CO2 absorption and desorption enhancement by nano-SiO2 in DBU-glycerol solution with high viscosity

Abstract

Nano-SiO2 was used to enhance the performance of CO2 absorption and desorption in viscous DBU-glycerol solution with a viscosity of about 60 mPa·s. The effects of ultrasonic time in the preparation of nanofluids, solids loading and particle/cluster size of SiO2 on absorbent properties and absorption performance were investigated. Meanwhile, the enhancements of heat transfer and mass transfer with nanoparticles in the desorption of CO2-loaded DBU-glycerol solutions were also analyzed. Proper ultrasonic vibration time and nano-SiO2 loading can both decrease the average particle size in the system which can improve the absorption. The increase of interfacial area between gas and liquid with the addition of nano-SiO2 dominates the enhancement of absorption and it has little effect on the enhancement factor when the nano-SiO2 size is 102 nm or below. But when the particle size is higher than 102 nm, the enhancement factor decreases with the increase of particle/cluster size. The addition of 0.10 wt% SiO2 nanoparticle with a particle size of 16 nm can increase the absorption rate by 31 % compared with base liquid. In desorption process, the desorption rate for CO2-loaded DBU-glycerol solutions can increase 18 % with the addition of 0.10 wt% nano-SiO2 with a particle size of 32 nm. The main reason could be that nano-SiO2 can improve the heating rate of the base fluid and supply plenty of nucleation sites for the formation of bubbles to improve the desorption rate. It shows that nano-SiO2 can be used to enhance both the absorption and desorption processes in solutions with high viscosity.