TY - JOUR
TI - Small wood pellet boiler 3-D CFD study for improved flue gas emissions employing flue gas recirculation and air staging
AU - Kokalj Filip
AU - Zadravec Tomas
AU - Jovović Aleksandar M
AU - Samec Niko
JN - Thermal Science
PY - 2023
VL - 27
IS - 1
SP - 89
EP - 101
PT - Article
AB - Wood biomass fuels have become increasingly important in terms of achieving  future sustainability targets regarding RES, especially to reduce GHG and  the use of domestic energy sources, on other hand with these fuels the  pulutant air emissions have to be addressed with great attention. Nowadays,  air staging and flue gas recirculation are often used as a primary emission  reduction measure in large scale biomass fuel fired boilers, but their  combined application in small scale commercial wood pellet boilers is not so  common. The implementation of this approach to the small scale burning  devices can enable further development of small boilers, in order to achieve  a more complete combustion and reduction of pollutant emissions, especially  CO, NOx, and PM. In the presented work a comprehensive numerical and  experimental study on the combustion parameters is performed, in order to  determine the overall combustion properties. A commercial 32 kW small-scale  hot water wood pellet boiler was modified numerically from the operating  point of view. The findings of this study, like different combinations of  recirculated flue gases and secondary air amount, can serve as useful  guidelines for the new innovative design and optimisation of the air and  recirculated flue gas injection process parameters. The scenarios of this  study, where recirculated flue gas was added to the secondary air, were  beneficial. Optimally, a CO reduction of 63% was achieved by adding 30% of  recirculated flue gas to the secondary air stream, and a 22% reduction was  achieved for the NO emissions.