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Show Introduction Industrial furnaces are used for many purposes such as reheating, forging, melting, drying, deodoring and heat treating. With their sizes and processes different from each other, industrial furnaces need to meet various requirements from thermal performance to exhaust gas emissions. Thermal efficiency needs to be improved while satisfying necessary temperature and heat flux profile to the materials. Toxic exhaust gas emissions, in particular NOx must be reduced to meet strict regulations being implemented worldwide. When designing new furnaces, various design parameters controlling furnace performances need to be considered, for example, furnace size and configuration, burner specifications, fuel input, etc. Trial-and-error approach used to be the only method to optimize these parameters. Unlike mass-produced boiler furnaces, no one industrial furnace is identical to each other. Industrial furnaces are in general too large to experimentally optimize their various designing parameters. The .design and optimization of industrial furnaces have, therefore, depended on designers' engineering experience accumulated over many years. The regenerative burner system has been attracting great interests from many furnace manufacturers and users. The system promises high thennal efficiency due by regenerating high temperature preheated air. Despite its high thermal efficiency, high thermal NOx emission has been one of the problems. To reduce NOx emission from the regenerative burners, Tokyo Gas has developed a innovative FDI (l).{3) (fuel direct injection) low NOx combustion technology. The FDI technology features a direct injection of fuel into a furnace chamber, with combustion air remotely injected into furnace (Fig. I ). At the operating temperature of 1300c the FDI technology reduces NOx emission from 115 to 1110 of that of conventional regenerative burners. The FDI low NOx technology is expected to boost the application of the regenerative burner system to a wide spectrum of industrial high temperature processes. When applying the FDI-regenerative burner system, effects of a number of new design parameters specific to the system need to be taken into account. The effect of the switching-over flames generated by the regenerative burners on heat transfer characteristics are of great concern to optimize the configuration and operation of furnaces equipped with the regenerative burners. The effect of unique flames generated by the FDI combustion needs to be carefully considered. Due to lack of experience on the FDI-regenerative burner system, further knowledge and insight needed of the detailed characteristics of the system. 2 |
