褐煤热解与燃烧时矿物转化和细灰形成的CCSEM研究

在沉降炉中进行了一种典型中国褐煤的热解与燃烧实验,热解气氛为N2,燃烧气氛为O₂/N₂=21:79,采用CCSEM分析原煤、煤焦与煤灰。CCSEM分析结果表明,铁氧化物、石英、黄铁矿、伊利石和高岭土是煤中主要的矿物成分,同时也是主要的外在矿成分,褐煤中57.26%的矿物粒径小于10μm。在热解与燃烧过程中,煤中主要矿物发生了明显转化。富Si矿物和硅铝酸盐在热解和燃烧过程中可能发生了破碎;而富Fe矿物部分明显破碎生成细小矿物,部分外在矿直接转化,未发生明显破碎。细灰少量来自于细小富硅矿、石英和铁氧化物等矿物的直接转化,70%以上的细灰由Ca、Fe含量很高的混合硅铝酸盐组成。     

煤燃烧过程矿物质行为研究

１前言煤中矿物质行为直接影响到煤灰熔融特性,影响到燃烧锅炉的结渣程度。以前曾对单种煤煤灰加热过程中矿物质行为特征［１,２］,以及混煤煤灰熔融行为与矿物形态间的关系［３,４］进行过研究。但这些研究均是以煤灰做为试样,静态加热处理并分析的基础性研究,而未考虑到燃烧锅炉内煤灰颗粒的加热燃烧速度、空间分布情况以及炉内温度分布。本研究将在四角燃烧炉内,煤燃烧过程中不同位置取出友样进行矿物质形态分析,并与煤灰静态加热过程矿物质组成及含量变化进行比较分析。２实验方法试样采用株州煤。制成８００”Ｃ灰样,株州煤的…     

铁系矿物对煤灰相变过程的内在影响规律研究

为深入研究煤燃烧与煤气化过程中煤中矿物的熔融变化行为对煤灰物理相变变化过程的内在影响规律,本文采用高温热显微镜、SEM-EDX等分析测试手段,实验研究了不同条件(煤燃烧与煤气化)下煤中矿物演变规律与煤灰物理相变变化行为间的内在联系和影响规律。研究结果表明:高铁含量的煤灰A在气化条件下发生初始熔融温度(T_(in))及快速熔融温度(T_(max))要比其在燃烧条件下对应的温度分别低144℃和113℃,而低铁含量的煤灰B则对应气化条件下的T_(in)和T_(max)分别比燃烧条件下的对应温度低25℃和62℃;不同气氛下灰中Fe的不同价态是导致这种差别的主要原因,高温下煤灰相变发生、发展过程中,灰中方铁石、铁铝榴石以及铁做榄石等铁系矿物是引发煤灰发生初始熔融的主要矿物。     

低比重分煤中结渣相关矿物质分布的实验研究

对结渣特性差异大的神华煤和山西贫煤比重分离制取低比重分煤,使用ICP-AES、XRD和穆斯堡尔谱分析低比重分煤及其原煤盐酸分离前后的样品,对比研究低比重分煤及其原煤中结渣相关矿物质,特别是黏土矿物分布。结果表明神华煤低比重分煤中钙主要为有机钙,铁基本以黄铁矿存在,并且该黄铁矿大部分溶于盐酸。煤燃烧时这些含铁、钙物质和黏土矿物的作用产物应该对该煤种的易结渣性具有重要贡献。两种动力煤的低比重分煤中黏土矿物种类和相对分布均与原煤中相同,并且黏土矿物在低比重分煤成灰物质中的份额均高于在原煤中的份额,针对黏土矿物在煤粉燃烧过程中的热反应产物的研究将为理解飞灰中易熔融物质的形成机理提供更深入的认识。     

煤燃烧中无机矿物向颗粒物的转化规律

为深入理解燃煤颗粒物的形成机理,利用计算机控制扫描电镜技术对煤及其颗粒物中的无机矿物进行了详细表征,研究了煤燃烧过程中主要矿物向颗粒物的转化规律.结果表明煤中粘土矿物由于含有K、Na、Ca、Mg和Fe等杂质元素,容易在较低温度下发生熔融和聚合,从而使颗粒粒径变大.黄铁矿在燃烧中易发生分解、破碎而使颗粒粒径减小,Fe氧化物与硅酸盐发生反应形成富Fe硅酸盐.方解石和铁白云石在高温条件下分解生成对应的氧化物,也可与硅酸盐发生反应形成富Ca或富Fe硅酸盐.石膏在燃烧过程中会经历脱水和分解反应,生成的CaO可与SO3和熔融硅酸盐发生竞争反应.     

高钙煤的成灰特性研究

神木煤的含钙量较高,使得燃烧后煤灰中氧化钙含量也很高.研究高钙煤的成灰特性,以分析在何种工况下燃烧产生的煤灰更适于作为脱硫剂使用.选取1000℃和1100℃两个燃烧温度,各温度下分别通入的4种不同气氛组织燃烧,燃烧完全后对煤灰的物理特性进行研究.研究发现随着燃烧气氛中氧气质量浓度的增加,煤灰颗粒的尺寸逐渐减小,孔隙结构逐渐疏松.当燃烧温度升高时,所得煤灰颗粒的尺寸减小,孔隙结构变得致密.     

燃煤含铁矿物的迁移转化特性研究

采用场发射扫描电镜结合X射线能谱分析仪(FSEM-EDX)系统研究了燃煤电站静电除尘器下各电场飞灰中磁珠的显微结构和化学组成,并利用热力学软件FACT计算预测了煤中含铁矿物的迁移转化过程．结果表明,外在含铁矿物在燃煤过程中易直接氧化形成结晶程度较好的铁氧化物相;内在含铁矿物与其他矿物在高温下熔合形成含Fe、Al、 Si的复杂的玻璃相,煤中含铁矿物的赋存特征、反应温度和气氛是影响含铁矿物迁移转化的主要因素。燃煤过程中Fe2 中间产物的形成以及Fe-O-S共熔体在炉内的长时间停留是结渣形成的重要原因。     

燃煤锅炉PM10形成与排放特性的实验研究

应用低压撞击器分别对某50 MW和100 MW燃煤机组锅炉除尘器前后飞灰颗粒进行采样,研究了除尘器前后煤灰颗粒的排放特性及元素分布特征,对颗粒物形成机理进行了探讨。结果表明,粒径小于0．377μm颗粒可能是通过气化-凝结机理形成,煤灰中元素Na、Mg、S、Cu、Zn和Pb约有10％-30％分布在粒径小于0．377μm颗粒中, 元素Al、Si和Ca相应的值只有1％左右,元素Fe、Cr和Mn相应的值约为3％-8％。两台锅炉除尘器入口和出口 PM10的质量粒径呈双峰分布,其峰值分别在0．1μm和4μm左右。除尘器对不同粒径颗粒除尘效果的不同导致了除尘器入、出口处颗粒组成特征的明显不同。     

元素钾、硅和铝在PM10的形态与分布研究

通过对平顶山烟煤在沉降炉内的燃烧试验,结合热力学平衡计算分析,研究了三种选定的矿物质成灰元素钾、硅和铝在可吸入颗粒物中的形态与分布.燃烧试验条件为煤粉粒径小于63 μm,燃烧温度在1400℃,炉内燃烧气氛为空气气氛.试验采用低压撞击器(LPI)按不同粒径大小从0.03～10 μm共分为13级,分别采集燃烧后的可吸入颗粒物.并采用热力学平衡计算分析方法研究了氧化性气氛中元素钾、硅和铝的化学形态和物理相.试验和计算结果显示钾元素主要以K单质的形式气化,大部分以K2SO4、KCl、K2HPO4的形式存在于亚微米颗粒中,极少量以KAlSi2O6相存在于PM1.0-10中;极少量Si和Al元素分别以SiO和OAlOH及A1OH的形式气化,以固相SiO2和Al2O3存在于亚微米颗粒中,而大部分则以SiO2和A16Si2O13的形式存在于PM1.0-10中.     

气化条件下灰的熔融行为及矿物质演变规律

本文利用XRD、SEM等测试手段,采用配气技术实验研究了高温气化条件下(29.9%H_2,66.2%CO,3.9%CO_2)高、低灰熔点煤灰及其混煤灰的熔融行为及矿物质演变规律。研究表明:气化条件下高灰熔点煤A含有较多的高岭石和石英,随着温度的升高,莫来石开始逐渐形成(960℃),当温度达到1300℃时煤灰A中的结晶矿物全部为莫来石;低灰熔点煤B含有较多的硬石膏和方解石,随着温度的升高,900～1200℃开始生成大量的钙长石、铁橄榄石、铁铝榴石等低熔矿物,在1300℃时煤灰B中的结晶矿物全部熔融;高温气化条件下,混煤灰A/B的熔融温度变化与其三元相图上相应的液相线温度具有良好的相似性,当混煤灰A/B的主要化学成分位于三元相图的二元共晶线或低熔融共晶点附近时熔融温度最低。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.