Gas-liquid-fiber flow in a cocurrent bubble column

Abstract

Effects of superficial gas velocity (Ul ≤ 10 cm/s), superficial liquid velocity (Ug ≤ 10 cm/s), and fiber mass fraction (0 ≤ C ≤ 2%) on gas holdup (ϵ) and flow regime transition are studied experimentally in well-mixed water-cellulose fiber suspensions in a cocurrent bubble column. Experimental results show that gas holdup decreases with increasing superficial liquid velocity when fiber mass fraction and superficial gas velocity are constant. Gas holdup is not significantly affected by fiber mass fraction in the range of C < 0.4%, but decreases with increasing fiber mass fraction in the range of 0.4% ≤ C ≤ 1.5%. The mechanisms behind the influences of superficial liquid velocity and fiber mass fraction on gas holdup in a gas-liquid-fiber bubble column are analyzed. The effects of gas distribution methods are also explained by comparison to previous results. The axial gas holdup distribution is shown to be a complex function of superficial gas and liquid velocities and fiber mass fraction. The drift-flux model is used to identify the flow regime transitions at different operating conditions. Three distinct flow regimes are observed when C ≤ 0.4%, but only two are identified when 0.6% ≤ C ≤ 1.5%. The superficial gas velocities at which the flow transitions from one regime to another are not significantly affected by Ul, and only slightly decrease with increasing C. © 2005 American Institute of Chemical Engineers AIChE J, 2005