Comparative analysis of thermodynamic theoretical models for energy consumption of CO2 capture

CO2 capture is considered an effective technology to control the CO2 level in the atmosphere, but its development has been restricted due to its high energy requirement during CO2 concentration. Theoretical thermodynamic models have been used not only to predict energy consumption, but also to elucidate the energy conversion mechanism. However, the existing theoretical models have been applied without a clear consideration of boundaries, conditions, and limitations in thermodynamic images. Consequently, the results from such theoretical models can lead to a misunderstanding of the energy conversion mechanism during CO2 capture. A comparative analysis of three theoretical thermodynamic models, namely the mixture gas separation (MGS), carbon pump (CP), and thermodynamic carbon pump (TCP) models, was presented in this paper. The characteristics of these models for determining the energy consumption of CO2 capture were clarified and compared in relation to their practical application. The idealization levels of these models were demonstrated through comparison of theoretical estimates of the energy required for CO2 concentration. The correctness and convenience of the CP model were proved through a comparison between the CP and MGS models. The TCP model proposed in this study was proved to approach the ideal status more closely than the CP model. Finally, an application of the TCP model was presented through a case study on direct capture of CO2 from the air (DAC).