Measurement of behavior of gas bubbles and gas holdup in a slurry bubble column by a dual electroresistivity probe method.

Abstract

Bubble properties such as gas holdup, bubble frequency, bubble length and bubble rising velocity in a slurry bubble column were measured by using a dual electroresistivity probe method. The radial distribution of local gas holdup, εg, was parabolic in the range, where mean solid holdup, εs, was less than 0.2. In the range of εs≥ 0.2, however, εg in the region of dimensionless radius, r/Rw, from 0.4 to 0.8 decreased considerably owing to the concentration of bubbles in the central region of the column. The value of cross-sectionally averaged gas holdup, εg, agreed fairly well with that predicted by Koide''s equation for heterogeneous flow in a slurry bubble column. The cumulative bubble length distribution, Fl followed a log-normal distribution. On the other hand, the cumulative bubble rising velocity distribution, Fv, followed a normal distribution. The superficial gas velocity, Ug, had little effect on Fl and Fv in the slurry bubble column with high solid content. When Ug was larger than about 4 cm/s, the median of Fl and that of Fv in the slurry bubble column were larger than the corresponding values in the bubble column. On the other hand, the variance of Fl in the slurry bubble column was almost the same as that in the bubble column and the variance of Fv in the slurry bubble column was smaller than that in the bubble column.