CRYSTALLIZATION OF ORGANIC MELTS IN EQUIPMENTS DEVELOPED FOR CRYSTALLIZATION FROM SOLUTIONS

摘要

A simple idea, to use already well-working solution crystallizers in the field of melt crystallization, is tested and evaluated concerning its limits. Advantageous for a melt crystallization process is a continuous operation, and compared to the types of processes used until now a higher volume to time yield with a lower energy consumption. However, not only the advantages but also the difficulties have to be taken into account. There is e.g. that supercooled melts tend to encrustate in the heat exchanger. For the realization of this project equipment as used in suspension cooling crystallization with an external heat exchanger was investigated. In the first set of experiments the conditions leading to the lowest possible encrustation risk of the heat exchanger are determined. Investigated parameters are the velocity and the supercooling of the melt. It was found that the encrustation time is higher for higher Reynolds numbers. Also a lower supercooling (higher temperatures) leads to higher retention times before encrustation starts. Different heat exchanger materials (glass, stainless steel) showed a very different encrustation behaviour. In long-term experiments the possibility of a continuous operation is investigated. The parameter settings are chosen based on the results of the test series. Exemplary results showing the effect of the different parameter variations (Reynolds number, supercooling temperature) are presented.