D. Ilievski et Et. White, AGGLOMERATION DURING PRECIPITATION - AGGLOMERATION MECHANISM IDENTIFICATION FOR AL(OH)(3) CRYSTALS IN STIRRED CAUSTIC ALUMINATE SOLUTIONS, Chemical Engineering Science, 49(19), 1994, pp. 3227-3239
Reported here are the results of a study on the mechanism for Al(OH)(3
) agglomeration during precipitation in caustic aluminate solutions. T
wo independent techniques are used to identify the agglomeration mecha
nism. Both identification techniques show that Al(OH)(3) agglomeration
may be described by a size-independent agglomeration mechanism. The r
esiduals between the experimental data and estimates from the proposed
model are normally distributed, with a mean of zero and a standard de
viation of 1. The size-independent model conflicts with the current vi
ew that there exists an upper limit, imposed by the hydrodynamics, to
the aggregate size. Tracer crystal experiments, using Zn-doped Al(OH)(
3) crystals, as well as the observed evolution of the experimental siz
e distribution with time both demonstrate that crystals (or crystal ag
gregates) were agglomerating at sizes larger than the expected maximum
aggregate size. This supports the size-independent model for the rang
e of conditions studied. The analysis of the experimental Al(OH)(3) pr
ecipitation data also confirms that the growth rate is size independen
t and that there is no growth dispersion.