Hindered settling factor

This equation defines the characteristic speed, that is, the kinematic wave speed. Note that for s = constant the characteristic speed drldt= which is analogous to the wave speed in the gravity sedimentation problem except that here is not constant with distance. The analogy also holds with s — s p) if s d sp)/dp is defined as a hindered settling factor G(d>) (Eq. 5.4.18). 

Ut = Terminal settling velocity, ft/sec Fs = CoiTection factor for hindered settling p, po = Density of water or oil, Ib/ff ... 

There are essentially three different approaches to describing hindered settling. One approach is to define a correction factor to the Stokes free settling velocity in an infinite Newtonian fluid (which we will designate F0), as a function of the solids loading. A second approach is to consider the suspending fluid properties (e.g. viscosity and density) to be modified by the... 

If the particle concentration in a suspension is high, then the particles do not sediment independently, but are influenced by the motions of surrounding particles (hindered settling). Hindered settling behaviour can be described by applying a correction factor to the Stokes Law terminal settling velocity (dx/dt from Eq. 2.20) to obtain a hindered settling velocity. Several equations have been advanced to describe the correction [69]. The Richardson-Zaki equation for this is ... 

Hindered settling behavior may be described as Stokes law correction (i.e., correcting the terminal settling velocity of a single particle) by introducing a multiplying factor, such as... 

The correction factor is presented in Table 7-8 as a function of weight concentration. This empirical coefficient was developed by Chemineer Inc., based on experimental work. It is often difficult to predict the nature of the flow or the drag coefficient near an impeller blade. At weight concentrations in excess of 15%, the solids start to interact, hindering settling so that the settling velocity must be adjusted. 

For.this hindered flow the settling velocity is less than would be calculated from Eq. (14.3-9) for Stokes law. The true drag force is greater in the suspension because of the interference of the other particles. This higher effective viscosity of the mixtureis equal to the actual viscosity of the liquid itself, fi, divided by an empirical correction factor,, which depends upon e, the volume fraction of the slurry mixture occupied by the liquid (SI). 

---