Kinetics secondary nucleation

Garside, J. and Jancic, S.J., 1979. Measurement and scale-up of secondary nucleation kinetics for the potash alum-water system. American Institute of Chemical Engineers Journal, 25, 948. 

The secondary nucleation kinetics could be empirically correlated by equation (2). 

This, and other similar equations, show that scale-up of secondary nucleation kinetics on the basis of constant specific power input, e, should at most produce only a modest increase in nucleation rate. Constant tip speed or constant stirrer speed to just maintain the crystals in suspension should both result in a decrease in nucleation rate with increasing scale of operation (Garside and Davey, 1980). 

Evidence for secondary nucleation has came from the early continuous MSMPR studies. MSMPR crystallization kinetics are usually correlated with supersaturation using empirical expressions of the form... 

Garside, J. and Davey, R.J., 1980. Secondary contact nucleation Kinetics, growth and scale-up. Chemical Engineering Communications, 4, 393. 

Before discussing the effect of short-chain branching on the kinetics of crystallization process, it is necessary to revisit the theory of secondary nucleation and the concept of regimes as given by Lauritzen and Hoffmann... 

A rate enhancement effect due to secondary nucleation has been identified in the solution-mediated transformation of the 7-phase of (i)-glutamic acid to its / -phase [82]. In this study, the kinetics of the polymorphic transition were studied using optical microscopy combined with Fourier transform infrared, Raman, and ultraviolet absorption spectroscopies. The crystallization process of n-hexatriacontane was investigated using micro-IR methodology, where it was confirmed that single... 

In this section, a brief description of the necessary experiments to identify the kinetic parameters of a seeded naphthalene-toluene batch crystallization system is presented. Details about the experimental apparatus and procedure are given by Witkowski (12). Operating conditions are selected so that the supersaturation level is kept within the metastable region to prevent homogeneous nucleation. To enhance the probability of secondary nucleation, sieved naphthalene seed particles are introduced into the system at time zero. 

Kinetics of Secondary Nucleation of Alumina Triliydrate in a Batch Crystallizer... 

Literature has revealed limited kinetic data on secondary nucleation of alumina trihydrate in the precipitator of the Bayer Process for alumina production. A batch agitated, isothermal, three litre crystallizer was used in the study. A Coulter-Counter was utilized as the particle sizing equipment. The effects of seed density, supersaturation and temperature on secondary nucleation were investigated. Maximum nucleation rates were found to occur at about 70 C and for any crystallization temperature, the nucleation rate passed through a maximum. The correlated equation for the effective secondary nucleation rate of alumina trihydrate is... 

One of the successes of the EH theory is its ability to provide an exphcit result for the lamellar thickness, based on kinetic considerations of secondary nucleation. In the EH theory, 8L is a natural result of the steady state and not due to any subsequent thickening. The form of Eq. (1.94) is exactly the same as Eq. (1.1), observed experimentally. However, one of the serious difficulties posed by Eq. (1.94) is that it predicts a divergence in 5L at... 

In contrast to more or less well defined kinetics of the crystal growth (5,6,12-16), various nucleation mechanisms have been proposed as zeolite particles forming processes. Most authors explained the formation of primary zeolite particles by nucleation in the liquid phase supersaturated with soluble silicate, aluminate and/or aluminosilicate species (1,3,5,7,16-22), with homogeneous nucleation (1,5,7,17,22), heterogeneous nucleation (5,2 1), cell walls nucleation (16) and secondary nucleation (5) as dominant processes of zeolite particles formation, but the concepts dealing with the nucleation in the gel phase are also presented in the literature (2,6,11,12,1 1,23-25). 

Once primary nuclei are formed the ensuing spherulites grow radially at a constant rate. Primary crystallization, which occurs initially on the surface of the primary nucleus and then on the surface of the growing lamellar, also involves a nucleation step, secondary nucleation. It is this step that largely governs the ultimate crystal thickness and which forms the focus of most kinetic theories of polymer crystallization. 

In addition, it is found that the rate of reaction is directly proportional to the inoculating seed concentration, thus confirming that the growth of the crystals takes place without interference from secondary nucleation. To have obtained a kinetic precipitation stoichiometry to this precision by techniques previously used would have required concentration analysis to at least 4 0.03%. Although, as mentioned previously, it had been assiamed that the ratio, R, was close to that for TCP, thereby invoking TCP as the precursor, it is clear from the results in Table I that the ratio is significantly lower than the Ca P = 1.50 required for TCP. 

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