Intermittent small particle removal is frequently used for particle property improvement in batch crystallization processes. This is generally solved by partial dissolution cycles, which for a cooling crystallization translates to temperature cycles - well suited for small-scale experimentation. However, implementing temperature cycles on a larger scale may face technical difficulties. This paper investigates a concept for fine particle removal, namely, the controlled external fines removal. Here, controlled dissolution is achieved in an external environment being attached to the crystallizer via a recirculation stream. Simulation-based external and internal fines removal is compared. The population balance model involves primary and secondary nucleation as well as crystal growth and dissolution. A two-level control system is developed: the low-level PI controller sets the vessel's temperature, whereas direct nucleation control (DNC) alternates between growth and dissolution cycles based on the actual particle number density. The paper demonstrates that the external fines’ removal results in slightly but consistently larger particles and a narrower size distribution in the majority of cases. Under optimal conditions, external fines’ removal leads to shorter batch times, and its convergence is significantly less sensitive to the DNC settings e.g., heating/cooling rates. From an energy utilization perspective, the internal fines removal requires less cooling and heating energy than the external configuration. The external configuration has great energy saving potential through heat integration as during the constant temperature recirculation the simultaneous heating and cooling duties in the crystallizer and heat exchanger match each other.

间歇性小颗粒去除经常用于批量结晶过程中颗粒性能的改善。这通常通过部分溶解循环解决，冷却结晶转化为温度循环 - 非常适合小规模实验。然而，更大规模地实施温度循环可能会面临技术难题。本文研究了细颗粒去除的概念，即受控外部细颗粒去除。在这里，受控溶解是在通过再循环流连接到结晶器的外部环境中实现的。比较了基于模拟的外部和内部细粉去除。种群平衡模型涉及初级和次级成核以及晶体生长和溶解。开发了一个两级控制系统：低级 PI 控制器设置容器的温度，而直接成核控制 (DNC) 根据实际粒子数密度在生长和溶解循环之间交替。该论文表明，在大多数情况下，外部细粉的去除会导致略微但始终如一的更大颗粒和更窄的尺寸分布。在最佳条件下，去除外部细屑会缩短批处理时间，并且其收敛对 DNC 设置（例如加热/冷却速率）的敏感性明显降低。从能源利用的角度来看，内部细粉去除所需的冷却和加热能量比外部配置少。