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Abstract Structured bubbling with a triangular lattice pattern has been demonstrated previously to form in fluidized beds with oscillated gas injection velocity. Here, we demonstrate using two‐fluid model simulations that dividing the gas distributor into slices and oscillating gas flow with a phase offset between consecutive slices enables structured bubbling to form with a wider range of bubble sizes and lattice configurations. Local particle solidification below bubbles leads to the formation of these structures, as manifested in high particle pressures in simulations. Varying the number of slices and phase offset enables a number of configurations that mix particles faster than cases with conventional structured bubbling or unstructured bubbling with the same overall gas flow rate.
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Dense Discrete Phase Model Coupled with Kinetic Theroy of Granular Flow to Improve Predictions of Bubbling Fluidized Bed Hydrodynamics
Formation, expansion, and breakage of bubbles in single bubble and freely bubbling fluidized beds were studied using an improved hybrid Lagrangian-Eulerian computational fluid dynamics (CFO) approach. Dense Discrete Phase Model (DDPM) is a novel approach to simulate industrial scale fluidized bed reactors with polydispersed particles. The model uses a hybrid Lagrangian-Eulerian approach to track the particle parcels (lumping several particles in one computational cell) in a Lagrangian framework according to Newton's laws of motion. The interactions between particles are estimated by the gradient of solids stress solved in Eulerian grid. In this work. a single bubble fluidized bed and a freely bubbling fluidized bed were simulated using DDPM coupled with kinetic theory of granular flows (KTGF). The solid stress was improved to include both tangential and normal forces compared to current hybrid methods with the consideration of only normal stress or solid pressure. The results showed that solid pressure (normal forces) as the only contributor in solid stress would lead to over prediction of bubble size and overlooking of bubble breakage in a single bubble bed. Also, the results showed the improved model bad a good prediction of bubble path in a freely bubbling bed compared to solid pressure-based model. It was shown that increasing the restitution coefficient increased the particle content of the bubbles and it lead to less breakage during the formation of the bubble. The probability of formation of bubbles was compared with experimental results and solid stress model showed less discrepancies compared to the solid pressure-based model.
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- Award ID(s):
- 1736173
- PAR ID:
- 10085263
- Date Published:
- Journal Name:
- Kona powder and particle journal
- ISSN:
- 2187-5537
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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