Secondary nucleation of K-alum by minimum size seeds in a stirred vessel

Secondary nucleation rate of K-alum was studied by adding controlled amounts into a stirred vessel. Change in number of produced nuclei against the elapsed time was observed by direct counting, and the results were featured by slight increase in number at the initial stage, followed by rapid increase in constant elapsed time specified by the particular supersaturation. The existence of a definite size to contribute to following nucleation was recognized, and this size was minimum for secondary nucleation and correlated with supersaturation. Minimum size was proposed as a new effective factor on the secondary nucleation rate, and secondary nucleation rate per unit surface of crystals near minimum size was correlated with supersaturation and agitation rate in the stirred vessel. Secondary nucleation rate in the stirred vessel was also discussed in comparison to that in the fiuidized bed. The primary nucleation in the stirred vessel and latent period for the produced nuclei to grow to minimum size to contribute to following nucleation were also discussed.