作为灵活发电的关键环节之一，长期稳定低负荷运行技术在可再生能源并网规模不断扩大的过程中发挥着重要作用。循环流化床（CFB）锅炉负荷调节过程中，为降低污染物排放或调平床温，常采用不均匀给煤的运行方式，这对CFB锅炉的设计和运行提出了更高要求。同时，低负荷时CFB锅炉炉膛出口烟气温度较低，如何保证再热蒸汽参数达到额定值是实现CFB锅炉灵活性运行亟待解决的问题之一。针对2台350 MW超临界CFB锅炉断煤低负荷运行工况参数进行深入计算分析，研究了低负荷时稳定再热汽温措施。研究发现，锅炉在部分给煤点中断的断煤工况下运行时，床温、炉膛出口烟温、炉膛出口氧量、高温再热器管屏出口蒸汽温度的变化趋势与各给煤口的给煤量基本呈正相关。但由于超临界CFB锅炉水冷壁具有正流动响应特性，给煤偏差及床温偏差对水冷壁的出口汽温偏差影响不大。基于上述研究，提出了一种针对长期调峰与低负荷运行超临界CFB锅炉稳定炉内高温再热器出口汽温的锅炉改造与运行优化技术方案。在低负荷下可保证高温再热器出口汽温基本稳定。

As one of the key process of flexible power generation, long-term stable low load operation technology plays an important role in the continuous expansion of renewable energy grid connection. It is very common to adopt the operation mode of uneven coal feeding in order to reduce pollutant emissions or adjust bed temperature in the process of load regulation of circulating fluidized bed (CFB) boiler, and this mode put forward higher requirements for the design and operation of CFB boilers. At the same time, the flue gas temperature at the outlet of CFB boiler is low at low load. How to ensure that the steam parameters reach the rated value is one of the urgent problems to be solved to realize the flexible operation of CFB boiler. The parameters of two 350 MW supercritical CFB boilers under coal cut-off and low load operation conditions were deeply calculated and analyzed, and the methods to stabilize the reheat steam temperature at low load were studied. The results show that when the boiler operates under coal cut-off conditions with partial coal feeding ports interrupted, the bed temperature, furnace outlet flue gas temperature, furnace outlet oxygen content and high-temperature reheated steam temperature are basically positively correlated with the coal feeding rate at each coal feeding port. However, the coal feeding deviation and bed temperature deviation have little effect on the outlet steam temperature deviation of water-wall because of the positive flow response characteristics of the water-wall of supercritical CFB boilers. Based on the above research, a boiler transformation and operation optimization technical scheme for stabilizing the outlet steam temperature of high-temperature reheater in supercritical CFB boiler under long-term peak shaving and low load operation was proposed, which could ensure the basic stability of steam temperature at the outlet of high-temperature reheater at low load.

0 引言

1 试验

   1.1 测点分布

   1.2 低负荷断煤运行工况

2 结果分析与讨论

   2.1 床温分布

   2.2 给煤中断对水冷壁出口汽温的影响

   2.3 给煤中断对炉内屏式再热器出口汽温的影响

   2.4 低负荷炉内高温再热器汽温稳定方法

3 结论