直吹式制粉系统风粉偏差对机组灵活性的影响

Influence of air-powder distribution deviation of direct-blowing pulverizing system on unit operation flexibility

近年来,风能发电和太阳能发电装机容量迅速增长,为提高新能源的消纳能力,燃煤机组灵活性运行是大势所趋。目前,大容量电站锅炉普遍配置直吹式制粉系统,磨煤机出口一次风管风粉分配偏差大的问题普遍存在,风粉分配偏差大直接限制机组灵活性运行。从制粉系统设备角度分析了磨煤机出口并联一次风管风粉分配偏差大的原因。对由于风粉分配偏差大导致锅炉运行过程中产生的各种问题如火焰偏斜、结焦、高温腐蚀、NO_x排放量高、飞灰可燃物高、锅炉效率低等进行阐述。该问题在机组灵活性改造过程中表现尤为突出,锅炉低负荷运行时,一次风管风粉分配偏差大会造成锅炉着火距离增大,燃烧不稳定甚至灭火的可能。炉内热负荷不均会导致锅炉汽水侧偏差加剧,恶化传热,受热面超温,直接影响机组运行安全。为改善一次风管风粉分配偏差,对比分析各种煤粉分配器的性能和优缺点,并阐述煤粉分配器在电站锅炉的应用情况和效果。随着灵活性运行工作的深入,需要对灵活性运行机组制粉系统进行改造,加装相匹配的煤粉分配器,改善风粉分配特性,提高机组运行稳定性和安全性。

In recent years,the installed capacity of wind power generation and solar power generation is growing rapidly.In order to improve the absorption capacity of new energy,the flexible operation of coal-fired units is the general trend.At present,large-capacity power station boilers are generally equipped with direct-blowing pulverizing system,and the large deviation of pulverized coal and air distribution in the outlet air pipe of coal mill is a common problem.With the development of flexible operation of the unit,large deviation of pulverized coal and air distribution directly limits the flexible operation of the unit.In this paper,the reasons for the large deviation of pulverized coal and air distribution of the coal mill outlet parallel primary air duct were analyzed from the point of view of the pulverizing system equipment.Various problems in the boiler operation process caused by the large deviation of pulverized coal and air distribution,such as flame deflection,coking,high temperature corrosion,high NO x emission,high fly ash fuel and low boiler efficiency,were described.The problem is especially serious in the process of unit flexibility transformation.During low-load operation,the deviation of pulverized coal and air distribution will increase ignition distance of the boiler,resulting in unstable combustion and even extinguishing the fire.Uneven heat load in the furnace will aggravate the deviation of the steam in the boiler,worsen heat transfer,and overheat the heating surface,which will directly affect the operation safety of the unit.In order to improve the deviation of pulverized coal and air distribution.the performance advantages and disadvantages of pulverized coal distributors were analyzed,and the application and effect of pulverized coal distributor in power station boiler in recent years were introduced.Therefore,with the development of flexible operation,it is necessary to reform the pulverizing system of flexible operation units,install the matching coal powder distributor,improve the pulverized coal and air distribution characteristics,and improve the operation stability and safety of units.