Yantai Longyuan Power Technology Co.,Ltd.

等离子体点火技术变负载灵活性高,点火启动时间短,有害气体排放低,经济效益好,在煤电机组深度调峰改造中应用广泛,是电站锅炉实现低负荷稳燃的主要措施之一。近年来,中速磨煤机在燃用高水分褐煤机组中的推广为高水分褐煤等离子体无油点火技术的应用提供了便利条件。然而,传统等离子体点火技术多适配于烟煤等优质煤种,对于燃用高水分低热值褐煤存在点火能量不足、需油枪辅助点火、燃油经济性差等问题。为此,开发了偏置浓缩狭缝式进粉多级筒结构等离子体点火煤粉燃烧器,在某入炉原煤全水分35%~40%的660MW褐煤基建机组锅炉上开展变工况等离子体无油点火试验,分析了入炉煤质及机组操作参数对高水分褐煤无油点火特性的影响。基于点火试验结果,提出了等离子体燃烧器改进方案,在基准工况下,对高水分褐煤等离子体燃烧器进行数值模拟,对比讨论了燃烧器改造效果。点火试验结果表明,新型等离子体点火系统可点燃发热量10900~13400kJ/kg的高水分褐煤,并实现机组无燃油启动,点火能力较强;燃烧器对煤质适应范围较小,点火能量过大,燃烧器中心筒与二级筒间隙较小,冷却效果较差,二级筒易超温,造成等离子体燃烧器二级筒结焦烧损;机组稳燃时,燃用胜利褐煤并投运等离子体发生器对锅炉NOx排放基本没有影响。数值模拟结果表明,点火试验所用燃烧器由于一级燃烧筒内煤粉吸收等离子体热量过于集中而提前燃烧,燃烧筒壁面超温,导致内壁结焦;改进后燃烧器一、二级燃烧筒内中心火焰温度显著降低,在三级燃烧筒末端火焰温度趋近一致,燃烧器壁面最高温度为376℃,较改进前降低约74℃;改进方案减少了浓煤粉对一级燃烧筒入口端面的冲刷,提高了一级燃烧筒内煤粉量,优化了点火过程。因此,开发并优化新型等离子体燃烧器可实现宽煤质范围高水分褐煤机组稳定高效点火,为建成国内首座高水分褐煤无油电厂提供技术支撑。

Plasma ignition technology has good flexibility in load variation,short ignition/ start-up time,low emission,and high economicefficiency. It is widely used in the deep peak shaving transformation of coal-fired power units and is one of the main measures to achievelow load stable combustion in power plant boilers. In recent years,the promotion of medium speed coal mills in high moisture lignite unitshas provided convenient conditions for the application of high moisture lignite plasma oil-free ignition technology. However,traditionalplasma ignition technology is mostly suitable for coal of high-quality such as bituminous coal. There are problems with insufficient ignitionenergy,the need for oil gun to assist ignition,and poor fuel economy when burning high moisture and low calorific value lignite. A bias concentration slit type multi-stage cylinder structure plasma ignition burner for pulverized coal was developed. Tests under different operating conditions using plasma oil-free ignition were conducted on a 660 MW lignite unit with a total moisture content of 35%-40% of theraw coal. The effects of coal quality and unit operating parameters on the oil-free ignition characteristics of high moisture lignite were analyzed. An improvement plan for the plasma burner was proposed based on the test results. A numerical simulation was conducted on thehigh moisture lignite plasma burner under the benchmark operating conditions. The effectiveness of the burner modification was comparedand discussed. The ignition test results show that the new plasma ignition system can ignite high moisture lignite with a heat generation of10 900-13 400 kJ/ kg and achieve oil-free start-up of the unit. The burner has a small adaptability range to coal quality. Excessive ignition energy,small gap between the central and the secondary cylinder of the burner,and poor cooling effect is prone to overheating of thesecondary cylinder,causing coke formation and burning damage. Putting the plasma generator into operation has little effect on NO emission when the units are under steady operation. The numerical simulation results show that the burner used in the ignition test burns prematurely due to the excessive concentration of plasma heat absorbed by the coal powder in the first stage combustion tube,resulting in overheating of wall of the combustion tube and coke formation on the inner wall. The central flame temperature inside the first and secondstage combustion tubes of the burner significantly decreases after being improved. The flame temperature at the end of the third stage combustion tube tend to be consistent. The highest wall temperature of the burner is 376 ℃ ,which is about 74 ℃ lower than that before improvement. The improvement plan reduces the erosion of concentrated pulverized coal on the end face of the inlet of the first stage combustion cylinder. The amount of coal in the first stage combustion cylinder is increased and the ignition process is optimized. In short,the development and optimization of new plasma burners can achieve stable and efficient ignition of high moisture lignite units with a wide rangeof coal quality. It can provide technical support for the construction of the first high moisture lignite oil-free power plant in China.

国家重点研发计划资助项目(2018YFB0604204)

李明,邹鹏,李冰冰,等.660MW高水分褐煤机组等离子体点火技术应用[J].洁净煤技术,2024,30(9):52-59.

LI Ming,ZOU Peng,LI Bingbing,et al.Application of plasma ignition technology in 660 MW high moisture lignite unit[J].Clean Coal Technology,2024,30(9):52-59.