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Numerical simulation on circulation and absorption
of sulfur dioxide inside droplet |
1. School of Energy and Power Engineering, Jiangsu University, Zhenjiang, Jiangsu 212013, China; 2. School of Mechanical and Aerospace Engineering, Gyeongsang National University, Gyeongnam Jinjusi 660701, Korea |
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Abstract When the droplets move in flow field in processes of spray flue gas desulfurization, the internal recirculation flow is formed inside droplet due to surface tangent stress to influence the internal mass transfer of droplet greatly and improve the SO2 absorption by spray droplet. The volume of fluid (VOF) method was employed to simulate the internal circulation flow and diffusion inside water droplet. The distribution of tangential velocity at interface and the effect of internal circulation on sulfur dioxide transfer were analyzed for different Reynolds numbers. The numerical results indicate that there are two symmetrical vortexes inside droplets when there is relative motion between gas phase and liquid phase. The distance between vortex core and droplet center is 23Rd, and the vortex velocity is raised with the increasing of Reynolds number. The absorption of sulfur dioxide by droplet is controlled by two mechanisms of radial diffusion by concentration gradient and diffusion by internal circulation. The comparison of characteristic times for radial diffusion inside droplet and vortex formation and sulfur dioxide mass transfer by circulation flow shows that the internal circulation flow has remarked effect on the sulfur dioxide mass transfer of water droplet. The effect of internal circulation is gradually enhanced with the increasing of Reynolds number.
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