Solid suspension in stirred tank reactor: Hysteresis in cloud height and solid velocity profiles by UVP and CFD simulation

Solid suspension in stirred tank reactor (STR) is commonly used in process industries for catalytic reactions, dissolution of a solid, crystallization, and so on. Understanding of solid dynamics in solid suspension phenomenon is the key issue in design and operation of stirred reactor. Experimental investigations on the measurements of cloud height and its hysteresis effect provided guidelines for limitations of available drag correlations. A comprehensive CFD model was developed in the present study to gain insight into solid suspension in stirred slurry reactor. The main objective of present study is to characterize solid distribution, cloud height; solid velocity profiles with visual and UVP technique respectively. This objective will provide new ways of understanding of solid suspension and drag acting on particle in turbulent medium. The knowledge and accurate estimation of particle drag coefficient is required for many industrially important multiphase processes and also CFD modeling for scale up of reactors. Fundamental approach of cloud height and its hysteresis is considered first time in the area of solid suspension in stirred tank reactor. Hysteresis data obtained with experimental measurements was used to assess the ability of the existing drag correlations used in CFD models for predicting the solid dynamics in a stirred tank. CFD model predictions were compared with own experimental data. Combination of experimental and CFD work will offer quantitative information about relative motion of particles and ultimately drag acting on particles. The computational model and results discussed in this work would be useful for extending the applications of CFD models for simulating large stirred slurry reactors.