Numerical investigation of reaction mechanisms on NOX emissions from biomass combustion with enhanced reduction

The present study examines the applicability of reaction kinetic mechanisms for predicting NOX emissions from biomass furnaces. These mechanisms are essential for numerical optimization of new innovative combustion technologies and therefore must be computationally affordable and provide reasonable accuracy in predicting NOX emissions. The selection of a suitable mechanism from literature is the goal of this work. The numerical investigations carried out utilized chemical reaction kinetic simulations with continuous stirred tank reactor networks. First, the predictions of a detailed benchmark mechanism are compared to experimental data and analyzed with regard to temperature, air-to-fuel equivalence ratio, residence time and producer gas composition. Then, various hybrid and reduced mechanisms are compared with the benchmark mechanism. The investigation showed a good agreement on the trends of NOX emissions from the detailed mechanism and measurements. The detailed mechanism can therefore be employed to find optimal operation windows in terms of temperature, airto-fuel equivalence ratio and residence time. Benchmarking of the hybrid and reduced mechanisms showed large differences between the mechanisms. In conclusion, only one reduced mechanism is considered suitable for application in a full-scale 3D CFD simulation, which will be investigated in future studies.