Production of large crystals by continuous ripening in a stirrer tank

A new bulk crystallisation process is described in which the supersaturation in the crystalliser is maintained by feeding very small subcritical crystals. Supercritical crystals that are present in the crystalliser grow at the expense of the dissolving subcritical crystals. The process is described by means of a mathematical model. With this model the influences of crystal concentration, production rate, and size of the feed crystals upon the average product crystal size are calculated. The model predicts an increase of the mean size of the product crystals with a decrease of feed crystal size for small feed crystals. The size of the product crystals also increases with an increase in crystal concentration in the crystalliser. The process has been studied experimentally for the growth of ice crystals from aqueous sucrose solutions. The theoretically predicted effects of crystal concentration and feed crystal size on product crystal size are confirmed by the experiments