A computational analysis of re-burn process in wood/sludge-fired stoker boilers

摘要

In recent years, the re-burn process has been incorporated in the design and development of stoker boilers to reduce the emission of NOx from such boilers in an attempt to preserve the clean air environment. In this paper, we use the existing modelled governing equations for turbulent fluid flow, laden with wood/sludge particles, along with the transport equations for different species to numerically investigate various mechanisms responsible for NOx production. These equations are simulated using the Fluent software to conduct a detailed study on NOx production under different operating conditions for boiler, after incorporating a new method for the re-burn process. This new method is known as METHANE DE-NOx and has been developed by the Gas Technology Institute. We present the numerical results obtained from the simulations for fluid flow properties and various species concentrations at different cross sections along the height of the boiler. These results suggest that the new method is effective in reducing NOx emission substantially. Further investigation on NOx reduction by the re-burn process is conducted for the effects of the boiler geometry, the over-fire arrangement, and the flue gas recirculation.