High performance promoter-free CO2 absorption using potassium carbonate solution in an ultrasonic irradiation system

•High frequency ultrasonic system is suggested for the CO2 capture using green solvent (potassium carbonate).•An ultrasonic-assisted absorption model has been developed in order to investigate the absorption mechanism.•Both of the physical and chemical effects are found to be the dominant factors for the absorption enhancement.

CO2 capture for power plant and natural gas purification using absorption process suffers two major drawbacks: large absorption body and high regeneration energy. The high energy penalty of absorption technology can be addressed using low heat of absorption solvent. However, the challenge of using low heat of absorption solvent is to develop a practical approach to intensify absorption rate. In recent years, high frequency ultrasonic system emerges as a potential technology for mass transfer process. In this study, the potential of using high frequency ultrasonic system have been investigated using the slow kinetic solvent: (potassium carbonate) without utilizing any chemical promoter. The ultrasonic-assisted absorption system with 20 wt% potassium carbonate (without promoter) has provides 1.75 times higher volumetric mass transfer coefficient than the Piperazine (PZ) promoted potassium carbonate using stirring method. The absorption rate has been increased up to 32 times as compared to the case without ultrasonic irradiation. Besides, the required absorption time to achieve 0.9 loading (CO2 mole/K2CO3 mole) has been significantly reduced to approximate 400 s. Furthermore, an ultrasonic-assisted absorption model has been developed by including the atomization, ultrasonic streaming, and ultrasonic chemical effect in order to investigate the mechanism involved in high frequency ultrasonic-assisted absorption. Based on the model validation study, the ultrasonic chemical effect is essential to be considered in order to match the simulated and the experimental results. The results of current study prove that, high frequency ultrasonic system possesses high potential to be utilized to enhance the absorption using promoter-free potassium carbonate.