Intensification of falling film melt crystallization process through micro and milli-structured surfaces

• New micro/milli-structured crystallization surfaces have been designed.
• Melt crystallization process has been intensified using these new surfaces.
• Sweating rates have been multiplied by 5.6 using finned crystallization tubes.
• Purification productivities have been increased until 64%.
• Heat transfer has been modeled in crystalline layer.

This paper shows how falling film melt crystallization process can be intensified by using micro/milli-structured surfaces. This work takes part in the development of purification techniques of bio-acrylic acid. The current acrylic acid synthesis is based on propylene, a petroleum derivative. Thus, a new production route of a bio-acrylic acid is developed, based on glycerol, a green by-product of oleochemistry and biofuel industry. However, the impurity profile of this bio-AA differs from that of propylene-based: crude bio-AA contains much more propionic acid (PA). Classical purification techniques do not allow the separation of these two chemicals whose structures are similar.[1] showed that falling film melt crystallization halves propionic acid contents in purified AA with yields reaching 60% and purification time less than five hours. Increasing the exchange surface between the cold surface and the melt to purify can improve heat transfer, decrease purification time and intensify melt crystallization process. Thus, micro/milli-structured crystallization surfaces have been designed and tested. Results show that these innovative surfaces can increase productivity by 84%. Heat transfer has been modeled during the crystallization process, and it clearly appears that thermal gradient is divided by ten with milli-structured surface compared to smooth surface.

Figure optionsDownload as PowerPoint slide