281266 Mixing of Solid Particles in Coarse Particle Fluidized Beds

Tuesday, October 30, 2012
Hall B (Convention Center )
Haihong Fan1, Yanxin Chen2, Hui Li2, Jinhe Fan2 and Yong Min2, (1)Xi’an University of Architecture &Technology, Institute of Powder Engineering, XI'AN, China, (2)Xi'an University of Architecture &Technology, Institute of Powder Engineering, Xi'an, China

The mixing of solid particles in fluidized bed reactions has been recognized as an important factor determining the heat and mass transfer rates as well as the overall reaction rates. Many studies have been made in the past in order to understand the underlying mechanisms and predict the behaviour of mixing and segregation, including the investigation of factors affecting the mixing/segregation. Almost all the studies in this area are concerned with monosized particles,and Few studies on mixing of single-size particles in Coarse Particle were reported. This paper extended the work of these work and aimed to the mixing behaviors of solid single-size particles and influencing factors by means of a discrete particle simulation.

In this simulation, the gas phase was taken as continuum medium and the particle phase was discrete phase. The distinct element method (DEM) based on Lagrangian approach was applied to calculate the movement of particles. By this approach, the particle trajectories, particle-particle and particle-wall interactions were considered distinctly for each particle existing within the studied system. The continuity and momentum equations was used for the fluid phase. The motion of the particles was calculated by solving Newton’s equation of motion for each individual particle by taking into account the gravity force, the drag force, the fluid pressure and the contact force.

The value of Ashton index was calculated to elucidate the dynamic mixing process.

The solid flow patterns were examined first to generate some visual understanding of the mixing process. The minimal mixing time was defined as the time to reach a macroscopically stable state.

In this simulation, the tracer particles were monitored momentarily to acquire their locations and the mixing index. This paper focused on five factors affecting the mixing extent, the gas velocities, the bed height, the gas temperature, the particle density and the particle size. It was showed that there is a maximum value of mixing index and a relevant minimum mixing time for a given operation condition. These five factors have different effects on particles mixing.

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