An assembly consisting of a string of hemispherical elements arranged concentrically on a rod essentially acted as a displaced augmentative device. This assembly was placed coaxially in a three-phase fluidized bed. Nitrogen gas, an electrolyte and glass spheres were used as gas, liquid and solid phases respectively. Limiting current technique was employed to obtain mass transfer coefficient data. Maximum augmentation realized in the present study was about 18 times in comparison with homogeneous pipe flow. Present investigation revealed that the fluctuations in mass transfer coefficients in axial direction were within ±10%. The mass transfer coefficient increased with superficial gas velocity and particle diameter. The mass transfer coefficient decreased with pitch and characteristic length. Superficial liquid velocity and promoter rod diameter have not shown any noticeable influence on mass transfer coefficient. The entire mass transfer coefficient data obtained in the present study were subjected to least squares regression analysis and a correlation equation has been obtained.
mass transfer coefficient, fluidized bed, three-phase fluidization, augmentation, turbulent promoter
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