The effect of bubble column diameter on gas holdup in fiber suspensions

Three bubble column diameters (D=10.2D=10.2, 15.2, and 32.1 cm) are employed to study the scale-up effect on gas holdup in air–water and air–water–cellulose fiber (hardwood, softwood, and BCTMP) systems. The effect of column diameter depends on flow regime and fiber mass fraction. When D⩽15.2cm, gas holdup decreases with increasing column diameter for the transitional and heterogeneous flow regime, and column diameter effects are negligible in the homogeneous flow regime. When D⩾15.2cm, gas holdup is only affected by column diameter in the transitional flow regime for an air–water system and low fiber mass fraction suspensions (C⩽0.25%C⩽0.25%); column diameter effects disappear at medium fiber mass fractions (e.g., C=0.8%C=0.8%) but are significant at high fiber mass fractions (e.g., C=1.4%C=1.4%).