Cross-Jet Mixing of Reburning Gas and Secondary Air in Municipal Waste Incinerators

The natural gas reburning is an attractive method for NOx reduction in municipal waste incinerators. The reburning de-Nox system utilizes hydrocarbonradicals' reduction effect of NO by injecting natural gas into the incinerator. The reburning is also expected to reduce CO emission and other hazardous components by promoting the mixing. In this technique, the natural gas is injected into the waste burned gas flows. The mixing degree of the reburning gas jet (the natural gas jet) with the burned gas flow is one of the most important factors to reduce them. Cross jet injection into the combustion chamber plays the key role in this mixing process. We do not. however, well understand the general relationship between the mixing degree and the jet conditions such as the nozzle diameter, the number of nozzles and the jet velocity. In this study, major design parameters are quantitatively investigated by the flow simulation results for simplified model incinerators. The degree of mixing of the jet with the cross gas stream is evaluated in terms of the standard deviation of the jet fluid concentration distributions normalized by mean concentration. The result of this study will provide useful information for designing the jet conditions issuing from the round nozzles in municipal waste incinerators.