适用于燃用贫煤1 025 t/h锅炉的中心给粉旋流燃烧器

提出了中心给粉旋流煤粉燃烧器,并针对某厂采用EI-DRB型燃烧器设计燃用贫煤的1 025 t/h锅炉稳燃能力差,不能燃用设计煤质的问题,进行了实验室冷态试验及锅炉冷、热态试验,得出了新型的燃烧器结构,并将下层8只燃烧器改造为新型燃烧器.试验表明,中心给粉燃烧器的回流区最大直径、长度与燃烧器最外层直径之比分别为1.40和1.89,可卷吸足够的高温烟气及时点燃煤粉,得出了外二次风叶片角度、一次风量、二次风量及三次风对燃烧器出口射流的影响规律;在实际运行参数下,EI-DRB型燃烧器没有回流区,不利于稳定燃烧.得出了二次风挡板开度和给粉机转数对燃烧器出口处温度场的影响规律.采用新型燃烧器后,锅炉效率提高,当电负荷降至140 MW时,锅炉可以不投油稳定运行,在燃用贫煤、无烟煤和贫煤的混煤时(混合比为11),锅炉在高负荷和低负荷下均可稳定运行.锅炉NOx排放下降.     

Observation of coal fragmentation in early stages of combustion

Measurements of coal fragmentation in the early stages of combustion were undertaken in the size range of crushed coals for Chinese Dongjin and Indonesian Roto coals. A flat flame burner fed with a premixed mixture of methane, air and partly hydrogen was used for the burning of a single coal particles. A high speed video camera system was used for the observation of coal fragmentation during approximately 80 msec. Fragmentation is consistently observed in the controlled combustion environment over a gas flame temperature range of 1220K–1320K. The data indicate that a single coal particle often disintegrates into two, three, and sometimes more fragments. The dominant mechanisim of fragmentation is that producing two fragments in primary fragmentation. The Dongjin coal breaks up more extensively than the Roto coal with the frequency of fragmentation exhibiting a strong particle size dependence and a weaker gas flame temperature dependence. The mean time of primary fragmentation for the Dongjin coal falls to between 10 msec and 20 msec and does not remarkably vary with particle size and gas flame temperature. The mean time of primary fragmentation for the Roto coal is strongly dependent on the particle size, whilst shows less gas flame temperature dependence.     

四角切圆锅炉炉内煤粉燃烧过程数值模拟

利用计算流体动力学软件PHOENICS 3.5对一台200 MW四角切圆水平浓淡燃烧煤粉炉进行数值模拟研究,采用多流体两相流动模型及煤粉燃烧综合模型,计算得出在垂直方向不同二次风风量分布的工况下,炉内各截面处的烟气温度、燃料浓度、燃烧产物组分浓度以及炉内辐射热流的分布。结果表明,在燃烧器出口处出现了高煤粉浓度和烟气高温区,并出现气固两相分离的现象,使得煤粉着火及时,燃烧器区域维持较高温度,并防止水冷壁结渣,炉内温度、炉膛出口氧量和飞灰可燃物的计算结果和试验结果相比,吻合较好。二次风分级配风工况下,下部燃烧器区烟气温度升高,但氧气推迟混入,相应位置飞灰可燃物有所增加。计算模型能够合理地模拟水平浓淡煤粉气流在大型锅炉炉膛内的燃烧过程,适用于运行工况的优化和炉内污染物的控制。     

Combustion characteristics of anthracite in a vertical cyclone combustor

Isothermal, gas combustion and coal tests were undertaken in order to characterise a vertical cyclone combustor for burning anthracite. Inert particles (alumina cement) were used during the first two series of tests, in order to characterise chamber temperatures, material collection efficiencies and size distribution of particles. Mixture ratios from 0.4 up to 1.6 were tested in steps of 0.2. Under isothermal conditions, an optimum penetration length of vortex finder into the combustion chamber was found to be approximately 10% of the chamber length. The highest temperature can be obtained in the lower section of the combustion chamber both in gas and in coal combustion. The collection efficiency of the cyclone combustor in the various modes of operation was found to be excellent. For coal tests, mixed firing with coal and gas was adopted to sustain the flame in the combustor. The mixed fuels investigated here contain 60, 70 and 80% by mass of coal, and the 70% case was found favorable in the context of carbon burnout and collection efficiency.     

Simplified Modeling of Deflagration in Vessels

A simplified method that models the deflagration process occurring in closed or vented vessels is described. When combustion occurs within the spherical or cylindrical vessels, the flame moves spherically or segmentally to the vessel periphery. The volume and area of each element along the propagating flame front are calculated by using simple geometrical rules. For instabilities and turbulence resulting in enhanced burning rates, a simple analysis results in reasonable agreement with the experimental pressure transients when two burning rates (a laminar burning rate prior to the onset of instability and an enhanced burning rate) were used. Pressure reduction caused by a vent opening at predetermined pressure was modeled. Parameters examined in the modeling include ignition location, mixture concentration, vented area, and vent opening pressure. It was found that venting was effective in reducing the peak pressure experienced in vessels. The model can be expected to estimate reasonable peak pressures and flame front distances by modeling the enhanced burning rates, that is, turbulent enhancement factor.     

1#锅炉房锅炉煤层燃烧工况优化

通过对1#锅炉房锅炉燃烧布置工况的研究,提出了锅炉煤层燃烧布置的优化方式,并根据研究成果提出了锅炉燃烧的改进意见,通过实施提高了锅炉热效率,节约了锅炉煤电消耗,节能效果良好。     

Investigation of a flame holder geometry effect on flame structure in non-premixed combustion

In this paper the effect of flame holder geometry on flame structure is studied. The obtained numerical results using realizable k-? and β-PDF models show a good agreement with experimental data. The results show that increasing in flame holder length decreases flame length and increases flame temperature. Additionally, it is observed that flame lengths decrease by increasing in flame holder radius and increase for larger radii. Furthermore in various radii, the flame temperature is higher for smaller flame lengths. It was found that behavior of flame structure is mainly affected by the mass flow rate of hot gases that come near the reactant by the recirculation zone.     

Modeling of aluminum particle combustion with emphasis on the oxide effects and variable transport properties

A simplified analytical modeling of single aluminum particle combustion was conducted. Ignition and quasi-steady combustion (QSC) were separately formulated and integrated. Both the heat transfer from the hot ambient gas and the enthalpy of heterogeneous surface reaction (HSR) served to cause the particle ignition. Conservation equations were solved for QSC parameters in conjunction with conserved scalar formulation and Shvab-Zeldovich function. Limit temperature postulate was formulated by a sink term pertinent to the dissociation of the aluminum oxide near the flame zone. Effective latent heat of vaporization was modified for the thermal radiation. Ignition and QSC of the aluminum particle were predicted and discussed with emphasis on the effect of the aluminum oxide and variable properties. The model was validated with the experiments regarding ignition delay time, burning rate, residue particle size, flame temperature, QSC duration, and stand-off distance of the envelop flame. Agreement was satisfactory and the prediction errors were limited within 10%.     

Combustion behaviors of wood pellet fuel and its co-firing with different coals

Biomass resources, which are carbon-neutral and sustainable, may help to address climate change and reduce greenhouse gas emissions. This study was performed to examine the effects of wood pellet (WP) particle size, environmental conditions (stoichiometric ratio; SR), and blending ratio on the combustion characteristics of single fuels and blends using a thermogravimetric analyzer and drop tube furnace (DTF). The results indicate that WP demonstrated a higher mass reduction in the devolatilization region and a faster reaction rate compared with coal. Blends tested in the analyzer showed the expected profiles for devolatilization and char oxidation without the presence of non-additive effects. However, the DTF results showed that simultaneous reactive and non-reactive phenomena occurred with increasing biomass-blending ratios. When WP fuel containing fine particles (< 200 μm) was blended with coal under low SR conditions, early-stage oxygen deficiency was caused by rapid combustion. WP fuel containing coarse particles (> 600 μm) showed that unburned carbon (UBC) increased owing to slower reactivity. WP fuel containing particles of 400 μm or less in size demonstrated superior UBC performance, indicating that biomass-coal blends were significantly affected by blending ratio, particle size, and the surrounding environment.

     

基于数字图像处理的火焰长度计算方法

提出了基于计算机视觉和数字图像处理技术的火焰长度计算方法。根据色度学和数字图像处理原理,通过对火焰图像进行阈值分割,去除噪声,寻找火焰边界,计算长度和面积,找出火焰最长值及最长点的坐标。根据火焰长度变化曲线和最长点坐标位置变化曲线,反映出了火焰燃烧的稳定性比较好。     

传统锅炉改流化床锅炉方案设计

从节能和控制污染物排放出发,阐述了流化床锅炉高效洁净煤燃烧技术的优越性及其对煤资源综合利用的意义,针时实例进行了传统锅炉改流化床锅炉方案设计,并分析了改造之后的特点.     

新型智能一体化火焰检测器在FSSS系统中的应用

本文通过分析锅炉炉膛煤粉燃烧火焰的状况,说明了火焰检测系统在锅炉炉膛安全系统中的重要作用。介绍一种新型智能一体化火焰检测器,并对该产品的工作原理、技术性能指标、应用等进行了论述。     

燃煤锅炉烟气脱硫工艺及其自控的探讨

通过对机关燃煤锅炉烟气脱硫技术途径、工艺选择等进行讨论,设计出适合机关采暖锅炉目前现状的烟气脱硫工艺改造方案和工艺流程图,并对其实施的可行性及实施效果进行了探讨。     

基于图像卷积变分自编码的电站锅炉 燃烧稳定性评价方法

为实现基于电站锅炉火焰图像的燃烧稳定性定量表征,并克服不稳定燃烧样本不足的训练难题,提出一种基于卷积变分自编码模型的燃烧稳定性实时、定量表征方法。首先使用稳定燃烧工况下的火焰图像进行模型训练,利用卷积变分自编码器得到稳定燃烧图像的高维潜在概率分布。记录该模型对应的隐变量分布特征,计算该分布与标准正态分布之间的KL散度值,利用该KL散度实现燃烧稳定性的定量表征。在仿真验证中,通过对比说明引入变分推断理论可提高模型对于燃烧图像的重构质量,图片重构前后均方根误差为0.005 48;通过磨煤机给煤量调整实验,人为制造不同稳定度的燃烧器燃烧工况,验证了该评价方法的准确性和有效性,评价准确率高达92.1%;通过与煤火检评价结果的比较,表明该方法具备煤火检系统对于火焰的定量判断功能,且感知能力更加灵敏,能在燃烧器灭火前167 s给出燃烧不稳定的预警,具有一定的工程应用价值。     

Numerical simulation on the erosion wear of a multiphase flow pipeline

The devices in coal chemical industries operate with harsh conditions, involving the high temperature, high pressure, and high concentration of pulverized coal particles. Therefore, leakages or perforations of pipelines occur frequently. In this paper, the numerical prediction on the erosion wear of a coal slurry transmission pipeline was conducted. The dense discrete phase model-kinetic theory of granular flow (DDPM-KTGF) and a modified erosion model were adopted to calculate the particle trajectories and erosion rates. In the numerical calculation, the erosion rate curve of 1Cr9Mo steel obtained in the experiments is incorporated into the erosion model. The results showed that the regions with high erosion risks predicted by the modified erosion model were in agreement with the experimental results. Then, the calculation method is validated. It is also found that the particle movements involve partial agglomeration under the drag of centrifugal force and the secondary flow, when they pass through the elbow. Larger particles are prone to impact on the back of the bend, which has more pronounced effect on the erosion wear. The positions of the maximum erosion rate on all the elbows were discussed, which provides a reference for the inspection on the wall thickness of pipeline.     

基于彩色相机的运动燃煤颗粒温度测量研究

基于McKenna燃烧器的平面火焰携带流燃烧器系统的燃烧环境,采用彩色相机测温系统对运动中的燃煤颗粒进行拍摄。彩色相机测温系统经过黑体炉进行温度测量标定后,利用其r、g波段的响应,采用双色法对燃煤颗粒的温度进行测量。测温系统的标定采用基于BP神经网络训练的方法进行,通过对蜡烛燃烧火焰的拍摄,将得到的颗粒温度与热电偶数据进行对比,验证了测温系统的可靠性。实验研究了燃烧器出口不同距离处燃煤颗粒的温度信息,结果表明,燃煤颗粒温度随颗粒到喷嘴出口距离的变化整体呈先上升后下降趋势。该结果为研究煤粉燃烧过程及着火机理提供了参考。     

MNS煤泥管道输送系统设计研究

为解决煤泥浆的远距离输送和流化床锅炉长期稳定燃烧的问题，一种新型的MNS煤泥管道输送系统研制成功。主要介绍了煤泥管道输送系统的国内外现状，MNS煤泥管道输送系统组成、工艺流程原理以及关键技术设备等。该系统为长期困扰煤炭行业的煤泥综合利用和环境保护问题提供了一条有效的途径，在煤泥高效利用和环境保护方面创造了巨大的社会效益和经济效益。     

燃烧室结构对天然气转子发动机燃烧过程的影响

以一台由端面进气汽油转子发动机改装而来的预混天然气转子发动机为研究对象,在FLUENT软件的基础上通过编程实现转子发动机三维网格的偏心运动,并选择合适的湍流模型、燃烧模型以及详细的CHEMKIN化学反应机理,建立基于化学反应动力学的端面进气天然气转子发动机三维动态数值模拟模型。通过与试验数据进行对比和分析,验证模型的可靠性。在此基础上,研究燃烧室结构对端面进气天然气转子发动机的缸内流场、温度场和中间产物浓度场的影响。结果表明,当燃烧室凹坑布置于转子曲面长度方向的前端和转子曲面宽度方向的中心时,燃烧过程同时利用了燃烧室后部的滚流以及燃烧室中部高速流区对火焰的加速作用,缸内整体燃烧速率最大。同时,其缸内压力最大以及中间产物OH的生成量也最大,其压力峰值比中置凹坑燃烧室提高了19.9%,但其NO质量分数仍在0.5%以内。     

Pressure dependence of mass burning rates in diluent premixed flames of H2/O2 at high pressures

Pressure dependence of mass burning of diluted hydrogen premixed flames is studied numerically over a full range of pressure. Mass burning rate is selected to be a parameter for burning capability of flames. First, positive linear dependence of mass burning rate has been confirmed at low pressures and negative pressure dependence has appeared in the medium range of pressure, which complies with the results reported in previous experimental works. And then, when the pressure range is extended more, positive pressure dependence is recovered or shows up again at high pressures. The flame structures of temperature and species profiles in each pressure regime are demonstrated. They show that the latter two dependences of negative and positive can be explained by enhanced recombination reactions producing HO₂ at high pressures and chain re-branching to OH production via H₂O₂, respectively. There are three distinct dependences of mass burning or global chemistry in hydrogen flames. Two onset pressures, at which pressure dependence changes, depend on equivalence ratio, degree of dilution, diluent species, and unburned-gas temperature. Accordingly, the onset pressure can be used as a parameter characterizing burning of premixed flames.     

DYNAMIC ANALYSIS OF PARTICLE FLYING VELOCITY IN HIGH VELOCITY OXYGEN FUEL SPRAY

0INTRODUCTIONIn thermal spraying process, the flying velocity of the particles is one of the most important factors that control the quality of thermal sprayed coatings［1,2］. The coating deposited by the particles with higher flying velocity is dense and well bonded. Many researchers［1,2］ had identified that the flying velocity of the particles for depositing depends on the velocity and mass rate of flow of a HVOF gun, and the time or length of the particles being accelerated. Based…