On the shape-size dependence of potassium sulfate crystals

Abstract

Shape factors of potassium sulfate crystals grown in a continuously cooled mixed-suspension, mixed-product-removal (MSMPR) crystallizer are shown to be strongly size-dependent and to exhibit a maximum. It is considered that this shape behavior is due mainly to the size-dependent growth of different crystal faces and to the effects of attrition on larger crystals. The significance of size-dependent shape in the determination of growth kinetics from steady-state MSMPR crystal-size distributions is discussed.

Model identification and control of solution crystallization processes: a review

“…= Jq7(L) Ap(L) Q(L) dL (22) where is the slurry turbidity, l is the flow cell width, AP(L) is the projected area for a crystal of characteristic size L, and Q(L) is the extinction efficiency factor. Assuming Fraunhofer diffraction is the dominant scattering phenomena, Q -2 for all L.…”

“…Neither of the growth rate models given above indicate dependence of G on L. This size-independent growth rate assumption is usually referred to as McCabe's AL law. McCabe's AL law; Canning and Randolph [26] give a discussion of such systems, and Budz et al [22] give an expression for the size-dependent growth rate of potassium sulfate. Size-dependent growth rate is usually attributed to either bulk diffusion effects or the Gibbs-Thomson effect, which suggests an increasing growth rate with increasing size because of an inverse relationship between solubility and size.…”

“…Randolph and White [244] assume that the crystals have the same time-averaged growth rate, but individual crystals experience stochastic fluctuations in the growth rate causing the growth rate dispersion. Janse and de Jong [89] and Berglund and Larson [22] postulate that each crystal has a constant, deterministic growth rate but that these growth rates differ from crystal to crystal; there has been some work that supports this hypothesis by relating mechanical stresses and strains of a crystal to its growth rate [23,66]. Modifications to the population balance, eq 5, required to described either of these cases are available.…”

Microcomputer programming of dosage rate during batch precipitation

“…Crystals grown from added seeds are denoted S-crystals. The calculation of the other quantities shown in Table 2 is described in detail previously (JONES, MULLIN 1974;JONES et al 1987). The transient values of supersaturation, metastable zone width (MZW) and growth rate were estimated as follows :…”

Direct Observation of Growth Rate Dispersion in the Enzymatic Reactive Crystallization of Ampicillin

“…The constant crystal growth model states that nuclei are created with an intrinsic growth rate based on surface features [10]. Still other models contend that different rates of attrition of different sized crystals [11] and different crystal faces explains GRD [12], surface charge distributions can cause GRD [13], or the presence of additives or adsorbing species can enhance or inhibit growth, leading to growth oscillations and GRD [14]. In this study we show that GRD observed in ampicillin trihydrate is most easily explained by the constant crystal growth model and that surface morphology and crystal imperfections (such as dislocations) are likely the cause, although the influence of additives, in this case the ampicillin precursors 6-aminopenicillanic acid (6-APA) and D-phenylglycine methyl ester (PGME), may have an important influence.…”