The Determination of Minimum Bubbling Velocity, Minimum Fluidization Velocity and Fluidization Index of Fine Powders (Hematite) using Gas-Solid Tapered Beds

Abstract: In this report the experimental determination of maximum pressure drop, minimum fluidization velocity, and minimum bubbling velocity and Fluidization index of fine Hematite powder has been done. A tapered bed having a tapered angle of 7.40º has been used in this study. Tapered beds have a velocity gradient along the axis unlike conventional beds. They have been used as an alternative to conventional cylindrical beds to deal with problems such as slugging. In this study pressure drop was measured using a U tube Manometer). Air at ambient conditions (310 K) was used as the fluidizing medium. The air flow rates were measured using a rotameter. Initially stagnant bed height of 5.5 cm was taken. The superficial velocity (Air flow rate/area) of the air passed from below the distributor was increased in small increments. The corresponding manometer readings were noted down. Pressure drop at the corresponding superficial velocity was calculated from the height difference between two arms of the manometer. The Superficial velocity at which maximum pressure drop was obtained was noted as the minimum fluidization velocity. At the onset of fluidization bubbles appeared and the superficial velocity at which the first bubbles appeared was taken as the minimum bubbling velocity. The fluidization index is the ratio of minimum bubbling velocity to the minimum fluidization velocity. Geldart in his works had shown that fluidization index is a very useful criterion to determine the hydrodynamic behavior of fine powders. The effect of variation of the tapered bed height on maximum pressure drop, minimum fluidization velocity, minimum bubbling velocity and fluidization index were studied by repeating the tests mentioned above for stagnant bed heights of 10cm and 15 cm