Evaporation and crystallization Overview evaporative crystallizer http://www.wzgoody.com/Product/jjq/562.html is a kind of mold, its internal structure is similar to the design of forced circulation evaporator, because maybe kind After the evaporator can be internal solvent evaporated and crystallized by, of course, different materials also make an important reason for our engineers to design a different mold programs. Here we Wenzhou Light Industry Machinery Co. Goode for everyone part of the knowledge about the evaporative crystallizer to share with you. Evaporative crystallizer operating its application www.wzgoody.com crystallization operating characteristics over the course of crystallization in supersaturated solution to generate a new phase, involving solid-liquid equilibrium. Transitive target specific product lines, the need to experiment to determine the appropriate operating conditions for crystallization, crystallization products meet quality requirements, improve crystallization production capacity and reduce costs through process. Crystallization operation problem in the degree of supersaturation increases the supersaturation degree can be increased nucleation rate and growth rate, help to improve the production capacity of the crystallization. 1. Supersaturated spent Assembly problems: 1) nucleation rate is too fast, a large amount of fine crystals, crystallization is difficult to grow; 2) crystal growth rate is too fast, affect the crystalline quality; 3) the mold wall prone to grain scale. There is a maximum degree of supersaturation, can guarantee a high nucleation and growth rate at the same time, does not affect the quality of crystallization. Carried out under difficult to produce crystal dirt over saturation. 2. PH of the solvent and the solvent and the pH value should be used in the crystallization operation of target solute solubility is low, in order to increase crystallization yield crystallizer. Solvents and pH on crystalline affected. Such as procaine penicillin crystals in the aqueous solution as a square crystal, crystallized from butyl acetate in the long rod-like. Before designing experiments to determine the crystallization action requires better crystal crystalline solvents and pH. 3. When using an external circulation loop flow rate crystallizer, circulation flow rate is set to be reasonable. 4. Improve circulation flow rate 1) in favor of eliminating the over saturation distribution within the device, the device inside the crystal nucleation rate and growth rate distribution; 2) to increase the solid-liquid mass transfer coefficient, increase the rate of crystal growth; 3) increase heat transfer efficiency, heat exchanger surfaces inhibit scale formation crystal; circulation flow rate is too high will cause crystallization wear broken. Whichever is greater value in the circulating flow rate should be broken in the absence of crystalline wear range. If the mold has crystallized classification function, circulating flow rate should not be too high, should ensure the normal functioning of the classification functions. 5. Temperatures of different temperatures, the crystal form and crystal water produced will change, the temperature is generally controlled within a small temperature range. When cooling crystallization, if cooling too rapidly, the solution quickly reach a high degree of supersaturation, generates a large number of tiny crystals, affecting the quality of the crystalline product. Temperature is preferably controlled between the saturation temperature and supersaturation temperature. When evaporation crystallization, evaporation speed is too fast, the degree of supersaturation of the solution is large, forming fine crystals attached to the surface of the crystal, affect the crystalline quality of the product. Evaporation rate should be compatible with the crystal growth rate, to maintain a certain degree of supersaturation. Industrial vacuum adiabatic crystallization operation is often evaporated, does not have external circulation heating means, the temperature of the lower evaporation chamber, can be prevented through the dramatic changes in saturation. 6. Crystal dirt mold wall and circulatory system crystallization system to produce grain scale, affecting the efficiency of the crystallization process. 7. Preventing or removing crystal grain scale scale method: 1) the inner wall surface using organic coatings, maintaining a smooth wall, to prevent the wall of the two-dimensional nucleation occurs; 2) increase the crystallization rate of fluid flow system, the flow velocity distribution, eliminate low velocity zone; 3) If the outer loop liquid is supersaturated solution, which does not contain the seed so; 4) the use of thermal insulation jacket near the wall way to prevent over-saturation is too high; 5) additional dirt eradicate crystal device, regularly adding solvent dissolution of the grain scale; 6) the evaporation chamber wall easily produce grain scale, can spray a solvent to dissolve the grain scale way. 8. Stirring and mixing the stirring speed is increased to improve the nucleation and growth rate, stirring speed will result in excessive shear crystal broken, affecting the quality of the crystalline product. In order to obtain better mixing state, while avoiding crystallization of the broken, stripping hybrid system may be employed, or the use of larger diameter stirring paddle or blade, reducing the rotational speed of the paddle. 9. Add the seed particles uniformly seed to the supersaturated solution in metastable zone. For higher solution viscosity of Mixture, nuclei hardly occurs, but at a high degree of fullness, once the nuclei, while there will be a large number of nuclei, prone polycrystalline phenomenon, product quality is difficult to control. High viscosity Mixture must be used in the metastable zone add method of operation of the seed crystal. 10. Effects of coexisting impurities object crystallization is Multicomponent Mixture, to selective crystallization of desired product. If the concentration of impurities is low coexistence, generally crystalline target product had no significant effect. However, if the impurity content in the crystallization operation in rising (e.g. using evaporative crystallization operation), the accumulation of impurities would adversely affect the purity of the target product crystallized. Crystallization operation need to control the content of impurities, often additional impurity removal device in the crystallization system. Ion exchange column or waste emissions. 11. Jing Jing pulp slurry concentration the higher the concentration, the unit volume of Crystallization The larger the surface area, the faster the rate of crystal growth, will help improve the crystallization speed of production (output). However, when the crystal slurry concentration is too high, the suspension of illiquid, difficult mixing operations. Crystal maximum plasma concentration should be taken within the allowed range of operating conditions. In a batch operation, the amount of the seed crystal should be based on the size of the final crystalline product, the crystal slurry concentration to meet the maximum requirements of efficient production.