Optimized solution of SCR ammonia injection
Current status and problems of denitrificationsystem of thermal power generatingunit
More ammonium bisulfate ((NH4)HSO4)was produced after the ultra-low emission of denitrification system has beenremodelled. (NH4)HSO4adhered to the air preheater (APH)caused serious blockage and a sharp rise of the operative piezoresistance (PZR),power consumption of combustion air fan has thus significantly increased. Underdifferent operating conditions of the unit, the “NOx distribution” of the AmmoniaInjection Grid (AIG) cross-section fluctuates obviously, and the manual valveof the AIG branch pipes cannot follow the adjustment. Hence, it is difficult toovercome the nonlinear and hysteretic features of the system with conventionalPID adjustment, and the excessive ammonia will be sprayed out.
Predictive-control-technology-based solution to denitrification and ammonia spray optimization
The control of ammonia spray can be predicted by means of artificial intelligence algorithm and anticipatory control technology, and the export fluctuation will thus be significantly reduced. The total ammonia spray amount of SCR system will be finely redistributed, the ammonia consumption rate of NOx per unit will be obviously decreased. And the self-taught learning function can adapt to more environmental changes, which avoids poor performance problems after a prolonged use.
Problem solution and benefit analysis
The solution improves the control accuracy and quality, and reduces ammonia spray amount of unit. It also reduces the blockage of APH and lowers the power consumption of combustion air fan. APH’s lifespan is thus extended by more than 10% on average, the blockage and wind resistance are reduced. The power consumption of combustion air fan after the denitrification device is reduced by an average of 20% or more. The average lifespan of denitrification catalyst is increased, since the production of ABS is decreased, and the blockage of denitrification catalyst reaction passage is avoided. Therefore, the lifespan of catalyst is extended by an average of 10%.
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