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。     

煤粉锅炉炉膛出口受热面结焦问题研究

燃用神华类易结焦煤种的电厂在持续高负荷运行时,其炉膛出口受热面易发生结焦问题,以往以控制炉膛出口烟温作为防止结焦的措施。根据工程实践情况并从煤灰颗粒与烟气的辐射传热特性不同出发,提出了烟温与煤灰颗粒温度的区别,并指出实际运行中炉膛出口受热面发生结焦问题的主要原因在于煤灰颗粒在到达炉膛出口处时其温度仍高于软化温度(ST)。基于此,以单个煤粉颗粒为研究对象,重点计算分析了燃烧速率对炉膛出口处煤灰颗粒温度的影响。结果表明,提高煤粉燃烧速率可以有效地降低炉膛出口处的煤灰颗粒温度,从而极大地改善结焦问题。介绍了上海外高桥第三发电厂首创的广义回热技术,对比分析可知,此技术对防治锅炉结焦更为经济、有效。     

煤粉粒子的发射率

本文基于均质光滑球形粒子散射的Ｌｏｒｅｎｔｚ－Ｍｉｅ电磁理论，利用实验测得的煤粉粒子的复折射率，计算了国产二十种动力煤煤粉粒子的发射率。计算结果表明，煤粉粒子的全波长发射率与粒径、粒子温度及煤种有关。并在很宽的粒径范围内远远偏离文献中常用的假定值０．８，粒径在１－２０μｍ范围内煤粉粒子的发射率常常大于１．０。本文解释了部分煤粒子发射率大于１．０的原因及其物理含义，并给出了国产二十种动力煤煤粉粒子发     

国产动力煤煤粉粒子系的辐射特性

基于均质光滑球形粒子散射的Ｌｏｒｅｎｔｚ－Ｍｉｅ电磁理论，利用实验测得的煤粉粒子的复折射率，在假定粒径符合Ｒｏｚｉｎ－Ｒａｍｍｌｅｒ分布的基础上，计算了国产２０种动力煤煤粉粒子系的辐射特性参数。计算结果表明，Ｐｌａｎｃｋ平均衰减系数、散射系数、吸收系数与粒径分布参数（Ｒ９０，ｐ）、辐射源温度Ｔ、粒子系体积份额ｆｖ有关，并可拟合成如下函数形式：Ｋ＝ａｐｂＲ９０ｃ（Ｔ＋２７３．１５）ｄｆｖ。在温度（３００～１７００℃）范围内，拟合误差小于±１５％。图４表１参５     

煤粉炉联产水泥熟料煤灰熔融特性的试验研究

选用高硫长广煤为试验煤种、分析纯 CaO 和 MgO 为添加剂,按照设定的配料方案配制为混合煤粉.依据 GB/T 219-1996煤灰熔融特性测试方法,使用 SE-AF 智能灰熔点测试仪对混合煤粉的灰熔点进行了测量.结果表明:随混合煤粉中 CaO 添加质量分数的逐渐增加,混合煤粉灰熔融特性温度呈现 V 型变化规律;按照联产 Q 相水泥熟料配料方案配制的混合煤粉煤灰的结渣趋势程度属于轻微,较长广煤的结渣趋势程度有所降低.对软化温度下混合煤粉煤灰的矿物组成进行了 XRD 分析,并利用 CaO-Al2O3一SiO2 三元系统相图,进一步分析了混合煤粉熔融特性温度变化机理.结果表明:随着混合煤粉中 CaO 添加质量分数的变化,煤灰矿物组成中不同程度地出现低温共融体是煤灰熔融特性温度变化的原因.     

降维后的离散传递法及其在煤粉火焰传热中的应用

针对具有二维特征的辐射传热问题，介绍了一种降维方法。用经过降维处理的离散传递法（DTM）对含有吸收、发射性介质的圆管形腔体和煤粉火焰的辐射传热进行数值计算，并与按三维辐射计算的结果和试验数据进行比较，结合符合很好。这表明：用降维后的离散传递法描述煤粉火焰的辐射传热过程是可行和精确的。     

炉内煤粉燃烧一维数学模型及其仿真

为了准确计算炉内煤粉的燃尽率，从研究煤粉粒子的燃烧机理入手，以炉膛内最复杂的燃烧器区域的煤粉燃烧过程为研究对象，通过合理简化煤粉中挥发分和焦炭的燃烧过程，建立了炉内煤粉燃烧沿高度方向上的一维宏观模型，在模型中考虑了煤粉燃烧过程中氧含量的变化，以单个煤粉颗粒燃烧的等密度模型为基础，通过多种煤粉粒径的燃烧过程反映煤粉燃烧的整体过程，推导出计算炉内煤粉燃尽率的显示公式，满足了实时仿真计算的要求。计算结果与实测数据和现有的文献相符，并对结果进行了分析。     

大型超(超)临界煤粉锅炉炉膛传热计算

考虑大型超(超)临界煤粉锅炉受热面的布置特点,将炉膛分为自由炉膛区段和含屏炉膛区段,对按照苏联1973标准计算得到的有效辐射厚度、辐射减弱系数和火焰中心高度系数等关键参数进行了修正,建立了新的一维分区段热力计算方法,并采用该方法对4个电厂的600MW超临界煤粉锅炉和2个电厂的1 000MW超超临界煤粉锅炉进行了传热计算.结果表明:采用该方法计算得到的炉膛出口烟气温度与设计值的偏差明显小于苏联1973标准,可以满足工程应用的精度要求.     

煤粉复合旋流火焰燃烧特性研究（2）：数值模拟

本文数值模拟了煤粉旋流火焰燃烧过程，燃烧数值计算包括理论物理模型建立，数值方法两个大部分，计算模型处理了气相湍流与燃烧、气固两相流动、煤颗粒燃烧过程和辐射传热等物理化学过程，以ｋ－ε模型模拟湍流流动；ＰＤＦ法模拟气相扩散火焰燃烧；颗粒运动计算颗粒运动少颗粒湍流浓度方程模拟颗粒湍流扩散；通量法计算火焰辐射传热，煤粉颗粒复杂燃烧模型计算了颗粒尺寸、形状变化和颗粒孔隙内部燃烧、表面平度对整个颗粒的燃烧过程影响。计算获得了气相速度分布场、气相ｋ和ε分布场、气相温度场、气相组份场和颗粒浓度场及运动过程，揭示了煤粉复合旋流燃烧特性。     

轴流透平中煤灰粒径分布对粒子动态特性和叶片磨蚀的影响

本文提出了轴流式燃气透平中煤灰粒径分布对粒子动态特性和叶片磨蚀方面影响的研究结果。在透平叶片流道内应用三元流分析法求解粒子动态特性及其对叶片的冲击。用由实验测量导出的经验公式来描述粒子的回弹情况和叶片材料的磨蚀特性。对典型的煤灰粒径分布所做的研究结果表明,煤灰粒径分布对叶片磨蚀的程度和图样有着显著的影响。     

Distribution of mineral matter in pulverized coal

Mineral transformations, and therefore fly ash evolution, during pulverized coal combustion, depend on the amount, composition and spatial distribution of the inorganic matter within individual pulverized coal particles. Thus, it is necessary to have information on the mineral composition of individual particles, as well as that of the raw pulverized coal. A model is proposed based on the assumption that mineral inclusions of size and composition determined using a CCSEM are distributed randomly in the coal. From this distribution it is possible to generate distributions of mineral content for any particle size and density fraction of coal. The model has been checked by comparing computed results with data on the compositional variations of narrowly and density classified fractions of an Upper Freeport bituminous coal. The results of individual coal particle compositions are used to generate information on the variability of the composition of the fly ash generated during combustion.     

硫铁矿在炉内结渣中所起作用的数值研究

以某台有结渣现象的国产300MW机组的1025t／h锅炉为对象,采用数值模拟对其中硫铁矿和煤粉及其飞灰颗粒的运动进行数值计算,通过对两者在炉内的运动和水冷壁附近颗粒浓度的比较,探讨结渣产生的机理和原因,并对与结渣有关的含硫量、FeS2密度、硫铁矿颗粒尺寸分布、缩小切圆直径的影响进行了数值研究。     

硫铁硫颗粒在炉内运动数值模拟及对结渣的影响

以一台存在结渣的国产300MW机组的1025t/h锅炉为对象，采用数值模拟对其中硫铁矿和煤粉及其飞灰颗粒的运动进行数值计算，通过对两者在炉内的运动和水冷壁附近颗粒浓度的比较，探讨结渣产生的机理和原因，并对与结渣有关的含硫量、FeS2密度、硫铁矿颗粒尺寸分布、缩小切圆直径的影响进行了数值研究。     

Experimental studies of ash film fractions based on measurement of cenospheres geometry in pulverized coal combustion

In pulverized coal particle combustion, part of the ash forms the ash film and exerts an inhibitory influence on combustion by impeding the diffusion of oxygen to the encapsulated char core, while part of the ash diffuses toward the char core. Despite the considerable ash effects on combustion, the fraction of ash film still remains unclear. However, the research of the properties of cenospheres can be an appropriate choice for the fraction determination, being aware that the formation of cenospheres is based on the model of coal particles with the visco-plastic ash film and a solid core. The fraction of ash film X is the ratio of the measuring mass of ash film and the total ash in coal particle. In this paper, the Huangling bituminous coal with different sizes was burnt in a drop-tube furnace at 1273, 1473, and 1673 K with air as oxidizer. A scanning electron microscope (SEM) and cross-section analysis have been used to study the geometry of the collected cenospheres and the effects of combustion parameters on the fraction of ash film. The results show that the ash film fraction increases with increasing temperature and carbon conversion ratio but decreases with larger sizes of coal particles. The high fraction of ash film provides a reasonable explanation for the extinction event at the late burnout stage. The varied values of ash film fractions under different conditions during the dynamic combustion process are necessary for further development of kinetic models.     

The effect of low-NOx combustion on residual carbon in fly ash and its adsorption capacity for air entrainment admixtures in concrete

Fly ash from pulverized coal combustion contains residual carbon that can adsorb the air-entraining admixtures (AEAs) added to control the air entrainment in concrete. This is a problem that has increased by the implementation of low-NO_x combustion technologies. In this work, pulverized fuel has been combusted in an entrained flow reactor to test the impact of changes in operating conditions and fuel type on the AEA adsorption of ash and NO_x formation.Increased oxidizing conditions, obtained by improved fuel-air mixing or higher excess air, decreased the AEA requirements of the produced ash by up to a factor of 25. This was due to a lower carbon content in the ash and a lower specific AEA adsorptivity of the carbon. The latter was suggested to be caused by changes in the adsorption properties of the unburned char and a decreased formation of soot, which was found to have a large AEA adsorption capacity based on measurements on a carbon black. The NO_x formation increased by up to three times with more oxidizing conditions and thus, there was a trade-off between the AEA requirements of the ash and NO_x formation. The type of fuel had high impact on the AEA adsorption behavior of the ash. Ashes produced from a Columbian and a Polish coal showed similar AEA requirements, but the specific AEA adsorptivity of the carbon in the Columbian coal ash was up to six times higher. The AEA requirements of a South African coal ash was unaffected by the applied operating conditions and showed up to 12 times higher AEA adsorption compared to the two other coal ashes. This may be caused by larger particles formed by agglomeration of the primary coal particles in the feeding phase or during the combustion process, which gave rise to increased formation of soot.     

煤粉超细化对炉内受热面积灰与结渣的影响

煤粉颗粒温度、环境气氛和惯性沉积是电站四角切圆煤粉燃烧锅炉炉内受热面积灰与结渣的主要外在因素，以此为依据采用超细化煤粉燃烧技术对炉内受热面积灰和结渣的影响进行了理论分析与实验研究，阐述了煤粉超细化对于减轻电站有四角切圆煤粉燃烧锅炉炉内受热面积灰与结渣具有优越性。     

煤粉射流吸热着火稳燃机理及新型稳燃技术的探讨

详细地介绍煤粉射流在炉膛内着火的机理，全面地分析了对流换热和辐射换热对不同粒径煤粉颗粒的加热作用，对传统的煤粉着火作了评论和分析，同时分析了其它影响火焰稳定的因素。分析了直流煤粉燃烧器和旋流燃烧器稳燃机理，着重指出了这两类燃烧器各自的优缺点。在综合了直流和旋流煤粉燃烧器优点的基础上，提出了一种多功能、可调节、自适应外旋流、内直流煤粉主燃烧器，初步讨论了其应用的可能性。     

分级燃烧最佳一次风空气系数的实研究

在一维煤粉燃烧炉上进行了不同煤种、不同细度的分级燃烧试验。实验发现，分级燃烧对高挥发份 煤种以及同一煤种的细煤粉的Nox排放浓度的降低效果更显著，而且在分级燃烧条件下，同一煤种细煤粉的 飞灰含量较粗煤粉低。另外，还得到了不同煤种在分级燃烧条件下的最佳一次风空气系数。图9表2参3     

加福煤粉燃烧过程的微观形态观察

应用光学显微镜和扫描电子显微对加福煤粉燃烧过程中微观形态的变化规律进行了详细的观察。研究结果表明，加福煤粉燃烧过程中出现白球，棕色球，黑球，黑块Ⅰ，黑块Ⅱ这五种形态各异的颗粒，热力工况对其燃尽过程有影响，降低飞灰含碳量关键在于设示将黑块Ⅰ完全燃烧，使黑块Ⅱ尽可能地着火燃烧。