Assessment of mixing by chemical probe in swirl flow hex reactors

Mixing is a fundamental issue in process engineering and many industrial fields. It is closely related to a large number of different applications, such as chemical reactions, thermal transfer, liquid-liquid extraction, crystallization, and the like. In fact, mixing whether at the reactor scale, sustained by the flow structures, or at molecular scales, influences the selectivity and hence the productivity of reactions. Understanding and quantification of the micromixing mechanism is critical in industrial chemical processes, especially for fast exothermal reactions. Micromixing can be characterized by chemical probe methods based on observation of a local chemical reaction that results from a competition between turbulent mixing at microscales and the reaction kinetics. Several chemical systems can be used to characterize transport phenomena and mixing efficiency. A system of parallel competing reactions producing iodine was developed by Fournier et al. [1] to study partial segregation in stirred tanks. The coupling of the borate neutralization and the Dushman reaction in this system allows the measurement of micromixing efficiency in reactors by monitoring the amount of iodine produced. Called the iodide-iodate method, this technique has been extensively used in different types of reactors. A novel adaptive procedure recently developed by the authors to improve the reliability of the iodide-iodate method is used here. In the adaptive procedure the kinetics of the chemical reactions is adjusted in such a way as to impose the same reactive volume for different hydrodynamics conditions, leading to more accurate results for the segregation index. Finally, the segregation index is related to the mixing time by using physical models. The heat exchanger-reactor presented here is an innovative geometry based on the addition in parallel of tubes equipped with helical inserts. It is expected to qualify as a low-cost compact heat-exchanger reactor and static mixer of high performance