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Show PAPER NO. 48 Techniques for NOx Reduction in Industr ial Furnaces Takashi Tatsuda, Industrial Sales Dept., Osaka Gas Co., Ltd. Abstract g: LA S ~ hSj¥j 1?J H~~7/0t.. J/Otr?S Low-NOx burners reduce NOx emission through two-stage combustion, exhaust gas recirculation or off-stoichiometric combustion. When these burners are installed in industrial furnaces, however, NOx emission levels may not be as anticipated i f the flame shape mismatches the furnace geometry. This is thought to be caused by interference between the flame and the multi-burner configuration, or between the in-furnace flow and the burner/furnace wall configuration. In this report, we measured NOx emission levels in test furnaces with different burner and furnace wall configurations. As a result, we established a low NOx-emitting furnace with a burner that does not increase NOx emission. Introduction As environmental regulations have become more stringent, low-pollution, energy-saving city gas (natural gas) has dramatically increased its market share as an industrial fuel. Since city gas contains no sulphur, it does not generate sulphur dioxide. However, thermal nitrogen oxides (NOx) are an inevitable product of combustion, and so even city gas generates NOx when burnt. Therefore, to satisfy environmental regulations, we have developed 10w-NOx burners using new city gas combustion technology. The burners to be based on 10w-NOx theories, such as the two-stage combustion and divided flame burners, successfully achieved low NOx emission levels when installed in furnaces with sufficient firing volume. However, when these burners were applied in some industrial furnaces, they were found to produce two or three-times the previous NOx emission levels. Repeated trial and error showed that NOx emission increases if the flame reaches the furnace walls, causing local heating, and that high-velocity burners are the most effective in reducing NOx generation in cylindricaltype furnaces. ,Originally developed for applications such as galvanization, high-velocity burners maintain uniform furnace temperature by rapidly mixing the air in the furnace. Even so, the precise effects of altered furnace configuration and high-velocity burner installation on NOx generation in cylindrical furnaces has yet to be determined. - 1 - |