热管及其换热器在烟气余热回收中的应用

简要介绍了热管技术,并分析了其传热机理。热管换热器具有许多独特的优点,已经获得了广泛的工业应用,应用主要集中在中低温余热资源回收利用方面,应完善高温热管,以拓宽热管换热器在高温余热资源中的应用。     

复合相变换热器在锅炉烟气余热回收中的应用

为了降低锅炉排烟温度,回收锅炉尾部烟气热量,提高机组效率,降低机组发电煤耗,确保电除尘、引风机安全运行,采用复合相变换热器加热同机组的凝结水,在避免换热器结露积灰的前提下,能大幅度降低锅炉排烟温度,回收锅炉尾部烟气的余热,减少汽轮机的抽汽量,增加机组发电能力,可获得较好的经济效益。     

湿法烟气脱硫系统的烟气换热器设置分析

通过对上海地区燃煤电厂湿法烟气脱硫系统安装和不安装烟气换热器(GGH)的运行分析,证实了安装GGH后的烟囱腐蚀,明显低于无GGH烟囱,尤其是针对GGH发生结垢、堵塞和腐蚀等问题采取的六大技术措施,能够达到环保考核要求,同时论述了脱硫系统取消GGH后,会给周边环境和生产运行安全带来隐患。为此,结合国家环保政策,提请各燃煤电厂在建设脱硫系统时,不应盲目取消脱硫系统的GGH装置。     

紧凑式空气换热器在工业锅炉排烟余热利用上的应用

针对现有燃煤工业锅炉排烟温度偏高的问题，提出一种紧凑式的换热器，利用排烟余热加热空气，其结构采用独特的旁通烟道设计，并且在管束外增加了均流板，减少了阻力损失，在6．5t/h工业锅炉改造中得到成功应用。     

烟气换热器堵灰原因及解决办法

介绍了数家电厂GGH堵灰情况，总结出GGH堵灰的主要原因，并且提出了对策。     

基于数据辩识算法的燃气热水锅炉运行特性研究

搭建了以泡沫铜翅片换热器为核心的烟气水分回收实验台,研究了冷却水进口温度、烟气雷诺数及烟气中水蒸气体积分数对该换热器水回收特性和换热特性的影响,基于实验数据,利用多元回归拟合得到对流换热的关联式,其预测值与实验值误差在6%以内。结果表明：水蒸气体积分数增大可以显著提升水回收特性,而冷却水进口温度及烟气雷诺数对其影响很小;冷却水进口温度与烟气雷诺数对换热效率的影响较大,冷却水进口温度与换热效率成反比,烟气雷诺数与之成正比,而水蒸气体积分数对其影响较小;实验获得的最大冷凝水产率为7.68 kg/h,最大冷凝率为56.94%,最大换热效率为96.95%。     

基于泡沫铜翅片换热器的烟气水分回收实验研究

搭建了以泡沫铜翅片换热器为核心的烟气水分回收实验台,研究了冷却水进口温度、烟气雷诺数及烟气中水蒸气体积分数对该换热器水回收特性和换热特性的影响,基于实验数据,利用多元回归拟合得到对流换热的关联式,其预测值与实验值误差在6%以内。结果表明：水蒸气体积分数增大可以显著提升水回收特性,而冷却水进口温度及烟气雷诺数对其影响很小;冷却水进口温度与烟气雷诺数对换热效率的影响较大,冷却水进口温度与换热效率成反比,烟气雷诺数与之成正比,而水蒸气体积分数对其影响较小;实验获得的最大冷凝水产率为7.68 kg/h,最大冷凝率为56.94%,最大换热效率为96.95%。     

Retrofitting Crude Oil Refinery Heat Exchanger Networks to Minimize Fouling While Maximizing Heat Recovery

Abstract

The use of fouling factors in heat exchanger design and the lack of appreciation of fouling in traditional pinch approaches have often resulted in crude preheat networks that are subject to extensive fouling. The development of thermal and pressure drop models for crude oil fouling has allowed its effects to be quantified so that techno-economic analyses can be performed and design options compared. The application of these fouling models is described here on two levels: the assessment of increasing heat recovery in stream matches (e.g., by adding extra area to exchangers) and the design of a complete network using the Modified Temperature Field Plot. Application to a refinery case study showed that, at both the exchanger and network levels, designing for maximum heat recovery (e.g., using traditional pinch approaches) results in a less efficient system over time due to fouling effects.     

电站锅炉烟气余热利用与空气预热器综合优化

针对常规电站锅炉余热利用系统中低温省煤器入口烟气温度的限制,对锅炉尾部受热面进行综合优化,将空气预热器分两级布置,在两级空气预热器之间布置低温省煤器;并通过改变Ⅱ级空气预热器出口空气温度,优化低温省煤器所处的烟气温度范围,从而得到热力学最优工况;最后结合技术经济性分析,得出符合工程实际的综合优化结果.结果表明:通过空气预热器分级设计和合理设定关键运行参数,在热力学最佳方案下机组供电煤耗降低约6.7g/(kW·h),结合技术经济性分析,在年平均运行5 500h工况下,每年净收益可达2 100余万元,经济效益显著.     

锅炉烟气余热回收效益明显

介绍锅炉房使用的6t/h燃煤蒸汽锅炉,原来排烟温度220℃左右,对老式省煤器进行改造,利用EC型锅炉余热回收器,最后使排烟温度降至50℃左右。既改善了引风风机的工况条件,又回收了大量的热能,使一般燃煤锅炉的效率有了明显的上升。     

退火炉废气余热综合再利用

对某厂镀锌退火炉高温废气余热回收利用进行分析,提出实施的工艺方案和技术改造过程,并对取得效果加以说明。     

一种监测换热器污垢的新方法

在考虑污垢对换热器传热性能影响的基础上,提出换热器当量总污垢热阻和污垢函数的概念,并给出换热器当量总污垢热阻的监测方法,讨论了换热流型、传热有效度ε和冷热流体热容量率比R对换热器当量总污垢热阻的影响。     

大型煤粉锅炉烟气余热利用装置在节能和减排中的应用

国家从2014-07-01开始执行新的粉尘排放标准,要求粉尘排放控制在30 mg/Nm3以内,因而一般需要对现有电除尘进行改造。新昌电厂实施电除尘改造后,能达到降低排烟温度加热凝结水,减少排烟热损失,同时又提高了除尘效率,满足了新的粉尘排放要求,既环保又节能。     

烟气余热回收利用节煤效益计算方法研究

利用热力学第一定律、热力学第二定律以及汽轮机热平衡图等方法对锅炉烟气余热回收用于供热或加热凝结水时的节煤效益进行了研究,并结合计算案例与工程实践的性能考核数据进行了比较与分析.结果表明:计算节煤效益的准确方法是首先计算回收的烟气余热量,然后计算得到汽轮机热平衡图、给出新的汽轮机热耗,最后按照给出的节煤效益计算公式计算机组供电煤耗降低值;为了提高节煤效益,在锅炉烟气余热回收工程性能设计时,应该尽量节约更高级抽汽口的蒸汽,而不是单纯追求尽可能低的烟气温度.     

Measuring Local Crystallization Fouling in a Double-Pipe Heat Exchanger

Abstract

Although fouling is a problem varying in space and time, sizing and assessment of a process apparatus is almost always based on one single integral fouling resistance value. Furthermore, the integral fluid dynamic behavior, e.g. the development of time-dependent pressure drop in a heat exchanger, can be influenced by local constrictions. While it is generally possible to determine the time dependency of the integral fouling behavior, local differences are not taken into consideration at present. Therefore, this paper introduces a metrological, an incremental and a segmental approach to study the local development of crystallization fouling by calcium sulfate in a countercurrent double-pipe heat exchanger. The consecutive approaches allow for thermal, volumetric, gravimetric, and optical fouling investigations, aiming to examine the axial distribution of deposit as well as local differences in the deposit morphology. All methods provided congruent results and local fouling could be described properly. An almost clean surface at the colder end of the heat exchanger and an exponential increase of deposit thickness were observed towards the hot end. Hence, the section near to the hot water inlet turned out to be a key area with regards to increasing fouling mass and structural changes of the layer.     

电站锅炉烟气余热回收工程改造实践

加设低压省煤器是电站锅炉节能减排的重要措施之一,以某电厂2台600MW的汽轮发电机组出现排烟温度过高的现象为研究对象,通过在引风机与脱硫塔的水平烟道内增设低压省煤器对其进行改造,改造之后排烟温度可以降低到85℃,节省标准煤耗1.99 g/kwh,年节约水费265.8万元.     

废液焚烧炉烟气余热回收锅炉改进设计

基于原有废液焚烧炉烟气余热回收烟管式锅炉的烟管结渣原因分析,提出了余热锅炉改进设计方案,并通过结渣周期计算和应用经济效益分析,证明其有效可行,在实际应用中也取得了显著的节能和经济效益。     

烟气余热回收装置的参数优化分析

针对我国电站锅炉排烟温度普遍偏高的情况,提出采用烟气深度冷却器以回收烟气余热,分析了其实施的可行性.通过建立热力计算分析模型,选取影响传热效果和投资成本的结构参数和运行参数作为分析对象,并以传热系数和折算成本作为设计参考,对烟气深度冷却器的设计参数进行优化.结果表明:选取合理的结构参数和运行参数可以有效地改善传热效果,降低设备投资成本和投资回收年限,保证节能改造的技术经济性.     

Heat Exchanger Fouling in Phosphoric Acid Evaporators

Multistage shell and tube evaporators are frequently used in phosphoric acid plants to increase the concentration of dilute phosphoric acid to 52–55 wt% P₂O_5. The concentrated phosphoric acid solution is supersaturated with respect to calcium sulfate. As a result, part of the calcium sulfate in the liquor deposits on the heat exchanger tube walls. Because the thermal conductivity of these scales is very low, thin deposits can create a significant resistance to heat transfer. Therefore, regular cleaning of heat exchangers is required, frequently at shorter than biweekly intervals. As the major costs in modern phosphoric acid plants are the cost of energy, a thorough understanding of the fouling kinetics and of the effects of various operational parameters on the behavior of calcium sulfate is required to improve operation and design of the shell and tube heat exchangers, which are extensively used. In this investigation, a large set of heat exchanger data was collected from shell and tube heat exchangers of the phosphoric acid plant of the Razi Petrochemical Complex in Iran, and the fouling deposits were analyzed with respect to appearance and composition. The overall heat transfer coefficients and fouling resistances were evaluated at different times, and a kinetic model for the crystallization fouling was developed. It is shown that the crystallization rate constant obeys an Arrhenius relationship with an activation energy of 57 kJ/mol. The average absolute error of 12.4% shows that the predictions of the suggested model are in good agreement with the original plant data.