摘要
针对添加晶种的间歇结晶过程,基于DL定律和粒数衡算方程,建立了晶体生长溶液浓度与晶种量及其生长速率的数学表达式。实验考察了晶种添加量对KNO3-H2O间歇冷却结晶过程的影响。结果表明:随着晶种量的增加,模拟溶液浓度与实测浓度之差DC减小;同时体系相对过饱和度逐步受到抑制,其变化范围和幅度均呈现下降趋势;当晶种添加量达到或超过0.332g(100gH2O)-1时,DC在整个过程接近于0,体系基本无新核产生,过程以生长为主导,即对于添加晶种的结晶过程存在最小晶种量。由实时测定的溶液浓度和透光率得到的参数DC可确定相应工艺条件下的最小晶种添加量,为结晶产品的质量控制和优化提供了分析手段。
By assuming growth only on the added seed with negligible nucleation, a solution phase concentration expression was given based on the population balance model and McCabe抯 DL law for the seeded batch crystallization processes. The effect of seed load on batch crystallization of potassium nitrate aqueous solution was investigated under a controlled cooling mode. The results show that with increase of seed load, the difference between the calculated and measured concentration DC gradually decreases to zero, and the relative supersaturation of solution is also suppressed on a lower level. As the seed load is increased to over 0.332g(100gH2O)-1, DC is near to zero during crystallization, which means there is a critical seed load for the seeded batch cooling crystallization with virtually no nucleation, where the crystallization is dominated by seed growth. On the other hand, at lower seed load below the critical seed load, DC is larger than zero, and generation of new particles by nucleation mechanisms is not suppressed in the system with higher relative supersaturation. The parameter DC estimated from on-line measurements of solute concentration and transmittance could be applied to minimize the seed load for a given seeded crystallization operation, and to control or optimize crystal quality.
出处
《高校化学工程学报》
EI
CAS
CSCD
北大核心
2004年第1期120-125,共6页
Journal of Chemical Engineering of Chinese Universities
关键词
间歇结晶
冷却结晶
晶种
浓度模拟
batch crystallization
cooling crystallization
seed crystal
concentration simulation
