Solids mixing 1374 INDEX

MIXING INDEX IN BLENDING GRANULAR SOLIDS. The effectiveness of a solids blender is measured by a statistical procedure much like that used with pastes. Spot samples are taken at random from the mix and analyzed. The standard deviation of the analyses s about their average value x is estimated, as with pastes, from Eq. (28.18). 

With granular solids the mixing index is based, not on conditions at zero mixing, but on the standard deviation that would be observed with a completely random, fully blended mixture. With pastes, assuming the analyses are perfectly accurate, this value is zero. With granular solids it is not zero. 

For granular solids the mixing index I, is defined as ajs. From Eqs. 

Mixing index for granular solids, ajs /j o. at zero time or zero mixing Number of fraction or increment also, screen number, counting from smallest size Ratio of pressures,... 

Representative plot of mixing time versus mixing index for solids. 

Engineering handbooks (see, e.g., [1]), extensive review articles (see, e.g., [2,7], Weidenbaum [21]), and the monograph by Kaye [5] on solids mixing provide comprehensive information on solids mixers and blenders. Detailed information on individual mixers or classes of mixers can be found in articles in technical and trade journals academic theses and dissertations and commercial publications by the makers of mixers. Many of the technical articles, theses, and dissertations are cited in the extensive reviews mentioned earlier they can also be identified by searching through publications such as Chemical Abstracts and Engineering Indexes. 

Mixing of Solids Sherman S. Weidenbaum Author Tndex—Subject Index... 

Treatment and Disposal of Wastes in Nuclear Chemical Technology Bernard Manowitz High Vacuum Technology George A. Safer and Harold C. Weingartner Separation by Adsorption Methods Theodore Vermeulen Mixing of Solids Sherman S. Weidenbaum Author Index—Subject Index... 

Centrifuges. Solid-bowl centrifuges have been proposed as an alternative classifying device to hydrocydones for cut sizes below 10 JJm. The results appear to be mixed (21). In one application, where the cut size was 6.5 Jim and the sharpness index 0.7, there was essentially no apparent bypass. However, in other applications operating at higher feed concentrations, the cut size ranged from 5—8 im, but the sharpness index was between 0.3—0.5 and the apparent bypass between 10—30% or higher (22). Smaller cut sizes have also been reported (23). 

Figure 3. Relationship between leaf area (A), epidermal cell density (B), stomatal density (C) and stomatal index (D) versus altitude for Nothofagus solandri leaves growing on the slope of Mt. Ruapehu, New Zealand (collected in 1999). Black diamonds indicate the mean of ten counting fields on each leaf, white squares are the averages of five to eight leaves per elevation, with error bars of 1 S.E.M. Nested mixed-model ANOVA with a general linear model indicates significant differences for all factors (p = 0.000). Averages per elevation were used for regression analysis A. y = -0.0212 + 73.1 R2 = 0.276 p = 0.147. B. y = 1.70 + 3122 R2 = 0.505 p = 0.048. C. y = 0.164 + 360 R2 = 0.709 p = 0.009. D. linear (dashed) y = 0.004 + 9.33 R2 = 0.540 p = 0.038 non-linear (solid) y = 0.00001 2 - 0.0206 + 21.132 R2 = 0.770.

Figure 5 Compilation of the U37 index of mixed-layer particulates in relation to in situ temperature (Conte et al., in press). The heavy solid line indicates the linear Prahl et al. (1988) paleotemperature relation used for sediment estimates.

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