Convex crystallizers are the most common crystallization devices and have been widely used in the pharmaceutical and chemical industries for decades. They are used for a range of processes, from crystallization of low-purity salts to high-purity characterization, crystallization of APIs and drying of intermediates.
A convex crystallizer is composed of a main vessel with a vapor-inlet pipe and vapor-outlet pipe, a turbulator, a crystallizer temperature-controlling device and a product separation device. The main vessel is usually made of stainless steel and is designed with a conical bottom to facilitate collection and separation of the crystals.
The vapor-inlet pipe supplies the crystallizer with a heated micron-sized vapor drop which acts as a seeding point for the crystallization. This seeding point is fed by a special curved pipe which deflects a portion of the vapor up, while the rest streams through the lower part of the vessel and enters the ring-shaped turbulator which moves the particles in a vortex pattern.
The crystallizer temperature-controlling device is an important part of a convex crystallizer. It maintains a desired temperature that can be adjusted for different crystallization conditions and applications. The device controls the rate of heating and cooling, which depends on the type of substance and temperature required. This device also helps in the collection of excess material, because the crystals tend to deposit on the cooled part of the vessel.
The product separation device is a crucial part of a convex crystallizer. It prevents the produced crystals from entering the vapor-outlet port and simultaneously separates the liquid from the crystals. The type of separation device used depends on the type of crystallization and the application.
The crystals produced from a convex crystallizer can be circular or irregular shaped depending on the type of material. These crystals generally have a constant size, shape and crystal structure. The crystals produced in a convex crystallizer can also be used for further processing of the materials, such as grinding and drying.
Convex crystallizers are widely used in the pharmaceutical and chemical industries due to their advantages, such as low cost, simplicity and versatility. They are also easy to operate and maintain with minimal troubleshooting. Convex crystallizers can be combined with other techniques to enhance the crystallization process. For example, they can be combined with hot and cold mixing processes to produce higher quality crystals, or with centrifugation techniques to separate the crystals quickly.
The design and operation of convex crystallizers depend on a variety of factors, including the size of the crystallizer, the type of material being processed, and the desired end-product quality. It is important to understand the fundamental principles of the process and choose the right equipment to get the desired results. Proper maintenance and troubleshooting techniques should also be followed to ensure optimal results.
