In this paper, a commercial small-scale boiler designed for wood-chips was modified and redesigned to enable detailed space-resolved extraction of the gaseous compounds above the fuel bed. Therefore the product gas was extracted at nine different points on the same level over the fuel bed. These experimental measurements are necessary to provide realistic boundary conditions for further freeboard numerical simulations. The space-resolved concentrations also provide an excellent data for optimization, and validation of fuel bed models. This approach is new in the field of commercial small-scale biomass boilers and shows the requirement of more than only one sampling point to gain the composition of the product gas. Additionally, the positive effect of an air staged combustion on particle emissions was tested and confirmed for wood-chips with high and highest fine and bark fraction. The experiments were performed for three different fuel moistures and various primary air ratios. During all experiments the water content and primary air ratio show a significant influence on the product gas and particle emissions. The varying parameters also affect the content of tar in the product gas. In the case of dry wood-chips and low primary air ratio the tar content reached its peak and represents a major part of the heating value.
- Biomass bioler
- Space-resolved extraction
- Primary combustion product gas