Waste Incineration Plant
A numerical model for the incineration of municipal waste on a grate has been developed at the department of Energy Plant Technology and is integrated into the parallel CFD-Code LORA. This waste conversion model describes the transport of the fuel matters combustibles, water, ash and inert fractions and the distribution along the grate. The local decomposition of these components into gaseous products is modelled by the processes of moving-bed drying, fuel pyrolysis and heterogeneous combustion (gasification) of residual char. These processes strongly depend on the temperature evolution along the bed and demand a precise representation of the thermal mechanisms, such as conduction, convection and radiation. The stoking effect of the grate and the resulting mixing processes are considered by using several bed layers. Additional to the known process parameters such as the furnace geometry, the mass flows of the fuel and the primary airs, the parameters void fraction, bulk density, particle porosity and particle diameter serve to adopt the grate firing model to the specific properties of the bulk material individually. The coupling of the waste conversion model with the CFD-Simulation enables a steady consideration of local interaction between chemical and physical processes of the furnace and the bed layer. At the moment the waste conversion model is coupled to the flow simulation at the calculated bed layer contour. The radiate fluxes, which are calculated values from the current flow solution and the bed surface temperature can be updated during the course of the overall iterative procedure. In dependence of the radiate fluxes the grate model calculates the contour of the bed layer along the grate, the mass flow, the composition and the temperature of the flue gas, streaming in the furnace of the boiler.