Influence of Buoyancy Effects on the Mixing Process and RTD in a Side-Injection Reactor Equipped with Static Mixers

The mixing process and the residence time distribution (RTD) of molecules inside reactors are well-known topics in chemical engineering; good radial mixing and poor axial mixing of chemical species are the essential conditions to achieve a plug flow behavior in a tubular reactor, which is often highly desirable. While the influence of viscosity and spatial velocities on mixing and RTD has been investigated in the literature, the influence of density differences between the streams to be mixed has been much less investigated, especially considering laminar regimes. Thus, the mixing and RTD of two miscible liquids with different densities and viscosities in a side-injection tubular reactor equipped with Sulzer Static Mixers were studied by RANS-based computational fluid dynamics (CFD) simulations. The results obtained show that if adequate configurations are used, it is possible to well-approximate radial mixing and a plug flow behavior, even when large differences in densities are involved. Moreover, graphics for a fast estimation of the maximum mixing length involved as well as for the corresponding Pe^–1 value were obtained as a function of the Re number.