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Show 7 in Fig.6. Configuration of the burner is optimized by experiment. The secondary fuel(F2) is supplied directly into the furnace at a high velocity. This causes the expansion of the secondary flame, and flattens the flame temperature distribution as shown by the solid line in the figure. The flattened temperature distribution supresses the formation of thermal NOx. Although, not shown in this report, experimental data shows that NOx emission from the burner is 40ppm ( @11% oxygen concentration ) at preheated air temperature 1570K. As shown in Fig.11, measured NOx emission at large-scale reheating furnace was surprizingly low compared to a conventional combustion system. 3-3. Major features of HRS NKK Corporation and Nippon Furnace Kogyo Kaisha, LTD. (NFK) have undertaken joint R&D work, and by the end of 1993, basic development work was completed. Challenge against "the common sence of a combustion engineer" came out with successful results. In 1992, NFK started marketing HRS, and applied HRS to various heating systems. The introduction of an all-regenerative-burner reheating furnace into a large scale hot strip mill process is the first trial in the steel making industry in Japan. More than 120 facilities have introduced 660 sets of HRS, and its application is widely spreading. Major features of HRS are; a) Use of a carefully designed low NOx burner reduces NOx emission. N0x<40ppm at 11% oxygen concentration, preheated air temperature 1600K, is confirmed. b) Preheated air temperature can be raised as high as the furnace gas temperature. c) The newly developed honeycomb regenerator is 1/4~1/6 in weight, 1/4~1/5 in volume compared to a ball regenerator. 4. APPLICATION OF HRS TO A LARGE-SCALE REHEATING FURNACE [6] 4-1. Background of application No. 1 hot strip mill in Fukuyama Works started its operation in 1966, and has |