Progress in enhancement of CO2 absorption by nanofluids: A mini review of mechanisms and current status

Review on combined heat and mass transfer characteristics in nanofluids

In this study, three different nanoparticles—SiO2, TiO2, and Al2O3—were employed to enhance the CO2 gas absorption by monoethanolamine (MEA) solvent. It is observed that, with increased solids loading, the total mass-transfer enhancement has a tendency to be dominated by the bubble breaking effect. It is concluded that nanoparticles result in an increased CO2 absorption rate of >10%. On the other hand, nanoparticles exhibit much more attractive impact on CO2 desorption. Under the same desorption extent, solvent with 0.1 wt % TiO2 nanoparticles saved 42% desorption time, compared to that without nanoparticles. Under higher heat flux density, more input heat would be supplied to the heat of desorption, rather than the heat of water evaporation, which is due to the enhancement of desorption rate by nanoparticles. The issue of particle aggregation was also investigated by analyzing the size distribution of nanoparticle clusters and zeta potential of MEA solvents.

Enhanced CO2 Absorption and Desorption by Monoethanolamine (MEA)-Based Nanoparticle Suspensions

In this work, suspensions of Fe3O4, CNT, SiO2, and Al2O3 nanoparticles in distilled water are produced and tested as new absorbents in a gas–liquid hollow fiber membrane contactor to investigate the effect of nanoparticles on the rate of mass transfer during CO2 absorption For this purpose, a pilot-scaled hollow fiber membrane contactor was constructed A gas mixture was passed through the shell-side, and the nanofluid flowed cocurrently through the lumen side of the fibers The effects of different operating conditions including gas flow rate, liquid flow rate, inlet CO2 concentration, and nanoparticle concentration on the CO2 absorption have been studied The results showed that among the operating parameters, liquid flow rate and nanoparticle concentration had the greatest effects on the CO2 absorption Moreover, UV–vis spectroscopy and DLS method were employed to explore the dispersion stability and hydrodynamic diameter of nanoparticles in the base fluid The results revealed that nanofluid stabilit

Experimental Investigation on the Absorption Enhancement of CO2 by Various Nanofluids in Hollow Fiber Membrane Contactors

Liquid nano-absorbents have become a topic of interest as a result of their enhanced mass-transfer performance for CO2 capture. They are believed to have revolutionized the conventional CO2 chemisorption process by largely improving CO2 capture kinetics and reducing the energy requirement for solvent regeneration. Two classes of nanomaterial-based CO2 capture absorbents, amine-based nanoparticle suspensions (nanofluids) and nanoparticle organic hybrid materials (NOHMs), have been developed, with significant progress achieved in recent decades. This review addresses two key questions for these two state-of-the-art nanomaterials: how are the physical and chemical properties of the prepared liquid nano-absorbents transformed relative to those of the base fluids? And how does the transformation of the properties affect the CO2 capture behavior? While the current synthesis procedure for liquid nano-absorbents is quite straightforward, more advanced synthesis methods for long-term nanoparticle stability have been suggested for the future. Nanofluids have been shown to increase the CO2 uptake by over 20% and the CO2 capture rate by 2-93% compared with the values observed with neat amine solvents. Nanoparticles with catalytic effects on CO2 capture can significantly increase the CO2 desorption rate by as high as 4000%. NOHMs exhibit the interesting feature of enhanced mass transfer in CO2 capture because of the unique pathway network that is created in them for CO2 to reach specific functional groups. NOHMs promise an effect of combined CO2 capture and conversion, and can be used especially as electrolytes for CO2 electro-reduction. However, there are still some challenges for the application of these materials in real life, such as poor stability and high viscosity. Therefore, efficient CO2 capture processes using these solvents need to be urgently developed and studied in the future.

Chung Woo Jung

Papers

Mass transfer enhancement during CO2 absorption process in methanol/Al2O3 nanofluids

A novel type solar assisted heat pump using a low GWP refrigerant (R-1233zd(E)) with the flexible solar collector

Characteristics on condensation heat transfer and pressure drop for a low GWP refrigerant in brazed plate heat exchanger

Study on ammonia/water hybrid absorption/compression heat pump cycle to produce high temperature process water

Thermal performance estimation of ammonia-water plate bubble absorbers for compression/absorption hybrid heat pump application