Influence of two- and three-dimensional simulations on bubble behavior in gas–solid fluidized beds with and without immersed horizontal tubes

In this work two- and three-dimensional simulations were performed using Eulerian two-fluid model for bubbling gas–solid fluidized beds with and without immersed horizontal tubes. Results of bubble properties such as aspect ratio, diameter and rise velocity as well as bed expansion were compared with experimental data obtained from pseudo-two-dimensional fluidized bed. The results showed some differences of bubble behavior between two- and three-dimensional simulations especially for beds without immersed tubes. It was found that bubble properties predicted using three-dimensional (3D) simulations were in better agreement with the experimental measurements. However, 3D simulations were computationally expensive and prohibitive for parametric studies. In a bubbling regime, two-dimensional (2D) simulations were also in reasonable agreement with the experimental as well as 3D simulation results. However, at higher superficial velocities and higher bed heights the predicted bubble properties largely deviated from experimental measurements. It was found that for a pseudo-2D bed the influence of the front and back wall became more significant as the bubble size increased. Therefore the validity of 2D simulations at higher superficial velocities where the bed approaches a slugging regime should be treated with great caution. For beds with immersed dense tube banks, both 2D and 3D simulations predicted similar bubble behavior. The shape, size and rise velocity of bubbles were controlled by the tube bank geometry and were found to be nearly independent of the used domain.