| In the general environment where national environmental awareness is gradually increasing and the flue gas emission standards of multiple coal-fired units have been successively issued by the state,higher requirements are placed on the accurate measurement and fine control of operating parameters in coal-fired units.If the SCR(Selective Catalytic Reduction)denitration system in a coal-fired unit can realize realtime monitoring of the flue gas velocity field of the ammonia injection section flue,it is of great significance to improve the operating effect of the SCR denitration system and achieve accurate ammonia injection control.With the help of electrostatic phenomena in dusty flue gas,this topic selects the electrostatic sensor in the crosscorrelation method as the front end of measurement,evelop signal conditioning circuit and data acquisition,calculation and display system to achieve online measurement of high-temperature dust-containing flue gas velocity and real-time monitoring and diagnosis of large cross-section flue gas flow and develop signal conditioning circuit and data acquisition,calculation and display system to achieve online measurement of high-temperature dust-containing flue gas velocity and real-time monitoring and diagnosis of large cross-section flue flow field.The main work of this topic is as follows:(1)The design and research of the the electrostatic velocity sensor based on the ring-shaped induction electrode for large cross-section flue,high temperature and dusty flue gas environment.Through the COMSOL Multiphysics simulation software to study the sensitivity of the sensor,the distribution characteristics of the sensitivity of the sensor and the effect of structural parameter changes on the sensitivity are obtained.Combined with free-fall experiment,the optimized design of electrostatic sensor is completed.(2)The integration of the speed measurement system based on the electrostatic speed sensor based on the ring-shaped induction electrode,including a conditioning circuit composed of impedance matching and adjustable multi-stage amplifier circuits and a cross-correlation calculator based on Lab VIEW with a modular design concept.(3)Using free-falling polyethylene particles as the measurement object,the structural parameters of the sensor and the calculation parameters of the crosscorrelation calculator are determined.On the basis of completing the relevant speed measurement,the measurement error is corrected,and the system is verified to have good precision and accuracy under the experimental conditions.(4)Use the built-in speed measurement system to carry out the measurement test of the high-temperature dusty flue gas velocity parameters.Through the denoising of the relevant speed,the stable output of the relevant speed is realized under the environment of high temperature dusty flue gas.And with the help of the smoke and dust comprehensive tester,it is obtained that the flue gas velocity has the same variation law as the relevant velocity.Based on this base number,relevant speed correction work is carried out.Through multiple comparisons,the measurement error of the speed measurement system is 0.47 m/s,which can meet the measurement needs of hightemperature dusty flue gas velocity in industrial environments.(5)This topic designs and builds a distributed measurement system for the velocity of dusty flue gas,and develops a software for monitoring and diagnosing the flow field of the large cross-section flue.The project implementation and on-site commissioning were carried out at Unit 2 of Hushan Project of Datang Huaibei Power Plant.Realize the large-section dust-containing flue gas velocity collection,storage and three-dimensional cloud image display,intuitively reflect the average flow rate,relative standard deviation,2D/3D flow field of the large cross-section flue(refresh frequency is only 1 time/second).This provides intuitive and effective operating data for the regulation and flow field adjustment of the SCR denitration system. |
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