烟气酸露点计算方法比较和分析

酸露点是锅炉设计和运行中重要参数之一,目前国内外计算烟气酸露点方法很多,但是不同方法计算结果差异较大.结合有关文献对几种计算烟气酸露点的方法进行了比较,分析了SO3浓度和水蒸气含量对烟气酸露点变化趋势的影响.研究结果表明,荷兰的A.G.Okkes公式和И.A.Bapahoba公式比较精确,前苏联热力计算酸露点经验公式、日本电力研究所经验公式和Haase & Borgmann公式的误差比较大.此外,对前苏联热力计算酸露点经验公式进行了修正.     

锅炉烟气低温腐蚀的理论研究和工程实践

从锅炉烟气低温腐蚀的机理、模拟试验和工程实践等多方面论述了烟气低温腐蚀的实质和现状,指出烟气是否会结露与烟气温度本身关系不大,而是取决于锅炉低温受热面金属壁温与烟气酸露点温度,提出了新的计算烟气酸露点温度的经验公式和理论上控制烟气低温腐蚀的措施.结果表明：采用新提出的烟气露点温度经验公式计算得到的烟气酸露点温度,能比较准确地判断烟气结露和低温腐蚀情况;只要能保证锅炉低温受热面金属壁温高于烟气酸露点温度,烟气温度降低到80~98℃是完全可行的.     

烟气酸露点计算公式中过量空气系数的修正方法

烟气酸露点是锅炉运行及节能改造工程的重要参数之一,现有文献中计算酸露点的方法很多,但不同方法的计算结果差异较大。对文献中酸露点的计算方法进行了比较,在不同过量空气系数条件下,将现行公式计算烟气酸露点变化规律与实际相反原因进行了分析。对烟气酸露点计算公式中的过量空气系数进行修正,并给出了过量空气系数的修正公式。这一方法具有一定的应用价值。     

烟气酸露点的测量与计算关联式的修正

为防止结露腐蚀粘污,一般排烟温度均要求高于烟气酸露点,为了进一步提高能源利用率,希望进一步降低排烟温度,这就要求烟气酸露点的确定更加精确。目前国内外酸露点的计算结果普遍偏高。分析了影响烟气酸露点的因素,通过自己设计的烟气酸露点测量装置,开发的利用饱和NaHSO3溶液吸收SO3的测量方法,对实际运行锅炉进行测试,提出了考虑烟气中SO3的浓度的酸露点关联式。     

烟气酸露点温度的影响因素及其计算方法

确定烟气露点温度，已成为避免低温受热面造成腐蚀、增加锅炉运行安全性和提高锅炉效率的关键所在。文章对影响烟气酸露点的主要因素进行了分析，对几种烟气酸露点温度的计算方法进行了对比和评价，并依据酸露点的图表数据，拟合出烟气露点计算方程。     

富氧燃煤锅炉再循环方式对烟气酸露点的影响

以某600 MW富氧燃煤锅炉为例,对其在3种不同再循环方式下烟气中H2O和SO2体积分数的变化进行了计算与分析,预测了烟气酸露点,并分析了再循环方式对尾部受热面低温腐蚀的影响.结果表明:富氧燃烧下烟气的酸露点比空气状况下高15K左右;再循环方式中脱硫脱水处理过程对烟气中H2O和SO2体积分数影响明显;3种再循环方式下烟气酸露点最大差值可高达11K;烟气酸露点随一次循环烟气比的增加呈下降趋势.     

燃气-蒸汽联合循环机组余热锅炉烟气酸露点温度计算

为了推进节能减排,在避免锅炉低温受热面腐蚀的前提下,进一步降低排烟温度,提高锅炉运行的安全性和经济性,对影响余热锅炉烟气酸露点的主要因素进行了分析,并通过对几种烟气酸露点温度计算方法的比较和评价,最终确定了适合燃气-蒸汽联合循环机组中余热锅炉烟气酸露点温度的计算方法及结果,并为日常运行中余热锅炉排烟温度的控制提供了依据。     

锅炉烟气酸露点温度计算及对预热器腐蚀的影响

锅炉烟气流经空气预热器时,当空气预热器金属壁温低于烟气酸露点温度时,即生成硫酸,从而导致空气预热器冷端腐蚀及堵灰。本文介绍了锅炉烟气酸露点温度的计算及对预热器冷端腐蚀的影响。     

烟气循环方式对SO_3生成的影响

基于化学反应动力学计算方法研究了富氧燃烧中不同循环方式对SO3生成的影响.结果表明:富氧燃烧方式下SO3体积分数急剧增大,其中湿烟气循环方式下的SO3体积分数最大;增大初始O2、SO2和H2O体积分数,增加了燃烧过程O、OH和HOSO2等自由基的浓度,促进了SO3的生成;SO3生成率随初始SO2体积分数的增大而减小,随初始O2体积分数和初始H2O体积分数的增大而增大;富氧燃烧导致烟气酸露点普遍升高,其中湿烟气循环方式下烟气酸露点最高,对烟气进行脱硫或者脱水处理,能够有效降低烟气酸露点.     

锅炉酸露点的研究进展及实例特性分析

燃煤锅炉的排烟热损失是锅炉第一大热损失,降低排烟温度是提高锅炉效率的重要环节。但排烟温度低于烟气酸露点会引起锅炉的低温腐蚀,影响锅炉的安全运行。对酸露点的研究进展及影响因素进行分析,并给出了10种计算酸露点的公式,对其计算结果进行对比。对比结果显示,各类方法结果相差较大,对于实际问题应先选择合适的计算公式。根据实际案例探究了酸露点的变化特性。最终计算得出,针对文中所述机组和工况,当煤种参数波动时,含硫量变化0.1%、含水量变化1%、含氢量变化0.1%,酸露点温度大约分别变化3℃、0.3℃～0.4℃和0.1℃～0.2℃。     

锅炉烟气酸露点温度计算公式的研究

我国锅炉行业的锅炉本体及辅助设备的多种计算中,一部分是改革开放后自己制定的,一部分来自于前苏联(如锅炉机组热力计算),还有一部分是近若干年引进国外技术带来的算法.若干书籍文章中所用的烟气酸露点温度的计算公式都不太准确.本文将对这部分进行分析介绍,为使用者提供服务.     

船用低速柴油机燃用重油的酸露点温度分析

以某型低速柴油机为研究对象,采用性能仿真软件搭建发动机模型,得到缸内温度、压力及成分变化规律;结合SO_3生成反应化学动力学模型,计算分析燃气酸露点温度随曲轴转角的变化规律。结果表明:随着活塞的下行,酸露点温度下降;且缸内温度下降的速度大于酸露点温度的降幅,因此在低负荷时下止点附近容易出现酸低温腐蚀现象。指出冷却系统设计时要充分考虑这个因素。     

天然气热利用率及影响因素

用热力学理论和燃烧理论建立了天然气排烟温度与热利用率的计算模型,计算得出了天然气热利用率与排烟温度的关系曲线,可供实际工程参考.对影响天然气热利用率的因素(排烟温度、过剩空气系数和烟气冷凝温度)的主要影响因素(燃烧空气含湿量)进行了定量分析,提出了提高天然气热利用率的措施,可使天然气的热利用效率提高1000/~2000/.     

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。     

炼油装置加热炉节能途径与制约因素

加热炉是炼油装置的能耗大户,其节能水平对于提高炼油装置的节能水平具有重要意义。介绍了加热炉主要的节能途径：优化换热流程,降低加热炉热负荷;加热炉与其他设备联合回收余热;降低排烟温度、降低过剩空气系数、减少不完全燃烧损失、减少散热损失以提高加热炉热效率。探讨了上述节能途径的主要技术措施及应注意的问题。阐述了进一步提高加热炉节能水平的制约因素：降低排烟温度,要考虑经济性和露点腐蚀;过分降低炉外壁温度,会导致费用过高;预热空气温度过高对环保不利。提出了进一步提高加热炉节能水平的建议;认真净化燃料,降低露点温度;开发新的余热回收工艺;开发并应用“蓄热式高温空气预热贫氧燃烧技术”等新的燃烧技术;加强运行管理。     

Review of flue gas acid dew-point and related low temperature corrosion

Acid dew-point (ADP) is the temperature at which the acid vapor, normally means sulfuric acid (H₂SO₄), in flue gas begins to condense. Acid condensation can result in low-temperature corrosion (LTC), which can threaten the safety of boilers. An exhaust temperature higher than ADP can relieve LTC, however, result in a low thermal efficiency. Therefore, ADP is regarded as a key parameter to guide safety and efficiency of boilers. Previous investigations on ADP are abundant, but a comprehensive review is absent. This work tried to fill this gap. First, the existing methods for ADP determination, including empirical models, semi-empirical models, and measurement methods, were explained. The empirical models were specially classified according to the transformation path of SO₃/H₂SO₄ in flue gas. Then, these methods were compared and evaluated, and the difficulty in identifying the beginning of the acid condensation was considered to result in the different results among varied methods. A new method which can reveal the acid condensing process was recommended for evaluating and discussing the issue of ADP. Moreover, this paper also involved the topic on preventing LTC below ADP focused by the currently popular deep waste heat recovery field. Finally, future research directions were suggested.     

Study on preparation and thermal property of binary fatty acid and the binary fatty acids/diatomite composite phase change materials

This study prepared a series of binary phase change materials by mixing decanoic acid, dodecanoic acid, hexadecanoic acid and octadecanoic acid each other. The phase-transition temperature of binary fatty acid and its corresponding mixing proportion are calculated with phase diagram thermodynamic method. The results are verified by the experimental result of the heat absorption curve and the Differential Scanning Calorimetry (DSC) analysis curve. The results show that the calculation method of phase diagram thermodynamic calculation can be taken as a basis for mixing proportion of binary fatty acid phase change materials. In addition, the decanoic–dodecanoic acid/diatomite composite phase change material (PCM) are prepared and its microstructure, thermal property and thermal reliability are characterized. The result shows that the decanoic–dodecanoic acid is uniformly adsorbed into diatomite and the form-stable PCM are formed. The phase-transition temperature and the latent heat of the decanoic–dodecanoic acid/diatomite composite PCMs is 16.74 °C and 66.8114 J/g, respectively.     

Characterization of the ash deposits along deep-cooling of the exhaust gas in coal-fired power plants

Ash deposition and condensation of acid vapors under deep-cooling of exhaust gas in a 1000 MW ultra-supercritical power plant were investigated. X-ray diffraction, X-ray fluorescence and laser particle size analyzers were employed to characterize the components, elements and particle size distribution of deposits at different metal wall temperatures. The results show that the deposits formed at the metal wall temperatures of 40 °C–60 °C were much thicker than the deposits at 70 °C–90 °C from the perspectives of the morphology and thickness. Fluorides and chlorides were observed in deposits formed at the metal wall temperatures of 40 °C–60 °C. Thin deposits were composed of Al-Si oxides and simple sulfates when the metal wall temperatures were 70 °C–90 °C. The dew-point temperatures of water, HCl and HF vapors were around 40 °C, 60 °C, and 60 °C, respectively. Basic ferric, aluminum and calcium sulfates, which were acted as traps to absorb the condensate and fly ash. Hydration played an important role in the growth of deposits formed at the metal wall temperature of 40 °C–60 °C.     

Climatic parameters for building energy applications: A temporal-geospatial assessment of temperature indicators

Understanding the climate and location aspects are usually the first step in energy applications – from buildings to renewable energy. With so many of the renewable energy sources being significantly dependent on weather, it is essential that the temporal and geospatial variability and distribution of climatic design parameters are investigated for effective planning and operation. ASHRAE-HOF is the most widely used climatic design conditions database for building energy and HVAC professionals, but gaps exist in the literature on the geospatial and temporal distributions of the HOF dataset. This research explored geospatial distributions of key HOF (2009) climatic parameters: temperature (dry-bulb, wet-bulb, dew-point and mean) and degree-days at various temporal scales. Identified spatial variability illustrate the effects of latitude, elevation, landuse and nearest coastline. Observed trends agree with conventional wisdom; however, sparse coverage in populated areas such as Africa and Asia diminish the versatility of the database. Variations in temperature exist, even between closely spaced sites – emphasizing the need to use location-specific data for enhancing the accuracy of the weather-related analysis. Moreover, latitudinal similarities in the distribution offer potential in identifying candidate locations for reciprocal transfer of knowledge on environmental design and operation.     

An experimental aluminum-fueled power plant

An experimental co-generation power plant (CGPP-10) using aluminum micron powder (with average particle size up to 70 μm) as primary fuel and water as primary oxidant was developed and tested. Power plant can work in autonomous (unconnected from industrial network) nonstop regime producing hydrogen, electrical energy and heat. One of the key components of experimental plant is aluminum-water high-pressure reactor projected for hydrogen production rate of ∼10 nm³ h⁻¹. Hydrogen from the reactor goes through condenser and dehumidifier and with −25 °C dew-point temperature enters into the air-hydrogen fuel cell 16 kW-battery. From 1 kg of aluminum the experimental plant produces 1 kWh of electrical energy and 5-7 kWh of heat. Power consumer gets about 10 kW of electrical power. Plant electrical and total efficiencies are 12% and 72%, respectively.