(204f) Heat and Mass Transfer within Dynamically Structured Bubbling Fluidized Beds Subject to Vibration: A Two-Fluid Modeling Study

Gas-solids bubbling fluidized beds are widely used in a range of chemical and petroleum processes. The dynamic coalescence, split up, and collapse of bubbles in fluidized beds are mathematically chaotic and hard to predict, which create significant difficulties in scale-up from laboratory- to pilot- to industrial-scale. In the past few decades, many different ways have been proposed to manipulate the overall bubble dynamics in fluidized beds to introduce more structures that can simplify the overall scale-up process. Among all of the methods used, it has been found that using pulsed gas flow or vertical vibration can cause otherwise chaotic gas bubbles to form a structured triangular pattern, which repeats itself every two gas oscillation or vibration periods. Therefore, the induced bubbling structure is highly predictable. Further, the characteristic bubble size and bubble distance remain unchanged when the system width is changed, and using a layered configuration with multiple stages of gas distributors can maintain the ordered bubbling structure to a higher particle height. The possibility to maintain the structured bubbling pattern with the system width and system height changed opens great opportunities to address key issues in scaling up traditional gas-solids bubbling fluidized beds. Based on Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) simulations and advanced measurement techniques, structured bubbling and its effect on the particle mixing and gas-solids contact patterns have been well characterized. However, the effect of the structured bubbling on heat and mass transport remains unclear. Herein, using two-fluid modeling (TFM), we studied the heat and mass transport within dynamically structured bubbling fluidized bed and compared with free bubbling fluidized bed. The heat transfer was initiated by cooling particles at high thermodynamic temperature using cool inlet gas flow and the mass transfer was conducted by removing the coke deposited on the particles with air combustion. The results showed that compared with free bubbling fluidized bed, the particles in the dynamically structured bubbling fluidized bed show a more uniform temperature distribution and more uniform coke concentration, suggesting that the dynamically structured bubbling fluidized bed has the potential to be used in in a range of applications, in which a narrow temperature distribution or a narrow species distribution within the particle phase is a key consideration.