A Simplified Model of Predicting SO2 Absorption by Single Atmospheric Raindrops with Chemical Dissociation and Internal Circulation

Wei-Hsin Chen, Yuan-Yi Chen, Chen-I Hung
2011 Aerosol and Air Quality Research  
A simplified model of predicting chemical SO 2 absorption by single freely falling raindrops with internal circulation in the atmosphere is developed in the present study. By multiplying a modification factor α into the model of interfacial velocity established from creeping flow, it is found that the relative error between the simplified model and the two-phase simulation method is less than 4%. Accordingly, the simplified model enables us to simulate the atmospheric SO 2 absorption process
more » ... sorption process with less computational effort and without losing accuracy. The simulated results indicate that the dissociation of H 2 SO 3 governs the mass transfer process and the concentration of HSO 3 − is by far larger than those of SO 3 2− and H 2 SO 3 . As a result, the chemical absorption takes a much longer period of time to achieve the uptake process. Specifically, for the raindrop radius in the range of 200-500 μm, the absorption time of chemical absorption is larger than that of physical absorption by the factors of 70-290. From the perspective of characteristic time, mass diffusion is the controlling mechanism for SO 2 absorption. When chemical absorption is carried out, the absorption period is 28-33 folds of the characteristic time of mass diffusion, implying that the former is always larger than the latter by over an order of magnitude.
doi:10.4209/aaqr.2011.08.0130 fatcat:nyuctfxqh5ga3kldndi3zkj46e