变负荷工况下锅炉对流受热面污染的监测

Ash Fouling Monitoring of Boiler's Convective Heat-Delivery Surfaces During Variable Load Operation

针对在线监测大型电站锅炉受热面污染的需要,讨论了稳定负荷的计算模型无法用于变负荷工况监测的原因,分析了变负荷过程中各物理参数的变化机理,从热量平衡出发,考虑了金属管壁蓄热及蒸汽蓄热对受热面污染计算的影响,推导了变负荷工况下的污染监测模型及实时计算方法。以某电厂300 MW机组锅炉的低温对流过热器为计算对象,采用现场实时数据进行了变负荷工况下受热面污染监测计算。提出了考虑金属及工质蓄热的锅炉变负荷污染监测模型与计算方法,基本能够消除负荷变化对受热面实际污染率计算的影响,得到比较合理的污染率计算结果,对改进现有的根据热平衡算法的锅炉受热面污染在线监测模型有重要的参考价值和工程实际意义。

With the rising demand for on-line ash fouling monitoring of heat delivery surfaces of large power plant boilers, the reason why conventional calculation models, suitable for stable load operations, can not be used for monitoring purposes under variable load conditions, is being discussed, accompanied by an analysis of the mechanism that governs load varying physical parameters. Starting with the heat balance principle;a monitoring model and a real time calculation method are derived which takes into consideration the influence on ash fouling calculation of the heat delivery surfaces and of the heat accumulating effect by the metallic walls and by the steam. Taking the low temperature convection superheater of a certain 300 MW power unit＇s boiler as the object of consideration, ash fouling, under variable load operating conditions,of the heat delivery surfaces has been calculated with real time data. Calculation results show that＇the above mentioned monitoring model and calculation method can basically eliminate the influence of load variations on actual fouling rate calculation, providing herewith relatively reasonable results, and may thus serve as a reference for later improvements. Figs 4 and refs 6.