When the yield of a chemical reactor is to be predicted, both macromixing and micromixing need to be considered. The large-scale flow determines the transport of reagents throughout the reactor. In addition, the power draw affects the size of the tiny Kolmogorov eddies and, hence, the micromixing. For large scale, a commercially available CFD code is used that applies a standard turbulence model, resulting in a velocity and dissipation-rate distribution in the vessel. Several micromixing models are applied to simulate the chemical reactions at small-scale flows. These fluid elements travel through the vessel with the turbulent velocities calculated by the CFD code, thereby encountering different regions of the dissipation rate. When the simulations are compared with measurements the results are not yet completely satisfactory. The inclusion of the scale reduction from the feed pipe to the Kolmogorov scale and of the turbulent dispersion results in a difference in the yield as high as 20%.