This paper evaluates the combustion process of solid biomass fuel in a 1 MW grate furnace by using data obtained from a real unit and mathematical modelling tools. Investigated grate furnace consists of combustion chamber with continuous feeding and heat exchanger. The combustion chamber is equipped with multiple primary, secondary and tertiary air inlets. Combustion air is distributed into four areas, two under and two above the grate bed. Temperature is monitored inside the combustion chamber by three thermocouples and gaseous combustion products are analysed in the stack.
The present mathematical model is based on an assessment of existing simplified approaches to the fixed bed modelling, see e.g. (Johansson et al. 2007; Frey et al. 2003). This approach means that the process may be simulated without specialised bed simulation software using the tools available in commercial CFD software. The discussed approaches differ mainly by the complexity of treatment of the solid fuel layer, but also by the degree of interaction between the fixed bed and the freeboard region.