Patent ID: 8658123

Claim:
Method for continuous production of a coarse-grained ammonium sulphate product of a grain size in the range of approximately 2.0-3.0 mm by crystallization of an ammonium sulphate solution in a crystallization stage which is operated in accordance with a draft tube baffled (DTB) principle, said method comprising: constantly circulating a suspension of mother solution and ammonium sulphate crystals in an internal circuit while evaporating water from the solution; drawing off a clarified partial flow of solution from a clarifying zone in an upper region of the crystallization stage into an external circuit; heating the solution so as to dissolve the solids contained therein and then guiding the solution back as a clear solution into a lower region of the crystallization stage, and continuously drawing off vapours from a head of the crystallization stage; supplying new ammonium sulphate solution from outside and drawing off a suspension flow containing the coarse-grained ammonium sulphate product from the lower region of the crystallization stage; and drawing off as a further partial flow a fine crystal suspension flow from the clarifying zone and guiding the fine crystal suspension flow back into the internal circuit of the crystallization stage without any previous dissolution of the solid proportion contained therein.