Experimental study of bubbling fluidized bed
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- Master i teknologi 
A series of experiments are performed in order to study the flow behaviour of bubbling fluidized bed. A two dimensional fluidized bed is built up with dimension 0.8 m (height) × 0.2 m (width) × 0.025 m (depth) and uniform porous gas distributor. Three powders with different particle size ranges are used in the experiments. The mean particle sizes are 153, 484 and 960 μm. The minimum fluidization velocities are measured for the three powders. The experiments are performed with different superficial velocities and with two different initial particle bed heights. According to experiments, the minimum fluidization velocity increases with increasing particle size. It is also observed that the size and the shape of the bubbles are strongly influenced by the particle size in the bed. The bubbles also change with the distance above the distributor. The bubble velocity increases with the height in the bed and with the inlet superficial gas velocity. Emphasis is given to study the effect of particle size distribution on flow behaviour in bubbling fluidized beds. Experiments have been performed with mixtures with different composition of the three powders. The mixtures have the same mean particle size, about 488 μm. The bubble behaviour changes significantly due to the differences in particle size distribution. The powders with a wide range of particle sizes show the tendency of segregation and the segregation influences on the bubble behaviour. Gas channels are also observed in some of the experiments. The study of the effect of particle size distribution on bubble behaviour is an important contribution to verify CFD modelling of fluidized beds. Experimental and computational results are compared, and it is found that multiple particle phases have to be included in the simulations to give a good agreement with the experimental results.