426170 Numerical Simulation of Polydisperse Gas-Particle Flow in a Vertical Riser with a Size-Velocity Quadrature-Based Moment Method

Wednesday, November 11, 2015: 10:43 AM
254C (Salt Palace Convention Center)
Bo Kong1,2 and Rodney O. Fox1,3, (1)Applied Mathematics and Computational Sciences, Ames Laboratory (U.S. DOE), Ames, IA, (2)Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, (3)Chemical and Biological Engineering, Iowa State University, Ames, IA

Polydisperse gas-particle flows are common in many fields of engineering, such as in fluidized beds and risers, which are widely used in a variety of chemical processes. Due to the various physical and chemical interactions between particles and gas, such as particle collisions and breakage, gasification and chemical reactions, the individual particle size and the overall size distribution of the particles changes as the flow develops. Because different size particles have different velocity distributions, and different particle velocity distributions again lead to different size changes, the joint number density function (NDF) of particle size and velocity has to be modeled in a gas-particle flow. In this work, quadrature-based moment methods (QBMM) are applied to solve numerically the kinetic equation of the joint NDF using the extended quadrature method of moments (EQMOM) and the assumption that the particle velocity follows an anisotropic Gaussian velocity NDF, which is valid when particle trajectory crossing is limited to small scales. By reconstructing the size-conditioned velocity distribution function, the spatial fluxes in the moment equations are treated using a kinetic-based finite-volume method. The particle-phase volume-fraction and momentum equations are then coupled with an Eulerian solver for the gas phase. This approach is implemented in an open-source CFD package, and then tested in a vertical riser flow. The results demonstrate the ability of the code to capture the size segregation in the riser, and that our approach is an effective way to model the complicated polydisperse gas-particle flows arising in industrial applications.

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