Prediction of regime transition in three-phase sparged reactors using linear stability analysis

• Model for homogenous to heterogeneous regime transition in three phase systems.
• Model is based on linear stability analysis.
• Predicts critical gas holdup for slurry bubble columns and three-phase fluidization.
• Good agreement with published experimental results.

The estimation of critical gas holdup at which the transition from homogeneous regime to heterogeneous regime occurs is crucial for the design and scale-up of multiphase reactors. A number of experimental and empirical studies are published in the literature, however, there exists a lack of modeling studies which can satisfactorily predict the flow regime transition in three-phase sparged reactors.In the present work, the theory of linear stability analysis has been extended to investigate the hydrodynamic stability of three-phase sparged reactors (slurry bubble columns and three-phase fluidization). A mathematical model has been developed for the prediction of regime transition over a wide range of bubble size (0.7–20 × 10−3 m) and terminal rise velocity (80–340 × 10−3 m/s), particle settling velocity (1–1000 × 10−3 m/s), particle concentration (0.0007–30 vol%) and slurry density (800–5000 kg/m3). It was observed that the developed model predicts the transition gas holdup within an absolute deviation of 12% for three-phase sparged reactors. It was also observed that the developed generalized stability criterion predicts the regime transition in two-phase systems satisfactorily when applied to bubble columns.