Dynamic Detection And Device Development Of Carbon Content In Fly Ash

As the key content of the 13th five year plan for electric power development,completely pushing the flexibility transformation of the thermal power units puts forward higher requirements in variable-loading speed and regulation accuracy,as well as fuel flexibility and combustion technology.In order to achieve the above requirements,it is particularly important to establish a reliable combustion system to improve the low-load combustion stability.The unburnt carbon content of fly ash is one of the important parameters to characterize the boiler combustion efficiency.The real-time accurate detection of this parameter is an effective way to adjust the boiler combustion condition and improve the combustion economics.At present,the calcination method and the microwave method are the common ways to detect the carbon content of the fly ash in the thermal power plant,However,due to the two techniques cannot meet the requirements of both real-time and high accuracy,it is difficult for operators to give guidance on boiler combustion optimization control.In view of the above problems,after analyzing the interaction between fly ash and microwave,a high-precision and real-time method of detecting unburnt carbon content in fly ash is proposed based on hollow metal waveguide,and the sensitivity and accuracy of the method are studied by experimental work.Three experimental platforms are built to carry out static experiment,minimum concentration experiment and dynamic experiment respectively.By measuring the phase change of S parameters of samples with different carbon content,the mathematical model is established and the measured samples are calibrated.The calibration model is used to obtain the value of unknown carbon content samples with the corresponding phase shift.The test results show that the sensitivity and resolution of waveguide method can achieve real-time detection on site.And the validity of the test data and method is verified by repeated experiments.On the basis of theoretical and experimental research,this paper designs and develops a dynamic device for the unburnt carbon content detection of fly ash suitable for engineering practice.The device includes sampling,waveguide measuring,ash discharging,purging and other units,which can realize wide band real-time detection in 9-15GHz.In addition,in order to adapt to the change of power load and coal type in the flexible transformation of thermal power plant,three test modes are designed for the dynamic detection device including dynamic mode,quasi dynamic mode and static mode,which allows the tester to select the optimal test frequency and test mode to adapt to the combustion condition.Finally,combined with the actual situation of Baicheng and Zhuanghe power plants,the sampling point and installation platform of the device are selected and constructed,and the device is installed in the field.The device effectively solves the existing problems and provides data support in the carbon content detection of fly ash in thermal power plants.