670t/h四角切圆锅炉反切消旋的数值模拟和工程实践

利用燃烧数值模拟程序对一台670t/h四角切圆锅炉进行了三次风与OFA反切工况数值试验研究.研究结果表明：三次风反切使反切层以上炉内流场旋转减弱,相对切圆直径和充满系数在反切层降低,炉内气流混合强度变化不大,对炉内主气流的空气动力结构影响不大;炉膛温度场和氧气浓度场显示,反切后改善了炉内温度分布,对主燃烧区的影响较小;壁面高温区减少,降低了结焦可能性;反切降低水平烟道入口左右侧温差,削弱了水平烟道入口的扭转残余,减小了水平烟道中的气流速度不均匀性,截面平均烟温略有下降,对受热面换热影响不大.工程实践表明,数值试验结果与实际运行吻合良好,采用三次风与OFA反切消旋方法,减少了残余扭转,改善水平烟道温度分布,较好地解决了四角切圆燃烧锅炉存在的出口烟温偏差问题。

NUMERICAL SIMULATION AND ENGINEERING PRACTICE OF A 670t/h CORNER TANGENTIAL BOILER WITH REVERSE-TANGENT AND SWIRLING-ELIMINATION

With the 670 t/h corner tangential boiler serving an object of study,reverse-tangent cases at tertiary air and OFA(Over flow air) were performed by using combustion numerical simulation program.The studying results indicates: the revolution of in-furnace flow field is weakened because of the reverse-tangent of tertiary air,the relative diameter of the tangential circle and the full extent of flame in the furnace decreased at reverse-tangent layers,and the mixing intensity of gases changes little,which has little influence to in-furnace aerodynamic field.Analyzing temperature field and oxygen concentration field,in-furnace distribution of gas temperature improves after retrofitting that has little influence to major combustion zone,and high temperature area on wall reduces,which reduces the possibility of slagging.Temperature deviation of horizontal flue inlet is reduced,the residual rotation is weakened,uniformity coefficient of flue gas velocity decreases,and cross-section mean temperature changes little,which has little influence to heat transfer of heating surface.Engineering practice indicates: numerical experiment result is in conformity with real operation condition,and the retrofitting can effectively weaken the residual rotation and improve the distribution of flue gas temperature,which settles the problem of outlet temperature deviation that exists in corner tangential boiler.