(467b) Large Eddy Simulations of Reaction Plumes and Micromixing

The reaction kinetics of many industrial processes, such as those involving crystallization and polymerization, typically occur order-of-magnitude faster than the time scales associated with blending and species homogenization. This disparity means that reactions often proceeded inhomogeneously across a reactor, leading to variances in production and process outcome. Further challenges are realized when reactions are controlled by molecular “micromixing”, which occurs over length and time -scales comparable to the smallest eddies that exist in the system.

In this work, we show how large eddy simulation can be used to perform time-accurate, three-dimensional simulations of chemically reacting turbulent systems. After a short theoretical overview, we use this approach to predict the time-evolution of an acid/base reaction plume evolving across an agitated tank. We compare these predictions to expectations from theory and investigate the effects of reactor design on product homogeneity. We then examine predictions involving a more complex Dushman reaction, which includes both a quasi-instantaneous component with an equilibrium reaction component. Since the Dushman is informed by sub-grid micromixing, it provides a useful testbed for assessing the effects of simulation time-step and resolution on the resulting reaction kinetics.