Flow Field Simulation Of Ammonium Persulfate Continuous Crystallizer

Ammonium persulfate manufacturing process is a process of crystallization, in which the solid matter precipitated from the solution, steam or a molten substance in crystal state. For the lacking of systematic theoretical research, the manufacturing process of ammonium persulfate is still an intermittent one in our country. The adoption of ammonium persulfate continuous crystallizer is an effective way to resolve the shortage of low production efficiency, and poor product quality in intermittent crystallization. So the study on thermodynamics, dynamics,flow field and temperature field in the process of ammonium persulfate crystallization can be of significant importance to the development of ammonium persulfate continuous crystallizer.Firstly, thermodynamics research was performed in the process of ammonium persulfate crystallization, then the solubility and super solubility of ammonium persulfate in water were obtained, and the width of interface stability zone was determined. The results show that the crystallization with the cooling rate of 40℃ per hour and ranging the crystallization temperature intervalfrom 20℃ to 45℃ is the suitable thermodynamic condition in the industrial manufacturing of ammonium persulfate. Secondly, suspension density and relative saturation of ammonium persulfate at different cooling rates were obtained from the dynamics research ammonium persulfate crystallization process. By doing so, nucleation rate0 B and crystal growth rate G of the 33℃ ammonium persulfate solution at the cooling rate of 40℃were obtained according to an empirical formula. The results showed that no seed crystal was needed to be added purpusly in the process of ammonium persulfate crystallization, and then the manufacturing process of ammonium persulfate was optimized.Consequently, the flow and temperature fields of ammonium persulfate in the crystallizer were simulated with the aids of Fluent software, the magnitude, direction and the size of the shear rate of single phase flow speed was obtained under the condition of 60 r/min, 100 r/min and 200 r/min of the stirring speed of box type impeller respectively, together with the flow field variation of continuous phase and solid phase after the addition of 800 mm crystal. The torque and input power per unit volume of box type impeller in 100r/min was calculated. It was found that the magnitude and direction impact of added particle on continuous phase of the is so small that can be negligible when the particles were added, and the volume fractiondistribution of the particle phase is homogeneous, shear rate is relatively less than that in single-phase flow field. The effects of flow field and volume fraction of particle distribution are optimal when the crystallizer stirring speed is 100r/min, and by doing so the crystal size has been effectively controlled. The temperature variation of crystallizer interior portion and from inlet to outlet of heat exchanging coil in the three different cooling brine flow rate plate tube are obtained by the calculation of temperature field. And then, the temperature field under0.6m/s cooling the brine flow rate was consistent with this temperature range which was obtained from the conclusion of thermodynamics analysis. It can be say that 0.6m/s cooling the brine flow rate is an appropriate choice for it can make sufficient heat transfer to crystallization process, and then improve the efficiency consequently.Through the theoretical, experimental and simulation studies above, important parameters affecting ammonium persulfate crystallization properties are obtained, which can provide a reference and theoretical basis to the industrial production of ammonium persulfate.