Experimental and computational studies on gas–solid fluidization in a cylindrical column with and without internals

Abstract

Gas-solid fluidization often suffers from inherent drawbacks like channeling, bubbling and slugging which affect the quality of fluidization. Efforts have been made in this present investigation to improve the quality of fluidization in gas–solid fluidized beds by conducting hydrodynamic studies in cylindrical fluidized bed column with and without internals. The effect of hydrodynamic parameters such as inlet air velocity, bed height and internal spacing on pressure drop, expansion ratio, fluctuation ratio, minimum fluidization velocity and fluidization index were studied. The pressure drop was found to increase with an increase in bed height regardless of presence or absence of internals. But in the presence of Internals (More Number of internals or less spacing) pressure drop initially decreases but beyond a certain level the resistance offered by the internals is more, and it caused a slight increase in pressure drop. The expansion ratio and fluctuation ratio reduces significantly with a decrease in the spacing of internals. The effect of the internals on quality of fluidization has been studied. By the introduction of internals, the quality of fluidization in terms of fluidization index has improved. The experimental data was used in the CFD simulations and the results obtained are in good agreement with the experimental observations. It is found from the simulation results that the bed height increased with increase in air velocity. The solids are more evenly fluidized in the presence of internals with smaller bubble size and lower bed height than the beds without internals.