(451g) Continuous Flow Sonochemical Reactor Using Cylindrically Converging Acoustic Waves: Design and Performance

High frequency sound fields known as ultrasound may induce chemical reactions in liquids. This process of sonochemistry principally involves cavitation – the formation of gas/vapour cavities within the liquid media owing to the rapid and large pressure changes within an acoustic field. Under specific conditions, cavitation bubbles may undergo a pseudo-adiabatic collapse, compressing the gas/vapour within the bubble and raising the local temperatures to an extreme of more than 5000°C. Under these conditions, molecules trapped within the bubble undergo pyrolysis to form various radical species. Water vapour splits into hydroxyl and hydrogen radicals. These radicals may then further react with each other or with chemicals in the bulk phase. Such conditions thus create unique chemistries under bulk ambient conditions and is ideal for greening chemistry for wastewater treatment, hydrogen production, and chemical valourisation.

Though there are many promises of sonochemistry, there has not yet been much industrial adoption. Conventional sonochemistry relies on sonochemical reactors that provide diffuse acoustic fields and stochastic cavitation operated under continuous wave for long durations. As such, sonochemical reactions 1) have low yields and slow kinetics, 2) are non-selective, and 3) lack any operational standards. Furthermore, these reactors are difficult to scale up and are not energy efficient. As a result, sonochemistry is not commercially widespread.

Recently, we developed a novel sonochemical reactor that intensifies acoustic fields and concentrates cavitation. As a result, we have measured increased yield and rates of hydroxyl radicals from pure water, which is a benchmark in sonochemistry. Yet this reactor operates in batch mode at millilitre volumes. Here, we present a conversion of this reactor from batch to continuous mode. Under continuous operation, we explore the impact of different operational conditions on the production of hydroxyl radicals and potential for scalabilty of our sonochemical reactor design.