The industrial experiments were carried out to study the bituminous coal blending in a 660-MWe supercritical down-fired boiler with anthracite combustion system under low load. The influence of the bituminous coal ratio on the boiler thermal efficiency, flue gas temperature, flue gas species, and heat transfer of various heating surfaces was analyzed in detail. The ignition distances of three experimental coals were measured, and the influence mechanism of bituminous coal blending on the combustion, heat transfer, and NO_x emission in the furnace was proposed. The results show that increasing the bituminous coal blending ratio is beneficial to reduce NO_x emissions. However, it leads to the rise of the exhaust gas temperature and the decrease of the boiler efficiency, which can be ascribed to the large amount of the cold primary air sent into the pulverizing system to control the air pulverized coal flow temperature at the mill outlet. The ignition distances of three experimental coals are different. The ignition distance from short to long follows the following order, that is, bituminous coal, lean coal, and anthracite. The earlier ignition of the bituminous coal leads to a sharp rise in the temperature of the airflow at the burner nozzle outlet, a rapid expansion of the airflow volume, and a sharp attenuation of the airflow rigidity, resulting in a short flame downward penetration depth and the upward movement of the flame center in the furnace. As the bituminous coal is blended, the change of the flame center and the flame fullness in the furnace affects the flue gas temperature distribution. Similarly, the change of the radiant heat transfer intensity and the convective heat transfer intensity affects the heat absorption distribution of the heating surface in the furnace.

中文翻译：

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无烟煤低负荷下燃锅炉配烟煤试验研究

通过工业试验研究了低负荷下无烟煤燃烧系统的 660-MWe 超临界下燃锅炉中烟煤的掺混。详细分析了烟煤配比对锅炉热效率、烟气温度、烟气种类以及各受热面传热的影响。测定的三个实验的煤的点火距离，并在燃烧烟煤混合，传热和NO的影响机制_X提出在炉内发射。结果表明，增加烟煤配合比例是有益的，以减少NO _X排放。但导致排烟温度升高，锅炉效率降低，可归咎于大量冷一次风送入制粉系统，控制磨机出口风粉煤流温度。 . 三种实验煤的点火距离不同。点火距离由短到长依次为烟煤、贫煤、无烟煤。烟煤过早着火导致燃烧器喷嘴出口气流温度急剧上升，气流体积迅速膨胀，气流刚性急剧衰减，导致火焰向下穿透深度变短，火焰中心在炉内向上移动。随着烟煤的混合，火焰中心和炉内火焰丰满度的变化影响烟气温度分布。同样，辐射传热强度和对流传热强度的变化影响炉内受热面的吸热分布。