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The reduction of bed temperature in fixed-bed biomass combustion is an effective measure to lower pollutant emissions. Air staging and bed cooling solutions are active strategies to decrease the fuel bed temperature. This work presents a CFD study of a biomass fixed-bed combustion plant that is equipped with an internal cooling bed system. Eight different cases are calculated to analyze the effect of the total airflow, air staging ratios and bed cooling system on biomass combustion. The findings are validated against experimental data from the literature. The results show good accordance between the numerical results and the experimental data. The primary airflow rate has the biggest influence on the bed's maximum temperatures. The internal bed cooling system is able to achieve an average bed temperature reduction of 21%, slowing the biomass thermal conversion processes. Bed cooling techniques can be combined with air staging and primary airflow reduction to reduce bed temperatures in order to reduce pollutant emissions and other undesirable phenomena, such as fouling or slagging. [ABSTRACT FROM AUTHOR]

Moving grate boilers are widely used in the combustion of solid biomass at industrial scale for heat and power production. This type of systems allows to use wide range of fuels, including those with a high moisture and ash content. However, biomass boilers present several associated problems, such as e pollutant missions or ageing phenomena that can reduce the efficiency of the boilers or damage them such as fouling, slagging or corrosion. CFD tools can be used to study biomass combustion systems providing information useful to optimize the operation and design of the boilers. In this work, an Eulerian fixed-bed biomass combustion model coupled with the CFD commercial code ANSYS-Fluent will be used to carry out the simulation of a large-scale moving grate biomass furnace. New procedures have to be developed to adapt the model operation to the characteristics of this case. The numerical results are compared with experimental data from literature. The new procedures provide a solution of the bed morphology, which is validated against the experimental data. • Three-dimensional transient simulation of a 4 MW biomass grate-fired furnace • Development of a new Eulerian feeding model • Validation of the simulation against experimental results from literature • Bed combustion pattern in accordance with literature data [ABSTRACT FROM AUTHOR]