Industrial engineering, particularly fluidized bed reactors, has progressed with the Tapered Fluidized Bed. This distinct bed has a tapered cross-sectional area that narrows with height. Engineers taper the bed to maximize reactor fluid dynamics and particle behavior. This design improves particle mixing and residence time, improving heat and mass transmission. The tapered shape better controls pressure drop and gas distribution, resulting in more uniform bed fluidization. Industrial applications like chemical synthesis and catalytic reactions require precise control and efficient operation, making the Tapered Fluidized Bed a good choice.

The simulation of a tapered fluidized bed requires deep expertise in ANSYS Fluent. This project targeted to do so with the aid of many reference papers, on top,the one entitled “Numerical investigation of gas bubble behavior in tapered fluidized bed [1]”.

• Reference [1]: Khodabandehlou, Ramin, Hossein Askaripour, and Asghar Molaei Dehkordi. “Numerical investigation of gas bubble behavior in tapered fluidized beds.” Particuology38 (2018): 152-164.
• Reference [2]: Sau, D. C., and K. C. Biswal. “Computational fluid dynamics and experimental study of the hydrodynamics of a gas–solid tapered fluidized bed.” Applied mathematical modelling5 (2011): 2265-2278.

Figure 1: Schematic diagram of tapered fluidized bed [1]

Simulation Process

The 2D geometry does not have specific challenges. The theta angle is 10°. Then, ANSYS Meshing generates a structured grid. In fact, the problem has two phases, including the gas and particles in the bed zone. Hence, the Eulerian Multiphase model is activated regarding 0.231mm particles and suitable granular properties. The unsteady state of the problem utterly increases the computational cost. However, this enables us to see changes over time.

Post-processing

The CFD modeling of the tapered fluidized bed shows interesting multiphase flow dynamics, especially in the ways that the gas and particles interact. The gas volume fraction distribution has clear zones within the 10° tapered shape, running from 0.371 to 1.000. Near the bed base, strong mixing forms different void structures, while the upper part of the layer stays mostly gas-phase dominant. The particle-rich areas, which can be seen through volume fraction outlines, show the formation of bubble-like voids that help particles move up and down. Together, these moving parts and the bed’s curved shape create a self-regulating system where the cross-section gradually shrinks, improving particle movement while stopping too much elutriation.

Figure 2: Both phases volume fraction inside the tapered fluidized bed

The particle volume fraction study, which ranges from 0 to 0.629, shows how the bed’s water moves and behaves in complex ways. It shows how dense particle clusters form along the walls and how bubbles explode on a regular basis at the bed surface. These are real-life events that have a direct effect on how fast heat and mass move through the system. When used on 0.231 mm particles, the Eulerian multiphase method accurately predicts how these structures will change over time. This shows that the tapered shape naturally creates a more stable fluidization regime compared to straight-walled beds. As shown by the warmer colors in the contour plot, the particle-rich areas show how well the bed keeps solids in place while letting enough gas percolate for long-term fluidization.