Study On The Crystallization Process Of Ammonium Sulfate

Ammonium sulfate major used in agriculture as nitrogen,is also provided as the main sources of sulfur that is needed for crop.At present,the domestic ammonium sulfate whose physical properties are poor,such as easy to raise dust,easy to agglomerate,easy to cause loss in use,poor in liquidity and not suitable for mechanical work exist in form of powder.Being different from it,granular ammonium sulfate crystals have good physical properties,such as high purity,not easy to kick up dust,not easy to agglomerate in long-term storage,good fluidity,fertilization easily,loss less,it also can have a slow-release effect,improve the fertilizer utilization.In addition,it can be directly mixed with different kinds of similar size granular fertilizer,more applicable for soil testing and fertilization.Study crystal habit of the ammonium sulfate under ideal conditions,through the experimental of cultivation of single crystal.The crystal structures of ammonium sulfate with different crystal habit was tested by X ray powder diffraction.And in order to judge whether the crystal structure is changed,this experiment compared the atlas with standard atlas of ammonium sulfate.In addition,towords analysising the additived ion content in the products,whether the the additived ions go into structure of ammonium sulfate was judged.Crystallization thermodynamics is the key factor for the production yield.in addition,it provide basis data for selecting crystallization process.In this thesis,the solubility and metastable zone of Ammonium sulfate in water was determined by laser method.And the effects of acidity and impurity on the metastable zone width were studiedThe nucleation and growth rate can affect the crystal size distribution(CSD).It is the basis for the crystallization operation and scale-up design.In this thesis,the unsteady state method was employed to measure the nucleation and growth kinetics and raw material were got.The effect of factors to the crystallization kinetics were discussed.Based on thermodynamcs and kinetics,in this article,this subject adopts Evaporation-cooling crystallization process,which through changing the operating conditions of crystalline system study crystallization environment(the additives policies,Crystallizing temperature,Crystallization environment pH value,seeding policies)affect on size,purity and crystal size distribution(CSD)of ammonium sulfate.Ultimately determine the optimum process conditions,prepare size of ammonium sulfate products in the 2～2.5 mm particles,provides the basis for the crystallizer for industrial design and industrial production condition.