燃煤机组变负荷调峰运行是提高可再生能源消纳能力的重要举措，但会对燃烧过程及系统产生重要影响。飞灰特性与锅炉结渣、除尘设备性能、颗粒物排放等密切相关，笔者研究了燃煤锅炉负荷变化对飞灰特性的影响规律，用于指导炉膛沾污结渣和颗粒物排放等相关问题的防控。针对1 000 MW燃煤锅炉，在60%和90%运行负荷下分别采集飞灰样品，利用先进的计算机自动控制扫描电镜（CCSEM）技术对飞灰化学和矿物成分、粒径分布以及形状特征进行深入表征，采用数字成像煤灰熔点分析仪对飞灰熔融温度进行分析，揭示了锅炉运行负荷变化对飞灰特性和熔融行为的影响。研究结果表明锅炉在不同运行负荷条件下飞灰化学成分相似。无机矿物元素交互作用是影响飞灰粒径分布的关键因素，低负荷运行工况下煤中含Ca和Fe的矿物与硅铝酸盐交互反应减弱，飞灰整体粒径分布向小粒径迁移，飞灰的D50（小于该粒径的颗粒占50%）由约40 μm减至约30 μm。相比高负荷运行工况，低负荷运行工况下飞灰在炉膛中的熔融受抑制，熔融飞灰比例相比高负荷运行工况降低约10%，低负荷运行条件下燃烧温度降低是导致飞灰熔融比例降低的主要原因。

The peak load regulation operation of coal-fired units is an important measure to improve the consumption capacity of renewable energy, but it will have an evident impact on fuel combustion process and system. Fly ash properties are closely related to ash slagging behavior, dust removal equipment performance and particulate matter emission. However, little research has been done in the past. The influence of load change of coal-fired boiler on fly ash characteristics was studied to guide the prevention and control of ash related problems such as furnace fouling and slagging and particulate matter emission. In this work, fly ashes were sampled before ESP in a 1 000 MW coal-fired boiler under 60% and 90% operating load. Chemical composition, mineral species, particle size distributions and shape characteristics of fly ash were analyzed by advanced computer automatically controlled scanning electron microscope(CCSEM). The fly ash fusibility was analyzed by a digital imaging coal ash fusibility system. The effects of boiler operating load changing on ash properties and ash melting behaviors were investigated. The results show that changing of operation load has insignificant effect on fly ash chemical composition. Degree of mineral interaction is the key factor affecting the particle size distribution of fly ash. Low operation load of boiler suppresses the migration of Ca and Fe bearing minerals in coal to aluminosilicates, which results in finer fly ash particle size distribution. The D50 of fly ash decreases from about 40 μm to 30 μm. Compared withfly ash in low load operation condition, the melting of fly ash in the furnace under the low load operation condition is restrained. The proportion of molten fly ash from low load operation condition is about 10% lower than that from the high load operation condition, which is mainly attributed to the lower combustion temperature under low load operation condition.

0 引言

1 试验

   1.1 锅炉型号及采样方法

   1.2 燃料特性和试验工况

   1.3 样品分析方法

2 结果与讨论

   2.1 飞灰化学成分和矿物分布特性

   2.2 飞灰粒径分布特性

   2.3 飞灰熔融特性

3 结论