Process Optimization And Research Of Ammonium Sulphate Evaporation Crystallization

As one of major nitrogenous fertilizers, there are still some problems in the industrial production of ammonium sulfate, such as small crystal size, uneven crystal size and bad color, which cannot meet the various needs of customers. Those problems also happen in the pro-duction of ammonium sulfate from acrylonitrile unit of Shanghai Petrochemical Co., Ltd. In order to solve such problems, a systematic study on the crystallization process has been per-formed in this paper.The optimized experiment of ammonium sulfate has been done on the basic of thermo-dynamic and kinetics data in this paper. Then the material balance and simulation of crystalli-zation process have been finished to optimize and improve the crystallization process.The thermodynamics and kinetics are the basic of the crystallization process optimization, which has an important guiding role. As for the thermodynamics, the solubility of ammonium sulfate in pure water and sulfuric acid and the super-solubility in solution under the condition that pH=3.0, stirrer speed is100r/min have been determined by balancing method and visual method respectively in this paper. As for the kinetics, the nucleation and growth rate have been measured under certain condition. It was also discussed the relationship between pres-sure and temperature under certain concentration of ammonium sulfate.In order to improve the particle size and size distribution of crystal, the optimizing expe-riment has been carried out on the basic of thermodynamic and kinetics. Several important factors, including pH of solution, evaporation temperature, temperature difference for heat transfer and stirrer speed, have been considered in the experiment. The optimized operation condition of crystallization process is as follow:pH value is3.0, the evaporation temperature is70℃, the temperature difference is5℃and stirrer speed is100rpm. The ammonium sul-fate crystals gotten under this operating condition are better in the particles size and size dis-tribution than those from acrylonitrile unit of Shanghai Petrochemical Co., Ltd.In order to improve the yield of the product, material balance and simulation have been done. Firstly, according to the analysis of the industrial production process, the material bal-ance of the whole process has been carried out. Then the whole process after each section’s simulation by chemical process simulation software Aspen Plus was simulated. Through anal-ysis of the entire process, the reasons for the low yield of ammonium sulfate have been reached and several improvements have been proposed.