Measuring the particle mixing parameters at multi positions in three-dimensional fluidized beds continuously remains a challenging task. A novel measurement method for the mixing and segregation of particles inside three-dimensional fluidized beds is developed based on capacitance probe. The measurement error is generally below 7%. The particle mixing parameters and dispersion coefficients at multi-positions of the three-dimensional fluidized bed are acquired. The effect of convection and diffusion mechanism on particle mixing is discussed. Results show that the governing mechanism of particle mixing at center and top of the bed is convection; meanwhile the governing mechanism for particle mixing at bottom and near the wall is diffusion. The radial dispersion coefficient at half-radius of the bed is mainly between 0.0038 and 0.026 m2/s, which is about 1.5 times that near the wall. The axial dispersion coefficient is mainly between 0.004-0.056 m2/s, which is about 2.3 times that in radial direction.

A novel measurement system for mixing property of binary mixtures in three-dimensional fluidized beds is developed based on capacitance probe method. The mixing processes at multi-positions of the bed are acquired simultaneously. A new dispersion coefficient is proposed to characterize the local dispersion of particles and a new mixing index is proposed to evaluate the local mixing quality in three-dimensional fluidized beds. The effect of convection and diffusion mechanism on particle mixing is discussed separately. Results show that the governing mechanism of particle mixing at the center and top of the beds is convection; meanwhile the governing mechanism for particle mixing at the bottom and near the wall is diffusion. The radial dispersion coefficient at the half-radius of the bed is mainly between 0.0038 and 0.026 m2/s, which is about 1.5 times that near the wall. The vertical dispersion coefficient is about 2.5 times that the radial dispersion coefficient.