Experimental Study And Numerical Simulation Of Stirred Crystallization Process

The crystallization technology is widely used in separation and purification,and the type of impeller and crystallization process will affect the crystallization yield and crystal size.In this study,the cooling crystallization process of KCl and the reactive crystallization process of 7-ACA were discussed respectively,and the numerical simulation of the 7-ACA pilot amplification scheme was conducted.In this study,the cooling crystallization process of KCl was studied experimentally,and the effects of the rotational speed,the position of the impeller,the amount of crystal seeds,the flow rate of cooling water and the type of the impeller on the cooling crystallization process and the average particle size were discussed respectively.The average particle size of KCl crystal first increases and then decreases with the increase of the rotating speed,the distance between theimpeller and the bottom of the kettle,and the increase of cooling water flow.The optimal operating conditions for the cooling crystallization process of KCl is shown as follows:the rotating speed 270 rpm,the cooling water flow 0.36 m3/h,and the position of theimpeller C/H=0.22,respectively.Compared with mixed impeller and radial impeller,axial flow impeller is more advantageous to generate KCl crystal with more concentrated particle size distribution,while ZCX impeller is more concentrated than KHX impeller.The study of 7-ACA reactive crystallization process showed that the optimum operating conditions of 7-ACA reactive crystallization were determined when using the four baffles:rotational speed 360 rpm,the reaction temperature 10?,the rate of titration of hydrochloric acid 0.445 mL/min and the concentration of 7-ACA 0.09 mol/L.At the same time,it was found that the growth rate of crystal was related to the grain size,and the kinetics of crystal growth is determinedG(L)=4.748 exp(-5.498 ×103/RT)?C0.8602{1-exp[-0.05863(L+3.7,2 x 10-5)]}The power parameters of fiveimpellers X(small test),MK,MS,ZCX and KHX were calculated by using the single-phase flow model;and the operating conditions of four impellers(MK,MS,ZCX and KHX)were determined with the suspension power ratio Z as the amplification factor.The numerical simulation of four agitations was carried out by using the liquid-solid two-phase flow mathematical model,and the simulation results were compared with the pilot experimental results.