TY - JOUR
T1 - Development and validation of CFD models for gas phase reactions in biomass grate furnaces considering gas streak formation above the packed bed
AU - SHIEHNEJADHESAR, Ali
AU - Scharler, Robert
AU - Mehrabian, Ramin
AU - Obernberger, Ingwald
PY - 2015/4/22
Y1 - 2015/4/22
N2 - State-of-the-art packed bed models supply continuous concentration profiles as boundary conditions for subsequent CFD simulations of gas phase, leading to pre-mixed combustion conditions. However, in reality the "porous" nature of the packed bed leads to streak formation influencing gas mixing and combustion. Therefore, in the present work, in order to account for the influence of the streaks on gas phase combustion, a gas streak model based on a correlation between the local gas residence time and a mixing time has been developed based on numerical simulations. Finally, the streak model was linked with an in-housed developed hybrid gas phase combustion model suitable for laminar to highly turbulent flow conditions and applied for an under-feed pellet stoker furnace (20 kWth) concerning the simulation of gas phase combustion and NOx formation. The results in comparison with a simulation without the streak formation model show that the flue gas species prediction can be improved with the proposed streak formation model. Especially, in the region above the fuel bed (in the primary combustion chamber), this is of special importance for NOx reduction by primary measures.
AB - State-of-the-art packed bed models supply continuous concentration profiles as boundary conditions for subsequent CFD simulations of gas phase, leading to pre-mixed combustion conditions. However, in reality the "porous" nature of the packed bed leads to streak formation influencing gas mixing and combustion. Therefore, in the present work, in order to account for the influence of the streaks on gas phase combustion, a gas streak model based on a correlation between the local gas residence time and a mixing time has been developed based on numerical simulations. Finally, the streak model was linked with an in-housed developed hybrid gas phase combustion model suitable for laminar to highly turbulent flow conditions and applied for an under-feed pellet stoker furnace (20 kWth) concerning the simulation of gas phase combustion and NOx formation. The results in comparison with a simulation without the streak formation model show that the flue gas species prediction can be improved with the proposed streak formation model. Especially, in the region above the fuel bed (in the primary combustion chamber), this is of special importance for NOx reduction by primary measures.
KW - Biomass
KW - CFD modelling
KW - Combustion
KW - Grate furnace
KW - Hybrid model
KW - Streak formation model
UR - http://www.scopus.com/inward/record.url?scp=84946476784&partnerID=8YFLogxK
U2 - 10.1016/j.fuproc.2015.07.029
DO - 10.1016/j.fuproc.2015.07.029
M3 - Article
AN - SCOPUS:84946476784
SN - 0378-3820
VL - 139
SP - 142
EP - 158
JO - Fuel Processing Technology
JF - Fuel Processing Technology
ER -