Mass transfer performance of CO2 absorption by alkanolamine aqueous solution for biogas purification

• We model enhancement factor mathematically based on second order chemical reaction.
• The effective gas–liquid interfacial area was measured experimentally.
• Mass transfer performance and enhancement factor increases with MEA concentration.
• The above parameters decrease with increasing CO2 concentration.
• The above parameters increase, then decrease, and steady finally with gas flow rate.

The CO2 absorption of an aqueous alkanolamine solution is an important research topic in the field of biogas purification. In this paper, an experimental packed tower was set up to investigate the high-concentration CO2 absorption of an ethanolamine (MEA) solution. A mathematical model of the enhancement factor based on a second-order chemical reaction was proposed. This model was used to calculate and analyse the enhancement factor and the mass transfer performance of high-concentration CO2 absorption by an MEA aqueous solution, respectively. The results show that the assumption of a pseudo-first-order reaction is not suitable for the high-concentration CO2 absorption process and the enhancement factor obtained via mathematical prediction by this model is in agreement with the experimental value. Moreover, the high-concentration CO2 absorption of the MEA aqueous solution is a liquid-controlled process. Furthermore, parameters such as gas phase overall mass transfer coefficient KG, liquid phase mass transfer coefficient kL and enhancement factor E increase with increasing MEA concentration but decrease with increasing CO2 concentration. When the gas flow rate is increased, the above parameters initially increase, then decrease, and finally level-off gradually. The results of this study may provide meaningful insights for the research and application of biogas purification technology.