PREDICTION OF BUBBLE-SIZE IN A FLUIDIZED-BED CONTAINING HORIZONTAL TUBES

A freely-bubbling fluidized bed containing horizontal banks of tubes was observed by means of X-rays. The number of rows of tubes, the distances between them, the distance of the first row above the distributor and the fluidizing gas velocity were all varied, the size distribution of bubbles rising through the tube banks being recorded on cine film for subsequent frame-by-frame analysis. In many cases interaction between bubbles and tubes caused the bubbles to break up into two or more "daughter" bubbles, the sizes of which were determined by the ratio of the diameter of the tube to that of the parent bubble as well as by the horizontal separation between the tubes. Following break-up at a row of tubes bubbles grew by coalescence before reaching the next row above, whereupon further break-up occurred. From measurements with a single row of tubes a correlation was developed for the breakage rate and this was combined with an expression for bubble growth to give predictions of bubble size at any point in a bed fitted with tubes. The predictions were found to be in good agreement with the measurements made in the multitubular bed. © 1990.