(408h) CFD-DEM Simulation of Tube Erosion in a Bubbling Fluidized Bed with a Tube Bundle

Yongzhi Zhao (yzzhao@zju.edu.cn), Lei Xu

Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China

The erosion of the immersed tubes in a bubbling fluidized bed is studied numerically using CFD-DEM method and a particle-scale erosion model, SIEM (shear impact energy model), which is proposed based on the shear impact energy of particles in DEM simulations. By analyzing the simulation results, some characteristics of the tube erosion in the fluidized bed are obtained. The distributions of the erosion around the tubes located in different positions of the bed are different. For the tubes in the center of the fluidized bed, the profiles of erosion rate around the tubes have two peaks at the lower surface of the tubes. On the contrary, for the tubes near the sidewall of the fluidized bed, the maximum erosion usually occurs on the upper surface of the tubes. The values of the erosion rates on the tubes located in different positions of the bed are also different. With the increasing of the vertical position, the erosion rate of the tubes, including the maximum erosion rate and the average erosion rate, increases gradually. In the horizontal direction, the erosion rates of the tubes at the center of the fluidized bed are larger than that of the tubes on both sides of them in the same horizontal plane. For all tubes in the fluidized bed, the maximum erosion rates are about 1~3 times to the corresponding average erosion rates and most of the ratios are near to 2. The erosion model and the algorithm are proved to be effective for predicting the erosion of the tubes in the fluidized bed. The accuracy of the approach is good for predicting not only the distribution of the erosion around the tube, but also the absolute value of the erosion rate. The micro-scale behavior of particles around the tubes is also revealed and the linear relationship between the erosion and the shear impact energy is confirmed by the simulation results and experiment (Johansson et al., Chem. Eng. Sci., 2004, 59: 31-40). The agreement between simulation and experiment proves that the micro-scale approach proposed in this paper has high accuracy for predicting erosion of the tubes in the fluidized bed, and has potential to be applied to modeling the process in other chemical equipment facing solid particle erosion.