Optimization and modeling of carbon dioxide absorption into blended sulfolane and piperazine aqueous solution in a stirrer reactor

In this study, carbon dioxide (CO2) absorption is investigated in blended sulfolane (TMS) and piperazine (PZ) aqueous solution in a stirrer reactor. The response surface methodology (RSM) was applied to design the experiments. The experiments were carried out in operating conditions, including PZ in range of 2–8 wt%, TMS in range of 10–30 wt%, temperature in range of 20–70 °C and CO2 partial pressure in range of 2–8 bar. The results show that CO2 loading in aqueous TMS-PZ solution increases with PZ concentration while decreases with TMS concentration. Since the studied pressure is low, the presence of TMS decreases CO2 loading in mixed solvent compared to aqueous PZ solution under the same conditions. Optimum parameters were obtained 3.95 wt% PZ, 15.01 wt% TMS, temperature of 32.5 °C and pressure of 3.5 bar. The maximum value of CO2 loading and absorption percentage under these optimal conditions were obtained 0.194 and 54.386%, respectively. In addition to experimental study, concentration of species in TMS + PZ + CO2 + H2O electrolyte system is obtained using modified Pitzer thermodynamic model. The trend of concentration is in good agreement with previous studies which obtained species concentration in PZ + CO2 + H2O system. By adding VLE equations to chemical equilibrium constant, charge and mass balances equations, it is possible to predict equilibrium CO2 loading by the model; calculated relative error between experimental and predicted loading was obtained 1.1–23.3%.