Development of a Laboratory Cement Quality Analysis Apparatus Based on Laser-Induced Breakdown Spectroscopy

Determination of the chemical composition of cement and ratio values of clinker plays an important role in cement plants as part of the optimal process control and product quality evaluation. In the present paper, a laboratory laser-induced breakdown spectroscopy (LIBS) apparatus mainly comprising a sealed optical module and an analysis chamber has been designed for possible application in cement plants for on-site quality analysis of cement. Emphasis is placed on the structure and operation of the LIBS apparatus, the sealed optical path, the temperature controlled spectrometer, the sample holder, the proper calibration model established for minimizing the matrix effects, and a correction method proposed for overcoming the ‘drift’ obstacle. Good agreement has been found between the laboratory measurement results from the LIBS method and those from the traditional method. The absolute measurement errors presented here for oxides analysis are within 0.5%, while those of ratio values are in the range of 0.02 to 0.05. According to the obtained results, this laboratory LIBS apparatus is capable of performing reliable and accurate, composition and proximate analysis of cement and is suitable for application in cement plants.     

A Study on the Characteristics of Carbon-Related Spectral Lines from a Laser-Induced Fly Ash Plasma

A 1064 nm Nd:YAG laser was used to ablate fly ash samples.The characteristics of the spectral lines measured from the laserablated fly ash plasmas are presented with special attention to atomic and molecular carbon emission.It is shown that the intensity of the atomic line C I 192.9 nm is weak and the shot-to-shot intensity is fluctuant.The carbon atomic line C I247.7 nm is relatively intensive and stable,however it is seriously interfered with by Fe I 247.8 nm.The intensity of the CN molecular line is close to that of C I 247.7 nm and the CN line is stable and less interfered with.The comparison of molecular CN emission under different conditions(air,Ar and N_2) shows that the CN lines detected from the plasmas formed in an atmospheric environment are correlated with the reaction of carbon atoms in the plasma with the nitrogen in air,which indicates that the CN line is also important in pulsed laser ablation fly ash plasmas and this information can be incorporated in the detection of unburned carbon content in fly ash.Finally,a calibration curve is established with a correlation coefficient R2 of 0.999,using C I247.7 nm and the CN molecular line as associated variables.In addition,accuracy is improved to a certain extent.     

Wavelength Dependence in the Analysis of Carbon Content in Coal by Nanosecond 266 nm and 1064 nm Laser Induced Breakdown Spectroscopy

The wavelength dependence of laser induced breakdown spectroscopy(LIBS) in the analysis of the carbon contents of coal was studied using 266 nm and 1064 nm laser radiations.Compared with the 1064 nm wavelength laser ablation,the 266 nm wavelength laser ablation has less thermal effects,resulting in a better crater morphology on the coal pellets.Besides,the 266 nm wavelength laser ablation also provides better laser-sample coupling and less plasma shielding,resulting in a higher carbon line intensity and better signal reproducibility.The carbon contents in the bituminous coal samples have better linearity with the line intensities of atomic carbon measured by the 266 nm wavelength than those measured by the 1064 nm wavelength.The partial least square(PLS) model was established for the quantitative analysis of the carbon content in coal samples by LIBS.The results show that both of the 266 nm and 1064 nm wavelengths are capable of achieving good performance for the quantitative analysis of carbon content in coal using the PLS method.     

Application of Laser Induced Breakdown Spectroscopy in Early Detection of Red Palm Weevil: (Rhynchophorus ferrugineus) Infestation in Date Palm

The Kingdom of Saudi Arabia is one of the leading date producing countries. Un?fortunately, this important fruit crop is under great threat from the red palm weevil (RPW) (Rhynchophorus ferrugineus), which is a highly invasive pest. Several techniques, including vi?sual inspection, acoustic sensors, sniffer dogs, and pheromone traps have been tried to detect the early stages of a RPW infestation; however, each method has suffered certain logistical and im-plementation issues. We have applied laser induced breakdown spectroscopy (LIBS) for the early detection of RPW infestation. Through the analysis of the observed LIBS spectra of different infested and healthy samples, we have found presence of Ca, Mg, Na, C, K elements and OH, CN molecules. The spectra also reveal that with the population growth of the pest, the intensity of Mg and Ca atomic lines in LIBS spectra increases rapidly. Similar behavior is observed in the molecular lines of LIBS spectra. The obtained results indicate that the LIBS technique can be used for the early detection of RPW infestation without damaging the date palms.     

土壤中Ba和Mn的激光诱导击穿光谱定量检测

传统的土壤重金属元素检测方法流程复杂,时间长.我们采用波长1 064 nm的调Q脉冲Nd:YAG激光器和多通道小型光纤光栅光谱仪,建立了一套可移动的激光诱导击穿光谱系统.详细研究了重金属元素Ba,Mn的特征谱线强度、标准偏差与数据采样方式以及采样平均次数的关系,在优化工作参数的基础上,采用一种新的光谱采样和数据处理方法,对土壤中金属Ba、Mn的含量进行检测,并获得了检测土壤中金属Ba、Mn含量的定标曲线,对元素Ba、Mn的监测的相对标准偏差分别为9.0%和10.24%,检测灵敏度分别为19.4 mg/kg和115.4 mg/kg,优于目前文献报道的结果.     

基于激光诱导击穿光谱的煤元素分析研究

介绍了利用激光诱导击穿光谱(LIBS)对煤粉进行元素分析的有关技术.利用脉冲激光器激发煤粉样品产生荧光;利用光谱仪、BoxCar、数据采集卡获得荧光光谱数据;利用LabView编程实现煤粉中元素成分分析.文章以煤中碳含量测量为例介绍了元素分析的关键技术.给出测量精度标准偏差(SD)值不超过1.6%,可以满足燃煤电厂对煤...     

Investigation of the Parameters Influencing the Accuracy of Rapid Steelmaking Slag Analysis with Laser‐Induced Breakdown Spectroscopy

Laser‐Induced Breakdown Spectroscopy (LIBS) is used for the analysis of steelmaking slags (EAF, Ladle Furnace (LF) and Vacuum Ladle Degasser (VLD)). In view of the potential industrial application of LIBS for rapid slag analysis, relatively simple criteria were employed in order to obtain calibration curves for the elements of interest. The LIBS experiments were performed on samples prepared after crushing and milling to a size less than 0.2 mm and on as delivered solidified slag samples. In general, the analysis of the solidified as delivered slag samples exhibited better results than the corresponding analysis of the pressed slag, mainly for the elements distributed in the matrix. Thus, for LIBS application, the time consuming sample preparation of the slag can be avoided. According to the results obtained, the potential of LIBS technique for in‐situ, multi‐element analysis of slag was examined at the 60t‐ EAF of Helliniki Halyvourgia SA (HH‐Greece). The most important parameters that influence slag analysis are the laser pulse energy, the number of accumulated laser shots, the laser beam focusing conditions and the gating conditions of the detector. LIBS accuracy was found to depend on both the distribution of elements in the slag and on their environment (i.e. if they are embedded in the matrix or in a specific crystallized phase) as well. LIBS limitations for quantitative slag analysis are also discussed. The accuracy of FeO_n LIBS analysis for as delivered solidified EAF and VLD slags of the steel plant of Georgsmarienhütte was satisfactory showing a Regression Coefficient (RC) of 0.93 and 0.95 respectively. The accuracy of SiO₂ and MgO analysis of VLD slags with RCs of 0.94 and 0.86 respectively was also satisfactory. In contrast, for the EAF slags the RC for MgO and SiO₂, due to the observed non‐homogeneous crystallized phases have shown insufficient values, with 0.55 and 0.43 respectively. Similar results were gained for the FeO_n, MgO and SiO₂ analysis of the HH slags. Due to the higher intensity of scattering, the analysis of CaO, Al₂O₃ and Cr₂O₃ was of lower accuracy than for FeO_n, MgO and SiO₂.     

Rapid identification of volatile organic compounds and their isomers in the atmosphere

Isomers are widely present in volatile organic compounds (VOCs), and it is a tremendous challenge to rapidly distinguish the isomers of VOCs in the atmosphere. In this work, laser-induced breakdown spectroscopy (LIBS) technology was developed to online distinguish VOCs and their isomers in the air. First, LIBS was used to directly detect halogenated hydrocarbons (a typical class of VOCs) and the characteristic peaks of the related halogens were observed in the LIBS spectra. Then, comparing the LIBS spectra of various samples, it was found that for VOCs with different molecular formulas, although the spectra are completely the same in elemental composition, there are still significant differences in the relative intensity of the spectral lines and other information. Finally, in light of the shortcomings of traditional LIBS technology in identifying isomers, machine learning algorithms were introduced to develop the LIBS technique to identify the isomers of atmospheric VOCs, and the recognition results were very good. It is proved that LIBS combined with machine learning algorithms is promising for online traceability of VOCs in the atmospheric environment.     

新型便携式激光诱导击穿光谱仪器及其应用研究

针对我国成熟且商业化的便携式激光诱导击穿光谱仪器缺乏,且现有便携设备光谱稳定性和抗干扰性能差的现状,提出并成功开发了一种新型小型化、集成化的便携式激光诱导击穿光谱仪器。采用该仪器成功实现了对24种金属矿石的准确分类和微合金钢样品中Cr、Ni、Si、Cu、Ti、V元素的精准定量分析,其对24种金属矿石的平均分类准确率达到了95.83%,微合金钢中各元素定量分析模型的决定系数R²分别达到了0.993、0.984、0.996、0.990、0.980、0.999,检出限(LOD,质量分数)分别达到了0.0355%、0.0587%、0.0773%、0.0120%、0.0085%和0.0082%,交叉验证的平均相对误差(ARECV)分别达到了5.20%、11.30%、18.18%、9.63%、9.73%、9.17%。结果表明,所开发仪器具备良好的定性、定量分析性能,其为便携式激光诱导击穿光谱仪器的国产化提供了新的解决方案。     

不同煤种煤粉颗粒流的等离子体特性研究

将激光诱导击穿光谱(LIBS)技术应用于煤粉颗粒流 的检测。选用无烟煤、烟煤和褐煤3种燃用特性差异较大的 煤样为研究对象,具体分析了不同煤种煤粉颗粒流的等离子体特性。在 大气环境下,使用1064nm脉冲激光击穿煤粉颗 粒流,并用光谱仪收集等离子信号。通过对等离子体信号 的分析,得出煤样颗粒流的Si、Al相对强度、等离子体温度以及电子密度与煤种的关系。 实验研究表明, 煤粉颗粒流的Si、Al相对强度随灰分含量的增大而增大;各煤种的煤粉颗粒流的等离子体温 度和电子密度从大到小排列依次为无烟煤>烟煤>褐煤。