The role of meso-mixing in anti-solvent crystallization processes

Recent Progress of Antisolvent Crystallization

Antisolvent crystallization is a significant unit operation in the pharmaceutical industry, especially on drug crystal properties optimization. This paper firstly highlights the applications of antisolvent crystallization in crystal engineering. Antisolvent...

An Ultrasound Tomography Method for Monitoring CO2 Capture Process Involving Stirring and CaCO3 Precipitation

In this work, an ultrasound computed tomography (USCT) system was employed to investigate the fast-kinetic reactive crystallization process of calcium carbonate. USCT measurements and reconstruction provided key insights into the bulk particle distribution inside the stirred tank reactor and could be used to estimate the settling rate and settling time of the particles. To establish the utility of the USCT system for dynamical crystallization processes, first, the experimental imaging tasks were carried out with the stirred solid beads, as well as the feeding and stirring of the CaCO₃ crystals. The feeding region, the mixing process, and the particles settling time could be detected from USCT data. Reactive crystallization experiments for CO₂ capture were then conducted. Moreover, there was further potential for quantitative characterization of the suspension density in this process. USCT-based reconstructions were investigated for several experimental scenarios and operating conditions. This study demonstrates a real-time monitoring and fault detection application of USCT for reactive crystallization processes. As a robust noninvasive and nonintrusive tool, real-time signal analysis and reconstruction can be beneficial in the development of monitoring and control systems with real-world applications for crystallization processes. A diverse range of experimental studies shown here demonstrate the versatility of the USCT system in process application, hoping to unlock the commercial and industrial utility of the USCT devices.

Ultrasonic Time-of-Flight Computed Tomography for Investigation of Batch Crystallisation Processes

Crystallisation is a crucial step in many industrial processes. Many sensors are being investigated for monitoring such processes to enhance the efficiency of them. Ultrasound techniques have been used for particle sizing characterization of liquid suspensions, in crystallisation process. An ultrasound tomography system with an array of ultrasound sensors can provide spatial information inside the process when compared to single-measurement systems. In this study, the batch crystallisation experiments have been conducted in a lab-scale reactor in calcium carbonate crystallisation. Real-time ultrasound tomographic imaging is done via a contactless ultrasound tomography sensor array. The effect of the injection rate and the stirring speed was considered as two control parameters in these crystallisation functions. Transmission mode ultrasound tomography comprises 32 piezoelectric transducers with central frequency of 40 kHz has been used. The process-based experimental investigation shows the capability of the proposed ultrasound tomography system for crystallisation process monitoring. Information on process dynamics, as well as process malfunction, can be obtained via the ultrasound tomography system.

A perspective review on mixing effect for modeling and simulation of reactive and antisolvent crystallization processes

Reactive and antisolvent crystallization processes are sensitive to mixing effects on various scales.

Improved crystallization of ammonium sulphate using ultrasound assisted approach with comparison with the conventional approach

In chemical processing industries, crystallization is one of the most important operations to obtain solid products with desired purity and characteristics. With distinct processing problems for the conventional approaches for crystallization, research into alternate approaches such as ultrasound assisted crystallization has been on the forefront. The present work deals with comparison of the conventional approach and ultrasound assisted approach for crystallization of ammonium sulphate followed by detailed understanding into the effect of important operating parameters (initial concentration, pH, agitation speed, depth of horn, and cooling approach) on the metastable zone width and average crystal size. Ultrasound assisted crystallization has been investigated using both ultrasonic bath and ultrasonic horn to understand the effect of type of irradiation. It has been observed that the maximum reduction in the MSZW was obtained using ultrasonic horn under conditions of optimized initial concentration. The order of average crystal size obtained for ammonium sulphate was conventional cooling crystallization>ultrasonic bath>ultrasonic horn. The average crystal size obtained was in the range of 411-450µm for conventional approach of cooling crystallization, 350-400µm using ultrasonic bath and 200-250µm using ultrasonic horn. The analysis of crystal size distribution and surface characteristics using the SEM analysis was also performed under set of optimized parameters established using the particle size analysis. Overall the work has clearly established that the ultrasound assisted crystallization gave better results as compared to the conventional cooling crystallization in terms of reduced metastable zone width, better crystal characteristics and less agglomeration.