attaining desirable responses in the range of temperature, pressure and absorbent concentration of 25–65 °C, 2–10 bar and 0.01–1.21 mol/lit, respectively. The effects of process variables and their interactions on the responses were investigated with the numerical model, obtained from experimental data fitting to a second-order polynomial model, to achieve the optimal conditions. The experiments and numerical model indicated that the increase in temperature and absorbent concentration decrease CO2 loading, and an increase in pressure increase CO2 loading. Optimum conditions were found to be the temperature of 35 °C, pressures of 4 bar and, KOH concentration of 0.412 mol/lit. The CO2 loading of 0.745 and CO2 removal efficiency of 32.221% were achieved in the optimal conditions. The modified Pitzer’s GE model was used for CO2 + KOH + H2O system, in order to investigate the species concentration in the liquid phase. The average relative error between predicted CO2 loading and experimental CO2 loading was 7.4%.