Suspension, Classified-Product-Removal Crystallizers

Mixed-Suspension, Classified-Product-Removal Crystallizers. 18-48... 

Utilizing the above factors, theoretical analyses of some possible design procedures for fluidized-bed classifying and mixed-suspension classified product removal crystallizers have been presented together with detailed worked examples by Mullin and N lt (1970) and Nyvlt (1992). 

K is a constant and Lr is the size of a crystal grown from a nucleus (zero size) in the draw-down time, t, i.e. the overall residence time, defined as the ratio of the mass of crystals in suspension to the crystal production rate, or the volume of suspension to the volumetric feed rate. Saeman also compared the cases of mixed-suspension, classified-product removal (MSCPR) with MSMPR operation and showed, for example, that the age of a product mean size crystal was... 

MSCPR crystallizer mixed suspension, classified product removal) with homogeneous mixing and classified product discharging... 

An even greater problem is the quantitative application of the population balance in the coarse grain crystallizers of DTB and fluidized bed design, which due to the cyclical behavior described above are almost impossible to describe with the MSCPR (mixed suspension classified product removal) and CSCPR (classified suspension classified product removal) approaches. 

Figure 7.10 Fines destruction and classified product removal during continuous mixed suspension crystallization...

Another mechanism that must be mentioned in connection with nucleation in real crystallization equipment is attrition. In a classic paper by Randolph (1969), this subject is reviewed. Randolph demonstrated that crystal breakage, classified product removal, and decrease in linear growth rate with crystal size all skew the crystal size distribution, producing a narrower size range of crystals than would be expected in a mixed suspension, mixed product removal system. This skewing results in a curve of the plot of In n versus L. 

Figure 9.7. Three basic types of continuously operated mixed suspension crystallizer, a) mixed product removal MSMPP, (b) clear liquid overflow CLO), (c) CLO with recycle through an elutriating leg classified product removal MSCPB. F = feed, E = elutriating leg, M = magma outlet, O = overflow...

Figure 9.10. Dynamic behaviour of a mixed suspension crystallizer showing a) mixed product removal - short period damped cycles b) classified product removal via elutriating leg - long period slowly damped cycles. P, production rate M, magma density S, supersaturation L, median crystal size various scales). After Nyvlt and Mullin, 1970)...

Figure 9.11. Mixed suspension crystallizer operating with fines destruction and classified product removal a) the R-Z model, b) population density plot...

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