颗粒度对不同煤种可见光-近红外光谱的影响

Effect of Granularity on the Characteristics of Visible-Near Infrared Spectra of Different Coal Particles

煤炭是我国最主要的能源,在开采、运输、洗选加工、精煤储运等过程中都需要及时了解煤的成分、含量以及混矸程度,以便掌握和监控煤炭质量。目前,基于可见光-近红外反射光谱的煤炭原位测试技术已经成为一个研究热点。颗粒度是影响光谱特征的重要因素,开展颗粒度对不同煤种反射光谱特征的影响研究,对于深刻认识煤的光谱特征,进而提高煤光谱识别精度具有重要意义。为此,选取我国主要煤炭富集区(包括内蒙古乌海、新疆哈密、山西阳泉)的褐煤、烟煤、无烟煤为研究对象,利用SVC HR-1024光谱仪对不同颗粒度煤样的可见光-近红外光谱进行测试,分析了颗粒度对煤样光谱反射率的影响规律,以及颗粒度对于不同煤种光谱影响的差异。在此基础上,对实验现象背后的物理机理进行了分析讨论。研究表明,变质程度不同的煤反射光谱特征基本相似,即在可见光波段反射率较低且随波长增加出现缓慢下降趋势,在近红外波段快速上升。当煤样颗粒度>0.10 mm时,颗粒度大小对光谱特征的影响较小,煤样反射光谱特征随颗粒度变化规律不明显;当颗粒度<0.10 mm时,颗粒度对煤样的光谱影响增大,且影响主要体现在近红外波段的反射率光谱曲线的斜率大小,颗粒度越小,光谱反射率曲线斜率越大。0.10 mm颗粒度可作为颗粒度对煤的光谱特征影响的敏感界限。不同煤种可见光-近红外光谱曲线受颗粒度的影响程度不同,褐煤的影响最大,烟煤次之,无烟煤影响最小。实验表明,利用反射光谱进行煤质分析和煤种识别时需要考虑颗粒度的影响,同时,选择颗粒度小于0.10 mm的粉末状样品效果要好于大颗粒或块状样品。

Coal is the most important energy source in China.In mining,coal cutting,transportation,washing,processing,and cleaning coal storage,it is necessary to know the composition and content of coal and the degree of mixed gangue in time of determining,master and monitor the quality of coal.At present,based on visible light to the near-infrared emission spectrum of coal,in situ testing technology has become a research hotspot,and the granularity is one of the important factors affecting spectral characteristics to carry out the granularity to study the influence of the different spectral reflectance characteristics of coal,to understand the spectral characteristics of coal deeply.Coal spectrum recognition accuracy is of great significance.For this purpose,this article selects the main coal enrichment region(including Inner Mongolia Wuhai,Xinjiang Hami,Shanxi Yangquan)of lignite,bituminous coal,and anthracite as the research object by using an SVC HR-1024 spectrometer with different granularity coal-near-infrared spectrum of visible light sample test,analyzes the particle degree of the influence law of spectral reflectance of coal samples,and the difference of the influence of granularity on the spectrum of different coal.On this basis,the physical mechanism behind the experimental phenomenon is analyzed and discussed.The results show that the emission spectrum characteristics of coals with different metamorphic degrees are similar.In other words,the reflectance is the low invisible band and decreases slowly with the increase of wavelength,while it rises rapidly in the near-infrared band.When the granularity of the coal sample is greater than 0.10 mm,the granularity has little influence on the spectral characteristics,and the change law of the reflection spectrum with granularity is not obvious.When the granularity is less than 0.10 mm,the influence of granularity on the spectrum of the coal sample increases.In addition,the influence is mainly reflected in the slope of the reflectance spectral curve of the near-infrared band.The smaller the granularity is,the more significant the reflectivity increment is and the larger the slope of the spectral curve is.A granularity of 0.10 mm can be used as the sensitive limit of granularity’s influence on the coal’s spectral characteristics.The spectral curves of different coal types are affected by particle size to different extents,and the impact on lignite is the largest,followed by bituminous coal,and the least impact on anthracite.It can be seen that when using the reflectance spectrum to analyze coal quality and identify coal species,the effect of selecting a powder sample with granularity of less than 0.10 mm is better than that of a large particle or lump sample.