(421f) Mixing Performance of a Novel, Continuous Confined Impinging Jets Reactor Using Competitive Reactions

In this work, a novel continuous flow apparatus featuring the impingement of fluid jet streams in the presence of ultrasonic energy provided by an ultrasonic probe was tested using competitive reactions in order to determine its mixing effectiveness. The ultrasonic energy enhances micromixing of the fluid jet streams, which results in an overall mixing effectiveness improvements in different physical and chemical processes. Such an apparatus has been shown by our group to provide improvements in crystallization and precipitation processes, as well as fast chemical reactions and selectivity improvement.

In the competitive reaction system used here (third Bourne reaction), one stream containing sodium hydroxide was continuously fed to the first the impinging jet, while an aqueous solution of hydrochloric acid and ethyl chloroacetate was fed to the second jet. At the end of each experiment, the concentration of ethanol (obtained from the conversion of the slower ethyl chloroacetate reaction) was experimentally determined by gas chromatography (GC) to determine the mixing efficiency: higher ethanol concentrations implied poorer mixing. In all experiments, the volumetric flow rate of the limiting solution, i.e., the sodium hydroxide solution, was always kept the same, while the flow rate of the other solution was changed while also changing, at the same time, their concentrations in order to ensure that the reactants were in the appropriate stoichiometric ratios. The sonication power was also varied.

It was experimentally found here that improved mixing was achieved by increasing volumetric flow rate with or without sonication. If sonication was applied, mixing also improved significantly and it was further improved when a higher sonication power was applied. This trend was especially evident at lower flow rates. At high flow rate, sonication played a smaller role. A quantitative comparison of the results based on the use of the Damkohler number is provided.