Eddy dissipation concept

EDC model is an extension of the Eddy dissipation model. Detailed Arrhenius chemical kinetics can be incorporated in turbulent flames. However, typical reaction mechanisms are invariably stiff, and their numerical integration is computationally costly. Hence, the model should be used only when the assumption of fast chemistry is invalid, such as modelling the slow CO burnout in rapidly quenched flames, or the NO conversion in selective non-catalytic reduction (SNCR). 

ref: ANSYS Fluent Theory Guide