An Experimental Study Of Co₂Bubble Absorption Into Binary Nanofluids

CO2is the principle greenhouse gas,as well as important resourse.It would bring a lot of environmental and economic benefits to develop carbon capture and storage(CCS) technology. CO2chemical absorption by organic amine solutions is the maturest commercial method adopted by many power plants for flue gas CO2removal.To enhance the gas-liquid mass transfer in the absorber has the advantages of improving the rate of CO2removal,reducing the volume of absorber and lowering costs of production.It is a novel method to add nanoparticles into solution to enhance the gas-liquid mass transfer process.In this paper,binary nanofluids were prepared by adding different nanoparticles into30%wt monoethanolamine (MEA) and methyldiethanolamine(MDEA) solutions,respectively. The nanoparticles employed here were SiO2,TiO2,Al2O3,and MgO,with the diameter between10and60nm,and solid loading ranging from0.2to1.0g/L. Some experiments were conducted in a bubble column to study CO2absorption processes in pure organic amine solutions and nanofluids,and their difference in CO2absorption ability was compared by the concept of enhancement factor E. The influences of experimental factors such as particle type,particle size,solid loading, gas mixture volume flow rate,initial CO2volume fraction and operating temperature on enhancement factor were discussed in detail,respectively. The results show that:the enhancement effect of nanoparticle on CO2absorption rate into MDEA-based nanofluids is larger than MEA-based one,indicating that nanoparticle is more effective in gas-liquid absorption systems with slow chemical reactions;for the nanoparticles used in this paper under the same solid loading,the enhancement factor of TiO2is much larger than others,while that of Al2O3is close to MgO,and SiO2has the smallest enhancement factor even lower than1;generally,as solid loading increases,the enhancement factor increases first to a maximum value then decreases,implying the existence of an optimal solid loading,which varies with different nanoparticles;for the nanoparticles employed here,the enhancement factor decreases with the decrease of particle diameter; the enhancement factor increases with increasing gas mixture flow rate and initial CO2volume fraction,but decreases as the operating temperature turns higher.A tentative interpretation of the results based on the mechanism of hydrodynamic effect in the gas-liquid boundary layer was present,considering the physical properties of nanoparticles and the performance of experimental apparatus,as a combination of factors such as the hydrodynamics in liquid phase, the total disturbance induced by the anomalous motion of nanoparticles to the mass transfer layer, and the particle interaction and aggregation.