Combustion and gas flow phenomena in waste incinerators have been studied usually by numerical simulations and have been focused mainly on the effects of the gas flow and its related parameters such as the secondary air injection and furnace shape, due to the difficulty in solving the combustion of the solid waste bed.
In this study, the combustion and gas flow characteristics were investigated by using a recently developed CSM, while various combustion parameters were studied such as distributions and oxygen-enriched level of the primary air and the waste retention time and the waste heating value. The CSM simultaneously solves a combustion model for the waste bed with the gas flow simulation, coupled by the heat and mass interactions of the two regions. And the ratio of conversion from the combustible matter to the products of incomplete combustion(PICR), the area ratio of the combustion on the grate(CAR) and the flame propagation speed(FPS) were introduced to explain the results of simulations.
PICR increases and flame could be extinguished by poorly distributed primary air. If oxygen is added into the primary air, CAR decreases and PICR increases because of increased FPS. Finally shortened retention time on the grate makes char combustion take place mainly on the downstream of the waste bed. The above results shows that the overall combustion characteristics are influenced by the interactions between the waste bed and the gas flow field.
