基于集箱效应控制CFB锅炉汽冷屏热偏差研究

Study of controlling thermal deviation in platen superheaters of a CFB boiler by utilizing header effect

提出利用集箱效应控制L形汽冷屏热偏差的方法,以某135 MW循环流化床(CFB)锅炉的汽冷屏为例,通过热偏差计算模型分析集箱效应优化设计的热偏差控制效果,并进一步分析该方法在锅炉不同负荷下的有效性。研究结果表明:通过合理选用蒸汽连接方式和优化集箱管径调节集箱效应,可使汽冷屏并联管组内蒸汽流量分配与管外热负荷分布相适应,从而明显降低汽冷屏热偏差,提高受热面金属安全性;锅炉负荷改变对汽冷屏热偏差未有明显影响,说明由集箱效应优化设计来控制汽冷屏热偏差是行之有效的方法;随锅炉负荷减小,汽冷屏的管壁温度降低,即在低负荷下受热面金属的安全性不会降低。建议在CFB锅炉设计或改造中充分利用集箱效应优化设计以抑制汽冷屏热偏差。

A method of controlling thermal deviation in platen superheaters of a CFB Boiler by utilizing header effect was advanced.With the use of a 135 MW CFB boiler as the reference unit,the effect of header optimization design on alleviating thermal deviation was analyzed based on a thermal deviation prediction model.Furthermore,the effectiveness of this method was examined under different boiler loads.The results show that,the steam mass flowrate distribution in parallel tubes of the platen superheater can be adapted to match the heat load distribution of the tube bank by selecting a suitable steam connection type and optimizing the diameter of headers,therefore significantly alleviating the thermal deviation,or improving the metal safety,of the platen superheater.The change of boiler load presents little influence on thermal deviation of the platen superheater,indicating that header optimization design is an effective method to control the thermal deviation of platen superheaters.The tube-wall temperature of the platen superheater tends to decrease with the decrease of boiler loads,meaning that the safety of the heating surface will not decrease at low boiler loads.Thus,it is suggested to make full utilization of header effect in the design or modification of a CFB boiler to control the thermal deviation of L-shape platen superheaters within a safe range.