Suspensibility correlation

Particle diameter is included in the correlation as (dp/D). Chowdhury (1997 Penney et al., 1997) and others have found that Njs is virtually independent of (dp/D) for (dp/D) > 0.01. This is of no practical importance for large vessels where D could be 40" and it would be unlikely to encounter particles larger than 0.4" diameter however, it could give underpowered agitators for scale-up from small vessels where the minimum D could be 2" and the maximum dp could be 0.2", for a maximum (dp/D) = 0.1, which is 10 times (dp/D) = 0.01. Scale-up at equal P/V, which is typical for sohds suspension, could give an Njs about 100/(10) 2 = 60% of the required Njs. Avoid this scale-up mistake by using accurate suspension correlations to determine Njs for plant vessels, when scahng-up from laboratory experiments where (dp/D) >0.01. 

Liquid-solid mixtures that do not settle out rapidly are usually treated as non-Newtonian fluids. This will usually be the case if the solid particle size is less than about 200 microns (0.2 mm). Larger particle sizes will form settling slurries and require a critical velocity to maintain the solids in suspension. Correlations for critical velocity and pressure drop are given in Perry and Green (1997). 

Hraste M., Husnjak M., Suspension Correlation in the Range of Critical Particle/ Vessel Diameter Ratio, Chem. Biochem. Eng. Q 9 (1995) 2,... 

Techniques for measuring the speed required for the condition for just suspension are discussed in Chapter 4 of this book and by Choudhury (1997). Also discussed are key aspects of the criteria, techniques, and precautions that one must take to obtain reliable data for solids suspension correlations. The Zwietering criterion of no particle remaining at the base of the vessel for more than 1 to 2 s is the basis for most of the published studies. 

Another approximation, one of the most enduring empirical correlations in multiphase systems, is the Richardson-Zaki correlation for a single particle in a suspension (3) ... 

Strictly speakiag, these correlations apply only to the cases where flocculation is absent, such as for coarse mineral suspensions. Suspensions of fine... 

In the present work the acid-base surface properties of three Al O samples for a chromatography are investigated acidic (I), basic (II) and neutral (III) ones with the using of heterogeneous titration of their suspensions by HCl and NaOH solutions. To establish the correlations between the acid-base and adsoi ption properties studied Al O the representatives of cationic dyes -diamond green (DG), fuchsine (F) and anionic dyes - eriochrom black T and chromic dark blue have been used. 

BD. Dynamical correlations in suspensions of charged rod-like particles were simulated [121]. 

The flow of compressible and non-compressible liquids, gases, vapors, suspensions, slurries and many other fluid systems has received sufficient study to allow definite evaluation of conditions for a variety of process situations for Newtonian fluids. For the non-Newtonian fluids, considerable data is available. However, its correlation is not as broad in application, due to the significant influence of physical and rheological properties. This presentation is limited to Newtonian systems, except where noted. 

Equal suspension of particles referenced to visual appearances and physical sample testing. Empirical correlations generalized to apply to most problems. 

At least, in absolute majority of cases, where the concentration dependence of viscosity is discussed, the case at hand is a shear flow. At the same time, it is by no means obvious (to be more exact the reverse is valid) that the values of the viscosity of dispersions determined during shear, will correlate with the values of the viscosity measured at other types of stressed state, for example at extension. Then a concept on the viscosity of suspensions (except ultimately diluted) loses its unambiguousness, and correspondingly the coefficients cn cease to be characteristics of the system, because they become dependent on the type of flow. 

Kato (K3) measured so-called critical gas velocities corresponding to the complete suspension of solids, and presents a graphical correlation of the results for glass spheres (diameters from 0.074 to 0.295 mm), magnetite particles (particle size from 0.038 to 0.175 mm), and sand particles (particle size 0.147 to 0.295 mm). 

Roy et al. (R3) define the critical solids holdup as the maximum quantity of solids that can be held in suspension in an agitated liquid. They present measurements of this factor for various values of gas velocity, gas distribution, solid-particle size, liquid surface tension, liquid viscosity, and a solid-liquid wettability parameter, and they propose the following two correlations in terms of dimensionless groups containing these parameters ... 

For suspensions of kieselguhr in water and oil, the following correlations were developed, in which the Nusselt and Reynolds numbers are based on the length of the heating element ... 

Another largely unexplored area is the change of dynamics due to the influence of the surface. The dynamic behavior of a latex suspension as a model system for Brownian particles is determined by photon correlation spectroscopy in evanescent wave geometry [130] and reported to differ strongly from the bulk. Little information is available on surface motion and relaxation phenomena of polymers [10, 131]. The softening at the surface of polymer thin films is measured by a mechanical nano-indentation technique [132], where the applied force and the path during the penetration of a thin needle into the surface is carefully determined. Thus the structure, conformation and dynamics of polymer molecules at the free surface is still very much unexplored and only few specific examples have been reported in the literature. 

There were several studies of hydraulic transport in the 1950s, sparked off particularly by an interest in the economic possibilities of transportation of coal and other minerals over long distances. Newitt et al.p2) working with solids of a range of particle sizes (up to 5 fim) and densities (1180-4600 kg/m3) in a 25 mm diameter pipe, suggested separate correlations for flow with a bed deposit and tor conditions where the particles were predominantly in heterogeneous suspension. 

The increase in Ca is initiated rapidly and begins to recover after 1 min. The order of potency correlates fairly well with the solubilities of these compounds in organic solvents (37) and their abilities to accumulate in phospholipid vesicles (38), i.e., 6>y>a>p, but not with their insecticidal activity (y 6>a p 39). At these concentrations, crystals of p-, a-, and y-HCH were evident in the cell suspensions when we made simultaneous measurements of the right-angle light scatter, indicating that the order of aqueous solubilities is 6>y>a>p. However, stimulation by 6-HCH at concentrations below its aqueous solubility limit shows a typical dose dependency of the response (Figure 10). 

For plant cell suspensions cultivated in shake flasks, Huang et al. [45] used the energy dissipation rate as a correlating parameter for system response. Specific power input was calculated using the empirical correlation proposed by Sumino et al. [46] and subsequently employed in other applications [47,48] ... 

BalHca and Ryu [158] correlated reductions in cell yield in Datura stramonium suspensions with the increased Reynolds stresses associated with higher aeration rates in a 1.2-1 ALR. A more recent study [159] of C. roseus suspensions cultivated in a 1.5-1 bubble column showed that the increased bubble sizes associated with both larger sparger pores and higher aeration rates caused a reduction in system performance. Here, also, it was postulated that the effects were due to increased Reynolds shear stresses in the flow field. However, it was not possible to rule out gas-stripping effects. 

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