回转式空气预热器传热元件阻力特性试验研究

回转式空气预热器的阻力特性是决定空气预热器转子尺寸的主要依据之一.回转式空气预热器的阻力特性主要受传热元件结构参数影响.试验利用大型传热风洞试验系统,在模拟回转式空气预热器实际运行工况条件下,通过测量试验段整包传热元件压降,得到了传热元件摩擦因子对数与雷诺数对数之间相互关系,为空气预热器数值计算提供基础数据.通过不同类...     

回转式空气预热器换热性能在线监测

以燃煤机组三分仓回转式空气预热器为研究对象,提出一种受热面换热性能在线监测方法。基于微元传热分析,计算流经空气预热器的烟气和空气温度分布,在此基础上利用能量衡算估计一次风和二次风漏风量。再由空气预热器进出口烟气与空气宏观能量平衡关系计算烟气放热量,进而得到空气预热器传热系数来表征受热面积灰程度。仿真结果表明:在线监测结果能满足需求。     

四分仓回转式空气预热器三维数值分析

针对四分仓回转式空气预热器实际运行中存在的低温腐蚀问题,基于CFD软件Fluent,将转子受热面温度定义为用户自定义标量(UDS)并求解标量方程,建立了四分仓回转式空气预热器的传热三维数值模型.以某300 MW循环流化床锅炉的四分仓空气预热器为例,模拟得到工质和受热面的三维温度分布,分析了转子热段和冷段受热面传热性能存在差异的原因.结果表明:受热面板型和板材的不同是造成热段、冷段受热面传热性能和传热量差异的主要原因;右二次风仓的热段入口处受热面是发生低温腐蚀的危险区域,使其壁温高于酸露点可有效减缓低温腐蚀.     

基于有限差分的二分仓回转式空气预热器热力计算

将二分仓回转式预热器沿转速方向周向展开,在蓄热元件单元和流体之间划分网格,通过建立每一有限单元内流体和蓄热单元热平衡方程及漏风量计算,并利用改良的高斯塞德尔迭代方法进行二分仓回转式空气预热器传热性能数值计算程序.整个计算过程采用FORTRAN程序语言,实现了耦合漏风计算在内的二分仓回转式空气预热器内蓄热元件金属温度场及烟空气温度场以及漏风的计算.     

三分仓回转式空气预热器传热的数值解法

根据回转式空气预热器的工作机理,通过理论分析,把金属蓄热元件视为某一假想的流体,将非稳态传热与金属蓄热元件的机械运动等同于稳态换热过程,采用控制容积法建立了回转式空气预热器的流体动力学传热微分方程组与对应的差分方程组,详细给出了数值解法的计算过程,并以某220 MW锅炉机组的三分仓冷、热分段回转式空气预热器为例,结合实际运行参数进行了校核热力计算.结果表明:该数值解法合理、收敛快且具有合理的计算精度,可以得到空气预热器运行中金属蓄热元件、烟气与空气的温度分布;经与实际运行参数校核,与设计工况参数较吻合.     

三分仓空气预热器热力计算的研究

给出了回转式三分仓空气预热器传热计算的模型和求解方法，并定义了三分仓空气预热器的传热系数和温压，屏蔽了空气预热器转子热容，给出了不涉及转子本身热参数的计算方法。该方法不仅有足够的传热计算精度．更适于三分仓空气预热器的积灰状态在线实时监测。同时分析了转子单位时间热容X，对三分仓空气预热器传热的影响。图5表2参5     

回转式空气预热器低温段传热元件阻力特性试验研究

试验利用大型传热风洞试验系统,在模拟回转式空气预热器实际运行工况条件下,通过测量试验段传热元件压降,得到了回转式空气预热器低温段搪瓷波纹板和陶瓷平板2种传热元件摩擦因子对数与雷诺数对数之间相互关系,为两类传热元件阻力特性数值计算提供了基础数据。通过具体实验数据对比分析,得到了陶瓷平板阻力是搪瓷波纹板3～4倍的试验结果,为低温段传热元件的优化选取提供了依据。     

2种热风循环方式对回转式空气预热器传热元件壁温和堵灰的影响分析

基于对回转式空气预热器的性能计算,分析了3.5分仓空气预热器方式和设置封闭热风再循环分仓方式空气预热器的循环热风进入空气预热器转子后的温度变化情况和传热元件壁温的变化情况,得出2种方案都只能有限提高空气预热器冷端局部深度的壁温,在超出一定深度后传热元件壁温反而会下降,导致硫酸氢铵凝结堵灰区向空气预热器热端移动,因而不能解决空气预热器堵灰问题的结论.同时也指出,2种方式均存在导致空气预热器传热量下降的问题.最后给出了几点治理空气预热器堵灰的建议.     

三分仓回转式空气预热器积灰分段监测模型研究

针对三分仓回转式空气预热器热段和冷段积灰分段监测的需求,基于空气预热器的传热模型,定义空气预热器利用系数作为清洁因子并建立积灰分段监测模型.通过分析空气预热器实时运行参数,根据热平衡原理确定了清洁因子计算步骤.以某1 000MW超超临界直流锅炉的三分仓回转式空气预热器为例,研究了热段、冷段清洁因子在空气预热器积灰和吹灰时的变化趋势.结果表明:根据所建模型计算出的分段清洁因子变化趋势在稳定负荷下能够反映此空气预热器的分段积灰情况,而在变负荷情况下虽有一定偏离,但由于电厂变负荷工况下很少吹灰故影响较小;该积灰监测模型可作为三分仓回转式空气预热器热冷分段积灰监测的有效手段.     

电站锅炉回转式空气预热器低温腐蚀研究

电厂燃煤含硫,易造成回转式空气预热器低温腐蚀。依据燃料工业分析得到的煤质成分计算出烟气中SO3浓度和酸露点温度,并依据SCR脱硝装置中SO2催化氧化转化率对酸露点温度进行修正。根据换热器传热计算原理计算出空气预热器冷段入口壁面平均温度和壁面最低温度,据此分析空气预热器的腐蚀情况,并调整配煤降低酸露点温度,保护空气预热器,提高锅炉效率,降低运行费用。     

三维内肋管管式空气预热器的设计与可行性研究

采用强化传热性能优良的新型三维内肋管与传统热能力强、漏风系数小的热管双级布置的方案对300MW电站锅炉机组空气预热器进行了优化设计和可行性研究。空气预热器总的漏风系数设计值为5％,加热一、二次风的上级三维内肋管卧式空气预热器的布置空间分别为螺纹管空气预热器的64．46％和47．87％,相应的受热面积为42．61％和37．32％,这有效地解决了回转式空气预热器漏系大,以及一航管式空气预热器体积庞大、难以布置的问题。     

Analysis and application of variable conductance heat pipe air preheater

The heat transfer analysis of variable conductance heat pipe air preheater was carried out. The temperature trans-fer matrix was obtained for the air preheater that comprises several discrete heat transfer units with same or different heat transfer surface area in a parallel or counter flow mode. By using the temperature transfer matrix, the outlet fluid temperatures could be easily calculated for a given air preheater and inlet fluid temperatures. The active length of condenser in a variable conductance heat pipe is determined according to the flat interface model. With the same initial conditions, the comparisons between variable conductance heat-pipe air preheater and regular heat pipe air preheater has been analyzed and tested in terms of heat pipe wall temperature, heat transfer surface area and outlet fluid temperatures. Based on the real industrial applications, it has been confirmed that the variable conductance heat pipe air preheater has excellent performance of anti-corrosion and anti-ash-deposition especially at the variable working condition and the sulfur coal (5%-6% mass fraction of sulfur) condition.     

延迟焦化装置空气预热器水热媒节能改造

克拉玛依石化公司150×104t/a延迟焦化装置加热炉热管空气预热器存在露点腐蚀和快速失效的问题,分析其原因和北方冬季严寒的天气条件有关:尽管烟气外排温度高于露点温度,但烟气侧底部热管管壁温度低于露点温度。对此,提出了采用水热媒技术的解决方案。实际改造过程中,为降低投资成本并满足除氧水系统压力的要求,采用了扰流子水热媒组合式空气预热器。改造完成后,烟气外排温度从改造前的234℃降低到152℃,降低了82℃;热空气温度从改造前的100℃升高到256℃,升高了156℃;热效率从改造前的87.35%提高到90.74%,提高了3.39个百分点;多回收烟气余热1901.31kW,每年节能54.76GJ,节约燃料费用121.3万元。该技术的成功应用,彻底解决了热管空气预热器存在的露点腐蚀和快速失效问题,可以保证装置长周期高效运行。     

Analysis and Application of Variable Conductance Heat Pipe Air Preheater

The heat transfer analysis of variable conductance heat pipe air preheater was carried out. The temperature trans-fer matrix was obtained for the air preheater that comprises several discrete heat transfer units with same or different heat transfer surface area in a parallel or counter flow mode. By using the temperature transfer matrix, the outlet fluid temperatures could be easily calculated for a given air preheater and inlet fluid temperatures. The active length of condenser in a variable conductance he...     

节能技术在新建芳烃联合装置中的应用

新建芳烃联合装置中节能技术被广泛应用:热联合技术将高温塔的塔顶和塔底物料作为低温塔的再沸热源,实现热源的联合应用,充分确保了低温热的二次利用,并且节约燃料和占地面积;传热效率更高、结构更紧凑的纯逆流板式换热器,换热效果突出,加热炉负荷显著降低;旨在预热空气、提高加热炉燃烧效率的烟气余热回收系统的应用,保证了每台加热炉热效率在90%以上,其板式空气预热器具有阻力小、不易积灰、结构紧凑、使用寿命长的优点;选用乙苯脱烷基型催化剂,乙苯单程转化率高(在70%以上),装置内部二甲苯循环量减少,从而降低了二甲苯分馏、吸附分离和异构化单元的规模,相应装置投资及能耗也得到一定程度的降低,其能耗比乙苯异构型催化剂的平均能耗降低5%左右;高效机泵、变频风机、高性能塔盘和精细控制系统的广泛应用,也是该装置的主要节能手段。     

椭圆扭曲管内数值模拟及其在热风炉空气预热器的节能应用

热风炉空气预热器是纳米碳酸钙生产过程中重要的节能设备,可以降低排烟温度,提高能源利用率。目前广泛采用的光滑圆管空气预热器体积庞大,换热效率低,造成排烟温度高,不仅污染环境,而且浪费大量的热量。为了解决这一问题,将椭圆扭曲管应用于热风炉空气预热器。结果显示,以椭圆扭曲管为换热元件的椭圆扭曲管空气预热器体积小、耗用钢材少、换热效率高,提高了烟气余热利用效率,降低燃料消耗量。以空气为工质,分别对椭圆扭曲管和圆管进行数值模拟,对比分析其传热性能。结果表明,相对于圆管,空气在椭圆扭曲管内湍动性更强,换热效果更好。通过对实际的工程案例进行分析,将椭圆扭曲管应用于热风炉空气预热器可减少换热面积27.9%,缩小体积37%,具有良好的节能节材效果。     

Design of A Single Tube Fuel Oil Preheater

This article presents design analysis of a fuel oil preheater. The preheater is a concentric tube heat exchanger where the fuel oil is on the tube-side and the heating medium flows in the annular space. Two situations were addressed in this study. In the first case, an analytical model was developed where the required heat exchanger length, diameter and the fluid velocity were determined for a given heat transfer duty and for an allowable pressure loss. A detailed study was conducted by individually varying parameters such as pressure loss, preheater discharge temperature, and mass flow rate of the fuel oil. In each instance their influence on the predicted design of the heat exchanger was investigated. In the second case, an optimization strategy was proposed for a certain heat transfer duty. The heat exchanger dimensions and the fluid flow rate were selected such that the annual operating cost of the heat exchanger was minimized. In addition, a detailed study was conducted to understand the total annual operating cost as a function of the fuel oil outlet temperature and the fuel oil mass flow rate.     

Three‐dimensional modeling method for heat exchange of rotary air preheater in coal‐fired power plant

A numerical modeling method based on a 3‐D heat transfer model and duct models for a dual‐sectional rotary air preheater have been developed in this paper. Owing to different boundary conditions for the heat transfer model obtained by modeling and calculation of the ducts, this method is capable of calculating the 3‐D metal and fluid temperature fields at different radial locations in the rotary air preheater along the rotor height as well as the rotating period, and furthermore, it can calculate temperature and flow field inside the flow passage as well. A case study with a dual‐sectional rotary air preheater of a typical 300 MW_e unit used as the research object is presented in this paper. The calculation results accord well with those obtained by verified numerical methods in published literature. The difference between the calculated and the measured outlet fluid temperature of the rotary air preheater is smaller than 3 °C. The numerical modeling method presented in this paper is proved to have high precision and is beneficial for the secure and economic operation of a rotary air preheater as well as the whole unit. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/htj.20325     

平板式空气预热器的推广应用

平板式空气预热器采用了平板设计以及独特的双程式分体结构,这些优化设计在很大程度上解决了传统的管式预热器的应力集中、易积灰,换热不均匀、换热效率低等问题以及波纹板式预热器的压降大、易结垢、露点腐蚀等问题。     

A numerical model for the analyses of heat transfer and leakages in a rotary air preheater

Air preheaters make a considerable contribution to the improved overall efficiency of fossil-fuel-fired power plants. In this study we used a combination of fluid dynamics and a newly developed three-dimensional numerical model for heat transfer as the basis for a theoretical analysis of a rotary air preheater. The model enables studies of the flue-gas flow through the preheater and the adjoining channels as well as the regenerative heat transfer and the resulting temperature distribution in the matrix of the preheater. Special attention was focused on the influences of leakages on the flue-gas parameters in the preheater. The numerical analysis and the experimental results showed an obvious dependence of the flue-gas parameters on various seal settings. Based on the results a method for online monitoring of the tightness of the radial seals is proposed.