Experimental study on combustion characteristics and NOX emissions of pulverized anthracite preheated by circulating fluidized bed |
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Authors: | Jun Wang Jian-guo Zhu Qing-gang Lu |
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Affiliation: | WANG Jun 1,2,ZHU Jian-guo 1 and LU Qing-gang 1 1.Institute of Engineering Thermophysics,Chinese Academy of Sciences,11 Beisihuanxi Road,Haidian District,Beijing,100190,China;2.Graduated University of Chinese Academy of Sciences,Shijingshan District,Beijing,100049,China |
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Abstract: | A 30 kW bench-scale rig of pulverized anthracite combustion preheated by a circulating fluidized bed (CFB) was developed. The CFB riser has a diameter of 90 mm and a height of 1,500 mm. The down-fired combustion chamber (DFCC) has a diameter of 260 mm and a height of 3,000 mm. Combustion experiments were carried out using pulverized anthracite with 6.74% volatile content. This low volatile coal is difficult to ignite and burn out. Therefore, it requires longer burnout time and higher combustion temperature, which results in larger NOX emissions. In the current study, important factors that influence the combustion characteristics and NOX emissions were investigated such as excess air ratio, air ratio in the reducing zone, and fuel residence time in the reducing zone. Pulverized anthracite can be quickly preheated up to 800°C in CFB when the primary air is 24% of theoretical air for combustion, and the temperature profile is uniform in DFCC. The combustion efficiency is 94.2%, which is competitive with other anthracite combustion technologies. When the excess air ratio ranges from 1.26 to 1.67, the coal-N conversion ratio is less than 32% and the NOX emission concentration is less than 371 mg/m3 (@6% O2). When the air ratio in the reducing zone is 0.12, the NOX concentration is 221 mg/m3 (@6% O2), and the coal-N conversion ratio is 21%, which is much lower than that of other boilers. |
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Keywords: | circulating fluidized bed preheat pulverized anthracite NOx |
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