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Crystallization is an important and widely used separation technique in the chemical and pharmaceutical industry. Control of the final particle properties is of great importance for these industries. The application of ultrasound in these crystallization processes, also referred to as sonocrystallization, has shown to impact nucleation, crystal growth and fragmentation. As a result this technology has potential to control the final particle size, shape and polymorphic form.This review provides a comprehensive overview of the recent advances in sonocrystallization. It reviews the observed effects of ultrasound on the different stages of the crystallization process. Recent insights in the mechanism behind these effects are discussed as well. Finally, guidelines for the operating conditions, such as ultrasonic frequency, power, type of cavitation bubbles, time window and moment of application are formulated.

Ultrasound-assisted nucleation is a promising method of controlling the crystal length within a narrow range in antisolvent crystallization. This article proposes novel model equations representing crystal nucleation and growth under ultrasound application in the antisolvent system of ethanol (solvent), water (antisolvent), and aspirin (pharmaceutical ingredient). The model considers the enhancement of nucleation by ultrasound, and also accounts for the heat generated from both the application of ultrasound and the mixing of solvent and antisolvent. We further employ a global sensitivity analysis to determine the parameters that have the most significant impact on model outputs before validating multiple experimental case studies that represent crystal growth for different antisolvent contents and initial supersaturation ratios. The model successfully captures the effect of the ultrasound, which is a function of temperature and supersaturation ratio, and has a strong impact on the refinement and the

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Biodiesel is a powerful alternative fuel that is less polluting and problematic to produce and implement. The production process of biodiesel also gives us the byproduct glycerol, which is a useful feedstock to produce hydrogen and syngas as fuels. With such high value as a fuel we are in need of better production technologies for biodiesel, which is currently being pursued through sonochemical reactors. The development of continuous sonochemical reactors for biodiesel production is a crucial requirement for the biofuel industry. Sonochemical reactors make use of ultrasound and acoustic cavitation to produce biodiesel from waste cooking oils (WCO). In this work we carried out both numerical simulation and experimental analysis of sonochemical reactors with multiple transducers. Through simulation, the effect of double vs a single transducer has been tested for a continuous flow sonochemical reactor. In experimental work three different cases with different ultrasound systems (bath, probe and bath+probe) have been tested. In both the studies, acoustic pressure and biodiesel conversion are analyzed. Results for the simulation show that in shorter reactors, the high cavitation from two transducers dampens the acoustic pressures leading to low conversion. However, at taller heights the effect of combined cavitation is less severe and the acoustic pressure and biodiesel yield are very similar between the designs having single and double transducers. From experiments it was found that the biodiesel conversion depends on several acoustic conditions mainly cavitation. A meticulous and insightful analysis was made to understand the difference in bath type and probe type ultrasound systems on acoustic pressure and biodiesel conversion.