In this study, the air-blowing process of iodine in nitric acid solution was studied through experiments and computational fluid dynamic (CFD) simulation. The impact of superficial gas velocity and nitric acid concentration on the gas holdup and bubble distribution during bubbling is tested. population balance model (PBM) and interfacial area concentration model (IACM) models are selected to simulate the bubble coalescence and breakup, and the slip penetration model is used to simulate the mass transfer process. The experimental results show that the size of the bubbles in the nitric acid solution is smaller than that in the water due to Gibbs–Marangoni effect and electrical repulsive forces, resulting in a larger gas holdup and a wider bubble distribution. When the concentration of nitric acid solution exceeds 1 mol/L, the effect of nitric acid concentration variation on gas–liquid-phase hydrodynamics becomes less significant. The CFD simulation results showed that the PBM–(EMMS)­Luo–Luo model can simulate the bubble coalescence and breakup in water, while the IACM–Hibiki–Ishii model is more suitable for those in nitric acid solution. In addition, it is found that the “slip penetration” model is suitable for the mass transfer calculation in the air-blowing process of iodine.

Bubble column is a commonly used multiphase reactor. Owing to the complicated nature of its flow structure, computational fluid dynamics has frequently been used as a useful instrument for studying the fluid mechanics in a bubble column. However, most of the previously studied systems are air-water system, while air-nitric acid solution system is rarely reported. In the present study, the differences in bubble size distribution of pure water and 1 mol/L nitric acid in the bubble column were observed through experiments. The bubble size was found to be smaller than that in water when the liquid phase was nitric acid. According to the actual situation, the bubbling process of nitric acid solution was successfully simulated by adjusting the coalescence factor of the bubble coalescence model (deviation less than 10%). Meanwhile, it was observed by simulation that the axial time-averaged liquid velocity distribution in nitric acid solution was flatter than that in water under the same gas flow rate.