| As a key step in the production of asphalt mixing plant,aggregate drying has great influence on the construction quality of asphalt pavement.Using pulverized coal burner as drying equipment can significantly reduce the cost of aggregate drying.However,the pulverized coal burner has many control parameters and is difficult to control effectively.In addition,the aggregate drying process is semi-closed,can not directly observe the state of pulverized coal combustion,operators usually rely on experience to adjust the pulverized coal burner,may cause environmental pollution and resource waste.Therefore,this thesis from the engineering practice,design and development of a set of up and down linkage aggregate drying pulverized coal burner control system,to achieve real-time monitoring of pulverized coal combustion and low nitrogen efficient combustion.The specific research content is as follows:1.Based on the aggregate drying process,the thermal efficiency of the burner and the control system were studied and analyzed,and the control parameter range,sensor installation position,data acquisition interval time,motor speed and hardware selection of the control system were determined through the analysis results.2.The mathematical model of the burner was established,and the orthogonal test method was used to design the air distribution test of the pulverized coal burner.The influence of different test schemes on the evaluation indexes was studied by Fluent air distribution simulation,and the optimal control scheme was determined by combining range analysis method and comprehensive balance method.The results show that: under certain conditions,the primary wind speed is proportional to the flame length,the NOx emission is inversely proportional,the secondary wind speed is proportional to the flame width;In the8 th group test(primary wind speed 30m/s,secondary wind speed 50m/s,tertiary wind speed40m/s),the pulverized coal burner has excellent performance in various evaluation indexes.3.Based on the engineering practice,the design of the up-down linkage control system is proposed,that is,Lab VIEW as the upper computer and PLC as the lower computer,to complete the hardware selection and software design.Hardware selection and design according to the requirements of preliminary data analysis and test;The software design of the control system will be divided into two parts.One is to complete the design of the login module,human-computer interaction module,data acquisition module and communication module through Lab VIEW.The other is to complete the design of the control program,data acquisition program and serial communication program through PLC.Finally,the normal communication of software and hardware is realized to achieve the goal of real-time monitoring of pulverized coal combustion behavior.4.Conduct combustion test of pulverized coal burner and test the performance of control system.Through the real-time monitoring of the temperature waveform of pulverized coal combustion flame and the oxygen content of flue gas,judge the pulverized coal combustion status of the burner,and then adjust the control variables(coal feed,primary wind speed,secondary wind speed,tertiary wind speed).The experimental results show that the control system of aggregate dried pulverized coal burner designed in this paper can effectively monitor the pulverized coal combustion state,carry out targeted regulation and control,and achieve the expected goal.In summary,on the basis of air distribution simulation,this thesis proposes a set of updown linkage control system design,and verifies the feasibility of the control system through experiments.The research results provide valuable reference and theoretical basis for energy saving,emission reduction and environmental protection of pulverized coal burners in actual operation. |
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