Experimental Study of Effects of Particle Size Distribution on Bubble Behavior for Validation of Cfd Modeling of Bubbling Fluidized Bed

The efficiency of fluidized bed reactors depends on bubble distribution, bubble size and bubble velocity within the reactor. The sizes and size distributions of particles used in the bed may lead to different bubble behaviour. The objective of this work is to study the influence of particle size distribution on bubble behaviour. The results from the experiments will be used for validation of CFD modelling of bubbling fluidized beds. A lab-scale two dimensional fluidized bed with a uniform air distributor is constructed. A video camera is used to record the bubble behaviour in the bed. Glass particles with a density of 2485 kg/m are used in the experiments. A series of experiments are performed with different particle size distribution. All the particle mixtures have a mean particle diameter of 488 μm. The minimum fluidization velocity for the different mixtures is measured by using a flow meter. The experiments are run with different superficial gas velocities. Bubble behaviour and bed expansion are studied. The results from experiments show that the bubble behaviour changes significantly due to changes in particle size distribution. The powders with a wide range of particle sizes show a clear tendency of segregation which influence on the bubble formation and bubble orientation in the bed. The results show that the bubble behaviour is not only dependent on the mean particle size, but also strongly influenced by the particle size distribution. Particle size distribution should be included in CFD models to obtain realistic simulations of fluidized beds.