| During coal-fired power generation in thermal power plants,harmful substances such as nitrogen oxides are produced.If these pollutants are not effectively controlled,they will pose a huge threat to the environment.Therefore,this paper takes the denitrification control of thermal power plants as the research object,and uses selective catalytic reduction technology(SCR)for flue gas denitration treatment.In the SCR denitration technology,the control of the amount of ammonia injection is the most important,and the control effect directly affects the denitration efficiency and production cost.However,due to the many interference factors on site,it is often difficult to achieve the ideal ammonia injection effect using traditional control methods.Therefore,in the face of increasingly strict environmental protection policies,how to adopt more effective control strategies for NOx emissions has become a technical problem.This article first takes the SCR denitrification system of a power plant as the research object,analyzes its working principle and system layout in detail,and makes a schematic diagram of the overall instrumentation of the system based on the process flow.On this basis,the ammonia injection control is used as the research object model,and the cascade control and the cascade-Smith predictive control are respectively used for simulation and comparison.Because the effect of the above two ammonia injection control methods is not very satisfactory,the two ideas of fuzzy control and variable universe fuzzy control are introduced into them,and a comparative analysis is made.By observing the trend of the response curve,it is concluded that the variable domain fuzzy control has strong advantages in terms of adjustment time and stability,which is obviously better than other control methods.Then the article discusses the uniformity of the flue gas field distribution,and designs experiments to improve the uniformity of the reactor flue gas field.Secondly,the system hardware is designed,using S7-300 PLC as the master station controller,and the slave station using ET200 M.After that,select the other equipment of the system,and design the electrical schematic diagram of the main circuit of denitrification and dust removal and the schematic diagram of the in-situ box control.Finally,use Portal V15 to write the software of the system.First,the system design goals are clarified,and the various functional blocks of the system are assigned.Then,the flowcharts and program diagrams of each subsystem are drawn and written,and the fuzzy control algorithm is used to write the ammonia injection control system.At the same time,the HMI touch screen is used as the operation interface to monitor the operation status of the entire system in real time.From the perspective of energy saving,environmental protection and high efficiency,the thesis conducts in-depth research on the SCR denitrification system.The on-site operation proves that the control method has obvious denitrification effects and has a significant role in promoting the safety and stability of power plant denitrification operations. |
