褐煤是我国现阶段的主要用煤, 但因为其较低的煤化程度, 使用时会产生污染环境的二氧化碳和黑灰, 而且烟尘中含有的金属离子会危害人体健康, 所以开展对褐煤烟尘的研究非常有意义。 而激光诱导击穿光谱技术(LIBS)具有快速、 多元素同时分析的特点, 适合用于煤烟的原位在线探测。 实验制备了含铅浓度不同的三种褐煤样本(O, H, L), 其中O为原始无铅样本, 利用LIBS对褐煤及煤烟进行原位在线探测。 实验仪器主要由激光器, 反射镜, 聚焦透镜, 触发装置, 载物平台和分析系统组成。 用高纯度铅块校准实验中的的波长漂移。 分析了褐煤样本O, H, L的元素成分。 发现褐煤O中含有C, Si, Fe, Mg, Al, Ca, Sr, Na等元素, 同时检测到空气中的元素N, O, Hα和Hβ等, 且含铅褐煤光谱中多出了8条铅元素的谱线, 最后给出了褐煤中主要元素的光谱鉴别表。 然后使用447 nm的连续光点燃褐煤, 将1 064 nm的脉冲光聚焦在煤烟上, 对褐煤煤烟进行了原位在线检测。 发现煤烟中含有Mg, Ca, Al, Sr, Pb等金属离子, 说明了褐煤中的一些金属离子会随着煤烟排放到空气中并危害人体健康。 经褐煤及煤烟的光谱比较, 发现煤烟的信噪比更差, 且所有元素的谱线强度都比在褐煤中弱很多, 另外发现在烟尘中碳原子谱线的相对强度是所有元素中最高的(无明火), 这说明LIBS可以有效探测CO2。 分析了实验中的CN分子谱, 给出了CN分子的具体波长, 并利用LIFBASE软件拟合了CN分子的转动温度和振动温度, 分别为6 780和7 520 K。 最后对样本H和L两种煤烟中的铅浓度进行分析, 选取参考线(Ca Ⅱ 363.846 nm)归一化之后比较了铅元素在363.956, 368.346和405.780 nm处的相对强度, 发现这三条特征谱线的相对强度与自身实际所含的铅浓度呈很好的线性关系, 验证了LIBS技术应用于煤烟中重金属元素半定量分析的可行性。

Due to the shortage of high-quality coal resources, lignite has become the main coal used in our country. Lignite has a low degree of coalification, which produce a lot of black ash and carbon dioxide when burning. The metal ions contained in the soot harm human health, so it is very meaningful to carry out the research on lignite soot. Laser-induced breakdown spectroscopy (LIBS) is a fast and multi-element method, which is suitable for in situ online detection of soot. Three lignite samples (O, H, L) with different lead concentrations were prepared in this paper, where O was the original lead-free sample. Laser Induced-breakdown Spectroscopy (LIBS) was used for insitu online detections of lignite and soot. The experimental instruments are mainly composed of laser, spectrometer, reflector, focusing lens, trigger device, carrier platform and analysis system. First, the wavelength drift of the experiment was calibrated using a high-purity lead block, and the elemental composition of the lignite samples O, H, and L was analyzed. It was found that lignite O contained C, Si, Fe, Mg, Al, Ca, Sr, Na and other elements, while N, O, Hα, Hβ and other air elements were detected. In addition, there were 8 more spectral lines of lead in the lead-containing lignite spectrum. Finally, a spectrum identification table of the main elements in lignite was given. Then the lignite was ignited with 447 nm continuous light, and 1 064 nm pulse light was focused on the soot for in situ online detectings. The qualitative analysis of the soot spectrum found that the soot contained metal ions such as Mg, Ca, Al, Sr, and Pb, indicating that some metal ions in the lignite would be discharged into the air with the soot and endanger human health. By comparing the spectrum of lignite and soot, it was found that the signal-to-noise ratio of soot was bad, and the spectral line strength of all elements was much weaker than that of lignite. In addition, it was found that the relative intensity of the carbon atom spectral line in soot was the highest among all elements (no open fire), which proved the effectiveness of LIBS for detecting CO2. In addition, the CN molecular spectrum in the experiment was analyzed, and the specific wavelength of the CN molecule was given. The rotation temperature of the CN molecule was 6 780 K and the vibration temperature was 7 520 K using the software LIFBASE fitting. At last, the lead concentration in the soot of samples H and L were analyzed, and the reference line (Ca Ⅱ 363.846 nm) was selected to normalize and compare the relative intensities of lead elements at 363.956, 368.346 and 405.780 nm. It was found that the relative intensities of the three characteristic spectral lines had a good linear relationship with their actual lead concentration, which indicates that the LIBS technology is feasible for semi-quantitative analysis of heavy metal elements in lignite soot.