| As one of the main environmental pollutants,NO_x emissions have attracted widespread attention.Waste liquid incineration plants widely use Selective Catalytic Reduction(SCR)flue gas denitration technology to control NO_x emissions.For SCR systems with strong nonlinearity and large hysteresis characteristics,denitrification control systems that apply traditional PID control strategies often have problems such as excessive NO_x emission concentration at the outlet and excessive ammonia escape.Therefore,this article makes full use of the collected on-site actual operating data,combined with the analysis of the SCR reaction mechanism,constructs the SCR denitrification system model,and introduces predictive control to improve the control quality of the denitrification system,while ensuring that the NO_x emission concentration at the SCR outlet meets the standard.Reduce operating costs and secondary pollution to the environment.The main research work of this paper includes:(1)Establishment of mechanism model of SCR systemFirstly,the process flow of the waste liquid incineration SCR flue gas denitrification section and the factors affecting the denitrification efficiency are analyzed.From the perspective of the material balance and energy balance of the denitrification process,the system mechanism model structure is constructed with the aid of the chemical reaction kinetic differential equations,and the site The collected operating data and the Improved Adaptive Inertial Weight Particle Swarm Optimization(AIWPSO)have identified the various parameters of the model.Subsequently,the collected field data was used to simulate the calculation accuracy of the model.The results show that the model can correctly describe the actual operation process of the SCR system,but the calculation accuracy of the model is not high.(2)The establishment of hybrid model of SCR system based on improved Least Square Support Vector Machine(LSSVM)Aiming at the problem of a certain deviation in the calculation results of the SCR mechanism model,a hybrid model of the SCR system was established.Firstly,based on the analysis of the mechanism characteristics of the SCR denitrification system,the input variables are initially selected,and the collected variable samples are standardized by the minimum-maximum,and then the negligent error and the random error are eliminated respectively with the help of the principle and the five-point-three method,and then use the high-dimensional k-nearest neighbor mutual information method to filter the input variables.Secondly,take the selected variable set as input,take the deviation between the measured value of outlet NO_x concentration and the calculated value of the mechanism model as output,use the improved LSSVM algorithm to establish a deviation compensation model,and superimpose its output with the output of the SCR mechanism model to construct A hybrid model of the SCR system.Finally,it was verified with actual collected data.The results show that the model has better fitting and generalization performance than the mechanism and data model.(3)Predictive control of NO_x concentration at the outlet of SCR systemIn order to reduce the amount of ammonia injection as much as possible while ensuring that the NO_x emission concentration at the outlet of the SCR reaches the standard,this paper combines the SCR hybrid model to construct a predictive control scheme for the NO_x concentration at the outlet of the SCR system.The control effect of the traditional control method is compared with the simulation experiment,and the predictive control performance is further verified.The results show that the effect of predictive control is more superior,achieving the goal of reducing the amount of ammonia injection while the NO_x emission concentration at the outlet reaches the standard.(4)Realization of SCR flue gas denitration control system for waste liquid incineratorSelect S7-1500PLC as the hardware development platform,Siemens TIA Portal v15.1+WinCC v7.5 as the software development platform,MATLAB as the realization platform of the control algorithm,the communication between MATLAB and WinCC is realized through OPC technology,and then the effective control of the NO_x concentration at the outlet of the SCR flue gas denitration of the waste liquid incinerator is realized.The system has been applied in the denitrification control of SCR flue gas from the incineration of high-salt organic waste liquid in a chemical enterprise in Zhejiang.The actual operating results show that the SCR system model established in this paper is effective,and the designed SCR denitration control system is feasible,which has certain practical significance for reducing NO_x emissions and ammonia slip. |
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