Nonsegregation

When the target population is segregated, or stratified, equation 7.5 provides a poor estimate of the amount of sample needed to achieve a desired relative standard deviation for sampling. A more appropriate relationship, which can be applied to both segregated and nonsegregated samples, has been proposed. ... 

In this chapter, we develop the basis for design and performance analysis for a CSTR (continuous stirred-tank reactor). The general features of a CSTR are outlined in Section 2.3.1, and are illustrated schematically in Figure 2.3 for both a single-stage CSTR and a two-stage CSTR. The essential features, as applied to complete dispersion at the microscopic level, i.e., nonsegregated flow, are recapitulated as follows ... 

For nonsegregation, the performance is obtained from the material-balance equation... 

For a first-order reaction in a CSTR, compare the predicted performance for completely segregated flow with that for nonsegregated flow. 

Table 14.1 Comparison of nonsegregated and segregated flow in a CSTR0...

Creation of uniform, nonsegregating blends of fine materials... 

The effect of mixing time on segregation is that nonsegregating mixtures continue to improve with an extended mixing time, but the reverse may be true for segregating mixes. 

Powders may be classified as nonsegregating (cohesive) or segregating (free-flowing). Representative samples can be more easily taken from cohesive powders, provided that they have been properly mixed. For wet samples a sticky paste should be created and mixed from which the partial sample is taken. 

Creation of nonsegregating blends of powder ingredients with ideally uniform distribution of key ingredients, as in sintering of fines for steel or agricultural chemical or pharmaceutical granules. 

With waste rubber goods, as with nonsegregated plastic wastes, it is possible to simply burn the rubber and regain the considerable fuel value. Whole scrap tires have been burned in cement kilns, for example, to obtain a proportionate saving in the usual oil or gas fuel supply used in these operations. At the extremely high kiln temperatures the combustion is complete and any steel belts or beading are incorporated into the cement klinker without problems. 

Figure 34. The increase in weight percent solids with time for one of the Suncor field test cells. The increasing solids content (approaching that of a stable soil) with constant fines ratio indicates that the suspension is nonsegregating.

Figure 35. Nomogram of the fines, water, and sand tailings mixtures, defining the fines and sand content that results in nonsegregating mixtures (18, 35, 79, 80 .

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