Crystallization agglomeration

A secondary particle formation process, which can increase crystal size dramatically, is crystal agglomeration. This process is particularly prevalent in systems exhibiting high levels of supersaturation, such as from precipitation reactions, and is considered along with its opposite viz. particle disruption in Chapter 6. Such high levels of supersaturation can markedly accentuate the effects of spatial variations due to imperfect mixing within a crystallizer. This aspect is considered further in Chapter 8. 

The effect of crystal agglomeration is generally to cause concave curvature on the log population density versus size plot (see Figure 6.11b). 

Crystal agglomeration and disruption 111 Both breakage funetions ean be eheeked for eonsisteney using the relation... 

The dynamics of reactor flow is also important for its effect on the crystal agglomeration, since the intensity of turbulent shear dominates the orthoki-netic mechanism for both processes of aggregation and disruption. The mean shear rate is estimated as (see Harnby etai, 1992)... 

Figure 8.17 EJfect of estimated shear rate on the size of crystal agglomerates Jones etal., 1992a)...

Figure 8.26 Monte Carlo simulation of MSMPR precipitated crystal agglomerate specific surface area Hostomsky and Jones, 1993a)...

If crystal agglomeration and breakage can be neglected and crystal growth is invariant then at steady state the familiar analytic form is... 

Wojcik, J. and Jones, A.G., 1998b. Particle disruption of precipitated CaC03 crystal agglomerates in turbulently agitated suspensions. Chemical Engineering Science, 53, 1097-1101. 

The anisotropy held arises from four contributions, and it may furthermore be influenced by the extent of crystal agglomeration ... 

Although the lipid phase in powdered toppings is finely dispersed in the form of small globules (< 1 /am), strong destabilization takes place after reconstitution in cold water, resulting in platelet-like crystal agglomerates (Figures 6 and 7). 

Carr, G., Simmons, N.L., and J.A. Sayer, 2006, Disruption of clc-5 leads to a redistribution of annexin A2 and promotes calcium crystal agglomeration in collecting duct epithelial cells. Cell Mol Life Sci. 63(3) 367-77. 

Fig. 35.10. Example of a co-crystal I ized sugar product. The ball represents many microsized sugar crystals agglomerated into a porous granule, which allows inclusion of a second ingredient throughout the structure.

The PBXs are powdered explosives to which plastic binders have been added. The binder is usually precipitated out of solution in the preparation process such that it coats the explosive crystals. Agglomerates of these coated crystals form pressing beads. The beads are then either die pressed or isostatically pressed at temperatures as high as 120°C. Pressures from 1 to 20 kpsi then produce pellets, or billets, with densities as high as 97% of the theoretical maximum density (TMD). The billets thus produced have good mechanical strength and can be machined to very close tolerances. Table 4.3 lists various PBXs in common use in the U.S. Department of Energy s (DOE) weapons laboratories. Table... 

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