Effect of bed diameter on mass transfer factors in a liquid fluidized bed

Abstract

THE SCALE-UP of laboratory and pilot plant data for fluidized systems has been difficult and many times the large scale units never met the performance demonstrated in smaller models. In this study, the mass transfer factor, JD, was investigated for a fluidized system as a function of the modified Reynolds number and column diameter to aid in future scale-up problems. The concept of the mass transfer factor, JD, was first introduced by Colburn ( 3 ) . Using the concept of the mass transfer factor, JD, as a function of modified Reynolds number, N k , , Chu, Kalil, and Wetteroth ( 2 ) were successful in correlating the published data of previous investigations for both fixed and fluidized beds. Also pertinent to this study, was the work of McCune and Wilhelm (8) involving mass transfer between liquid and solid particles for both fixed and fluidized beds. Few published data, however, exist pertaining to the effect of bed diameter in a fluidized system. Most of the early studies were in bed diameters ranging from 1.75 to 4.0 inches. Parent, Yagol, and Steiner (IO) studied fluidization of fine mesh graphite and coke (100-mesh) in 2and 4-inch columns. They found that a t low Reynolds numbers, materials which were fluidized well in a 4-inch column, slugged in a 2-inch unit. In other areas, the effect of diameter on mass transfer was noted. Barker and Treybal ( I ) measured mass transfer coefficients for the dissolution of boric acid in stirred vessels and reported an effect of column diameter. Liebson and Beckman (6) studied the effect of packing size and column diameter in liquid-liquid extraction and found both factors affected the height of a transfer unit. In summary, therefore, apparently diameter effects in mass transfer have been observed for a variety of systems. Published data relating the effect of column diameter on mass transfer in a fluidized system, however, have not been available.