垃圾焚烧时碳黑的形成与燃烧分析

根据已有的一种生活垃圾的燃料成分及其干镏后可燃气成分，导出了其可燃基组分分子式和热解反应质量守恒关系式。参照煤燃烧的基本假设，计算了垃圾焚烧时碳黑的生成量、浓度、燃烧速率和燃烧时间。并讨论了空气量对碳黑生成和燃烧的影响。     

气化钠对伊敏煤热解衍生碳黑微晶结构的影响

为研究热解气中的气化钠对煤衍生碳黑微晶纳观结构的影响,本文进行了担载氯化钠前后伊敏酸洗煤粉的热解实验.通过高分辨透射电镜与拉曼光谱仪分析1250℃、不同停留时间条件下收集的碳黑样品,并分别采用图像处理技术与曲线拟合方法获得基本碳黑粒子内部结构参数.两种煤粉的对比实验表明:进入到微晶堆栈区的气化钠可以抑制微晶长大、增加微...     

天然气火焰FTIR测量试验台的设计和调试

从研究天然气锅炉中碳黑生成、辐射换热和NOx排放相互关系的角度出发,设计并制作了一套采用傅立叶变换红外光谱仪(Fourier Transform Infrared Spectroscopy,FTIR)作为测量仪器的试验台,整个试验台由三大部分组成:加热器、燃烧器和燃烧室.试验台能够实现包括不同的预混度和不同的炉膛热环境在内的多种工况,通过调试,证实了不同的预混度对火焰形状和火焰温度有很大影响,今后的FTIR测量试验将进一步考察不同的预混度和不同的炉膛热环境对碳黑生成量、辐射换热量和NOx生成量的影响.     

煤粉燃烧产物的辐射特性

以Ｅｄｗａｒｄｓ指数宽谱带模型为基冷比较了几种常见的二氧化碳、水蒸汽混合物的吸收系数计算公式。在粒子为光滑、均质假设的基础上，利用Ｌｏｒｅｎｔｚ－Ｍｉｅ理论计算了煤粉粒子、焦炭粒子及碳黑粒子的辐射特怀。经比较，发现国产动力煤煤粉料屯煤灰粒子的辐射特性与原茵联的差别很大。针对国产动力煤，给出了适用于炉内过程数值计算使用的煤粉燃烧产物辐射特性的计算方法。     

煤热解过程中碱金属对碳黑形成的影响

通过分析担载碱金属Na的酸洗煤热解产物的浓度分布、化学结构与微观结构,研究碱金属对煤衍生碳黑形成的影响.结果表明煤热解产物的粒数与质量浓度分布分别在0.12μm与0.20μm附近存在峰值,无Na酸洗煤超细颗粒生成量较多;随着煤中含量增加,热解使Na先赋存于半焦中,抑制焦油的释放;之后过量的Na气化并抑制焦油向碳黑转化;Na可增加样品中含氧官能团含量,减少脂肪族化合物尤其是短链或支链化程度较高脂肪族化合物含量、增加芳香族化合物含量并降低芳香环稠化度;气化的Na可以造成碳黑微晶体晶格缺陷,形成一些嵌套或类晶体特异结构.     

燃烧过程中碳黑颗粒生成机理的研究进展

从两方面论述了碳黑的生成机理：气体火焰中碳黑的生成模型和煤燃烧过程中碳黑的生成模型。从而对碳黑的生成机理作了一个详细的综述。在气体火焰的碳黑生成模型中，运用化学动力学来诠释在层流预混火焰中大分子芳香族烃的形成。芳香族烃形成的主要步骤是乙炔和小分子芳香族烃的组合，主要是因为H原子萃取和共振稳定基团的组合，包括聚戊二烯的组合、丙炔对苯的粘附和丙炔对芳香环的连续粘附，由此建立了HACA模型(H萃取乙炔加入模型)。在此基础上，加以对共振稳定基团的分析研究，进一步建立气H原子萃取乙炔加入和共振稳定基团组合模型。对于煤燃烧过程中碳黑的生成模型，其过程非常复杂，国内外论述的比较简单，一般认为煤颗粒经过快速加热、热解过程生成焦炭和挥发分，而挥发分进一步裂解生成碳黑。     

FTIR 发射/透射光谱对含颗粒气流的温度测量

在改进的FTIR和自制的微量给粉加热／燃烧实验装置上，对粘土颗粒气流和煤粉火焰进行了FTIR发射／透射测量。通过发射／透射光谱可以得到颗粒温度和气体温度，其相对误差小于5%，满足实验室和工业测温要求。当被测样品中存在碳黑和其它颗粒时，基于碳黑的吸收特性，给出了消除碳黑辐射影响的一种近似处理方法，即将吸收光谱外推至0cm^-1，以0cm^-1处的数值为准对整个光谱进行校正，所得光谱就认为是去除碳黑影响后的吸收光谱．对于CO2气体温度，研究表明，可以用通过CO2峰值的黑体理论曲线来简单估计．研究还发现炭粒温度可以高出气体温度200—300K，一个可能的原因是CO在颗粒边界层点燃引起了颗粒温度突然升高并高于气体温度，对这种现象的理论解释和更多的实验验证尚需进一步展开。     

挥发分喷射对碳烟生成和火焰辐射的影响

利用激光诱导白炽光和增强型 CCD 拍照研究了煤燃烧中挥发分喷射对碳烟体积分数和火焰辐射强度的影响.结果表明:煤燃烧挥发分喷射会导致碳烟的大量生成以及碳烟分布位置的急剧变化,碳烟体积分数的最大值能从120×10-6增加到170×10-6,甚至更高.煤燃烧时挥发分喷射会对火焰辐射产生显著的影响,辐射的总体强度和最大值会突然出现显著的增加.模型分析表明,喷射是挥发分集中在一个较窄通道释放而形成,而不是挥发分经过时间累积之后集中释放     

水蒸气对液体燃料高温分解碳黑形成影响的研究

考察了水蒸气的加入对液体燃料高温分解时碳黑形成的影响。采用直接测量碳黑沉积质量的方法,得出水蒸气能够抑制液体燃料中碳黑颗粒形成的结论,并总结出碳黑在图壁表面沉积的一些规律特征。在进行实验的同时,采用Fluent软件,模拟了两种实验工况下炉内的碳黑颗粒浓度场,证实了实验结论。最后,给出了计算公式,选取合适的待定参数,则计算结果与实验结果符合很好。     

碳烟催化氧化最优升温速率与颗粒质量分数的试验

通过傅里叶红外光谱(FT-IR)、场发射扫描电子显微镜(FESEM)对纳米MoO3催化剂的物化特性进行表征.MoO3催化剂主要以均匀球形或类球形颗粒组成,球形形状增加了比表面积且具有较高的分散性,从而大幅提高MoO3的催化性能.以Printex-U碳黑作为发动机尾气中碳烟颗粒的替代物,利用热重分析仪(TGA),基于CoatsRedfern法对不同升温速率、不同碳黑颗粒与催化剂配比下碳黑氧化的动力学参数进行分析.结果表明:当升温速率为20,℃/min时指前因子呈现较高的值,而当颗粒质量分数在15%,时的活化能亦较高,这是由于催化剂与颗粒低效接触以及可能存在非催化氧化而导致的传热和传质限制引起的.故进行颗粒物催化氧化试验时,颗粒物质量分数宜控制在10%,以下,升温速率宜选取在15,℃/min以下,颗粒氧化反应动力学参数只有微小变化,几乎不受扩散控制的影响.     

A Comparative Exploration of Enhancing Thermal Characteristics of Natural Gas Flame by Synchronous Combustion Technique

This article is a comparative study of how the injection of micro kerosene droplets and pulverized anthracite coal particles affects soot particle nucleation inside natural gas flame and, subsequently, radiation. To this end, the yellow chemiluminescence of soot particles and IR photography were used to locate radiative soot particles and discover their qualitative distribution. The IR filter was tested with a Thermo Nicolet Avatar 370 FTIR Spectrometer for its spectral transmittance to be specified. Also, the spectral absorbance of soot particles, which are formed in flame, was measured by BOMEM FTIR. Furthermore, the variations of flame temperature, transient heat transfer, and thermal efficiency were investigated. The results indicate that, for equal heating values, kerosene droplets are more effective than coal particles in improving the radiation and thermal characteristics of natural gas flame. Also, kerosene droplets cause a higher rise in the temperature in flame downstream and make the axial flame temperature more uniform than coal particles do. In quantitative terms, when kerosene droplets were injected, the radiative heat transfer and thermal efficiency of flame were 93% and 35% higher than the corresponding values for the coal particles injection mode.     

炭黑非催化燃烧特性的固定床实验研究

含碳燃料在还原气氛下燃烧会生成炭黑，在动力设备的燃烧装置中，炭黑的后期氧化对污染控制是非常重要的。利用石英管固定床反应器对天然气扩散火焰中生成的炭黑在不同氧浓度下（20％、15％、10％和5％）的燃烧特性进行了研究，并选用了蜡烛炭黑、丁烷炭黑和煤焦作为对比。根据实验中得出的燃烧特性，与煤焦相比，炭黑的着火温度较低，但是炭黑的燃烧活化能相对更高。氧浓度对各试样着火温度影响不大，而却影响各试样燃烧过程。还进行了水蒸汽对天然气炭黑燃烧的影响研究，水蒸汽能引起炭黑燃烧速率的显著增大。图9参12     

Effects of radiation on spray flame characteristics and soot formation

Two-dimensional numerical simulations are applied to spray flames formed in a laminar counterflow and the effects of radiation on spray flame characteristics and soot formation are studied. N-Decane (C₁₀H₂₂) is used as the liquid fuel, and the droplet motion is calculated by the Lagrangian method. A single-step global reaction is employed for the combustion reaction model. A kinetically based soot model with a flamelet model is used to predict soot formation. Radiation is taken into account using the discrete ordinate method. The results show that radiation strongly affects the spray flame behavior and soot formation. Without the radiation model, flame temperature and soot volume fraction are greatly overestimated. The soot is formed in the diffusion flame regime, and its radiation emission increases with the increase in the equivalence ratio of the droplet fuel. This trend is in good agreement with that of the luminous flame behavior observed in the experiments.     

天然气炭黑燃烧特性的热天平研究

利用热重分析天平对天然气扩散火炬中直接取样得到的炭黑的燃烧性能进行了研究,并选用了蜡烛炭黑、4种商业炭黑以及一种无烟煤焦炭作为对比。基于试验结果确定了燃烧动力学特性参数,并分析了它的燃烧特性。天然气扩散火焰中生成的炭黑具有着火相对容易、着火温度较低（与煤焦或挥发份较低的煤比）、前期燃烧较弱、后期燃烧较缓慢、燃尽时间较长等燃烧特性。这些结果为利用天然气燃烧过程的炭黑生成强化火焰辐射特性并进行有效控制提供了依据。     

Effects of water vapor addition to the air stream on soot formation and flame properties in a laminar coflow ethylene/air diffusion flame

The effects of adding water vapor to the air stream on flame properties and soot volume fraction were investigated numerically in a laminar coflow ethylene/air diffusion flame at atmospheric pressure by solving the fully elliptic conservation equations and using a detailed C₂ reaction mechanism including PAH up to pyrene and detailed thermal and transport properties. Thermal radiation was calculated using the discrete-ordinates method and a statistical narrow-band correlated-k based wide band model for the absorption coefficients of CO₂ and H₂O. Soot formation was modeled using a PAH based inception model and the HACA mechanism for surface growth and oxidation. Addition of water vapor significantly reduces radiation heat loss from the flame primarily through reduced soot loading and flame temperature. The added water vapor affects soot formation and flame properties through not only dilution and thermal effects, but also through chemical effect. The chemical effect is as significant as the dilution and thermal effects. The primary pathway for the chemical effect of water vapor is the reverse reaction of OH + H₂ ↔ H + H₂O. Our numerical results confirm that the reduced H radical concentration leads to lower PAH concentrations and consequently lower soot inception rates. In contrast, the radiation effect due to the added water vapor was found to have a minor influence on both flame structure and soot formation in the laminar diffusion flame investigated.     

The influence on the soot distribution within a laminar flame of radiation at fluxes of relevance to concentrated solar radiation

An assessment of the influence of high intensity radiation on the distribution of soot within a laminar ethylene flame is performed. Radiation at fluxes of up to 4.3 MW/m², of a similar order encountered with concentrated solar radiation, is provided by a CO₂ laser at 10.6 μm. Radiation at this wavelength, in the configuration used in this paper, allows effective isolation of three possible mechanisms of influence: molecular excitation of the fuel, irradiation of the soot, and irradiation of soot precursors. The influence of the radiation on the soot distribution is assessed by laser induced incandescence (LII) imaging in a plane that intersects with the CO₂ laser beam. It is found that the high intensity radiation has a dramatic influence on the flame. The high energy radiation acts to increase the peak volume fraction of the soot by up to 250%. The results show that whilst the effect is most pronounced due to heating of the fuel, heating of the soot can also be significant.     

Nongray radiation from gas and soot mixtures in planar plates based on statistical narrow-band spectral model

The nongray behavior of combustion products plays an important role in various areas of engineering. Based on the statistical narrow-band (SNB) spectral model with an exponential-tailed inverse intensity distribution and the ray-tracing method, a comprehensive investigation of the influence of soot on nongray radiation from mixtures containing H₂O/N₂+soot, CO₂/N₂+soot, or H₂O/CO₂/N₂+soot was conducted in this paper. In combustion applications, radiation transfer is significantly enhanced by soot due to its spectrally continuous emission. The effect of soot volume fraction up to 1×10^-6 on the source term, the narrow-band radiation intensities along a line-of-sight, and the net wall heat fluxes were investigated for a wide range of temperature. The effect of soot was significant and became increasingly drastic with the increase of soot loading.     

Furnace water-wall slag deposition testing in a 0.5 MWt combustion pilot plant

This article presents combustion pilot-plant test results obtained using newly developed ash deposition probes (ADPs) designed to measure both the thermal and mechanical properties of furnace ash deposits. The ADP measurements are obtained at multiple elevations in the furnace to provide detailed heat absorption and ash deposition time constant profiles for 8 h soot-blowing cycles. Profiles of incident radiation are also presented. Results are presented for four different coal types representing major steam-coal-producing regions in the United States. The furnace heat absorption profiles are distinctly different for each coal type and also vary significantly with furnace elevation. Combined furnace heat absorption and time constant data are used to recommend optimal use of soot-blowing resources, or to specify soot blower and water-wall surface addition and location according to coal type.