某330 MW W型火焰锅炉燃烧系统灵活性改造方案研究

Research on the flexibility transformation plan of a 330MW W flame boiler combustion system

为了解决某330 MW W型火焰锅炉低负荷运行时水冷壁易破裂、热损失大和NO_(x)排放量高等问题,保障该类型机组灵活性运行时的性能,对锅炉燃烧系统原始设计参数与同类机组进行对比分析,提出了燃烧系统改造方案并在现场实施了改造。研究表明:炉膛截面热负荷原始设计值偏低及炉内热负荷输入不平衡是造成水冷壁管易开裂的主要原因;仅有少量的二次风从拱上进入炉膛达不到对一次风煤粉气流的引射作用,不能保证一次风的穿透性和刚度;拱下二次风入射位置及角度对着火和燃尽不利;炉膛整体上空气分级燃烧的程度很差,无独立的OFA喷口,NO_(x)生成控制能力弱。提出的改造方案主要包括:在拱上新增二次风喷口、将乏气喷嘴置于浓煤粉气流的背火侧和拱上OFA喷口水冷套改造等。改造后测试表明,210 MW负荷,飞灰可燃物比改造前下降低约0.95%,脱硝前NO_(x)浓度A、B侧分别比改造前降低了140 mg/m^(3)和129 mg/m^(3)。

In order to solve the problems of water wall breakage,large heat loss and high NO_(x)emission in low load operation of a 330 MW W flame boiler,and to ensure the performance of this type of unit in flexible operation,the original design parameters of boiler combustion system were compared with those of similar units,and the reconstruction scheme of combustion system was put forward and implemented on site.The results showed that the low original design value of furnace section heat load and the unbalanced input of furnace heat load were the main reasons for the cracking of water wall tube;Only a small amount of secondary air entering the furnace from the arch could not reach the injection function of the primary air pulverized coal flow,which could not guarantee the penetrability and rigidity of the primary air;Incident position and angle of secondary air under arch were unfavorable to ignition and burnout;The degree of staged combustion of air on the whole furnace was very poor,there was no independent OFA nozzle,and the control ability of NO_(x)generation was weak.The proposed renovation scheme mainly included:adding secondary air nozzle on the arch,placing the exhaust gas nozzle on the back fire side of the concentrated pulverized coal airflow,and reforming the cold sleeve of OFA nozzle on the arch.The field test after the transformation showed that the combustibles of fly ash were reduced by about 0.95%,the NO_(x)concentration AB side before denitration was respectively reduced by 140 mg/m^(3)and 129 mg/m^(3)compared with that before transformation under the 210 MW load condition.