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Show above from the furnace floor and 100 m m inside from the furnace side wall (see Fig. 4). The furnace was equipped with six refractory-lined water-cooled heat sinks on the floor to simulate the furnace load. The experiment used a typical natural gas supplied in Japan. Table 2 shows the compositions of the natural gas. Produced fromLNG (liquefied natural gas), the natural gas contains virtually no molecular nitrogen. Liquefied, and thus pure, oxygen was used and supplied via a vaporizer. The oxygen had no molecular nitrogen either. The flow rate of fuel gas and oxygen were kept at 22.8 m3/h and 55.0 m3/h respectively, yielding the total thermal input of 265 k W (LHV) with the excess oxygen ratio of 1.05. The furnace pressure was kept positive in the range of 10 - 50 Pa (1 - 5 m m H20) to prevent the ambient air from leaking into the furnace. 3.2 Measurement equipment The furnace had inspection holes in the center of the load simulators. Six inspection holes were used to measure total hemispherical radiative heat flux to the furnace load. Total radiative heat flux was measured by an ellipsoidal radiometer developed by EFFtF. For safety reasons the furnace was equipped with a U V flame detector (Yamatake-Honeywell), which was cooled by injecting a known flow rate of C O , gas instead of normally used fresh air. Use of C 0 2 gas prevented unnecessary nitrogen from entering into the furnace. The exhaust gas was sampled at the exit of the furnace and analyzed after removing the water vapor with a gas cooling unit. The dry exhaust gas was analyzed by Shimadzu URA-107 (CO, CO,), MAG-6000A (O,) and CLM-107 (NOx) instruments. The exhaust gas temperature was measured by a suction pyrometer with a type-R thermocouple (Pt/Pt- Rhl3 % ) developed by IFRF. 3.3 Experimental method First the experimental furnace was preheated by a conventional air-fuel burner until the furnace temperature reached around 1273 K. Then the oxy-fuel burner was ignited and the conventional air-fuel burner was switched off. The total radiative heat flux measurement and exhaust gas analysis were conducted after the furnace flue gas was completely converted to an oxy-fuel flame. The furnace temperature at which measurement was started was 1673 K for each test case. The furnace temperature increased about 30 KVhour during the total radiative heat flux measurement. The furnace was in a transient condition and thus overall furnace energy 4 |