低NO_x燃烧技术改造对切圆燃烧锅炉热量分配的影响

Influence of Low NO_x Combustion Technology Modification on Tangentially-Fired Boiler Heat Distribution

基于调试和试验数据,对切圆燃烧锅炉低NOx燃烧技术改造后存在的锅炉主、再热汽温偏低的问题进行了分析。结果表明:低NOx燃烧技术改造后,锅炉主、再热汽温偏低主要是由锅炉热量分配向水冷壁区前移引起;前移原因是由于新增SOFA风加大了燃尽区氧量,导致燃烧速率随氧量增加大幅提高;同时SOFA风分流作用也使主燃烧区由燃烧速率随氧量平缓变化区间转入快速变化区间;低NOx燃烧技术改造后主燃烧区和燃尽区同时处在燃烧速率随氧量快速变化区间,使得氧量变化会对锅炉热量分配产生明显影响,导致汽温、汽压和汽包水位等参数出现大幅波动。

Based on the tuning and testing data,the issues of low temperatures of main and reheat steam existing in the tangentially-fired boilers after low NOx combustion enhancement are analyzed.It concludes that the moving forward of heat distribution to the water walls after the enhancement is the main reason for the excessively low temperatures of main and reheat steam.And the reason for the moving forward of heat distribution is caused by the new separated over-fire air （SOFA） which increases the oxygen concentration of burn-out zone,and further,leads to a significant rise of burning rate.Meanwhile the secondary air flow redistribution caused by SOFA shifts the changing pattern of burning rate on oxygen concentration in the primary combustion zone,so that,both the primary combustion and the burn-out zones lie in the rapidly changing range of the burning rate.In this range,the change of oxygen concentration will significant affect the boiler heat distribution,and consequently,lead to the wide fluctuation of some parameters,such as the steam temperature,steam pressure and the water level in the drum.