Mixing of dense binary suspensions: Multi‐component hydrodynamics and spatial phase distribution by PEPT

Abstract

The three-component flow field and spatial phase distribution of binary mixtures of glass particles suspended in water in a stirred vessel have been resolved using positron emission particle tracking (PEPT). The Lagrangian flow data provided by the technique have been converted to give a detailed Eulerian description of each of the three phase components of the flow generated by a pitched blade turbine. For the first time, it has been possible to determine the full 3D velocity and concentration fields of the liquid phase and both the solid components within opaque dense slurries of this type containing up to 40 wt % solids. Spatial distributions of local time-averaged slip velocity have also been obtained for each solid component showing wide variations. The detailed PEPT measurements have enabled the solids mass balance and the mass continuity of the three phase components to be accurately verified throughout the vessel.

Lagrangian tools for the analysis of mixing in single‐phase and multiphase flow systems

“…For example, the time-averaged volume concentration of each of the two solid components and of the liquid in binary solidliquid suspensions has recently been mapped experimentally using single particle tracking and newly developed threecomponent concentration maps. 23 As shown in Figure 8m, the occupancy map in a turbulent single-phase system is almost uniform and O E $ 1, which is in agreement with Eq. 20 because in a single-phase system the time-averaged phase concentration is 100% everywhere.…”

“…A broad set of single particle tracking experiments were conducted on single-phase and solid-liquid systems in fully baffled flat-base cylindrical vessels 17,22,23 having a diameter T varying in the range 150-290 mm (Figure 1). Newtonian and non-Newtonian single-phase fluids were used to study mixing under turbulent and laminar/transitional flow conditions including cavern formation, using neutrally buoyant particle tracers.…”

Lagrangian particle tracking in mechanically agitated polydisperse suspensions: Multi-component hydrodynamics and spatial distribution

“…Their results also showed that the homogeneity of the solid-liquid suspension improved with increasing average solid concentration. We recently observed the same effect using coarse monosized or binary suspensions of glass particles (d ~ 1, 3 mm) (Guida et al, 2010a(Guida et al, , 2011Liu and Barigou, 2013).…”

“…PEPT has been validated by comparing its measurements with PIV in water, and has been shown to be an accurate and reliable technique (Pianko-Oprych et al, 2009). More details about the technique can be found in our earlier papers (Barigou, 2004;Guida et al, 2009;Barigou et al, 2009;Guida et al, 2010aGuida et al, , 2011Guida et al, , 2012.…”

A multiple radioactive particle tracking technique to investigate particulate flows

“…The optical methods are essentially limited to transparent systems while radioactive techniques can be applied in opaque systems, because gamma rays can penetrate relatively easily through various materials. PEPT uses two positron‐sensitive detectors mounted on the opposite sides of a system to detect pairs of exactly back to back gamma rays resulting from the annihilation of a positron . This technique is able to detect a tracer when this tracer is within the volume covered by the detectors.…”