From cloudy suspensions to clear data: Particle imaging enabled by automated dilution

We present a novel dilution device designed for accurately and robustly diluting dense suspensions to enable real-time particle characterization using optical imaging systems. The device employs tangential flow filtration, allowing for continuous operation at high solid weight fractions typical in industrial crystallization processes. It demonstrates the ability to monitor suspensions continuously over 24 h and to quickly adapt to changing particle densities, whilst continuously enabling accurate measurements. This paper presents also a study of the impact of particle density on measurement accuracy; extensive testing confirms the reliability of the dilution device for distributions of various particle sizes and shapes. The dilution device successfully tracks the evolution of the particle size and shape distribution (PSSD) during cooling crystallization. The innovation presented here, overcomes the limitations of existing methods hindered by high particle densities, providing a significant advancement in real-time monitoring and characterization capabilities under realistic conditions. This technology holds potential for broad applications, including the validation of new crystallization theories and, thus enhanced development of efficient crystallization processes. Synopsis: A novel dilution device for the rapid and automated dilution of dense suspensions is designed and performance tested. The device uses a tangential flow filter to extract clear mother liquor from the suspension. Extensive testing has confirmed the accuracy and reliability of the device. In addition, its ability to monitor crystallization processes has been successfully demonstrated. • Accurate particle characterization is enabled through dilution in a closed system. • Particles are removed from mother liquor using tangential flow filtration. • Reliable operation even when exceeding suspension densities common in industry. • The device is used to monitor both wet milling and cooling crystallization processes.