Bubble Size and Frequency in Corrugated-Wall Bubbling Fluidized Beds—Image Analysis and Neural Network Correlations

Abstract

Digital image analysis was implemented to monitor bubbling dynamics in corrugated-wall bubbling fluidized beds (CWBFB) loaded with Geldart D particles. Various geometrical configurations were investigated in terms of corrugation angle, interwall clearance, and rest bed height and gas superficial velocity. Implementation of wall corrugation led to improved gas–solid fluidization quality with respect to flat-wall bubbling fluidized beds (FWBFB) as measured in terms of retreat of the onset of bubbling as a function of gas flow rate, of reduction of bubble sizes and rise velocities, and of increase of bubble frequency. Two artificial neural network correlations valid both for FWBFB and CWBFB were recommended for estimation of bubble frequency and size using a common set of independent variables, that is, gas superficial-minimum bubbling velocity ratio, bed rest height, corrugation angle, average clearance, and vertical location. The bubble frequency explicit correlation accounted additionally for interwall minimum clearance and distance between side wall and either neck or hip of front plate, at a given elevation, whereas bubble size correlation needed bubble frequency as a supplementary input variable.