CFD modelling of a RDF incineration plant

The operation of waste-to-energy plants based on incineration inevitably implies the production of greenhouse gases and the emission of harmful species to the human health. The European Directive on the construction and operation of incineration plants fixes strict rules concerning the temperature and the residence time of the combustion products within the combustion chamber. Indeed, acting directly on the combustion process to limit the emission of pollutants at the source is a well assessed alternative to post combustion technologies. The peculiar characteristics of the treated waste or Refuse Derived Fuel (RDF) may also cause problems to the long term operation of the burner, as in the case of deposits formation due to the presence of ash. The ash particles, entrained in the in-chamber flow, may stick on the walls even at relatively low temperatures, thus modifying the heat transfer coefficient, reducing the system efficiency and imposing frequent stops for overhauling. Therefore, the characterization of the phenomena occurring in a RDF combustor through experimental and/or numerical techniques is strongly demanded for assisting its optimal maintenance. This work presents the assessment and validation of a Computational Fluid Dynamics (CFD) model of a real scale waste-to-energy plant operating in central Italy, which couples the thermo-chemical conversion of the solid RDF to the gaseous combustion of the released syngas. The model allows to characterise into detail the temperature and residence time of the combustion products, for the verification of the fulfilment of the existing regulation for dioxin formation in incineration plants.