Research On Measurement Method Of Carbon Content In Fly Ash Based On Software Radio

Due to the characteristics of high emissions and high energy consumption,coal-fired generating units are in a disadvantageous position against the background of the current shortage of fossil energy and the rapid rise of coal price.Coupled with the impact of new energy generation on the stability of the power grid,thermal generating units are in urgent need of improving the power generation mode,improving power generation efficiency,reducing environmental pollution,achieving flexible power generation and deep peak adjustment,so as to transform to low carbon and high efficiency.Carbon content of fly ash is an important index to characterize the combustion stability of boiler and an important parameter to calculate the heat loss of mechanical incomplete combustion.Timely and accurate measurement of carbon content of fly ash can better master the combustion state of boiler,so as to adjust the combustion strategy.It is of great significance to improve the bidding capacity of thermal power units and the comprehensive utilization of fly ash.At present,most power plants use the burning weight loss method to detect the carbon content of fly ash.Although it is more accurate,the detection period is long and can not meet the needs of real-time measurement.Microwave method as a new detection method,because of its high timeliness and good accuracy,has been widely studied,hollow metal waveguide method as a more prominent performance of the method,has been gradually used in the actual measurement.In this paper,microwave method as the core,on the basis of improving the existing sampling scheme,a set of independent online measurement of fly ash carbon content test bed is designed,which can realize the integration of sampling,measurement,ash discharge process.By calculating the velocity of microwave in the waveguide,a method of measuring the height of the medium in the waveguide is given.According to the experiment,it is determined that the characteristic of the medium is not the key factor affecting the height of the medium.Then,the fitting formula between microwave transmission attenuation and carbon content in fly ash is given,and the calculation method of carbon content in fly ash under the condition of low carbon content is discussed.The experimental results show that the absolute error of this method can be controlled within 0.4%,which has good accuracy.Then,in order to solve the uneven top of the sample in the waveguide,the influence of different inclined planes on height measurement and microwave attenuation is found by using paraffin material,and the conversion coefficient of paraffin material to carbon-containing fly ash is defined.Then the error between the measured value and the real value under different inclined planes is analyzed,and the influence of different ash positions on the measurement results of carbon content in fly ash is obtained from the theoretical level.In order to reduce the cost of measuring equipment,this paper designs and develops an alternative system of vector network analyzer based on software radio.By analyzing the measurement principle of vector network analyzer,the hardware circuit and corresponding software are designed and developed,and the measurement results of S parameter at 9.6～14GHz are obtained preliminarily.At last,carbon content in fly ash is measured by the system,and the results show that the scheme is feasible,and the system can be used to measure carbon content in fly ash within the allowed error range.