| Crystallization,as an important unit operation process, is widely used in many traditional industries to obtain solid products with high purity and perfect crystal structures from vapor, solution or melts. With the prompt development and application of new materials, biochemical products and novel energy sources in recent years, it also plays an indispensable role in separating and purifying the final products. As a sophisticated process with multiple flows, crystallization is fundamentally governed by thermodynamics equilibrium and process kinetics. Compared with thermodynamics, kinetics is more complex. The progress in kinetics research lags far behind than that in thermodynamics, which largely impedes the industrialization of crystallization. Recently, with the rapid progress in computer simulation, modern analytic and measurement techniques, some active and efficient methods have been applied to further disclose the mechanisms of crystallization process. Therefore, crystallization and its related fields have become one of the focuses not only on academic but also on industry circles.In this paper, an ideal binary solution was selected as the modeling system to evaluate the effectiveness of the experimental apparatus, the analytical methods and the data treatment. The primary research indicates that the purity of the final product is greatly influenced by the rates of nucleation and crystal growth. Aimed at seeded batch cooling crystallization of potassium nitrate aqueous solution, the mechanisms of nucleation and crystal growth were investigated. Uridine-5'-monophosphate (5'-UMP), an important biochemical product, is generally prepared by solvent out crystallization. To improve the quality and enhance the added value of the final product, some fundamental research on solvent out crystallization were carried out.In order to obtain the information occurred in both liquid and solid phases, aset of self-made apparatus equipped with dynamic light scattering (DLS) units and densitometer was established in this paper. The relationships of DLS vs. the crystal size distribution (CSD) and the density vs. the concentration of the potassium nitrate aqueous solution at 20 ℃ were experimentally determined, respectively. The stability of transmittance on-line measurement was improved efficiently by the dual-optical detection circuit. Moreover, the temperature of the crystallizer was also programmable, which could be controlled accurately on requirement.For investigating the different influences of the nucleation and crystal growth on the crystallization process, a series of seeded batch cooling crystallization experiments were conducted for nitrate potassium aqueous system. A method, which originated in the difference between the real and the simulated concentration, was proposed in this paper. The results indicated that the generation of the new nuclei could not be fully inhibited if insufficient seeds were added to the system. With the increase of the seed load, the nucleation was gradually weakened and crystal growth dominated over the crystallization process. The further analysis indicated that the real influence of seed load on crystallization could be practically attributed to its direct influence on the supersaturation, which is commonly considered as the driving force of crystallization. The level of the supersaturation was greatly inhibited with the increase of the seed load and under the lower level of supersaturation, no new nucleus was observed.Based on the preliminary research performed on batch cooling crystallization for ideal binary system, another setup for solvent out crystallization of 5'-UMP was also established. In this apparatus, the temperature and the amount of the precipitant were automatically controlled. Meanwhile, the solubility of 5'-UMP at 20℃ in alcohol-water mixed solvents and the density of solution were measured simultaneously. On the basis of the data analysis, the relationship between the concentration of 5'-UMP and the density of the solution waspresente...
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