Crystal growth of L(+)-ascorbic acid in a batch crystallizer

The measurements of the crystal growth rate in L(+)-ascorbic acid - water and L(+)-ascorbic acid - alcohol - water systems are presented. The influence of methanol, ethanol and isopropanol on the crystallization system has been studied. Measurements were carried out in the batch crystallizer with inner circulation of a suspension. The effect of the saturation temperature and the cooling rate has been determined. It was found that the rate of crystal growth decreases with the temperature increase, reaching the lowest value (ca 1.3-10-m/s) in the aqueous solution (Teq = 343.5 K) of initial concentration 50 mass % of L(+)-ascorbic acid. At the same temperature, the presence of 20.0 mass % of methanol, ethanol or isopropanol in the solution causes 2 - 3-fold increase of this rate. It may be assumed that for moderate cooling rates the type of alcohol does not influence the crystal growth rate. For higher cooling rates (R,. >16.6710^3 K/s) the differences are ranging from 0.5-10-8 to ca 2-10"8 m/s.