An improved detailed chemical mechanism for numerical simulations of the gas-phase of biomass combustion

Abstract

The design of efficient and clean biomass combustion systems requires a good understanding of the combustion process. Computational Fluid Dynamics (CFD) can play a key role. However, the success of CFD simulations depends, to a great deal, on the chosen chemical kinetic reaction mechanism, among others. Due to the greater computational cost when using detailed chemical mechanisms, reduced or semi-reduced chemical mechanisms have always been the preferred option in the simulations of biomass combustion. This is mainly due to the limitations of the most widely used combustion model − the Eddy Dissipation Concept (EDC). A computationally inexpensive flamelet-based partially premixed combustion model has recently been proposed as an alternative combustion model for CFD studies of biomass combustion. To further improve the predictions of this combustion model, the present study introduces an improved detailed chemical mechanism. This is achieved via the addition of NOx steps to an existing detailed chemical mechanism. The computational performance of this combustion model, which adopts the improved chemical mechanism, is then evaluated by studying the thermal and velocity fields as well as emissions of a biomass combustion furnace. The results reveal that the improved chemical mechanism produces superior predictions compared to its original version. More importantly, the results show that the improved chemical mechanism can overcome the limitations of the partially premixed combustion model's inability to predict NOx emissions.