Experimental investigation of bubble behavior in gas-solid fluidized bed.

• Origin of pressure fluctuations of a single bubble from formation to eruption is discussed. • Effects of density, size of particles, and injection velocity on pressure profile are investigated. • Maximum amplitude of bubble formation is related to the injection velocity and density of particles. • Amplitude of bubble eruption is related to the bubble diameter, density and size of particles. In this work, to investigate the source of pressure fluctuations, behavior of a single bubble in a two-dimensional gas–solid fluidized bed was studied. Pressure sensors located at different heights of the bed measured presure fluctuations, and simultaneously a high speed camera was used to pursue all steps from formation to eruption of bubbles. Two types of particles were applied with different sizes and densities. Experiments showed that the maximum amplitude of formation was independent of the bubble diameter. But, it depended on density of particles, velocity of injection and the distance from bed surface. When injection stopped, there was a minimum in pressure profile related to the higher dense phase voidage for a higher superficial gas velocity after injection. Also, the maximum pressure fluctuation of bubble eruptions was related to the bubble diameter, density and size of particles. It was concluded that pressure fluctuations of formation, passing and eruption of bubbles in fluidized beds are originated due to changes in dense phase voidage, bed voidage and movement of particles during bubble eruption. [ABSTRACT FROM AUTHOR]