Cooling Crystallization: Does Gassing Compete with Seeding?

Abstract

Cooling crystallization processes are most often controlled by adding seed crystals within the metastable zone to induce nucleation. Seeding is a challenging task and involves the risk of contamination. Its success depends on a lot of aspects, namely, seed size and amount, time point and place of addition, and experience of the operator. Gassing to induce nucleation is an innovative technology that has shown in the past that nucleation control and product design is possible. The purpose of this Article is to show that gassing competes with seeding during a cooling crystallization process. Two different cooling process concepts with and without a holding time were considered. As model system succinic acid/water was used. Gassing as well as seeding enhances production capacity by shortening the production time by a quarter for product crystals with desired mean crystal size in comparison to a normal cooling crystallization process. Production capacity is slightly higher for seeding than for gassing, but gassing competes with seeding in many ways: it is simple and ensures constant product quality.