SCALING LAWS FOR NOX EMISSION PERFORMANCE OF BURNERS AND FURNACES FROM 30 KW TO 12 MW

A general analytical approach for scaling NOx, emissions from burners and furnaces is presented, together with the scaling model for NOx emi ssions performance that results when this approach is applied to a bro ad class of swirl-stabilized industrial gas burners. The model is base d on results from a sea of collaborative burner scaling experiments on a generic gas burner and furnace design at five different scales havi ng near-uniform geometric, aerodynamic. and thermal similarity and uni form measurement protocols. This collaborative effort provides the fir st NOx scaling data over the range of thermal scales from 30 kW to 12 MW, including input-output measurements as well as detailed in-flame m easurements of NO, NO2, CO, O-2, unburned hydrocarbons, temperature, a nd velocities at each scale. The in-flame measurements allow identific ation of keg; sources of NOx production. The underlying physics of the se NOx sources lead to scaling laws for their respective contributions to the overall NOx emissions performance. It is found that the relati ve importance of each source depends on the burner scale and operating conditions. The scalings fur these NOx sources are combined in a comp rehensive scaling model for NOx emission performance. Results from the scaling model show good agreement with experimental data at all burne r scales and over the entire range of turndown, staging, preheat, and excess air dilution, with correlations generally exceeding 90%. The sc aling model permits design trade-off assessments for a broad class of burners and furnaces, and allows performance of full industrial-scale burners and furnaces of this type to be inferred from results of small -scale tests. (C) 1998 by The Combustion Institute.