蓄热式加热炉内NOx生成的数值模拟

目前蓄热燃烧技术已经在加热炉上广泛应用,但NOx生成机理仍不很清楚。本文以鞍山热能研究院建造的蓄热式加热炉为原型,对低热值煤气蓄热燃烧过程进行了数值模拟。通过比较不同预热温度、不同空气系数、不同空气喷口倾角和不同煤气与空气喷口间距,发现当这些条件改变时,低热值煤气燃烧过程的NOx生成量也随之发生变化。     

用电子计算机进行极值调节

一、问题的提出轧钢厂均热炉生产的一般生产流程如图1。要想在整个加热过程中得到较高的加热速度,就应该经常根据当时的条件去调节煤气和空气,使煤气/空气配比始终处于或接近最佳值。     

用阿牛巴流量计替代孔板流量计带来的经济效益

我厂煤气站空气输送管线上,原设计安装的是孔板流量计对入炉空气进行计量。由于标准孔板的压力损失较大,使空气鼓风机的能耗较大,并且安装也不方便。若采用阿牛巴流量计替代孔板流量计对入炉空气进行计量,就可起到增加空气流量,减少煤气生产的循环时间,增加煤气的产量,减少空气鼓风机的电能     

简易煤气加热炉

我在山西长治锻压机床厂工作时,曾设计制造了煤气加热炉,效果不错,解决了一些生产问题。考虑到我国的能源政策,现介绍给大家参考。一、煤气发生炉煤气发生炉的结构示意图见图1。煤气化的原理是:煤中碳和空气中氧反应生成一氧化碳。煤在煤气发生炉中的气化过程可分成五个区域(参见图1)。     

用于锻造加热炉的自换热烧嘴

自换热烧嘴是英国新发展的最成功的节能烧嘴。其类型有两种,一种以煤气为燃料,另一种以煤气和油为燃料。自换热烧嘴的主要特点是把高速烧嘴、换热器和烟道的功能集为一体,并配有辅助自动控制系统。加热炉废气通过烟道,与助燃空气一起进入一个镍铬合金的同心管式热交换器,废气与助燃空气对向流动,使助燃空气预热。预热     

高炉煤气烧结点火炉的优化设计及生产应用

为节约点火成本、实现高炉煤气的循环利用,将高炉煤气用于烧结机点火炉。文章主要介绍了广西柳钢中金不锈钢有限公司的烧结机点火器采用高炉煤气和天然气三元点火器的设计方案,并辅以低负压点火装置。利用点火料面热辐射+环冷机三段废热气加热空气进行低负压点火,达到了料面点火及节省煤气的效果,使得高炉煤气的基本消耗维持在22.2 m³·t^-1,天然气消耗为0.0 m³·t^-1。     

关于HPF脱硫方法及注意事项的研究

随着经济的发展和科学技术的进步,从20世纪80年代开始,我国在煤气脱硫方面的发展速度十分迅猛。本文着重对煤气脱硫净化展开研究,同时,顺应了我国实现经济循环、发展绿色工业、打造节约型社会的趋势。随着科学技术的发展,我国在原有的基础上优化了煤气脱硫技术,同时,去除了煤气中氨、苯、焦油、萘等有害物质,避免空气受到大范围污染。本文详细阐述了HPF煤气净化脱硫的方法,希望通过本文的研究能够为相关领域的研究提供参考,具有一定的借鉴价值。     

蓄热式燃烧技术——工业炉窑节能降耗的先进技术

目前，国外热处理炉发展趋势是多用电和天然气作能源，而在国内，冶金、机械行业的大量的周期式工作的加热炉和热处理炉，燃料多用煤气或重油，其中低热值煤气(如发生炉煤气等)也占了一部分比重。虽然采用了换热器和轻质筑炉材料等节能措施，在炉体密封、炉体结构方面也做了很多改造，但排烟温度高、空气预热温度低，烟气短路、燃烧不完全等现象     

锻模燕尾回火煤气炉的改进

我厂工具车间锻模生产量很大,每月大约60～70套,原用燕尾回火炉工作时噪音很大,在远离50米的地方也会被它的轰鸣声搅得头昏脑胀、不得安宁。为了减小噪音我们将它改成如图所示的结构。炉子主要由煤气喷嘴、混合室、烧嘴、支承架所组成。煤气的正常压力为200毫米水柱左右,煤气与空气由煤气喷嘴引进混合室,再经混合室上面     

煤气生产中空气鼓风机停车后的操作

分析空气鼓风机停车事故产生的原因,介绍煤气倒流进入炉底鼓风箱,形成爆炸性混合气体的原理。在此基础上,通过建立应急操作规程,以及对设备进行适当改造,在遇到空气鼓风机停车时有效避免炉底或空气管道发生突破甚至爆炸事故。     

An experimental study on combustion efficiency of low grade anthracite in AFBC

This is the basic study to develop a fluidized bed combustion boiler which can use low grade anthracite. In this study, the anthracite of about 3400 kcal/kg was burned in the bench scale non-recycling atmospheric fluidized bed combustor of 200mm diameter and 2215mm height with the static bed height of 250mm and the combustion temperature range of 800–950°C. During the combustion, the effect of factors such as the superficial gas velocity in bed, the air ratio, the coal supply location and the coal particle size on the combustion efficiency, the elutriation ratio and the unburned carbon content both in elutriated ash and in drained ash was thoroughly analyzed. When the superficial gas velocity in bed is 0.7～2.2m/s, the air ratio is 1.0～1.6 and coal supply locations are 300,500 and 700mm above the air distributor, the combustion efficiencies range from 66% to 83.5% for the mean coal particle size of 0.209mm, and from 71% to 88% for the case of 0.265mm. The combustion efficiency decreases as the superficial gas velocity in bed and the air ratio increase. The lower the coal supply location is, the better the combustion efficiency becomes in general.     

The characteristics of pulverized coal combustion in the two stage cyclone combustor

Numerical investigations on air staging and fuel staging were carried out with a newly designed coaxial cyclone combustor, which uses the method of two stage coal combustion composed of pre-combustor and main combustor. The pre-combustor with a high air/fuel ratio is designed to supply gas at high temperature to the main combustor. To avoid local high temperature region in this process, secondary air is injected in the downstream. Together with the burned gas supplied from the pre-combustor and the preheated air directly injected into main combustor, coals supplied through the main burner react rapidly at a low air/fuel ratio. Strong swirling motion of cyclone combustor keeps the wall temperature high, which makes slagging combustion possible. Alaska, US coal is used for calculations. Predictions were made for various coal flow rates in the main combustor for fuel staging and for the various flow rate of secondary air in the pre-combustor for air staging. In-scattering angles are also chosen as a variable to increase residence times of coal particles. Temperature fields and particle trajectories for various conditions are described. Predicted temperature variations at the wall of the combustor are compared with corresponding experimental data and show a similar trend. The in-scattering angle of 20° is recommended to increase the combustion efficiency in the main chamber.     

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。     

Concentration measurement with thermal probe for pulverized coal in the pneumatic pipeline of power plant

The concentration measurement of pulverized coal in a pneumatic pipeline is a challenging issue in power plant. A thermal probe manufactured with abrasion-proof steel was developed for coal concentration measurement in such a situation. The probe generates 15 W of heat. This method is based on the heat transfer between the thermal probe and the gas–solid two-phase flow. Experiments were conducted in a horizontal pneumatic pipeline to assess the accuracy of the thermal probe, where the gas was air and the solid was pulverized coal with mean diameter of 65 µm. The wall temperature of the thermal probe was found to be dependent on both coal powder concentration and air velocity. A new heat transfer correlation was proposed in terms of the modified Reynolds and Nusselt numbers for the gas–solid two-phase flow across the thermal probe. In the range of coal powder concentration from 0.1 to 0.65 kg/kg, the standard deviation is 0.01 kg/kg for the thermal probe. The thermal probe has potential application for concentration measurement of pulverized coal in the pneumatic pipelines of power plants.     

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.     

空气分级炉膛煤粉燃烬模型及实炉试验对比

传统的炉膛分区段传热设计模型忽略了煤粉燃烬计算,适用于非空气分级燃烧。随着空气分级低NOx燃烧技术的普遍应用,在炉膛分区段传热计算中引入煤粉燃烧模型以确定沿炉膛高度燃烬分布,对于提高炉膛上部屏式或辐射受热面蒸汽温度设计准确性有较为重要的意义。建立了改进型分区段传热计算和煤粉燃烧相耦合的空气分级炉膛燃烬和传热模型,对一台空气分级低NOx燃烧锅炉进行了全负荷工况试验,采用该模型对试验工况进行燃烬和传热模拟,得到空气分级锅炉炉膛煤粉燃烧过程的物理图景以及煤粉沿炉膛高度燃尽分布,并研究了燃烧模式和表面反应动力学参数等对燃烬度分布的影响。结果表明,炉膛出口煤粉颗粒燃烬度数值解与大部分测试数据吻合较好,煤粉颗粒燃烧后期灰分引起热退火抑制效应以及炉内局部烟气含氧量分布不均匀是引起模型误差的主要因素,所建立的燃烧和传热耦合模型与传统的炉膛分区段传热模型计算量相当,适合工程应用。     

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.     

煤气流量测量的解决办法

在分析煤气流量测量的困难问题的基础上，提出了采用WZ-2188型超声波气体流量计，着重介绍WZ-2188型超声波气体流量计的工作原理和该仪表的技术特点。     

高压给水空排止回阀特性分析

在讨论宝钢N2 炼钢煤气冷却高压给水系统控制过程的基础上 ,通过空排止回阀系统动态特性试验研究 ,并根据企业节能技术改造实践和现场长期运行使用情况 ,分析了空排止回阀系统的开发应用前景及其社会经济效益     

高浓度粉体气力输送特性试验研究

在高浓度粉体气力输送试验台上,以压缩空气为输送介质,进行了两种粉体(黄沙、煤粉)的高浓度输送试验。试验结果表明,物料输送量和流化罐压力随着流化空气量的增加而增加;流化罐出口物料固气质量比随着流化空气量的增加而减小。试验还得到了物料输送量与流化空气量的关系式。