Experimental and numerical investigation of a small-scale fixed-bed biomass boiler

Experimental campaigns were carried out on a 140kW fixed-bed biomass boiler to investigate the effect of primary and secondary air distribution on temperature and combustion products and to validate a numerical model. Specifically, a Computational Fluid Dynamics model for the freeboard, based on a single-phase turbulent reactive flow model, was coupled to an off-line biomass bed model that encompass evaporation, devolatilization and char oxidation of the biomass, using an iterative procedure to take into account the radiative transfer between the biomass bed and the freeboard. The inlet turbulence level affects strongly the turbulent mixing of volatiles and it was proposed to assimilate the flow from the biomass bed as that coming from a perforated plate.