Patent ID: 7942939
Filing Date: 2011-05-17
Classification: B01D,C01C,C05C

Abstract:
1. Method for the continuous production of a coarse-grained ammonium sulphate product by crystallization of an ammonium sulphate solution in a product crystallization stage which is operated in accordance with a draft tube baffled principle, said method comprising: during evaporation of water, constantly circulating a suspension of mother solution and ammonium sulphate crystals in an internal circuit; constantly drawing off a clarified partial flow of solution from an upper region of said internal circuit in an external circuit and heating said solution so as to dissolve solids contained therein and then guide the heated solution back as a clear solution into the lower region of the product crystallization stage; continuously drawing off vapours from the head of the product crystallization stage, supplying new suspension from outside and drawing off a partial flow of the suspension containing the coarse-grained ammonium sulphate product from the lower region of the product crystallization stage; producing a new suspension in a pre-crystallization stage located upstream of the product crystallization stage, draw off the solids proportion of the new suspension by means of a classifying suspension discharge without an appreciable proportion of fine crystallizate, which has a grain size of less than 0.5 mm, and of crystallization nuclei, and is supplied with a proportion of undersaturated mother solution, which is sufficient to ensure further crystal growth to the desired grain size, from the pre-crystallization stage directly to the product crystallization stage; and heating the clarified solution in the external circuit of the product crystallization stage by heat from vapours drawn off from the pre-crystallization stage.