Determination of CO2 diffusion coefficient in sodium carbonate solutions and implications for decarbonization kinetics

Sodium carbonate solution is a promising carbon capture absorber due to its low cost, rich content, environmental friendliness, and low heat requirement for regeneration, but its large-scale application is limited by its low diffusion coefficient and thus unsatisfied chemical absorption kinetics. Most importantly, the diffusion coefficient parameters of CO2 absorption into sodium carbonate solutions at different concentrations and temperatures are lacked in the existing literature, which leads to a certain bias in the understanding of its absorption kinetics. Based on this, in this paper, a molecular dynamics simulation method was used to calculate the diffusion behavior of CO2 in sodium carbonate solution at different parameters and compared with the existing fitting equations in the literature. The data calculated from literature presented a severe overestimation of diffusion coefficient in low temperature solvent, underestimation of diffusion coefficient in high temperature solvent. The maximum deviation between our simulated data and calculated data of fitted formula in literature exceeded 30%. Based on this, a new fitting formula was proposed in this paper using the temperature adjusted method. The results showed that the maximum error between simulated data and fitted new formula is 24.82%, AARD, SD, RMSD are only 9.21%, 11.13%, and 11.15% respectively. The maximum absolute error was 11.73%, AARD, SD, RMSD are only 4.55%, 5.53%, and 5.53% for CO2 mass transfer kinetics calculation, which significantly contributes to the accuracy of carbon capture process calculations.