METHOD FOR SYNTHESISING CRYSTALLINE AMMONIUM SULPHATE Russian patent published in 2021 - IPC C01C1/24 C01C1/248 

FIELD: chemistry.

SUBSTANCE: invention relates to a method for synthesising crystalline ammonium sulphate. The method includes crystallisation of an initial solution of ammonium sulphate by means of: feeding an initial solution of ammonium sulphate into a container for the initial solution of ammonium sulphate; supplying the initial solution of ammonium sulphate from the container for the initial solution of ammonium sulphate in three streams: into the lower part of the crystalliser, into a hydroclassifier and into the pipeline connecting the crystalliser and the evaporator; separating crystals from the mother solution by evaporating in a crystalliser provided with: an evaporation area located in the upper part and a crystallisation area located in the middle and lower parts in form of a vertical central pipe; resulting in two streams, the first whereof, taken from the lower part of the crystalliser, is directed into the hydroclassifier, and the second stream taken from the middle part of the crystalliser is directed through the pipeline and a circulation pump to the evaporator resulting in a vapour-liquid stream, wherein the second stream with the pipelines connecting the middle part of the crystalliser, the circulation pump, the evaporator and the evaporation area located in the upper part of the crystalliser, and with the vertical central pipe, form a circulation circuit; directing the vapour-liquid stream from the evaporator by means of the pipeline to the evaporation area located in the upper part of the crystalliser; introducing the condensate produced in the evaporator into the pipeline connecting the evaporator and the evaporation area located in the upper part of the crystalliser; directing crystalline ammonium sulphate in a solution through the pipeline from the hydroclassifier to the accumulator of the ammonium sulphate solution wherefrom part of the solution is supplied through the pipeline to the container for the initial solution of ammonium sulphate, the other part is supplied through the pipeline to the centrifuge to separate the ammonium sulphate crystals from the mother solution inflowing through the pipeline into the container for the initial solution of ammonium sulphate, and the ammonium sulphate crystals inflow into a dryer with an air-heater, to a belt conveyor and to a warehouse for the finished product. An additional circulation circuit is therein created by collecting part of the flow of the circulation circuit containing small ammonium sulphate crystals from the crystallisation area using of a pump, heating this part of the flow and introducing into the upper part of the vertical central pipe. The process is executed with introduction into the additional circulation circuit of a water solution of magnesium chloride at a concentration of 0.01 to 0.02% wt. and with a mass ratio of the flow of the circulation circuit and the flow of the additional circulation circuit of (2 to 4):1, wherein the point of collection of the part of the flow of the circulation circuit is located in the upper half of the vertical centre pipe.

EFFECT: presence of an additional circulation circuit increases the time of crystal growth and intensifies mixing, leading to an increase in the concentration of large ammonium sulphate crystals of 80% and more.

1 cl, 2 dwg, 1 tbl, 10 ex