Abstract: Zhundong Coal Field is located in Xinjiang Changji Hui Autonomous Prefecture,which is currently the largest packaged coal field in China. However,Zhundong Coal is prone to coking during the combustion process of boilers. Kaolin is usually mixed to ease coking. In a 350 MW unit burning Zhundong coal,after the coal was burned with kaolin in a boiler,the amount of dust particles and dust carried by the flue gas increased,which resulted in the serious ash accumulation in the SCR denitration system and a significant increase in ammonia injection. The air preheater was blocked by ammonia hydrogen sulphate,which made the unit unable to run stably for a long period. After compared with the domestic boilers of multiple units of the same type,it is found that the denitration system has ash deposits in the denitrification steering room,over the catalyst,and the air preheater inlet slope. Aiming at the existing problems,by the calculation and analysis of setting the correct model and incorrect installation model modeling,the optimal design of the deflector layout,the CFD flow field distribution,the optimization of the SCR system deflector design,and the combination of sonic and steam soot blowers and the optimization and upgrading of ammonia injection grid were performed. Using Testo 480 anemometer measured wind speed test,it was found that the original deflector of the denitration flue was unreasonable in design and construction and installation deviation; the horizontal section of the original deflector has a large span and insufficient support,resulting in the guide plate to collapse and deform and affecting the distribution of the flue gas field. The coal burned by the boiler is high-sodium coal. To prevent the boiler from coking and adding kaolin,the amount of fly ash particles and dust in the flue gas is increased,and the fly ash is quite sticky. It is easy to deposit on the flue deflector and the flue wall. Therefore,it is proposed to optimize the deflectors inside the denitrification system,add sonic sootblower to the ash-prone parts of the denitration system,upgrade the number of ammonia injection grid nozzles and ammonia air mixer,and carry out boiler SCR test work on thermal adjustment and optimization of denitrification and ammonia spraying. Through relevant work,the relative standard deviation of the flue gas field of the SCR flue gas system was optimized by 5%,and the consumption of liquid ammonia was reduced by 45% under the same load. The problems of ash accumulation in the denitration system and the blockage of the air preheater were completely solved to achieve the stable operation of the full load of the unit. After the boiler was shut down for half a year after long-term operation,it was found that the ash deposits of up to 1 m in the flue of the previous denitration system were completely resolved,and the catalyst surface was clean and free of debris,which solved the problem of ash accumulation in the denitration system. At the same time,the blockage problem of the air preheater of the boiler was completely solved by cooperating with the measures to improve the comprehensive temperature of the cold end of the air preheater.At the same time,the economic benefits are significant,which can save 700 000 yuan in liquid ammonia costs,1 million yuan in fan power consumption,800,000 yuan in maintenance and cleaning of dust and overhaul,and 200,000 yuan in air preheater cleaning and treatment costs. The comprehensive cost saving is 2.7 million yuan/year,and the expected effect is achieved to realize the safe and economic stable operation of the unit group leader cycle.