Abstract
CDC (Cooling Disc Crystallizer) can be considered as a series of completely stirred vessels or compartments, where the feed is cooled stepwise while it is flowing from one compartment to the next. Each compartment is separated by a cooling disc and since the surface of this disc is cleaned by wipers mounted on the shaft of the CDC, the overall heat transfer coefficient is large. This renders possible to select the temperature difference between the cooling side and the process-side such that nucleation is minimal and encrustation is avoided. The crystal population density is kept high to enhance crystal growth. Therefore, crystal with large mean diameter and small distribution is obtainable.In this paper, crystallization of KDP (potasium dihydrogen phosphate) from its aqueous solution has been investigated. The size distribution of the diameter of KDP crystal from the CDC has been compared with that from MSMPR (Mixed Suspension Mixed Product Removal). It has been concluded that the magnitude of the oscillation of this distribution from the CDC is substantially smaller than that from the MSMPR and that the crystal from the CDC is extraordinary longer than that from the MSMPR. These can be due to the plug flow characteristics of the CDC over the MSMPR and small supersaturation in the CDC.
Thus, even though it is well known that KDP crystal is presently produced in the batch operation, it is highly plausible this crystal can be produced with the CDC in the continuous operation in the industrial size.
