Tracer analysis was applied to a secondary combustion chamber of a, rotary kiln incinerator simulator to develop a computationally inexpensive networked ideal reactor model and allow for the later incorporation of detailed reaction mechanisms. Tracer data from sulfur dioxide tracer experiments were reconstructed using a least-squares approximation that eliminated the intrinsic response of the measurement device and produced a residence time distribution between various points of the combustor. A model was chosen based on the best fit to tracer data, and consistency with physical geometry and temperature measurements. The resulting model showed that the active path was I s shorter than the mean residence time calculated from the total volumetric flow. The analysis found that complete mixing between the kiln gas and burner stream occurs farther downstream than originally expected. Results underscore the importance of turbulent mixing in reactor design and suggest that different design criteria are needed to ensure complete combustion.