电站锅炉再热汽温异常原因分析及解决方法

Cause Analysis on and Solution to Abnormal Reheat Steam Temperature of Boilers

再热汽温异常是电站锅炉中较为普遍的现象。针对再热蒸汽压力低、比热容小、温度对吸热量变化敏感、再热蒸汽减温水量对机组经济性影响大的4个特点,分析了锅炉设计中再热器受热面为何采用负裕量布置和采用烟气侧调整手段调整再热汽温的原因,这也正是再热汽温易受煤种、燃烧方式、排汽温度等各种运行条件变化严重干扰的原因。对各种因素影响再热汽温的现象、规律、判定方法及相应对策进行了总结,强调了解决再热汽温问题先综合分析、再运行调整、然后进行受热面改造的顺序。针对再热器受热面改造的要求,总结了串联增加壁式再热器受热面、串联增加对流再热器和并联增加对流再热器受热面3种方式的优缺点,并指出并联增加对流再热器受热面具有更加明显的优势。可为分析和解决再热汽温问题提供全面借鉴经验。

Abnormal outlet reheat steam temperature is a common problem for boilers. Facing the issues of low pressure and low specific heat capacity of reheat steam, its temperature-sensitiveness to changes of absorbed heat and the evident negetive effect on the total unit efficiency due to the desuperheater water amount reduction, the reasons why the arrangement of lean-margin reheating heat exchange area and the flue-gas-side temperature adjustment on the reheat steam temperature are adopted in the boiler design are anlyzed. They are also found to be the root causes of why the reheat steam temperature is so easily disturbed by the minor operation changes such as coal type, the boiler combustion mode, the exhausting steam temperature of turbine high pressure cylinder. Targeting at these factors, the phenomena, laws, judgment methods and the corresponding measures to solve theabnormal reheat temperature problem are discussed and summarized. to It is emphasized that the right order to solve this problem should be comprehensive analysis, combustion adjustment, and reheater retrofit. The advantages and disadvantages of three methods-adding serial radiant reheater, adding serial convectional reheater and adding parallel convectional reheater, are discussed in order to meet the strict demands of reheater retrofitting. By comparison, it is concluded that the method of adding parallel convectional reheater works better than the other two. The study result may provide references for sovling the abnormal reheat temperature problemes.