Chemical Engineering Science 56 (2001) 6047–6053 www.elsevier.com/locate/ces Eect of pseudoplastic behaviour of liquid in co-current three-phase uidized beds on bed expansion H. Miura, T. Takahashi, Y. Kawase * Department of Applied Chemistry, Toyo University, Kawagoe, Saitama 350-8585, Japan Abstract Gas hold-up and bed expansion measurements were carried out for a bed of glass beads uidized in Newtonian liquids and non-Newtonian liquids with gas. The value of gas hold-up increased and decreased with increasing particle size and liquid velocity, respectively. The eect of rheological properties on gas hold-up was insignicant and therefore the gas hold-up data for both Newtonian and non-Newtonian uids were reasonably tted by the available correlation which had no liquid viscosity term. The bed voidage increased with increasing supercial liquid velocities and supercial gas velocities. The increase of the viscous non-Newtonian ow behaviours resulted in an increase of the bed voidage. The correlation for the bed voidage in three-phase uidized beds was developed for gas-Newtonian or non-Newtonian liquid–solid three-phase systems by combining the generalized wake model and the correlation for liquid–solid two-phase systems proposed previously by the authors. The predictions for bed voidage were in reasonable agreement with the present experimental data for three-phase systems with Newtonian and non-Newtonian liquids in a wide range of Reynolds numbers. ? 2001 Elsevier Science Ltd. All rights reserved. Keywords: Three-phase uidized bed; Bed voidage; Non-Newtonian liquid; Gas hold-up 1. Introduction Gas–liquid–solid three-phase uidized beds have been widely used in chemical, petrochemical and biochemical industries. During recent years, therefore, considerable progress has been made in exploring and understand- ing the hydrodynamics in three-phase uidized beds (Fan, 1989; Nigam & Schumpe, 1996). Bed expan- sion characteristics are the most important design pa- rameters. Although several uidized beds operate with non-Newtonian liquids in food and polymer process- ing and biotechnology, most of the work on the bed expansion characteristics in three-phase uidized beds has been restricted to three-phase uidized beds with Newtonian liquids. Patwari, Nguyen-Tien, Schumpe, and Deckwer (1986) reported the data of gas hold-up and bed expansion in a 0:14 m i.d. three-phase u- idized bed with non-Newtonian uids. Dharwadkar, Sawant, and Joshi (1987) measured gas hold-up in highly ∗ Corresponding author. Tel.: +81-492-39-1377; fax: +81-492- 31-1031. E-mail address: bckawase@eng.toyo.ac.jp (Y. Kawase). viscous non-Newtonian liquids and proposed an empiri- cal correlation for gas hold-up in three-phase sparged re- actors. Zaidi, Deckwer, Mrani, and Benchekchou (1990) and Lee, Kim, and Kim (1993) measured gas hold-ups and bed voidages and proposed empirical correlations for gas hold-up. However, earlier bed expansion stud- ies in the literature have been limited to small Reynolds numbers and there is no satisfactory predictive expres- sion for bed expansion in three-phase uidized beds with non-Newtonian liquids over a wide range of ow con- ditions. The knowledge on bed expansion characteristics in gas-non-Newtonian liquid–solid three-phase uidized beds is far from satisfactory. Hence, it is necessary to study the inuence of non-Newtonian ow behaviours on the bed voidage of three-phase uidized beds over a wide range of Reynolds numbers. The aim of this work is to examine bed expansion characteristics in co-current three-phase uidized beds with Newtonian and non-Newtonian uids. Experimen- tal data on the gas hold-up and the bed voidage are pre- sented in a wide range of Reynolds numbers. Based on the generalized wake model and the voidage correlation for liquid–solid two-phase systems, the correlation for 0009-2509/01/$-see front matter ? 2001 Elsevier Science Ltd. All rights reserved. PII:S0009-2509(01)00219-6