飞灰粒径对金属波导内飞灰含碳量测量影响

Effect of fly ash particle size on fly ash carbon content measurement in metal waveguides

微波衰减法是近年来在线测量粉煤灰含碳量的常见方法之一。然而,由于飞灰的取样位置及取样装置的差异,飞灰的粒径大小存在较大的不确定性,从而造成飞灰含碳量测量的误差较大。现有的含碳量拟合模型均以飞灰对特征频率信号的衰减与飞灰含碳量的关系为基础,存在着误差大、适应性差等问题。为了解决含碳量拟合模型误差大和适应性差等问题,提出使用信号的时域主峰衰减来代替信号在特征频率处的衰减作为飞灰含碳量在线拟合的优化方法。为了修正飞灰粒径不确定性引起的误差,在研究灰位和含碳量测量的基础上,比较了不同粒径范围的飞灰对灰位和飞灰含碳量测量的影响。结果表明:采用信号的时域峰值衰减来计算含碳量,其结果与实际值吻合良好;对于波导中相同质量的灰样,飞灰的粒径大小对灰位的测量精度没有显著的影响;当使用微波法测量波导内飞灰含碳量时,对于相同质量的灰样,随着飞灰粒径的减小,波导内飞灰对微波信号的衰减逐渐减小,从而使含碳量的测量值随着飞灰粒径的减小而增加。

The microwave attenuation method is one of the common methods for online measurement of carbon content in fly ash in recent years.However,due to the differences in sampling locations and sampling devices of the fly ash,there is a large uncertainty in particle size of the fly ash,which results in a large error in the measurement of carbon content in fly ash.The existing carbon content fitting models are all based on the relationship between the attenuation of the characteristic frequency signal by fly ash and the carbon content of fly ash,which has problems such as large error and poor adaptability.In order to solve these problems,this paper proposes to use the time-domain main peak attenuation of the signal instead of the attenuation of the signal at the eigenfrequency as a method for online fitting of the carbon content in fly ash.To correct the error caused by the uncertainty of fly ash particle size,the effects of fly ash with different particle size ranges on the measurement of ash level and fly ash carbon content are compared on the basis of the study on ash level and carbon content measurement.The results show that,the peak attenuation of the signal in the time domain is used to calculate the carbon content,and the results are in good agreement with the actual values.For the same mass of ash samples in the waveguide,the particle size of the fly ash does not have any significant effect on the measurement accuracy of the ash level.When the microwave method is applied to measure the carbon content in the fly ash in the waveguide,for the same mass of ash samples,the attenuation of the fly ash on the microwave signal inside the waveguide decreases gradually with the particle size of the fly ash.Thus,the measured value of carbon content increases as the particle size of the fly ash decreases.