Experimental studies of a biomass boiler suitable for small district heating systems

Abstract Extensive experiments have been carried out in a newly developed furnace suitable for small district heating networks. The fuel is wood-chips with moisture content in the range of 30–58%. One of the unique features of this new furnace is the broad thermal output span, which makes it possible to run the boiler down to 10% of maximum heat load, with maintained low emissions of CO and total hydrocarbons (THC). The aim of this study has been to evaluate the performance of the combustion chamber during steady-state operation in the complete thermal output range. The experiments show very good results over the entire thermal output range. In the range 60 kW up to 500 kW , the average CO content in the stack gases is typically below 25 mg Nm −3 (20 ppm ) and the NOx concentration below 195 mg Nm −3 (95 ppm ) during steady state conditions. At lower thermal outputs, the average CO content is below 105 mg Nm −3 (84 ppm ) . (All values standardised to 10 vol % O2.)