Experimental study of carbon dioxide desorption from ethanolamine/non-aqueous CO2-rich absorbent solvent using microchannel

Abstract

Microchannels have a wide range of applications in the chemical industry, therefore the use of microchannels for desorption of CO2-rich absorbent solvents is of great importance to achieve a wide range of applications for efficient and cost-effective CO2 capture. To further investigate the characteristics of the desorption process, an experimental study of the desorption of ethanolamine/non-aqueous CO2-rich absorbent solvent was carried out using circular microchannels with 0.8 mm, 1.0 mm and 1.2 mm internal diameters and 70 mm lengths of quartz microchannels. Response surface methodology was used to reduce the number of experiments and optimize the operating conditions, while a high-speed camera was used to record the gas–liquid two-phase flow inside the microchannels during desorption. A 4-factor, 3-level response surface design was constructed, in which the four factors are solvent flow rate (0.1, 0.2, 0.3 mL/min), desorption temperature (60, 70, 80 °C), amine percentage in solvent (10, 20, 30 wt.%) and microchannel diameter (0.8, 1.0, 1.2 mm). The results show that the desorption temperature of the desorption process can be significantly reduced by using microchannels and MEA/non-aqueous absorbent, and the desorption of CO2-rich absorbent solvents can be achieved at temperature of 60 °C. During the desorption process of the microchannels, six flow states were demonstrated: bubble flow, bubble-Taylor flow, merging and growth of the Taylor flow, Taylor flow, annular flow, and breakage of the annular flow. The CO2 desorption ratio was generally high when the flow pattern was Taylor flow, with the highest ratio reaching 93.84%. The bubble average velocity and dimensionless variation length increase due to mass transfer between the liquid and gas phases, both of which reach a maximum at a solvent flow rate of 0.2 mL/min.