高风温技术在迁钢高炉上的应用

通过历年我国钢铁企业、宝钢和首钢风温变化,反映了我国近年的风温现状和技术进步,特别指出了首钢风温的巨大进步。从热风炉高风温、热风管道输送高风温和高炉接受高风温三方面介绍了高风温技术研究进展。通过高风温技术在迁钢2号高炉的应用,首钢在2008年高风温试验基础上,2009年取得重大突破,实现日均风温最高1283℃,连续4月月均1270℃以上风温,年均风温为1258.7℃。通过分析2008和2009试验风温均匀性,表明风温均匀指数有所提高。并分析了热风炉炉顶温度、混风、空煤气预热温度、操作制度等风温影响因素,从高炉原燃料、技术指标和操作方面,阐述了高风温在高炉使用情况,反映了高风温受热风炉系统、热风管道和高炉等因素制约。提出了本次高风温试验存在的风温潜力、高风温节能作用和风温稳定性等问题,为进一步高风温研究提供指导。     

大容量电站锅炉过热器再热器温度偏差原因及防止对策

本文分析了电站锅炉过热器、再热器发生超温爆管的各种原因,并提出了防止汽温偏差过大的对策。文中总结了多年来在解决电站锅炉过、再热器超温方面的科研成果,并列举了若干国产及进口大容量电站锅炉过、再热器超温爆管问题的实例及解决办法。     

623℃超超临界锅炉高温受热面壁温监测优化实践

田集发电厂二期工程开展了高温受热面壁温校核计算、末级再热器出口集箱T92管接头过渡段壁温监测和分析、实施高温受热面壁温在线监测系统等壁温监测优化实践,为锅炉在再热蒸汽温度623℃下安全、可靠和经济运行提供了保障。     

有隔热涂层的气膜冷却火焰筒壁温计算

对薄壁火焰筒,给出了壁温计算模型和计算方法,应用该方法进行了某环管型燃烧室火焰筒壁温计算,查找了该燃烧室火焰筒一次主燃孔出现裂纹的原因,并研究了气膜冷却、隔热涂层及其厚度对壁温径向和轴向分布的影响.结果表明:火焰筒最高壁温946℃,符合火焰筒对最高壁温的设计要求;火焰筒一次主燃孔附近壁温分布梯度较大,是热应力易集中的地方,为查找火焰筒故障原因提供了依据;气膜冷却和隔热涂层能显著降低火焰筒壁温,有效改善壁温径向和轴向分布;隔热涂层厚度对火焰筒壁温影响很小.     

论新型减温减压装置中减温系统的优越性

减温减压装置是用来将新蒸汽压力、温度降低到用户所需要的蒸汽参数的一种专用装置。旧型减温减压装置采用的是给水分配阀、节流装置、喷嘴等组合结构形式的减温系统 ,存在着许多的弊端和不足之处。经分析研究 ,重新设计开发了一种新型喷水调节阀式减温系统 ,完全取代了旧型系统 ,具有高可调比、低泄漏量、管路简单、可调压差范围大等优点。通过对旧型与新型减温系统工作原理及特点的比较 ,阐述了新型减温系统的优越性。     

300MW CFB锅炉床温和床压的控制

介绍了300MW CFB锅炉床温、床压控制的必要性,阐述了影响床温、床压变化的因素,重点论述了床温、床压高低的控制方法,从而为锅炉更加安全、稳定和经济运行提供了可靠的保证.     

巴基斯坦某电厂温排水对水域的影响程度分析

为研究电厂温排水对水域的温升影响,以巴基斯坦某火电厂下游温排水工程为例,应用水动力与输移联合数学模型建立了以非结构网格为基础的河道区域地形文件,对温排水运动的流场和温度场进行了二维数值模拟,获得了水面线、流速、温升影响范围、温升线沿岸扩散长度及包络面积,并与模型试验结果进行了对比验证。结果表明,该模型可正确地模拟温排水的流场并准确预测温排水对水域的影响。     

350MW机组锅炉水平烟道烟温偏差调整试验

本文分析了四角切圆燃烧水平烟道烟温偏差的成因，针对宝钢自备电厂2号锅炉三再超温爆管现象，通过燃烧调整，使二再、三再出口烟温偏差得到了明显改善，降低了水平烟道热力不均匀性，使再热器恢复汽温运行成为可能。     

低低温电除尘器运行优化策略研究及应用

为解决现有低低温电除尘技术煤种适应性弱、低温腐蚀风险高的问题,研究了一种利用燃煤机组低低温电除尘器低温腐蚀因子来判断除尘设备发生低温腐蚀概率的方法,结合对烟气酸露点和亚微米颗粒物控制的研究,提出了基于最佳运行烟温范围的低低温电除尘器运行优化控制策略,提升了低低温电除尘器对全粒径颗粒物的脱除效果.将该策略应用在浙能嘉兴电...     

对流过热器与再热器的汽温偏差对烟温偏差的敏感性研究

在大型电站锅炉中,烟道内烟温偏差是影响过热器与再热器系统汽温偏差的主要因素之一,因而在设计与运行过程中颇受关注。该文从理论上建立了对流过热器和再热器的出口汽温偏差与其进口烟温偏差之间的关系,据此分析了汽温偏差对烟温偏差的敏感性以及减小过热吕与再热器系统汽温偏差的措施。     

The demand function for residential heat through district heating system and its consumption benefits in Korea

The demand for residential heat (RH) through a district heating system (DHS) has been and will be expanded in Korea due to its better performance in energy efficiency and the abatement of greenhouse gas emissions than decentralized boilers. The purposes of this paper are two-fold. The first is to obtain the demand function for DHS-based RH in Korea and investigate the price and income elasticities of the demand employing the quarterly data covering the period 1988–2013. The short-run price and income elasticities are estimated as −0.700 and 0.918, respectively. Moreover, the long-run elasticities are −1.253 and 1.642, respectively. The second purpose is to measure the consumption benefits of DHS-based-RH employing the economic theory that they are the sum of the actual payment and consumer surplus for the consumption. Considering that the average price and estimated consumer surplus of the DHS-based RH use in 2013 are computed to be KRW 87,870 (USD 84.1) and KRW 62,764 (USD 60.1) per Gcal, the consumption benefits of the DHS-based RH are calculated to be KRW 150,634 (USD 144.2) per Gcal. This information can be beneficially utilized to conduct an economic feasibility study for a new DHS project related to RH supply.     

Hydrogen permeation across super‐thin membrane and the burning limitation in low‐temperature proton exchange membrane fuel cell

Hydrogen permeation across the membrane is unavoidable in proton exchange membrane fuel cells, especially for super‐thin membranes, which lowers the open‐circuit voltage and could even be a safety concern. In this paper, hydrogen permeation across two membranes (25‐um‐thick Nafion^® 211 and 18‐um‐thick reinforced composite membrane) are evaluated at various temperatures, relative humidity (RH), and gas pressure differences between the anode and cathode. The results indicate that the hydrogen permeation rate in both membranes increases almost exponentially with temperature and linearly with pressure differences. Compared with RH, the effects of temperature and pressure differences are more crucial to hydrogen permeability. However, the effect of RH on the hydrogen permeation is quite complicated. The permeability exhibits a minimum value at intermediate RH (approximately 40% RH) for both applied membranes. The permeability of Nafion^® 211 appears more sensitive to RH than that of reinforced composite membrane at elevated temperature. Copyright © 2013 John Wiley & Sons, Ltd.     

侧底复吹RH真空精炼中均混特性的物理模型研究

基于相似原理,建立了几何相似比为1：5的水模型,对RH精炼过程钢液循环流动行为进行研究。考察了提升气体流量、真空度、不同吹气方式以及不同形状的浸渍管对混匀时间的影响规律。结果表明：均混时间随吹气量增大先减小后增大,随真空度增大而减小。在相同吹气流量下,单独采用侧底复吹方式或单独采用椭圆形浸渍管,均混时间减小。     

Research on electrochemical impedance spectroscope behavior of fuel cell stack under different reactant relative humidity

The reactant relative humidity (RH) is a key parameter to keep a suitable water content in the large active area fuel cell. Electrochemical impedance spectroscopy (EIS) is one of the effective methods to identify the water state within the membrane. In this work, the EIS behavior of fuel cell stack under different reactant RH and current density is investigated. Both the whole stack and individual cell impedances are experimentally measured. The internal reactions of the stack and individual cells with different current densities and different reactants RH can be distinguished by impedances. Based on the experiment results, the low frequency impedance has a greater variation than high frequency impedance when the reactant RH changes. And the impedance is more sensitive to the reactant RH under low current density. With the current density increases, the internal self-humidification can be realized to obtain a good performance for large area fuel cells.     

南京城区可吸入颗粒物日变化特征及物理特性

采用电称低压冲击器(ELPI)对南京城区可吸入颗粒物的粒径分布和数密度进行了连续监测,得到了可吸入颗粒物的日变化特征和物理特性,数据分析表明南京城区物质燃烧产生的可吸入颗粒物占有较大比例,其中PM2.5数密度高,占有较大的表面积份额.结合气象参数进一步分析表明,相对湿度小于7000/时,各级颗粒物的数密度随相对湿度增大而升高,可吸入颗粒物总的数密度也相应升高;相对湿度大于7000/时,细颗粒物数密度随相对湿度的增大逐渐降低,粗颗粒数密度则逐渐升高,而可吸入颗粒物总的数密度逐渐降低.     

Electrochemical analysis of polymer electrolyte membrane fuel cell operated with dry-air feed

Electrochemical analysis of a commercial polymer electrolyte membrane fuel cell (PEMFC), operated at varying cathode relative humidity (RH) and current density, has been conducted to understand the factors that affect power performance when the PEMFC is operated with a dry-air feed. With a change in the cathode RH from 80 to 4%, the electrochemical area and double-layer capacitance of the cathode are reduced by 9 and 8%, respectively. This indicates that exclusion of the catalyst layer (CL) of the cathode from proton access occurs to some extent at low RH. It does not, however, explain the observed increase in activation loss. For the dry-air feed, the ionic resistances of the membrane and cathode CL are comparable in magnitude. Impedance analyses show that drying of the cathode at low RH and low current density leads not only to an increase in the ionic resistance of the CL, but also to increases in both charge-transfer and mass-transfer resistances. The simultaneous decrease in all the resistance components with decrease in the air permeability of the cathode diffusion layer highlights the importance of cathode design for operation with dry-air feed.     

The effect of through plane pore gradient GDL on the water distribution of PEMFC

The effect of through plane pore gradient of gas diffusion layer (GDL) on the performance of Polymer Electrolyte Membrane Fuel Cell is investigated experimentally. The performance with GDLs having no, medium and high pore gradient are compared at 2 different relative humidity (RH) conditions. The medium pore gradient GDL shows generally the best performance in both RH conditions. The performance difference is analyzed based on the water distribution. The water distribution is measured through the X-ray visualization. The amount of water is reduced with the pore gradient GDL. This change reduces the concentration over-potential, and thereby increases the performance at high RH condition. However, the reduction of liquid water results in dehydration of the membrane at low RH condition. This makes lower performance with high pore gradient. The highest performance is not matched with the highest pore gradient. The effect of pore gradient is distinct when water exists sufficiently.     

某电厂600MW亚临界锅炉末再管屏变形分析

从某电厂末级再热器管屏变形受损情况入手,简要介绍了600MW亚临界锅炉末再管屏的结构特点,并基于管屏的结构特点,深入分析了其在正常运行及启停炉过程中的热膨胀机理,阐明了该电厂锅炉末再管屏变形的原因及处理结果.     

Design and thermodynamic analysis of supercritical CO2 reheating recompression Brayton cycle coupled with lead‐based reactor

A reheating process is generally incorporated in a supercritical CO₂ (S‐CO₂) Brayton cycle to enhance its efficiency. The heat transfer process from the reactor coolant to the working fluid of the power cycle is a key issue encountered when designing reheating power systems for the lead‐based reactor. The traditional reheating system, called RH‐1, utilizes an intermediate coolant circuit. In this paper, a novel reheating system, called RH‐2, is proposed. It eliminates the intermediate coolant circuit and combines the processes of the primary heating and reheating in a single heat exchanger. A thermodynamic analysis of three different systems for the lead‐based reactor integrated with the S‐CO₂ power cycle with or without reheating was conducted to evaluate the performance of the proposed system. The results confirmed that the performance of RH‐2 was the best of all the three systems. Under the same reactor conditions, the system efficiency of RH‐2 was greater than those of RH‐1 and the recompression (no reheating) system by 1.2% and 1.7%, respectively. RH‐2 could also maintain higher efficiency when the main operating parameters varied. The efficiency of RH‐2 was higher at different core outlet temperatures and split ratios. The maximum efficiency at optimal maximum pressure of RH‐2 was greater than those of the other two systems. RH‐2 was less sensitive to the variations in the isentropic efficiencies of the components than the other two systems, while the turbine isentropic efficiency demonstrated a significantly higher impact on the system efficiency than the two compressors (approximately 3.8 times).     

Numerical analysis on transport properties of self-humidifying dual catalyst layer via 3-D reconstruction technique

Developing a fuel cell model with fundamental structural properties such as distribution of pore size, geometrical network of individual phase, and volume-specific interfacial area are critical in evaluating the accurate cell performance. Therefore, herein, by Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) tomography, three-dimensional (3-D) microstructure of CLs is reconstructed from two real-time samples: (i) High tortuosity humidifying catalyst layer (HTH CL) and (ii) standard catalyst layer. From the reconstructed microstructure, water imbibition behavior at different levels of capillary pressure is simulated and the effective transport properties such as gas permeability, gas diffusivity, surface area and water permeability are derived as well. By coupling the effective structural and transport properties, a 2D model is developed to predict the performances of the two CLs, at relative humidity (RH) levels of 20% and 100%. Since the effective transport properties are derived from real-time samples, this 2D model is expected to have a greater accuracy in predicting the fuel cell performance. Finally, the mechanism of self-humidifying MEA at lower and higher RH conditions (20% RH and 100% RH) is demonstrated as a function of liquid water saturation in the cathode CL and water dry-out in the anode CL.