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

Nano-SiO 2 was used to enhance the performance of CO 2 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 SiO 2 on absorbent properties and absorption performance were investigated. Meanwhile, the enhancements of heat transfer and mass transfer with nanoparticles in the desorption of CO 2 -loaded DBU-glycerol solutions were also analyzed. Proper ultrasonic vibration time and nano-SiO 2 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-SiO 2 dominates the enhancement of absorption and it has little effect on the enhancement factor when the nano-SiO 2 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% SiO 2 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 CO 2 -loaded DBU-glycerol solutions can increase 18 % with the addition of 0.10 wt% nano-SiO 2 with a particle size of 32 nm. The main reason could be that nano-SiO 2 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-SiO 2 can be used to enhance both the absorption and desorption processes in solutions with high viscosity.