Benefits of Melt Crystallization

Melt crystallization can have advantages and features that establish it as an alternative separation technique compared to other thermal unit operations in chemical engineering. 

About 60% of the substances examined have melting points between 0 and 210 °C. Therefore, the much lower level in temperature and the clear smaller 

The above-mentioned advantages of the melt crystallization processes concerning the temperature level of the product component do not exist if the comparison is made to the crystallization from solutions, because the product is crystallized in solution at temperatures lower than its melting point. However, the solvent has to be separated (evaporated), usually in larger amounts, and is often to be treated as impurity. Hence, melt crystallization does not need any additional substance compared to extraction or solution crystallization. Therefore, no wastewater will be produced and no other chemical (solvent) has to be reprocessed. The capital and energy costs for solvent recycling can represent a major portion of a product isolation process utilizing solution crystallization. 

Further advantages of melt crystallization are the smaller volume of the liquid compared to the vapor phase. A smaller volume requires less space or less construction work, which means less capital costs. These advantages are sometimes lost if the process of crystallization and remelting is very slow. Therefore, the residence time in the apparatus is high. The nonexistence of a vapor phase, however. 

Concepts of plants can be divided into solid layer and suspension crystallization. Furthermore, these two techniques can be split into continuous and batchwise as well as into static and dynamic (stagnant or flowing melt) operating modes. A detailed overview of the different designs of existing and commercially available plants in solid layer as well as suspension crystallization is provided in Chapter 16. In the Sections 

A very important point is that crystallization processes are highly selective and can lead to a 100% pure product within one separation step—at least in theory—if the mixture to be separated 

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