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.

李明(1967—),男,北京人,教授级高级工程师,博士。E-mail:13811012695@139.com

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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.