Gas holdup and oxygen transfer studies in non-Newtonian suspensions of cellulose fibres conducted in two large (0.098 m3 each) reactors are described. Both reactors—a bubble column and a similar internal loop airlift—were unusual in that they had rectangular cross-sections. In all cases gas holdups and kLaL declined with increasing solid concentration and, under identical conditions, the bubble column performed better than the airlift. The fluid systems used were carefully selected to represent mould fermentation broths.
The behavior of true mass transfer coeffcient kL with changes in bubble size is discussed for these systems.