Different numerical approaches for the analysis of a waste-to-energy plant

Waste-to-Energy (WtE) plants are critical for sustainable waste management, with European legislation mandating that gaseous combustion products remain above 850 °C (for non-hazardous waste) for at least 2 s after the last injection of combustion air to facilitate the thermal destruction of dioxin precursors. Accurate assessment of this temperature, referred to as T2s, is essential for compliance but challenging due to the impracticality of direct measurement. Simplified 0D models, typically adopted for T2s estimation, rely on empirical correlations from similar plants, limiting their precision. In contrast, Computational Fluid Dynamics (CFD) offers higher accuracy by resolving velocity and temperature fields within the combustion chamber, potentially contributing to the optimization of WtE plant operations. A systematic comparison of these approaches for modelling Refuse-Derived Fuel (RDF) combustion has been lacking in the literature. This study aims to address this gap by comparing a simplified 0D lumped-parameters model, previously developed by the authors, with two detailed 3D CFD models simulating the combustion chamber − one based on a non-reacting model and the other on a reacting chemistry model. Results from the three models are compared with experimental data, demonstrating that the 3D reacting model presents the best agreement (with an average error of 2.8%, against the 6.1% of the non-reacting model and 8.9% of the lumped-parameters model) while the 0D model allows the fastest calculation. The findings also highlight the trade-offs between computational efficiency and accuracy, offering valuable insights to help select the most suitable modelling approach for specific applications.