Particle flow modelling in slurry-fed stirred vessels

In this paper experimental information on the retention time distribution (RTD) of solid particles in a high-aspect-ratio vessel, stirred by three equally spaced Rushton turbines, is presented. The relevant data were obtained by a special technique named twin system approach (TSA) that greatly simpli+es the handling of particle-laden streams and is therefore particularly suited for investigating particle RTD in 9ow systems. The technique fundamentals are +rst summarized, together with the data analysis procedure. This lastly requires a numerical deconvolution operation that is easily performed with the help of Z-transforms. Two di;erent approaches for excluding the spurious contributions of…

Residence time distribution of solid particles in a continuous, high-aspect-ratio multiple-impeller stirred vessel

Abstract In this paper experimental information on the retention time distribution (RTD) of solid particles in a high-aspect-ratio vessel, stirred by three equally spaced Rushton turbines, is presented. The relevant data were obtained by a special technique named twin system approach (TSA) that greatly simplifies the handling of particle-laden streams and is therefore particularly suited for investigating particle RTD in flow systems. The technique fundamentals are first summarized, together with the data analysis procedure. This lastly requires a numerical deconvolution operation that is easily performed with the help of Z -transforms. Two different approaches for excluding the spurious co…

Axial dispersion model for solid flow in liquid suspension in system of two mixers in total recycle

The measurement of residence time distribution of solid particles in solid-liquid suspension is experimentally difficult. However, the twin system approach is particularly suited for the assessment of particle RTD in flow systems as it allows overcoming some of the usual difficulties generally encountered in this kind of measurement. Twin system consists of two vessels and external piping in total recycle. Experimental results from this system can be evaluated using Z-transforms to derive particle RTD for subsequent testing of alternative flow models. Recently, the axial dispersion model was applied using the "advection diffusion equation" (sometimes called the"diffusion with bulk flow equa…

CFD simulations of the clear liquid layer formation in dense solid-liquid suspension

Residence Time Distribution of Solid Particles in a High-Aspect Ratio Multiple-Impeller Stirred Vessel

Despite its importance, experimental information on the Residence Time Distribution (RTD) of solid particles in continuous-flow stirred vessels is still scant. In this work, experimental data on particle RTD in a high-aspect-ratio vessel stirred by three equally-spaced Rushton turbines, was obtained by means of a special technique named Twin System Approach (TSA). Quite surprisingly, results indicate that, among the various possibilities that could have been devised (e.g. 6, or 3, or 1 ideal tanks in series), the flow model closest to reality for the particle phase, at least in the experimental range here investigated, is that of a single perfectly stirred vessel.