煤样高度对激光测量煤灰分准确度影响的研究

激光诱导击穿光谱是一种新型的物质元素分析技术,有无需样品预处理以及可同时测量多种组分等特点,是未来实时煤质检测的重要方法之一,其中关键的一个重要参数是煤灰分准确度。透镜到样品表面距离可以通过控制煤样高度来实现,煤样高度影响的信噪比以及稳定性需要深入的研究,对测量的煤灰分准确度有很大影响。本文搭建了一套激光测量煤灰分的实验平台,选取代表不同产地的三种国标煤样为对象,采用相同压力下压饼机制成的不同高度片状煤样在同样光路结构下进行实验。通过谱线强度和相对标准偏差比较煤样高度对激光测量煤灰分准确度的影响。我们以0.1 mm为间隔,比较不同位置的光谱强度以及相对标准偏差,实验结果表明:虽然煤样高度为6 mm时,激光恰好聚焦在煤样表面,但是当聚焦位置在样品表面以下0.1 mm,煤样高度为6.1 mm时,光谱强度适中,稳定性更好。综合考虑稳定性和信噪比,煤样高度的研究为进一步产品化奠定了基础。

Study on the influence of coal sample height on the accuracy of laser measurement of coal ash content

Laser-induced breakdown spectroscopy is a new technique for analyzing material elements. It can be used for coal quality testing without the need for sample pretreatment and simultaneous measurement of multiple components. It is one of the important methods for real-time coal quality detection in the future. One of the key parameters is the accuracy of coal ash content. The distance from the lens to the surface of the sample can be achieved by controlling the height of the coal sample. The signal-to-noise ratio and stability of the coal sample height need to be studied in depth,which has a great influence on the accuracy of the measured coal ash content. In this paper,a set of experimental platform for laser measurement of coal ash is built. Three national standard coal samples representing different origins are selected as objects. Different height flaky coal samples made by pressing cake machine under the same pressure are tested under the same optical path structure. The influence caused by coal sample height in the measurement of coal ash content was showed by spectral line intensity and relative standard deviation. We compare the spectral intensities and relative standard deviations at different heights at 0.1 mm intervals. The experimental results show that although the height of the coal sample is 6mm,the laser just focuses on the surface of the coal sample. When the focus position is 0.1mm below the surface of the sample and the height of the coal sample is 6.1mm,the spectral line intensity is moderate and the stability is better. Considering stability and signal-to-noise ratio,the study of coal sample height lays the foundation for further productization.