Improving batch cooling seeded crystallization of an organic weed-killer using on-line ATR FTIR measurement of supersaturation

In previous papers, a method for the calibration of ATR FTIR measurement of dissolved solid concentration during cooling crystallizations was presente d, and efficient basic procedures for the determination of solubility and m etastability curves were described. The present paper reports new experimen tal results. The crystallization of an organic product is studied thanks to on-line FTIR measurements of supersaturation and off-line crystal size dis tribution (CSD) determinations. The obtained information is shown to potent ially allow a deeper examination of major industrial issues such as the red uction of batch-to-batch variations and the improvement of the CSD of the f inal particles. A particular attention is focused on the determination of a ppropriate seeding parameters such as the cooling rate of seeded slurries, the temperature of introduction and the amount of seed. The results obtaine d demonstrate that, although any modelling approach is outside the scope of this paper, the analysis of the measured supersaturation profiles allows s ome interpretation of mechanisms governing the final CSD, and consequently, the proposal of improved operating parameters. (C) 2001 Published by Elsev ier Science B.V.