Experimental Study On CO₂ Capture By Mdea-based Nanofluids

The chemical absorption method is the most potential technology to achieve large-scale CO₂ capture in the short term,but it still encounters issues such as high energy consumption in the process of desorption.In this work,the N-methyldiethanolamine（MDEA）absorbent was modified by adding nanoparticles in order to improve the CO₂ capture performance.Through the establishment of bubble absorption/desorption experimental system,and the design of visualization experiment of desorption,effects of various factors on CO₂ absorption and desorption by MDEA-based nanofluids and underlying enhancement mechanisms were explored in detail,together with the dynamic analysis of bubble formation process during desorption.It is found that the CO₂ absorption rate of MDEA-based nanofluid is enhanced attributed to the reason that nanoparticles can prevent bubbles from coalescence to increase the effective reaction area.Furthermore,the enhancement is affected by various factors such as the nanoparticle mass fraction,the nanoparticle size,the nanoparticle type,the MDEA concentration,and other external disturbances.The results indicate that the mass fraction of nanoparticles and the concentration of MDEA can be optimized to realize the maximized absorption enhancement.For instance,when the mass fraction of Ti O₂ was 0.06wt%and the concentration of MDEA was 30wt%,the absorption enhancement of Ti O₂-MDEA was stronger than that of Si O₂-MDEA and Al₂O₃-MDEA.In addition,the enhancement of nanofluid on CO₂ absorption is weakened by increasing gas flow rate.Electromagnetic stirring can enhance the absorption enhancement of nanofluids,up to 11.5%;while the ultrasonic vibration can significantly inhibit the enhancement of nanofluids on CO₂ absorption.During the desorption process,with the addition of nanoparticles,the number of bubbles and the bubble detachment frequency both increases and the average diameter of bubbles becomes smaller,which makes the CO₂desorption rate of rich-loading MDEA-based nanofluids higher than that of rich-loading MDEA solution.The desorption enhancement due to nanoparticles is dependent on numerous factors including the nanoparticle mass fraction,nanoparticle size,the nanoparticle type,the MDEA concentration,and the external desorption conditions.When the mass fraction of Si O₂ is 0.06wt%and the concentration of MDEA is 30wt%,the desorption enhancement of rich-loading Si O₂-MDEA is the highest,which is larger than that of rich-loading Ti O₂-MDEA and rich-loading Al₂O₃-MDEA.When the mass fraction of 40nm Ti O₂ is 0.09wt%and the concentration of MDEA is 40wt%,the desorption enhancement of rich-loading Ti O₂-MDEA is the lowest to be 10%.Besides,increasing the desorption temperature,imposing electromagnetic stirring and ultrasonic vibration can all improve the desorption enhancement of nanofluid.The improvements of electromagnetic stirring and ultrasonic vibration on the desorption of rich-loading nanofluids can reach the maximums at 70℃ and 60℃,respectively.