Abstract The accuracy of the particulate matter emission measurement in coal-fired power plants has been enhanced to meet stricter environmental standards. This study discusses the effect of particle size on the in situ concentration measurement of particulate matter by the integrated light scattering method and optimization of the detection angle. The mass concentration sensitivities of five common particles with aerodynamic sizes ranging from 0.05–10 μm have been calculated based on Mie scattering theory at different scattering angles. The scattering light intensity of particles at forward scattering angles has larger magnitudes than that of the back-scattering angles, and the mass sensitivity is remarkably great at small angles. In addition, the fly ash and quartz particles are found to have nearly the same sensitivities at any particle size and scattering angle, and both have maximum values near 1 μm. Then, a real-time aerosol concentration measurement setup was built to study the effect of the particle size and the best detection angle. The results indicate that the optical measurement setup performs in real time and accurately shows good agreement with the calculations. Four quartz particles were represented in the fly ash after the dust collection in power plants was tested and the size factor was found to vibrate with the detection angles. Additionally, 25° is found to be the best detection angle to reduce the size effect. Finally, the optimal detection angle is comprehensively discussed based on the sensitivity, zero drift and size factor, also allowing for the particle density and refractive index. It is found that at angles of ~25°, the size factor and zero drift are lowest, while the sensitivity is relatively high; this outcome helps to reduce the measurement error of the real time-mass concentration of particulates.

中文翻译：

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通过光散射法测量颗粒物浓度：检测角度的优化

摘要 燃煤电厂颗粒物排放测量的准确性得到了提高，以满足更严格的环境标准。本研究探讨了粒径对综合光散射法原位浓度测量颗粒物浓度的影响及检测角度的优化。基于米氏散射理论在不同散射角度计算了空气动力学尺寸范围为 0.05-10 μm 的五种常见颗粒的质量浓度灵敏度。粒子在前向散射角处的散射光强度比后向散射角处的散射光强度大，在小角度处质量灵敏度显着提高。此外，发现粉煤灰和石英颗粒在任何粒径和散射角度下都具有几乎相同的灵敏度，并且两者的最大值都在 1 μm 附近。然后，建立了实时气溶胶浓度测量装置来研究粒径和最佳检测角度的影响。结果表明，光学测量装置实时执行并准确地显示出与计算的良好一致性。在对电厂除尘器进行测试后，飞灰中存在四种石英颗粒，发现其尺寸因子随检测角度而振动。此外，发现 25° 是减少尺寸效应的最佳检测角度。最后根据灵敏度、零漂和尺寸因子综合讨论最佳检测角度，还考虑到粒子密度和折射率。发现在~25°的角度，尺寸因子和零漂移最低，而灵敏度相对较高；这一结果有助于减少颗粒物实时质量浓度的测量误差。