基准物质燃烧红外吸收法测定硅中硫

采用基准物质硫酸钾 ,配成一系列标准溶液 ,在通有纯氧气的高频炉中燃烧 ,红外吸收法测定硫含量 ,绘制校准曲线。对硅标准物质的测定值与推荐值基本一致 ,方法准确、结果满意。方法适用范围为0 .0 0 2 %— 0 .0 4 0 % ,RSD在 2 .0 %— 8.0 %之间。     

高分辨连续光源原子吸收光谱法测定植物中的硫

硫元素在富燃的乙炔/空气火焰可形成CS双原子分子,在某些特定的波长下,这些CS分子吸收谱线具有原子吸收的轮廓和一定的吸收强度。文章主要研究利用高分辨连续光源原子吸收光谱法,通过测定硫元素在富燃-乙炔/空气火焰条件下形成的CS双原子分子的吸光度值,从而测定植物样品中的硫元素含量。实验对乙炔-空气比例和燃烧器高度等仪器条件进行了优化;实验研究了五种有机溶剂对CS分子吸收产生的影响情况、其他共存元素的光谱干扰和化学干扰以及不同的消解酸种类对测定结果的影响。在优化的条件下,硫在CS 257.961 nm的检出限为14 mg·L-1。通过对植物标准物质中硫含量的测定比对和精密度实验证明, 利用连续光源原子吸收光谱法,在富燃-乙炔/空气焰条件下以CS分子测定植物样品中的硫元素是一种简单、快速、有效的方法。     

氧弹燃烧-ICP-OES用于柴油标准物质中硫含量的定值

本文是柴油系列标准物质研究课题中的子课题,研究了用氧弹燃烧-电感耦合等离子发射光谱法对柴油中硫系列标准物质的定值。通过实验条件的最佳化,包括氧弹燃烧消解样品的影响因素、仪器分析的最佳条件等,利用新型的电感耦合等离子发射光谱仪器(SPECTRO CIROS)真空紫外谱线灵敏高,重现性好的优点,测量两个水平的硫标准物质,使用内标元素Y和进行基体匹配达到消除基体影响而提高测量准确度的目的。该方法展伸不确定度优于2％,测定的结果与其它的不同方法测定的结果一致。     

不同变质程度煤燃烧反应性及FTIR分析其热解过程结构变化

利用TG/DTA 6300的热重分析仪对胜利褐煤(SL)、神华烟煤(SH)与塔旺陶勒盖无烟煤(TT)三种不同变质程度的原煤进行空气气氛下燃烧反应;通过FTIR(傅里叶变换红外光谱)分析了三种煤样及不同终温下固定床热解半焦的官能团组成;运用数学高斯函数对FTIR曲线重叠吸收峰进行分峰拟合,利用拟合峰面积计算FTIR的芳香度指数(R)、芳香结构稠合指数(D)及有机成熟度指数(C)结构参数。结果表明： SL,SH与TT煤着火温度分别为299.3,408.2及441.0℃;最大失重速率峰温度分别为348.6,480.5及507.0 ℃,即随煤样变质程度的不同,着火点和最大失重速率温度都不同程度提高。煤中官能团结构较复杂,不同变质程度的煤样的红外光谱曲线中均可以观察到羟基(—OH);脂肪烃(—CH₂,—CH₃);芳环(CC); 含氧官能团(CO, C—O)等主要官能团的振动吸收峰。随着热解炼焦温度的升高,三种煤样中脂肪烃类(—CH₂—,—CH₃)红外振动吸收峰均逐渐减小;炼焦后CO在1 700 cm-1伸缩振动峰在炼焦温度到达550 ℃时基本消失;SL原煤样在1 000～1 800 cm-1 含氧官能团吸收峰区域红外曲线更为复杂,随炼焦温度升高较之其他煤样变化最为显著;而SH及TT煤芳环CC吸收峰在温变过程中峰位及峰强度均无显著变化。通过R,D及C值随热解终温的变化曲线,三种变质程度煤在热解反应过程中主体官能团变化趋势存在差异。     

典型块状煤的可见-近红外光谱特征研究

因可见-近红外波段反射光谱测试方便,仪器成本较低,适用于在线分析,为此针对煤在可见-近红外波段的反射光谱曲线特征规律及其产生机理进行了研究分析。从晋、鲁、宁、吉地区煤矿收集了无烟煤、烟煤、褐煤三大类型中的12种典型煤样,按煤阶从高到低具体包括无烟煤一号、无烟煤二号、贫煤、贫瘦煤、瘦煤、焦煤、肥煤、1/3焦煤、气肥煤、气煤、褐煤一号、褐煤二号,在实验室利用地物光谱仪采集了块状煤样在可见-近红外波段的反射光谱曲线。通过对光谱曲线特征分析,发现无烟煤的反射光谱曲线整体上趋于水平方向,吸收谷特征不明显,随煤阶的降低,光谱反射率、近红外波段光谱斜率整体上呈增加趋势,较明显的吸收谷特征增多且吸收强度增加,有13个较明显的吸收谷特征波段。通过X射线衍射分析（XRD）测定了煤样的碳材料结构和矿物成分,煤非晶质性分子结构的芳构化趋势对煤阶升高时光谱反射率降低、反射曲线趋于平缓起到主要作用。当煤阶降低时,以脂肪侧链为主的有机吸收基团的中红外波段基频在近红外波段的倍频和合频产生众多吸收叠加,绝大多数吸收谷特征不明显,相对较为明显的吸收谷产生在1 700和2 300 nm附近。同时含Fe等过渡金属的矿物、H₂O、粘土矿物等无机物成分也是煤反射光谱曲线吸收谷特征增多的因素。通过对实验煤样X射线荧光分析（XRF）和工业分析测定了煤样中Fe和Al等矿物元素成分含量和空气干燥基水分、灰分、挥发分、固定碳含量,得出煤反射光谱曲线的近红外波段光谱斜率与挥发分产率、固定碳含量分别呈正、负相关性。H₂O谱带吸收深度之和与内在水分含量线性相关性较好,Fe和Al含量与相关波段吸收谷深度之和基本呈线性关系,而主要由有机基团倍频和合频所产生的1 700和2 300 nm附近两处吸收谷深度之和与挥发分产率线性相关性较差。获得典型块状煤种的可见-近红外波段反射光谱特征,为煤矿区高光谱遥感以及煤光谱数据库的建立提供依据,也为直接利用可见-近红外波段的反射光谱曲线波形特征快速、低成本、定性地识别煤种类提供参考;同时对煤矿用煤炭探测光谱传感器的研制具有重要意义。     

激光诱导等离子体光谱用于煤中氧的定量分析

利用激光诱导等离子体光谱(LIPS)技术实现对燃煤电厂输煤管中煤质的在线检测对于提高锅炉燃烧效率具有重要的现实意义,但对煤中氧含量的测量却是个难题.提出了一种新的数据处理方法,主要包括内标法、最佳分析线选择法、温度校正法及多线法等,来提高对煤中氧含量定量分析的准确性和重复性.实验中先通过8组煤样获得了煤中氧的定标方程,然后又利用其它6组煤样来验证该定标方程的准确性.实验结果表明,利用本数据处理方法对煤中氧含量测量的绝对误差小于1.1 %,多次测量的相对标准偏差(RSD)小于5.9%,显示了较高的测量精度和重复性.     

原子吸收光谱法测定铬元素的最灵敏线

对国内原子吸收文献中记载的原子吸收光谱法测定铬元素的最灵敏线提出了不同观点.文献记载,原子吸收光谱法测定铬元素的最灵敏线为357.9nm,次灵敏线为359.3nm.经过对铬元素进行原子吸收光谱扫描证实,最大吸收峰位置在359.3nm处;次吸收峰位置在357.9nm处.同时,分别在357.9nm和359.3nm处进行校准曲线的测定,359.3nm处所测的有效吸收值和灵敏度均高于357.9nm处的吸收值和灵敏度.结果表明,原子吸收光谱法测定铬元素的最灵敏线应为359.3nm.     

煤热解气中汞连续测量方法及应用

针对煤热解气中烃类物质对连续测汞仪的影响,本文采用高温载氧体处理煤热解气消除此影响,研究了煤热解气处理后汞连续测量的效果并进行实际应用。结果表明:烃类物质造成冷原子吸收测汞仪测量结果完全错误。经载氧体处理后氧化了热解气中烃类物质,使热解气中汞能被准确连续测量。使用前后载氧体XRD分析也验证这一结果。在煤程序升温热解汞的连续测量应用中,发现实验所用煤中汞主要有两个温度释放峰,且在600℃已基本释放完全。     

荧光增白剂CXT紫外吸收测量不确定度的评估

对荧光增白剂CXT紫外吸收测量不确定度进行了评估,分析了整个检测过程中不确定度的来源,测量结果的不确定度由重复性测量、仪器的校准及仪器显示读数的分辨力等所引入的不确定度分量组成.评估结果表明,重复性测量是影响该方法不确定度的主要因素.     

高灵敏度浓度测量及显示系统设计

随着对环境污染的日益重视,污染物质的浓度检测在大气污染检测、高温燃烧环境监测、工业废水排放监测,以及在造纸、食品加工等领域有着越来越重要的作用.我们在分光光度计光谱定性测量的基础上,以甲基橙水溶液做为指示剂,设计制作了基于激光吸收光谱技术的差分式高灵敏度浓度测量及显示系统,通过实验测量得到了甲基橙的电压-浓度标准输出曲线.此系统利用多次反射长程吸收池,大大提高了浓度测量的灵敏度;利用光电二极管偏置放大实现了光电变换,减小了暗电流及热噪声;利用差分式光学检测及数字电路处理方法,有效地抑制了激光器能量起伏及探测器、电子元件的低频噪声的影响.     

Application of Kβ/Kα in selecting calibration standards for X-ray fluorescence analysis

A method for improving the accuracy in X-ray fluorescence spectroscopy analysis with pressed pellets was established through matching the calibration standards by the Kβ/Kα ratios. The Kβ/Kα ratios of four major elements (Al, Si, Ca, and Fe) were measured in 14 certified reference materials (CRMs) for geochemistry. The deviation of the biggest Kβ/Kα values relative to the smallest ones for the same element was from 1.52% (Si) to 20.98% (Al) when pressed pellets were used. The relative deviation of Kβ/Kα values for Ca was as high as 3.56% even for two soil CRMs (GBW07404 and GBW07408). X-ray diffraction analysis confirmed that the Ca elements in the two CRMs were in distinct phases, thereby leading to the different Kβ/Kα values. The Fundamental Parameter Method (FPM) results of two calibration strategies were compared. When one of the 14 CRMs was selected as unknown sample whereas the other 13 CRMs were used for calibration to determine Al₂O₃, SiO₂, CaO, and Fe₂O₃, the relative errors were 10.80%, 8.77%, 8.33%, and 10.91%, respectively. Another strategy, where only one CRM was used for calibration of samples with large errors, was adopted by matching Kβ/Kα values. The results of calibrating using CRM with similar Kβ/Kα values were more accurate than those with different Kβ/Kα values.     

Investigation of sulfur speciation in particles from small coal-burning boiler by XANES spectroscopy

Sulfur K-edge X-ray absorption near-edge structure (XANES) spectroscopy was employed to study the speciation of sulfur in raw coal, ash by-product and fine particulate matter from a small coal-burning boiler. By means of least square analysis of the XANES spectra, the major organic and inorganic sulfur forms were quantitatively determined. The results show that about 70% of the sulfur in raw coal is present as organic and a minor fraction of the sulfur occurs as other forms: 17% of pyrite and 13% of sulfate. While in bottom ash, fly ash, and PM_2.5, the dominant form of sulfur is sulfate, with the percentage of 80,79 and 94, respectively. Moreover, a number of other reduced sulfur including thiophenic sulfur, element sulfur and pyrrhotite are also present. During coal combustion, most of organic sulfur and pyrite were oxidized and released into the atmosphere as SO₂ gas, part of them was converted to sulfate existing in coal combustion by-products, and a small part of pyrite was probably reduced to elemental sulfur and pyrrhotite. The results may provide information for assessing the pollution caused by small boiler and developing new methods for the control of SO₂ pollution.     

The roles of added chlorine and sulfur on ash deposition mechanisms during solid fuel combustion

The focus of this paper is on effects of chlorine and sulfur on coal ash deposition rates, under practically relevant but systematically controlled combustion conditions. This problem is important, not so much for coal, but to understand and predict deposition rates for biomass combustion where chlorine contents can be high. To this end, ash deposition rates on a controlled temperature surface were measured for controlled amounts of chlorine and sulfur added to a pulverized coal, doped with potassium and burned in a 100 kW rated combustion rig. Previous work with 35 tests on 11 coal, biomass and petroleum coke fuels burned under a range of operating conditions had strongly suggested that the deposition rate of the tightly bound inside deposits was independent of the ash aerosol composition, and depended only on PM₁ in the flue gas. The loosely bound outside deposition rate was dependent primarily on the total alkali content in the flue gas. The new results using chlorine added to the fuel (in the form of ammonium chloride) required these previous conclusions to be drastically revised. They showed that chlorine, not alkali alone, had large effects on the deposition rate of the inside deposits, which now were orders of magnitude higher than without chlorine addition, and did not fit previous (multi-fuel) correlations with PM₁. Sulfur addition, together with chlorine, did not affect deposition rates much, although it did lower the chlorine content of the deposit. These results are interpreted in terms of the ash aerosol size segregated composition, which was also measured, and potential sulfation reactions within the deposit.     

An in-situ method for time-resolved sodium release behaviour during coal combustion and its application in industrial coal-fired boilers

To mitigate the slagging, fouling and high-temperature corrosion problems caused by alkali metals during coal combustion process, measurement of time-resolved alkali metals release is very important. The paper proposed an in-situ approach for measuring sodium (Na) release in coal combustion by Flame Emission Spectroscopy (FES). Through the analysis of spontaneous emission spectra and a calibration procedure, the concentration of gas phase Na, temperature and thermal radiation can be obtained. Firstly, experimental measurement of Zhundong coal particles burning in a flat flame burner was done. Two kinds of Zhundong coal with similar proximate and ultimate analyses, but different ash composition were used. The Na-release history measured by FES was compared with that by LIBS. Results showed that the Na-release at the devolatilization, char, and ash stages can be distinguished by FES. The higher Si/Al content in ash can suppress the Na-release at the ash stage. Moreover, FES method was extended to the measurement of Na-release in four industrial boiler furnaces of two Zhundong coal-fired power plants. Results showed the Na-release measured by FES can reflect the change of fuel and load, and both temperature and thermal radiation play key roles in Na-release in coal combustion.     

煤中硫化物硫的间接火焰原子吸收法测定

研究了测铬的间接原子吸收法测硫的实验条件，结果表明，硫酸盐与铬酸钡的交换平衡时间也会影响分析结果。本文提出了间接原子吸收法测定煤中硫化物硫的方法。吸光度Ａ与ＣＳＯ４＾２－在０￣１６μｇ／ｍＬ范围内成线性关系。用于煤样品测定。平行测定结果的相对标准偏差为３￣５％，加标回收率为９５￣１０２％。     

Experimental and modeling assessment of sulfur release from coal under low and high heating rates

Coal combustion releases elevated amounts of pollutants to the atmosphere including SO_X. During the pyrolysis step, sulfur present in the coal is released to the gas phase as many different chemical species such as H₂S, COS, SO₂, CS₂, thiols and larger tars, also called SO_X precursors, as they form SO_X during combustion. Understanding the sulfur release process is crucial to the development of reliable kinetic models, which support the design of improved reactors for cleaner coal conversion processes. Sulfur release from two bituminous coals, Colombian hard coal (K1) and American high sulfur coal (U2), were studied in the present work. Low heating rate (LHR) experiments were performed in a thermogravimetric analyzer coupled with mass spectrometry (TG-MS), allowing to track the mass loss and the evolution of many volatile species (CO, CO₂, CH₄, SO₂, H₂S, COS, HCl and H₂O). High heating rate (HHR) experiments were performed in an entrained flow reactor (drop-tube reactor – DTR), coupled with MS and nondispersive infrared sensor (NDIR). HHR experiments were complemented with CFD simulation of the multidimentional reacting flow field. A kinetic model of coal pyrolysis is employed to reproduce the experiments allowing a comprehensive assessment of the process. The suitability of this model is confirmed for LHR. The combination of HHR experiments with CFD simulations and kinetic modeling revealed the complexity of sulfur chemistry in coal combustion and allowed to better understand of the individual phenomena resulting in the formation of the different SO_X precursors. LHR and HHR operating conditions lead to different distribution of sulfur species released, highly-dependent on the gas-phase temperature and residence time. Higher retention of total sulfur in char is observed at LHR (63%) when compared to HHR (37–44%), at 1273 K. These data support the development of reliable models with improved predictability.     

K‐edge XANES analysis of sulfur compounds: an investigation of the relative intensities using internal calibration

Sulfur K‐edge XANES (X‐ray absorption near‐edge structure) spectroscopy is an excellent tool for determining the speciation of sulfur compounds in complex matrices. This paper presents a method to quantitatively determine the kinds of sulfur species in natural samples using internally calibrated reference spectra of model compounds. Owing to significant self‐absorption of formed fluorescence radiation in the sample itself the fluorescence signal displays a non‐linear correlation with the sulfur content over a wide concentration range. Self‐absorption is also a problem at low total absorption of the sample when the sulfur compounds are present as particles. The post‐edge intensity patterns of the sulfur K‐edge XANES spectra vary with the type of sulfur compound, with reducing sulfur compounds often having a higher post‐edge intensity than the oxidized forms. In dilute solutions (less than 0.3–0.5%) it is possible to use sulfur K‐edge XANES reference data for quantitative analysis of the contribution from different species. The results show that it is essential to use an internal calibration system when performing quantitative XANES analysis. Preparation of unknown samples must take both the total absorption and possible presence of self‐absorbing particles into consideration.     

Ultrasonic coal-wash for de-sulfurization

Coal is the one of the world's most abundant fossil fuel resources. It is not a clean fuel, as it contains ash and sulfur. SOx as a pollutant are a real threat to both the ecosystem and to human health. There are numerous de-sulfurization methods to control SO(2) emissions. Nowadays, online flue gas de-sulfurization is being used as one such method to remove sulfur from coal during combustion. The biggest disadvantage associated with this method is formation of by-products (FGD gypsum). A way for effective usage of FGD gypsum has not yet been found. This will lead to acute and chronic effects to humans as well as plants. Power ultrasound can be used for the beneficiation of coal by the removal of sulfur from coal prior to coal combustion. The main effects of ultrasound in liquid medium are acoustic cavitation and acoustic streaming. The process of formation, growth and implosion of bubbles is called cavitation. Bulk fluid motion due to sound energy absorption is known as acoustic streaming. In addition, coupling of an acoustic field to water produces OH radicals, H(2)O(2), O(2), ozone and HO(2) that are strong oxidizing agents. Oxidation that occurs due to ultrasound is called Advanced Oxidation Process (AOP). It converts sulfur from coal to water-soluble sulphates. Conventional chemical-based soaking and stirring methods are compared here to ultrasonic methods of de-sulfurization. The main advantages of ultrasonic de-sulfurization over conventional methods, the mechanism involved in ultrasonic de-sulfurization and the difference between aqueous-based and solvent-based (2N HNO(3), 3-volume percentage H(2)O(2)) de-sulfurization are investigated experimentally.     

X射线荧光光谱法测定一氧化碳助燃剂中的铂

介绍用X射线荧光光谱法测定CO助燃剂中Pt含量的分析方法.考查了影响Pt元素测定的各种因素,分别以Al2O3和丝光沸石为载体配制铂的校准曲线,使标准样品与样品的基体基本一致,减少了基体效应的影响.待测元素的线性范围为:0.002％-0.2％,相关系数均为0.9999,测定结果的相对标准偏差小于1.5％.该方法的测定结果与原子吸收光谱法的测定结果相吻合.方法简便、快速,测定结果准确.