(573f) A Nature-Inspired Approach to Aid the Understanding and Improve the Performance of Fluidized Beds

Gas-solid fluidized beds remain fascinatingly complex, despite many decades of research and industrial use. Chosen for their desirable mass and heat transfer properties for processes as diverse as drying, chemical production, waste-to-energy, fuel combustion and gasification, the complex fluid and particle dynamics are notoriously difficult to model, leading to a predominance of empirical approaches for scale-up and design.

Our research has focused on ways to structure fluidized beds, imposing more uniformity in mixing and bubble patterns, so that their behavior becomes more predictable, and they become easier to operate and scale-up. Biology provides us with wonderful examples of efficient, scalable hierarchical transport networks, such as the airways of the lungs and the vascular network, while regular sand ripples on dunes and beaches form despite the complexity of granular dynamics. This has inspired, respectively, the use of a fractal branching fluid injector for bubbling fluidized beds to facilitate scalability and promote more uniform mixing, and the pulsation of the gas flow to turn a chaotic bubble flow into a periodic bubble pattern.

An unexpected side-effect to our most recent work on pulsed fluidization is that it provides fundamental insights into the mesoscopic physics of fluidization, and helps to validate computational methods. Experimentation with a variety of particles and operation parameters allows us to survey the conditions for which regular bubble patterns appear. Coupling computational fluid dynamics (CFD) simulations with discrete element modeling (DEM) for the particles, helps us to understand how the patterns form, by comparing the numerical results with the experimentally observed patterns. As the patterns are sensitive to the drag law and particle friction, they also serve as an excellent fingerprint to investigate the physics of fluidization more generally.