Experimental And Theoretical Investigation Of The Multistage Countercurrent Melt Crystallizer With Inclined Sieve Plates

Melt crystallization is a green teclnology for separating and purifying organie compounds; it not only can produce high purity produets but also can separate isomers and heat-sensitive organic compounds which can’t be separated economically by other methods. Meanwhile, among crystallization devices, crystallizer is widely used because it realizes washing, recrystallization and sweating mechanisms at the same time in one single piece of equipment. Therefore, the development of a new crystallization technology withi ndependent intellectual property rights and the design of a continuous column crystallizer with high effieieney, have a very important significance.In this paper, a new multistage countercurrent melt crystallizer with sieve plates was proposed combined with the advantage of the TNO column crystallizer and the inclined column crystallizer. With the naphthalene-indene solid solution system, the purification process of organic materials in the new multistage countercurrent melt crystallizer with sieve plates under total reflux was investigated. Two of the influencing factors on the separation and purification performance in the new multistage countercurrent melt crystallizer with sieve plates were crystal settling velocity and crystal broken capabilities which were controlled by stirring speed, the sieve plates, the angle of the sieve plates, the diameter of the porous, particle sedimentation area, and the number of plates. The results of this study show that the optimum stirring speed was determined to be20rpm, sieve plates can obviously increase the separation and purification effect, the optimum angle of the sieve plates was determined to be45°, the optimum diameter of the porous was determined to be8mm, the optimum particle sedimentation area was determined to be0.5r,2plates in the crystallizer shown the best. During continuous operation, the experiment is the biggest impact of the reflux ratio, reflux ratio increase, improve product purity, but production is reduced, on the contrary, reflux ratio decreases, and the output of products increases, but decreases the purity.In order to better describe the mass transfer and feat transfer procrsses between two phases in column cryatallizer, a general mathematical model is developed by considering the various purification mechanisms. All the reported model in literature can ba formulated by simplifying the common model.The solid-liquid two-phase fluld flow in column crystallizer is simulated by Fluent software. Calculation results confirm that the distribution of suspension density undergone three different regions, which coincide with the experimental observation, and with the one-dimensional mathematical model.