Simulation And Operation Characteristics Analysis Of 1000MW Coal-fired Boiler Flue Gas Denitrification Device

Selective catalytic reduction flue gas denitrification technology is widely used in thermal power plants due to its advantages of simple structure,high efficiency and reliability.In the unit operation,effect of SCR denitration system parameters of boiler load,flue gas flow and temperature,molar ratio of ammonia,the reactor entrance NOx concentration is larger,in order to ensure the nitrogen oxides of ultra low emission requirements of environmental protection,to study the removal operation characteristics of denitrification system is becoming more and more attention.The application of computer simulation technology to establish reliable models,accurately simulate and study the operation characteristics of denitration system will greatly reduce the cost and save manpower,which is an effective way to improve the operation level of denitrification in power plants.In this paper,the flue gas denitrification device of 1000MW coal-fired boiler generator set is taken as the research object.The relationship between the combustion and the flue gas system.SCR denitrification system process and system is described.Through the whole process flue gas analysis,The research object is reasonably divided into milling system,combustion and smoke system,SCR denitration reactor system.Combining with the purpose and characteristics of modeling and simulation research,the mathematical modeling of each system is carried out.The calculation model of furnace combustion,the model of NOx generation in furnace,the flue gas model of furnace outlet,the mathematical model of denitration reaction,the mathematical model of reducing agent consumption model and mathematical model of ammonia/air mixer and other mathematical models.The above model is compiled by means of Fortran language to become a computer recognizable algorithm.The IMMS model development platform is used to build and simulate the whole system and debug the model.Based on the above real-time simulation model,the change rule of combustion temperature,furnace outlet flue gas flow and NOx concentration under different loads are analyzed in the static characteristic study.According to the stable condition of 1000MW,the static change law of the denitrification efficiency with the mole ratio of ammonia and nitrogen,the temperature of the flue gas,the velocity of air and so on was analyzed.The results show that:The combustion temperature in the furnace,the discharge of the flue gas at the furnace outlet and the concentration of NOx increase with the increase of the load.The denitrification efficiency is the highest when the ratio of ammonia to nitrogen is 1.1 and the temperature is about 630K-640K.With the increase of gas flow velocity,the denitrification efficiency is decreasing.Under the working condition of 1000MW,the dynamic simulation test of the combustion and smoke air system and the SCR reactor system is carried out.The 5parameters of coal feeder speed,ammonia nitrogen molar ratio,reactor inlet flue gas flow,NOx concentration and temperature were discussed,and the variation of operation parameters of the system under single variable step disturbance was discussed.The results show that:The speed step of the coal feeder is reduced,the amount of coal,the combustion temperature in the furnace and the flow rate of the flue gas decrease,and the response has a certain delay.When the ammonia nitrogen mole ratio step is bigger,the amount of ammonia,the denitrification efficiency and the escape amount of ammonia show a big trend.At the inlet of the reactor,the gas flow rate and the NOx concentration step up,and the denitrification efficiency and the escape amount of ammonia are decreasing.The step disturbance of the flue gas temperature at the inlet of the reactor has great influence on the reaction process of NH₃ and NOx,and affects the denitrification efficiency.The simulation results are in good agreement with the actual operation results,which can provide a simulation model reference for the study of the safety and economic operation of the flue gas denitrification device and the control strategy of the SCR automatic control system.