Wood combustion is related to ambient air pollution by CO, organic compounds, particulate matter (PM10), and NOX. To increase the contribution of wood energy, technologies to achieve low emissions are needed. In addition, the use of low quality wood fuels is becoming more important.
The aim of the project is to develop a multi-stage concept for biomass combustion in the size range from 500 kW to 50 MW. Special attention is given to different combustion sections on the grate assisted by multi-stage air injection. During the reporting period, the following progress was achieved:
- The instationary one-dimensional fuel bed model (FBM) was extended from one to four independent grate sections. Calculation runs show that a variable air distribution can be applied to control the combustion at varying fuel moisture content.
- Combustion experiments in the grate boiler were performed to investigate the influence of the air distribution and of the grate movement. Pyrolysis gas analyses were performed for the fuel conversion process, while flue gas analyses were performed for the gas reactions. The results show that the grate movement exhibits a dominant influence on the solid fuel conversion.
- To optimise the gas phase reactions, CFD modelling and aerodynamic model experiments with particle image velocimetry (PIV) were performed to investigate the secondary air injection described as a jet in cross flow (JICF). From these investigations, design recommendations are derived.