Study On Multiphase Flow Characteristics Of MDEA Desulfurization In Rotating Packed Bed

Rotating packed bed (RPB) is a kind of new and efficient Chemical Equipment which using centrifugal force to simulate hyper gravity environment, and strengthen the gas-liquid Mass Transfer and reaction. Currently, few studies are on strengthening absorption in RPB, but most focus on the experimental and applied. Besides, there are few studies on basic theoretical research of gas-liquid contact, movement and variation.In this paper, with amine sweetening process as the research object, a two-dimensional and three-dimensional models was established. By means of CFD technology, the MDEA desulfunzation process was simulated in RPB. First, with unstructured meshes spliting the fluid region and " Realizable " k-s model, the single-phase gas-liquid flow field was simulated under three-dimension, analyzed the distribution of gas and liquid velocity field, and got distribution characteristics of gas and liquid phase velocity field and pressure drop; Secondly, MDEA of flow distribution was simulated under the two-dimensional by using VOF model and sliding mesh model.The influence of speed, inlet velocity and packing layer thickness on the flow distribution was analyzed. Finally, trajectories of MDEA in RPB was simulated by using DPM model. The effect of speed and inlet velocity on droplet trajectories, average residence time of liquid droplets and average particle size distribution of droplets was analyzed.Research shows:Gas-liquid velocity mainly distributed in radial and tangential in RPB. Radial velocity of the liquid mainly controlled by inlet velocity and speed has minor impact on it. However, tangential velocity on the contrary. Compared to conventional absorber, dry bed pressure drop is small, generally between a few hundred to several thousand Pa. It is mainly from wire packing area. Cavity region is small and increases with inlet velocity and speed. Different from traditional packed tower with liquid membrane, MDEA is in forms of orifice flow, droplet flow and liquid film flow in RPB. As the speed increases, the size of droplet flow is reduced, the gas-liquid contact surface area is increased, and the desulfurization process is profitable. Through this study, improving the relative circumferentially collision velocity between the MDEA and wire packing, can make the solution to distribute more evenly and strengthen to micronize MDEA in RPB. The average residence time of MDEA is shorter in the apparatus, and the order of magnitude is about1x10"2sec generally. It can enhance the selectivity of H2S and CO2, and reduce total absorption rate of CO2. Near the inner wall portion, droplet size decreased rapidly. When reached a certain value, the droplet size decline slowed, and the overall size showed a decreasing trend.RPB is desulfurization unit which can strengthen the mass transfer process. By simulating MDEA desulfurization process, it provide a theoretical basis for the RPB to strengthen the application of conventional gas sweetening by amine and industrial design.