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。     

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。     

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.     

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。     

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。     

基于综合性能评价的SCR静态混合器优化研究

为综合考量选择性催化还原(SCR)系统静态混合器的混合效果和对系统造成的阻力损失,提出了一种结合流场均匀性和阻力特性的综合性能评价指标——无量纲混合效率η。结合现场需求,采用数值模拟方法,以圆形、花瓣形和SMV混合器为例对系统的综合性能进行评估。结果表明：圆形混合器、SMV混合器、花瓣形混合器的η分别为16.18%、22.50%和26.88%,其中花瓣形混合器综合性能最佳;在顺序排列、同向布局、覆盖率为37%的条件下,花瓣形混合器的综合性能达到最佳,其无量纲混合效率η为28.60%,较优化之前提高6.40%。     

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.     

生物质焦反应活性及其与拉曼光谱表征关联性研究进展

生物质能作为目前使用量最大的可再生能源形式,具有储量巨大、零碳排放、可再生及供应稳定等优点。生物质焦作为生物质能利用的重要形式,其反应活性因原料种类不同表现出巨大差异,严重阻碍了生物质能的进一步研究和利用。生物质焦的反应活性主要受无机元素、织构特性及碳结构的影响。拉曼光谱作为近年来发展迅猛的碳结构表征技术,已广泛应用于生物质焦的物理、化学结构特性研究。从生物质焦拉曼光谱的特征峰位置、特征峰宽、特征峰强度比和特征峰面积等光谱参数出发,综述国内外生物质焦的碳结构,并解析了生物质焦在热化学转化中碳结构的演化规律。拉曼光谱能有效表征生物质焦的碳骨架结构,高度有序的芳香或石墨化结构会降低生物质焦的反应性。目前对生物质焦反应活性与拉曼光谱参数表征的碳骨架结构之间的相关性研究仍较少,且多聚焦在单一种类生物质,其结论普适性仍需验证。也有少量关于多种生物质原料的焦反应活性和拉曼光谱表征研究,但未给出定量的结论。介绍笔者在多种生物质原料的焦反应活性与焦的拉曼光谱指标的关联性方面的研究进展,以期为生物质燃料的反应活性后续研究提供参考。展望未来,生物质焦的拉曼光谱研究发展潜力很大,目前主要研究仍基于一阶拉曼光...