Experimental Research And Simulation Of Aspirin Crystallization On Kinetics

Crystallization kinetics plays an important role in the development of crystallization technology.It is not only the basis of crystallization operation,crystallization kettle selection and design,but also the premise of crystal process prediction and crystal shape prediction.The crystallization kinetics of Aspirin-ethanol cooling crystallization system was studied in this paper,basis on the understanding of crystallization kinetics.In this paper,the basic thermodynamic data including solubility,metastable region and process parameters including temperature,solution concentration,suspension density and particle size distribution are obtained through process analysis technology.The effects of cooling rate and stirring rate on the crystallization process were investigated.The experimental results show that more concentrated size distribution and larger average particle size of Aspirin crystals are obtained at a lower cooling rate of 0.1 K/min and the average particle size of Aspirin crystals are larger at high stirring rate of 200 rpm.Based on the particle number balance model,batch dynamic method is used in obtaining the kinetic model of nucleation and growth of Aspirin.Then discussed the effects of supersaturation,stirring rate and suspension density on nucleation rate.In addition,the kinetic model is verified by particle size distribution.The results show that the established kinetic model can well predict the crystal growth process.Monte Carlo method is used to simulate the process of aggregation and fragmentation.The aggregation and fragmentation are regarded as the result of particles collision.The modeling process is divided into three steps: constructing simulation system,setting up particle collision model and establishing collision result model.Monte Carlo method is a stochastic algorithm and effects with many factors.In this paper,analyzed the influence of time step and the number of virtual particles.The effects of agglomeration and fragmentation on the size of crystalline products were discussed.The particle size distribution is shifted to a smaller size range due to fragmentation,while the particle size distribution is shifted to a larger size range by aggregation.The effect of stirring rate on the quality of crystal products also was investigated.The results show that the larger the agitation rate,the greater thechange of the average particle size,that is,the agitation rate has an effect on the agglomeration and fragmentation process.Considering the effect of nucleation,growth,aggregation and fragmentation on the quality of crystal products at the same time,which can help deep understanding of crystallization mechanism and provide theoretical basis and practical guidance for the quality control and optimization of crystalline products..