Characterisation of particle stress in turbulent impeller flows utilising photo-optical measurements of a flocculation system - PART 2

The study aims at utilising the clay floc system and methods of Panckow et al. (2023) to characterise the hydrodynamic stress acting on particles in a lab-scale stirred tank reactor. The effect of the flocculation phase on steady-state characteristics, as well as the system's reversibility are examined. Conventional and nonconventional impeller types and varying impeller geometrical features are investigated regarding their breakage intensity. The median floc size, the characteristics of the particle size distributions and the floc shape analysis provide a comprehensive characterisation of the various impellers in terms of stress intensity and breakage mechanism. Radial-flow impellers are beneficial for applications with stress-sensitive particles. Studies of the authors' research group with different particle systems (emulsion and filamentous fungi) were used to compare the results extensively. A modelling attempt based on literature correlations indicates the maximum energy dissipation rate as the primary physical cause behind the breakage at this reactor scale.