Development of nanoemulsion CO2 absorbents in an impinging stream rotating packed bed reactor

Suspended nanodroplets affect the transfer process within fluids through micro-perturbation or micro-convection effects. Therefore, adding dispersed nanodroplets as the dispersed phase into the liquid phase to form nanoemulsions can enhance the CO 2 absorption process. The quality of nanoemulsions mainly depends on the emulsification equipment. Traditional physical mechanical effects can only achieve large-scale macroscopic mixing, which usually takes a long time to complete, resulting in issues such as low production efficiency, batch operation, and long preparation cycles. This paper uses an impinging stream-rotating packed bed as a reactor, with span60 and tween60 as surfactants, and adopts a high-gravity process intensification technology to prepare undecane/methanol nanoemulsions with good dispersion stability. Nanoemulsion absorbents for CO 2 capture applications have been developed. The effects of different operating conditions on the dispersion stability of nanoemulsion were investigated. Furthermore, CO 2 absorption performance of nanoemulsion absorbents and methanol were investigated in a bubbling reactor. Based on the results, the reasonable mechanism for the enhancement of mass transfer was also discussed in detail. Further experiments on CO 2 absorption using nanofluids were conducted and compared with pure methanol. The results indicate that when the undecane volume fraction is 0.01 %, the high-gravity factor is 27, the impinging velocity is 14.1 m·s −1 , and the circulation time is 20 min, the nanoemulsion exhibits the highest stability, with the narrowest particle size distribution of oil droplets, an average particle size of 20.5 nm, and the highest uniformity. Simultaneously, the change in turbidity over time is minimal. The corresponding thermal conductivity at 25°C is 0.2003 W/m·K. The addition of nano-oil droplets significantly accelerates the CO 2 absorption rate, allowing the absorbent to reach saturation earlier, while the total amount of CO 2 absorbed remains the same. Compared with pure methanol, the nanoemulsion enhances the CO 2 absorption rate by 4.48 %. This work may provide a promising green method for efficient production of nanoemulsions for carbon dioxide capture.