Grate-firing is one of the main technologies currently used for biomass combustion for heat and power production. However, grate-firing systems are often reported to have relatively high un-burnout, low efficiency and high emissions and they need to be optimized. The purpose of this report is to establish a reliable baseline CFD model for a biomass grate-fired boiler for an EFMGT (Externally Fired Micro Gas Turbine) plant. The numerical model can be used for diagnosis and to signal critical regions, such as high temperature zones, and the spatial distribution of chemical species within the boiler. Different modelling of the fuel bed and their impacts on CFD analysis are discussed and compared. The prediction clearly show that a detailed fluid dynamic above the fuel bed (e.g. modelling the air injection nozzles) is required to obtain reliable results such as exact temperature field and a correct distribution of chemical species, whereas the model is rather insensitive to the conditions of the gas phase above the fuel bed.
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