煤粉在四角切向燃烧煤粉锅炉炉膛内的燃烧行为

本文对煤粉在四角切向燃烧煤粉锅炉炉膛内的燃烧行为进行了数值研究。在计算中,将煤岩学对煤进行分类研究的思路引入燃烧学,对煤粉中所含不同煤岩类别的煤粒分别进行了研究。结果表明,煤粉中的部分难燃组分在炉膛内未能燃烬;炉膛出口处颗粒的浓度存在较明显的偏差,右侧浓度较大,未燃成分较多;煤粉的未燃烬及浓度偏差对四角切向燃烧煤粉锅炉的局部超温爆管现象有直接的影响,且三次风的影响更为严重。     

燃煤过程中多环芳烃污染物生成排放的影响因子研究

区分出影响燃煤过程中多环芳烃有机污染物生成排放的外因条件和内在因素。外因条件包括：锅炉燃烧温度及排烟温度;内在因素包括：炉前煤显微煤岩组成、挥发份及发热量。研究结果为煤燃烧有机污染控制提供了重要的基础信息和理论依据。     

低氧浓度下煤燃烧特性的热重实验研究

煤燃烧的部分过程是在低氧浓度下进行的,本文利用热重实验研究煤在低氧浓度下燃烧特性的变化,重点研究着火特性、燃尽特性和燃烧速率的变化;同时计算分析低氧浓度下,煤燃烧反应动力学参数的变化。实验结果表明,低氧浓度下煤燃烧反应的TG和DTG曲线均向高温区靠近,着火温度基本不变,燃尽温度提高,燃烧速率下降;低氧浓度下燃烧反应的动力学参数活化能E和频率因子k_0之间存在着补偿效应。     

燃煤易挥发微量重金属元素行为的试验研究

为了解煤燃烧过程中易挥发微量重金属元素的行为及其控制因素,对黔西南烟煤和无烟煤进行了层燃实验和流化床燃烧实验。结果表明,层燃实验,煤中Hg在150℃挥发率达50.25％。到815℃几乎全部释放,Se的挥发率平均在98％以上。950℃下煤中As、Sb的挥发率平均为36.77％和34.47％。流化床燃烧,煤中绝大部分Hg以气态排放到大气中,部分Se以气态排放;微细颗粒吸附Hg、Se、As和少量的Sb以吸附态排放。赋存状态、燃烧方式以及燃烧工况等对微量重金属的挥发性有明显的控制作用。     

煤浆燃烧特性的实验研究

一、前言 近年来已有许多学者对煤浆的燃烧特性进行了大量的理论及实验研究。 如黄兆祥、吴忆峰等研究了水煤浆粒度配比对流动性及着火温度的影响;岑可法等将水煤浆燃烧分为蒸发、挥发份析出及燃烧和固定碳燃烧三个阶段;付维标等认为在强迫对流下,随来流速度的增加水煤浆滴着火温度提高,着火时间提前;T.Sakai和M.Saito认为油煤     

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…     

水煤浆滴燃烧过程的简化数学模型

作者以前的工作表明水煤浆滴的燃烧过程可分为水份蒸发、挥发份析出燃烧和焦团燃烧三个有重迭的阶段。本文根据实验数据对这三个阶段进行分析的基础上提出了水煤浆滴燃烧过程的简化数学模型,并与实验结果进行了对照。     

粉尘环境下典型煤岩近红外光谱特征及识别方法

针对煤矿井下近红外煤岩识别中所存在的粉尘问题,采用无烟煤与抑爆剂9∶1混合的混合物模拟煤矿井下粉尘环境,构建了粉尘环境煤岩光谱识别实验装置。为了研究粉尘环境对典型煤岩近红外光谱的影响,从全国各地收集了页岩、砂岩、灰岩3类岩石样本及无烟煤、烟煤、褐煤3类煤类样本的原位典型煤岩试样23个,采集无粉尘情况下的23个煤岩样本表面近红外波段1000-2500nm的反射光谱作为实验标准数据库,分别从实验标准样本库中3类典型煤样本与3类典型岩样本中随机选择1个样本作为实验样本,分别采集测试样本在600, 1 000, 1 500和3 000 mg·m~(-3)粉尘浓度下的近红外波段的反射光谱数据,结果显示:粉尘的加入导致1 000～1 200 nm波段与2 400～2 500 nm波段的光谱图像信噪比降低;随着粉尘浓度的增加,粉尘中的无烟煤的不透明物质使得实验样本中的特征吸收谷减弱;采用光谱角度匹配SAM以及皮尔逊相关系数对试样和标准样本库进行相关性分析,无烟煤类样本、烟煤类样本、砂岩类样本、灰岩类样本在光谱角度匹配SAM匹配模型下有着较高的匹配度,匹配度在各个粉尘浓度下均处于0.9以上;相关系数匹配模型匹配度受粉尘的影响剧烈,平均相关系数为0.73;实验标准数据库及实验样本经SG卷积和SNV标准正态预处理后,预处理后的样本数据库与实验样本光谱角度匹配SAM匹配模型匹配度无明显变化,相关系数匹配模型匹配度显著提升,平均相关系数为0.78;除褐煤2号外,所有的样本光谱相关系数平均提升0.13,无烟煤2号样本各个浓度平均相关系数提升76.3%,而样本12褐煤2号的光谱相关系数经光谱预处理降低。建立光谱角度匹配SAM以及皮尔逊相关系数煤岩识别模型,二值化煤岩样本,煤为"0"岩为"1",通过两种识别模型对不同浓度下的6个实验样本进行煤岩识别,光谱角度匹配SAM的识别准确率P为100%,识别时间为8 ms,皮尔逊相关系数的识别准确率P为87.5%,识别时间为852 ms。     

煤燃烧过程中汞、砷、硒反应机理研究

本文以三种典型煤为对象,测定了煤及灰中汞,砷,硒的浓度,了解了元素的挥发性。对钱家营褐煤进行了不同温度的燃烧实验。测定了在不同温度下燃烧灰中汞,砷,硒的含量变化。将所得实验结果与化学热力平衡分析工具F~*A~*C~*T2.1模拟系统结果相比较。推测了其中可能发生的反应。     

基于拉曼成像的煤岩组分化学结构原位研究

采用显微拉曼面扫描技术对三个典型煤种微尺度下二维平面进行了分析,研究了煤岩显微组分原位定量方法及其化学结构。结果表明:采用本研究提出的拉曼光谱参数可实现煤岩显微组分高质量化学成像,耦合聚类分级方法还可实现显微组分原位识别与定量。煤在微尺度下化学结构非均匀性显著,且随煤阶升高而降低。煤中壳质组小芳香环和杂原子官能团数量最多,化学结构最无序,惰质组相反,镜质组居中。显微组分化学结构随煤阶变化差异明显。     

混煤氮的热解析出特性及燃料NO_x的形成规律

混煤氮的热解析出特性及燃料ＮＯ_ｘ的形成规律邱建荣，马毓义，曾汉才，吕焕尧，喻秋梅（华中理工大学煤燃烧国家重点实验室武汉４３００７４）关键词：混煤，ＮＯ_ｘ，混合比，燃烧。ＥＭＩＳＳＩＯＮＯＦＮＩＴＲＯＧＥＮＣＯＭＰＯＵＮＤＳＡＮＤＮＯ_ｘＦＯＲＭＡＴ?..     

煤粉燃烧火焰辐射光谱实验研究

针对煤粉燃烧辐射光谱问题,利用光纤光谱仪对煤粉平面火焰炉实验装置煤粉燃烧火焰辐射光谱进行了测量,详细分析了煤粉辐射光谱特征,并基于普朗克辐射传热定律,通过对光谱仪波长响应特性的标定,得到火焰绝对辐射强度随波长的分布情况,进而利用最小二乘法获得火焰温度与辐射率参数,由此提出基于煤粉燃烧火焰辐射光谱测量的火焰参数测量方法。利用该方法对不同燃烧条件下煤粉燃烧参数进行测量,开展了不同燃烧参数下煤粉火焰辐射光谱实验研究,研究结果表明：煤粉燃烧火焰辐射在200～1 100 nm波段具有较强且连续的光谱特征,基于普朗克辐射定律与最小二乘法可实现煤粉燃烧火焰温度与辐射率的测量;煤粉燃烧火焰辐射光谱在590,766,769和779 nm附近可见明显的Na和K等碱金属痕量元素原子光谱发射谱线,并且这些原子谱线的出现与火焰温度有关;随着煤粉浓度的提高,虽然燃烧温度变化不大,但由于火焰辐射率的增加,造成辐射光谱强度的大幅提升。这对锅炉煤粉燃烧优化具有重要参考价值。     

Investigation of unburned carbon particles in fly ash by means of laser light scattering

A new optical method to determine the percentage of unburned carbon particles in fly ash from combustion of pulverized coal has been developed. The technique exploits the different properties of particles of ash and coal in the elastic scattering of polarized light.     

基于神经网络的电站锅炉入炉煤粉含碳量在线测量研究

电站锅炉燃烧的煤种来源不稳定,经常与设计煤种偏差较大,造成锅炉出力不足、燃烧效率下降以及结焦等问题出现,影响锅炉燃烧的经济性和安全性。针对锅炉燃烧煤种的不稳定性,提出了一种基于静电法在线测量入炉煤粉含碳量的方法,研究静电信号与煤粉含碳量之间的关系。对煤粉颗粒静电测量过程中的几个影响因素进行了试验分析,并采集了足够具有代表性的数据,在此基础上建立了锅炉一次风管中入炉煤粉含碳量的BP神经网络模型。结果表明,所建立的模型预测效果较好,能较好预测进入锅炉燃烧的煤种。     

Experimental and modeling study of H2S formation and evolution in air staged combustion of pulverized coal

High-concentration H₂S formed in the reduction zone of pulverized coal air-staged combustion can result into the high temperature corrosion of water wall tube of boiler, so it is of great importance to accurately predict H₂S concentration for the safe operation of boilers and burners. H₂S formation and evolution depends on two steps: the sulfur release from coal conversion and gas-phase reactions of sulfur species. In this study, the sulfur release characteristics from the pyrolysis of 17 coals, including 5 lignite, 9 bituminous coals and 3 anthracites, are investigated in a drop tube furnace (DTF). Sulfur release model is developed to describe the relationship between sulfur release and coal types. A global gas-phase reaction mechanism of sulfur species composed of ten reactions is used to calculate and predict the formation and evolution of H₂S, COS and SO₂ in the reduction zone of pulverized coal air-staged combustion. A wide range of air-staged combustion experiments of 17 coals are conducted in the DTF at different temperatures and stoichiometric ratios to validate the developed model. The results show that the prediction errors of sulfur species, including SO₂, H₂S and COS, are within ± 30%, which indicates that the developed prediction model of sulfur species is of great assistance for CFD modeling of actual engineering application.     

Spherical turbulent flame propagation of pulverized coal particle clouds in an O2/N2 atmosphere

The present study aims to clarify the effects of turbulence intensity and coal concentration on the spherical turbulent flame propagation of a pulverized coal particle cloud. A unique experimental apparatus was developed in which coal particles can be dispersed homogeneously in a turbulent flow field generated by two fans. Experiments on spherical turbulent flame propagation of pulverized coal particle clouds in a constant volume spherical chamber in various turbulence intensities and coal concentrations were conducted. A common bituminous coal was used in the present study. The flame propagation velocity was obtained from an analysis of flame propagation images taken using a high-speed camera. It was found that the flame propagation velocity increased with increasing flame radius. The flame propagation velocity increases as the turbulence intensity increases. Similar trends were observed in spherical flames using gaseous fuel. The coal concentration has a weak effect on the flame propagation velocity, which is unique to pulverized coal combustions in a turbulent field. These are the first reports of experimental results for the spherical turbulent flame propagation behavior of pulverized coal particle clouds. The results obtained in the present study are obviously different from those of previous pulverized coal combustion studies and any other results of gaseous fuel combustion research.     

The effects of oxygen concentration and gas temperature on coal stream ignition and particle surface temperature in reducing-to-oxidizing environments

In the near-burner region of pulverized coal burners, two zones exist, with very different oxygen concentrations. The first zone is a locally reducing environment, caused by the fast release of volatiles from a region of dense coal particles, and the second zone, which is surrounding the first zone, is a hot oxidizing environment. The transition of coal particles from the reducing zone to the oxidizing zone affects early stage coal combustion characteristics, such as devolatilization, ignition and particle temperature history. In this work, we used a two-stage Hencken flat-flame burner to simulate the conditions that coal particles experience in practical combustors when they transition from a reducing environment to an oxidizing environments. The composition of the reducing environment was chosen to approximate that of a typical coal volatile. Three oxygen concentrations (5, 10 and 15 vol%) in the “ambient” oxidizing environment were tested, corresponding to those at different distances downstream from a commercial burner. The corresponding gas temperatures for the oxidizing environments were adjusted for the different oxygen concentrations such that the “volatile” flame temperatures were the same, as this is what would be expected in a commercial combustor. High speed videography was used to obtain the ignition characteristics, and RGB color pyrometry was used to measure particle surface temperatures. Two different sizes of coal particles were used. It is found that when particles undergo a reducing-to-oxidizing transition at high temperatures, the particles are preheated such that the critical factor for ignition delay is point at which the particle is in the presence of oxygen, not the concentration of oxygen. The ignition delay of large particles is found to be 53% longer than that of small particles due to their higher thermal mass and slower devolatilization. The oxygen concentration in the ambient have a negligible effect on early-stage particle temperatures.     

涡旋燃烧炉流动、传热和燃烧特性的研究

本文应用强旋湍流气一固两相流动和煤粉燃烧的数学模型，对新型涡旋燃烧炉内的流动、传热和燃烧过程进行了系统的模拟和分析，得到了与实验相符合的结果。结果表明，涡旋燃烧炉内的湍流空气动力场分布具有强旋、回流和正在发展流的特点。水冷壁总吸热量随燃烧热负荷的增大成比例地增加。煤粉颗粒在炉内的平均停留时间随初始粒径的增大而加长。炉内可实现煤粉的低温、强旋、高效率和高强度燃烧。     

Investigating particle and volatile evolution during pulverized coal combustion using high-speed digital in-line holography

Devolatilization is an important process in pulverized coal combustion because it affects the ignition, volatile combustion, and subsequent char burning and ash formation. In this study, high-speed digital in-line holography is employed to visualize and quantify the particle and volatile evolution during pulverized coal combustion. China Shanxi bituminous coal particles sieved in the range of 105–154 µm are entrained into a flat flame burner through a central tube for the study. Time-resolved observations show the volatile ejection, accumulation, and detachment in the early stage of coal combustion. Three-dimensional imaging and automatic particle extraction algorithm allow for the size and velocity statistics of the particle and stringy volatile tail. The results demonstrate the smaller particle generation and coal particle swelling in the devolatilization. It is found that the coal particles and volatiles accelerate due to the thermal buoyancy and the volatiles move faster than the coal particles. On average, smaller particles move faster than the larger ones while some can move much slower possibly because of the fragmentation.