12Cr1MoV晶粒度等级与激光诱导击穿光谱特性的关联性研究

为了将激光诱导击穿光谱(LIBS)应用到受热面金属材料特性的研究,选择不同晶粒度等级(7级、6级、5级和4级)的12Cr1MoV合金钢为对象,研究不同实验条件下(不同激光能量和光斑直径),12Cr1MoV晶粒度等级与激光诱导击穿光谱特性的关联性。研究结果表明,当光斑直径为206μm时,在不同能量条件下,不管是基体元素Fe还是合金元素Cr的谱线强度,均与样品的晶粒度等级之间存在较好的关联性。分析Fe离子线与原子线比值时发现,当采用100.6mJ激光能量、206μm光斑直径时得到的拟合度达到0.987,优于直接根据谱线强度得到的拟合效果。     

TDLAS直接吸收法和波长调制法在线测量CO2的比较

据统计,2015年我国消耗了39.65亿吨煤炭,而其中发电及热力供应占据了煤炭消耗总量的46.38%。发电及热力供应行业排放的CO2占据了我国温室气体排放量的很大比例,因此对于燃煤电厂CO2气体排放的实时监测是非常重要的。利用测量精度高、响应迅速、非接触测量的可调谐半导体激光吸收光谱（TDLAS）技术对CO2浓度检测。选用了中心波长在1 580 nm的分布式反馈激光器作为光源,参考电厂尾部烟气CO2浓度配置实验气体,分别使用直接吸收和波长调制方法对CO2浓度进行反演。对比研究结果表明,直接吸收和波长调制法重复测量的相对标准偏差分别为0.94%和0.22%,最大相对误差分别为2.64%和1.65%,检测限分别为0.013 6%和0.001 4%。波长调制法比直接吸收法在测量性能指标上更具优势,但由于波长调制法在现场应用时受定标方式的影响很大,且谐波线宽会受到压力、温度等参数变化的干扰,而直接吸收法无需标定,且测量精度足以满足电厂CO2在线监测的需求。因此在电厂锅炉烟气等高浓度CO2的测量中,直接吸收法是更好的选择。     

激光诱导击穿光谱技术应用于煤质分析的研究综述

实时掌握入炉煤的煤种特性,有利于燃煤发电机组的安全经济运行,但由于煤质在线分析技术的缺乏,一定程度地制约了火力发电燃烧优化技术的实质性发展,激光诱导击穿光谱(laser-induced breakdown spectros-copy,LIBS)技术作为一项潜在的在线分析技术被引入煤质在线分析领域。为此,分别从基础实验研究、定量分析方法研究和工业应用研究3个方面综述了国内外关于LIBS技术在煤质分析方面的研究现状,探讨了其中需要解决的关键问题。在LIBS技术现有发展的基础上,需要重点解决LIBS检测煤质所需的定量分析模型的精确度和煤种适应性、分析装置良好的现场适应性和长期运行的可靠性等问题。     

Improved Measurement Performance of Inorganic Elements in Coal by Laser-Induced Breakdown Spectroscopy Coupled with Internal Standardization

Laser-induced breakdown spectroscopy was employed to determine the inorganic elements in coal. To improve the measurement’s accuracy and precision, a new internal stan?dardization scheme, which we named changed internal standardization, was compared with the traditional internal standardization and no internal standardization for the analysis of inorganic el?ements. The new internal standardization scheme used the atomic line of carbon at 247.86 nm and the molecular band of CN at 388.34 nm and C2 at 516.32 nm to normalize the lines of inorganic elements that were distributed in the same spectral channel. The performance of the utilization of the new internal standardization scheme was evaluated using a set of coal samples, including twenty calibration samples and five validation samples. The results show that the coefficients of determination R2 and the slope of calibration models coupled with changed internal standard?ization are better than that of the calibration models coupled with fixed internal standardization and no internal standardization. Moreover, the measurement accuracy and reproducibility of changed internal standardization for the analysis of five validation samples also yielded further improvement. The results that we obtained suggest that changed internal standardization could compensate for the matrix effects, as well as the influence of the difference in the spectral response of the light collection system.     

Hybrid classification of coal and biomass by laser-induced breakdown spectroscopy combined with K-means and SVM

Laser-induced breakdown spectroscopy(LIBS) is a new technology suitable for classification of various materials. This paper proposes a hybrid classification scheme for coal, municipal sludge and biomass by using LIBS combined with K-means and support vector machine(SVM)algorithm. In the study, 10 samples were classified in 3 groups without supervision by K-means clustering, then a further supervised classification of 6 kinds of biomass samples by SVM was carried out. The results show that the comprehensive accuracy of the hybrid classification model is over 98%. In comparison with the single SVM classification model, the hybrid classification model can save 58.92% of operation time while guaranteeing the accuracy. The results demonstrate that the hybrid classification model is able to make an efficient, fast and accurate classification of coal, municipal sludge and biomass, furthermore, it is precise for the detection of various kinds of biomass fuel.     

不同硬度受热面材料的激光诱导等离子体光谱特性分析

将激光诱导击穿光谱(LIBS)用于锅炉受热面材料特性分析,选用受热面常用的珠光体耐热钢12Cr1MoV,并通过热处理工艺制备了不同硬度的实验样品。选择样品中基体元素Fe和合金元素Mn、Cr、V合适的分析谱线,对比分析了不同硬度条件下离子谱线与原子谱线的强度比和等离子体温度的变化规律。实验结果表明,由于等离子体冲击波特性差异和激光烧蚀质量的变化,导致了特征元素离子谱线与原子谱线强度比随着样品硬度的增加而增强,等离子体温度随硬度的增加而升高。     

复合肥氮磷钾元素含量的激光诱导击穿光谱同步测量

将激光诱导击穿光谱(LIBS)技术应用于复合肥样品中N,P和K元素含量的同步测量。选用10个已知样品作为定标样品,使用偏最小二乘法(PLS)分别建立各个元素定量分析的回归模型;然后使用5个待测样品检验这些模型的定量分析结果,并将预测结果与电感耦合等离子体发射光谱法测得的参考含量作对比。结果表明,激光诱导击穿光谱技术能够同时检测出5个待测样品的N,P和K元素的含量,待测结果的平均相对误差(REP)小于8%质量分数,平均相对标准偏差小于7%质量分数,检测极限值分别为0.16%,0.21%和0.50%质量分数。实验验证了LIBS技术同步快速准确测量复合肥中三大营养元素的能力。     

实验条件对煤粉着火稳定性指数测定的影响

采用热重分析(thermogravimetry,TG)可以快速、准确地评价煤的燃烧性能,但缺乏统一的判定和评价准则。JB/T10440—2004《大型煤粉锅炉炉膛及燃烧器性能设计规范》(以下简称"设计规范")规定了利用TG测定煤粉着火稳定指数的方法,其中氧量(氧的体积分数)和样品量的设定与众多文献有较大差异。为探讨这两个参数设定的必要性,针对性地开展了氧量和样品量的对比实验,所得结果表明,提高氧量和增加样品量可促使煤粉由非均相着火模式向均相着火模式转变;设计规范中79%氧量和以含10 mg可燃物质(以下简称"可燃物")为基准的实验条件设定合理,所测得的着火稳定性指数更易于明确区分不同煤样的着火特性。