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Show ABSTRACT The objective of the work reported here was to characterized the pre-rebuilt combustion performance in the natural-gas-fired, partially oxygen-enriched, aluminum recycling furnace (Furnace 8) operated by Roth Brothers Smelting Corporation in Syracuse, N e w York. Measurements of gas temperature and species concentration (02, C O , N O , and C02 ) were made in the exhaust of the furnace. Local gas temperature, species concentration, incident wall radiant flux and furnace wall temperature measurements were also made in the combustion space. Average exhaust gas temperatures varied between a low of 1558°F (1121K) and a high of 2281°F (1523K) for the conditions of low-fire and highest oxygen enrichment, respectively. It was observed that changes in furnace stoichiometry were important in controlling the overall N O production. The highest N O level (3509 ppmvd) was observed for the normal high-fire condition when the temperatures were high in the furnace and there was enough excess air available (more than 1 0 % excess). A significant reduction in N O production (from 3509 to 1390 ppmvd) was observed when the stoichiometry was reduced. Values of C O concentrations of 10,820 and 7700 ppmvd were measured in the stack with oxygen excess values of 0.5 and 5%, respectively. Temperatures in the combustion space very quickly reached the service ceiling of the type S thermocouple used in the suction pyrometer (3500°F), which prevented full profiles in all access holes available. Oxygen concentration profiles indicate that typically early in the centerline of the jet flames the concentrations are higher. N O profiles in the combustion space indicate high concentrations in locations where the oxygen concentrations and gas temperatures were high. Peak values of 8000 ppmvd were detected in the flame region. C O concentrations reached values as high as 10 vol% earlier in the flame at the initial stages of combustion and C 0 2 values were largest in locations where combustion is complete as indicated by the correspondingly low values of C O concentrations. Near-constant values of wall radiative heat fluxes were measured of 140.5 Btu/h/ft2 (443 W / m 2 ). INTRODUCTION Significant progress has been made in the combustion process in large furnaces over the past two decades in reducing energy consumption and maximizing product yield. Nonetheless, escalating global competition and increasingly restrictive government regulations on pollutants in furnace effluents are prompting the examination of even more aggressive measures to increase combustion efficiency while reducing the impact of the combustion process on the environment. The objective of the work reported here was to characterize the combustion performance in a natural-gas-fired, partially oxygen-enriched, aluminum recycling furnace. Measurements of gas temperature and species concentration (02, C O , N O , and C 0 2 ) were made in the exhaust of the furnace. Gas temperature, species concentrations, wall incident radiant flux, and wall temperature were also measured in the combustion space through a specially designed wall insert placed in an existing side door used for dross removal during the normal operation of the furnace. Stack measurements in this furnace included five operating conditions, i.e., normal high and low firing, high fire with only air as the oxidizing agent, high fire low stoichiometry, and high fire with the highest possible oxygen enrichment (without requiring any manual valve adjustments). Combustion space measurements were made only for the baseline, high-fire operating condition. FURNACE DESCRIPTION A schematic of the Roth Brothers Smelting Corporation reverberatory aluminum melting Furnace 8 can be seen in Fig. 1. The furnace is generally of rectangular cross-section. The combustion space |
