Gas Interchange between Bubble Phase and Continuous Phase in Gas-Solid Fluidised Bed at Coalescence

Abstract

By investigating the phenomena of coalescence of bubbles from the view point of gas interchange, the mechanism of interchange at coalescence in the case of two bubbles on the same vertical line was explained with the aid of Murray's method which gave the gas stream function. CO₂ gas bubbles were blown into a two dimentional air-fluidised bed at the point of minimum fluidisation through a single nozzle. The concentration of the bubble and of the continuous phase was measured and the gas interchange coefficient was obtained. From it, the amount of gas that flowed out from the cloud was obtained and it coincided fairly well with that obtained from the gas stream line. Although the experimental system was a special case where bubbles were formed only from a single nozzle, the method for obtaining the gas interchange coefficient, that includes the effect of coalescence, was explained if the distribution of the frequency and the rising velocity of the bubble were known.