| Thermal power plant is one of the major emission source of nitrogen oxides in the air pollution.At present the power plant boilers are equipped with flue gas denitrification system,and the SCR denitrification technology has been widely used.However,due to the complexity of SCR denitrification process and system,power plant denitrification system's automatic control input rate is still low.Many power plant denitrification system is in manual control,and the level of automatic control of denitrification system has to be improved in the further.In this paper,the SCR denitrification system of 600 MW boiler unit of Wangqu Power Plant is studied,and the working principle,process flow and system constitution of SCR flue gas denitrification system are analyzed.Based on the historical data of the DCS recorded in the operation of the power plant,the large amount of operational data of the SCR system under different operating conditions were analyzed and processed.Combined with the SCR denitration mechanism,the dynamic and static characteristics of the SCR system are obtained.The dynamic changes of the relevant parameters were analyzed when the parameters such as load and ammonia injection were changed.The changes of denitrification efficiency were analyzed when the boiler load,ammonia nitrogen ratio and oxygen content were changed.This paper emphatically analyzes the structure,principle,control logic and control mode of SCR control system of Wangqu Power Plant.Based on the whole unit operation data,the system was identified by recursive least squares method,and the transfer function model of Nox concentration in SCR outlet and ejected liquid was obtained under typical operating conditions of the unit.The simulation results show that the error between the model output and the actual output is in the allowable range.And the model is verified and analyzed,which can provide a reference for the design of SCR automatic control system of Wangqu Power Plant. |
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