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Crystallization is a separation and purification technique, defined as a phase change in which a crystalline product is obtained from a solution mixed of two or more species forming a homogeneous single phase. |
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Materials of flat or inverted solubility is necessary to use evaporative crystallization instead of cooling crystallization. Crystallization is initiated by neucleation at very high level of supersaturation at start up stage of industrial process. Besides this homogeneous or hetrogeneous nucleation, attrition bewteen crystalline products and secondary nucleation caused by contacts between crystals and metal objects are significant source of crystallizer seed. Once seeding is rooted, supersaturation is controlled to reside within a metastable zone by maintaining a low △T in the heat exchanger with high recirculation flow rate. When the crystall sizes are allowed below 0.5mm, forced circulation crystallizer (MSMPR= mixed suspension, mixed product removal) is used for the crystallization of wide range of organic and inorganic compounds. |
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| The right photo shows MSMPR crystallizer for Threonine crystal production with an evaporation rate of 11,640 kg/h. If the crystal size is to be bigger than 0.5mm and CSD is crucial requirement, Draft Tube & Baffle (DTB) crystallizer is recommended. |
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| MSMPR crystallzer delivers mixed suspension both for crystal slurry discharge and recirculation, that high circulation flow rate and cycle incur attritions between crystals and metal parts. DTB crystallizer circulate growing crystals through draft tube by propeller agitator and separate mother liquor containing fine crystals by baffle, bigger crystals with sharp CSD is attained. |
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