空气预热器进风温度变化时基于燃料高位和低位热值的锅炉排烟热损失计算

锅炉排烟热损失是评价燃煤火力发电厂技术经济性的关键,详细分析了利用烟气余热来提高空预器进风温度对锅炉排烟热损失的影响,给出了以燃料高位热值和低位热值为基准的各项排烟热损失计算公式。计算结果表明,空预器进风温度提高时,锅炉热效率增加,且以高位热值为基准和以低位热值为基准计算的排烟热损失与锅炉主机厂的性能计算结果一致,为空气预热器进风温度变化时锅炉排烟热损失的计算提供了可行的方法。     

基于不同燃烧模型的二甲基醚发动机工作过程模拟研究

利用韦伯(Wiebe)模型、Watson模型、Whitehouse-Way模型以及化学动力学着火模型模拟计算了DME发动机的燃烧放热率，并将模拟计算结果与试验结果进行了对比。在对喷油正时、燃烧始角、循环供油量以及燃料热值等计算初始参数进行适当调整的基础上，上述模型的模拟计算结果与DME发动机实测数据基本吻合，说明上述各模型不仅适用于柴油发动机的性能预测分析，亦适用于DME发动机运行参数的预测。     

甲醇燃料-地沟油双燃料燃烧热效率研究

甲醇燃料、地沟油以及甲醇燃料-地沟油加热装有20 kg水的铝锅进行实验研究。通过实验以及在模型计算下,改变双燃料的热值,分别分析相应的热效率变化规律。研究表明:双燃料热值低于18.85 MJ/kg时,双燃料热效率随着双燃料热值的增加而迅速增加;在双燃料热值高于18.85 MJ/kg时,双燃料热效率达到峰值38.31%,此后变化很小。理论计算热效率亦随着双燃料热值增加而增加;而双燃料热值在大于18.85 MJ/kg后,理论热效率值仍然缓慢增加且并未达到峰值。     

应用神经网络方法预测生物质的热值

应用人工神经网络方法对生物质的热值进行了预测，网络的训练数据集来自美国Biomass Feedstock Composition and Property Database of U．S．Department of Energy。神经网络以生物质的工业分析结果作为输入数据．采用56组数据对网络进行训练，以7组数据对网络进行验证，对网络输出值与实际值进行比较，相对误差在0．08％以内。人工神经网络成功地预测各种生物质的热值，说明人工神经网络能够处理生物质的热值与工业分析各组分间的非线性关系。     

生物质水蒸气气化利用过程数学模型的建立

分析了甘蔗渣的水蒸气气化过程,基于气化过程的物料平衡和化学平衡关系,建立了一种生物质气化过程的数学模型。用该模型模拟计算甘蔗渣在水蒸气氛围下气化后的气体成分,计算结果与试验数据基本相符,尤其在温度950℃之后,计算值和测量值更接近。以甘蔗渣和木薯渣为例,研究该气化模型的特性。甘蔗渣和木薯渣水蒸气气化的最佳水蒸气/燃料值(S/B)分别为0.3和0.2。气化气组分和气化效果随温度和S/B变化的结果表明:提高温度有利于气化反应的进行,提高S/B,可以增加气体产率,气体热值有所降低。     

神经网络法用于预测城市生活垃圾热值

采用神经网络方法对垃圾热值进行了预测。通过对垃圾组分与热值的相关性分析得知城市生活垃圾的热值与塑料和纸的关系最密切,并采用多元线性回归方法得出热值与物理组成的关系。针对垃圾成份的复杂多变性,采用神经网络方法对城市生活垃圾的热值进行了预测。神经网络以垃圾的物理组成（塑料、纸、食品、草木和织物）作为输入,采用108组数据BP算法对网络进行训练,发现采用隐层单元数为7,学习速率为0．1时,网络收敛速度较快,同时给出均方差随计算次数的变化关系,并将计算结果与实验测量值进行了比较。结果显示108组数据中仅有4组数据与测量值的相对误差超过5％,其余数据均在5％误差范围内,比多元线性回归方法有较大改善。     

标准煤和标准油

不同能源的实物量是不能直接进行比较的。由于各种能源都有一种共同的属性,即含有能量,且在一定条件下都可以转化为热,为了便于对各种能源进行计算、对比和分析,我们可以首先选定某种统一的标准燃料作为计算依据,然后通过各种能源实际含热值与标准燃料热值之比,即能源折算系数,计算出各种能源折算成标准燃料的数量。所选标准燃料的计量单位即为当量单位。     

基于新型循环载氧体的天然气化学链燃烧热力学研究

以CH4为燃料对基于CaSO4载氧体的化学链燃烧的热力学性能进行了分析研究,计算了CaSO4在CH4氛围中的还原-氧化的热力学参数与温度的关系,分析结果显示,在一定的温度范围内,以CaSO4为载氧体实现化学链燃烧具有可行性,是一种理想的载氧体。基于Gibbs能最小化方法建立了化学链燃烧技术模型,模拟了温度,CH4与CaSO4摩尔比对燃料反应器和空气反应器的影响。结果表明,燃料反应器最佳反应温度850℃～900℃,空气反应器最佳反应温度为1000℃～1050℃,CH4与CaSO4的摩尔比最佳摩尔比为1。研究结果对燃煤化学链燃烧具有参考价值。     

天然气/柴油双燃料发动机不同天然气供给量计算方法及试验研究

基于试验的方法研究等热值法、理论等空气消耗量法和实际等空气消耗量法3种不同的计算方法对发动机动力性、经济性及排放特性的影响。试验结果表明:等热值法和理论等空气消耗量法对发动机的性能影响差异较小,各工况差异低于5%。实际等空气消耗量法确定的天然气供给量能明显提升发动机动力性,平均增加动力42.33%。不同天然气供给量计算方法在未对燃料供给进行优化时,未能有效降低发动机有效燃料消耗率,在大负荷工况有效燃料消耗率偏差平均为6.85%。双燃料模式下NOx排放得到明显改善,HC+NOx排放在中、高负荷工况时能满足排放限值要求,CO排放在低转速工况满足排放限值要求。     

输入/损失技术

输入 /损失技术 ,是一项独一无二的技术 ,它通过对燃料及其渗漏的流动、燃料化学性质、燃料热值和热效率的分析 ,为全面理解电厂热力过程创造了条件。低位 (净 )发热量与高位 (总 )发热量和热效率可以确定 ,而直接的燃料流量或排放物流量的测量没有给定。鉴于打算将其用于燃煤电厂 ,输入 /损失技术是根据透平循环的能量流动和锅炉运行特性 ,通过迭代技术与发散测量方法来确定煤的流动与燃烧热值的。发散测量方法 ,是以多维最小化技术来校正的。多维最小化技术对于给定的煤种可以校正燃料的特性参数在小于±2 %的标准误差范围内 ,校正后的结果可以证明是基本稳定的。典型的热值可以在 0 .5 %的精确度下进行预测。它是为在线监测器而设计的。这种方法已经被 1 2 0 0次元素分析和 1 0年的指导性测试结果广泛验证。图4表 3参 2 0     

Correlation for estimation of the chemical availability (exergy) from ultimate analysis of pyrolytic oils obtained from fast pyrolysis of biomass

The purpose of this study is to evaluate the chemical exergy (E^CH) of liquid products obtained from fast pyrolysis of biomass. I have calculated the chemical exergy values from a formula in literature and have developed a formula for estimating the chemical exergy of biomass from the higher heating value and their ultimate analysis values. The mean differences between these values range from –0.391% to 0.460%. The formula developed for estimating the chemical exergy of biomass from the higher heating value and their ultimate analyses had a correlation coefficient (R² = 0.9999), and the prediction of this formula is good. The goal is to identify desirable attributes that may serve as the basis for decision-making for future biofuel options. Studies on the pyrolytic oils showed that the oils obtained from chestnut cupulae and maple fruit can be used as a renewable fuel and chemical feedstock.     

热力循环温差传热不可避免损失研究

~~热力循环温差传热不可避免损失研究@张晓晖$上海理工大学动力工程学院!上海200093 @杨茉$上海理工大学动力工程学院!上海200093 @章立新$上海理工大学动力工程学院!上海200093 @卢玫$上海理工大学动力工程学院!上海200093~~~~~~     

The calculation of the chemical exergies of coal-based fuels by using the higher heating values

This paper demonstrates the application of exergy to gain a better understanding of coal properties, especially chemical exergy and specific chemical exergy. In this study, a BASIC computer program was used to calculation of the chemical exergies of the coal-based fuels. Calculations showed that the chemical composition of the coal influences strongly the values of the chemical exergy. The exergy value of a coal is closely related to the H:C and O:C ratios. High proportions of hydrogen and/or oxygen, compared to carbon, generally reduce the exergy value of the coal. High contents of the moisture and/or the ash cause to low values of the chemical exergy. The aim of this paper is to calculate the chemical exergy of coals by using equations given in the literature and to detect and to evaluate quantitatively the effect of irreversible phenomena increased the thermodynamic imperfection of the processes. In this paper, the calculated exergy values of the fuels will be useful for energy experts studied in the coal mining area and coal-fired powerplants.     

基于火用分析的水体热污染评价方法

将火用分析与水体热污染结合在一起,从火用分析角度阐述了水体热污染的概念,并建立了水体热污染的火用分析模型,给出了温排水和水环境生态系统火用的计算公式,在此基础上,定义了水体热污染率,并运用于水体热污染评价上。以美国某电厂温排水为例,根据火用分析法计算了水体热污染率。结果表明,火用分析能够定量和统一地评价水体热污染程度,与其他评价方法相比,该方法能更加直观地评判水体热污染状况,为水体热污染控制和水资源开发利用提供了科学决策依据。     

火电机组回热系统[火用]损分布的通用矩阵方程

根据[火用]平衡方程，首次导出了火电机组回热系统[火用]损分布的通用矩阵方程。利用这一方程可方便地得出不同机组回热系统的[火用]损分布规律，同时这一方程也为建立回热系统乃至整个机组与[火用]损分布通用矩阵方程相关的通用的[火用]分析模型、[火用]经济学分析模型、[火用]经济学优化模型和[火用]经济学故障诊断模型奠定了基础。利用这一方程还可以方便地开发出实时监测回热系统[火用]损分布的计算机程序，为降低机组能耗提供一个实用化的分析工具。图3表1参6     

火电机组回热系统(火用)损分布的通用矩阵方程

根据平衡方程,首次导出了火电机组回热系统损分布的通用矩阵方程。利用这一方程可方便地得出不同机组回热系统的损分布规律,同时这一方程也为建立回热系统乃至整个机组与损分布通用矩阵方程相关的通用的分析模型、经济学分析模型、经济学优化模型和经济学故障诊断模型奠定了基础。利用这一方程还可以方便地开发出实时监测回热系统损分布的计算机程序,为降低机组能耗提供一个实用化的分析工具。图3表1参6     

Thermodynamic analysis of reheat cycle steam power plants

In this study, a thermodynamic analysis of a Rankine cycle reheat steam power plant is conducted, in terms of the first law of thermodynamic analysis (i.e. energy analysis) and the second law analysis (i.e. exergy analysis), using a spreadsheet calculation technique. The energy and exergy efficiencies are studied as 120 cases for different system parameters such as boiler temperature, boiler pressure, mass fraction ratio and work output. The temperature and pressure values are selected in the range between 400 and 590°C, and 10 and 15 MPa, being consistent with the actual values. The calculated energy and exergy efficiencies are compared with the actual data and the literature work, and good agreement is found. The possibilities to further improve the plant efficiency and hence reduce the inefficiencies are identified and exploited. The results show how exergy analysis can help to make optimum design decisions in a logical manner. Copyright © 2001 John Wiley & Sons, Ltd.     

A new approach for simplifying the calculation of flue gas specific heat and specific exergy value depending on fuel composition

In this paper, a new approach is proposed for simplifying the calculation of flue gas specific heat and specific exergy value in one formulation depending on fuel chemical composition. Combustion products contain different gases such as CO₂, SO₂, N₂, O₂, H₂O and etc., depending on the burning process. Specific heat and exergy of the flue gas differ depending on the chemical composition of fuels, excess air ratio and gas temperature. Through this new approach, specific heat and specific exergy value of combustion products can be estimated accurately in one formulation by entering the chemical composition of fuels, excess air ratio and gas temperature. The present approach can be applied to all carbon based fuels, especially biomass, fossil fuels and fuel mixtures for co-combustion and is so suitable for practical estimation of flue gas specific heat and specific exergy values provided that the fuel chemical composition is given.     

Standard chemical exergy of elements updated

The chemical exergy of a substance is the maximum work that can be obtained from it by taking it to chemical equilibrium with the reference environment at constant temperature and pressure. This exergy is normally taken or calculated from tabulated values obtained for standard conditions, i.e. an ambient temperature of 298.15 K, an atmospheric pressure of 1 atm, and a model of reference species which considers the concentration of the most common components of the atmosphere, the oceans and the Earth's crust. The model proposed by Szargut for the calculation of the standard chemical exergy of elements and organic and inorganic substances has been revised. As a result of this revision, updated values of standard chemical exergy of elements are presented and compared with the ones estimated by Szargut. Because of some anomalous behaviour in the chemical exergy when a different salinity of seawater is assumed, some different reference species than those used in the latest version of the Szargut model were proposed for the following elements: silver, gold, barium, calcium, cadmium, copper, mercury, magnesium, nickel, lead, strontium and zinc. A complete set of updated values of chemical exergies of elements for the standard conditions (298.15 K and 1 atm) is tabulated.     

Exergy analysis of hydrogen production plants based on biomass gasification

Biomass gasification is a promising option for the sustainable production of hydrogen rich gas. Five different commercial or pilot scale gasification systems are considered for the design of a hydrogen production plant that generates almost pure hydrogen. For each of the gasification technique models of two different hydrogen production plants are developed in Cycle-Tempo: one plant with low temperature gas cleaning (LTGC) and the other with high temperature gas cleaning (HTGC). The thermal input of all plants is 10 MW of biomass with the same dry composition. An exergy analysis of all processes has been made. The processes are compared on their thermodynamic performance (hydrogen yield and exergy efficiency). Since the heat recovery is not incorporated in the models, two efficiencies are calculated. The first one is calculated for the case that all residual heat can be applied, the case with ideal heat recovery, and the other is calculated for the case without heat recovery. It is expected that in real systems only a part of the residual heat can be used. Therefore, the actual value will be in between these calculated values. It was found that three processes have almost the same performance: The Battelle gasification process with LTGC, the FICFB gasification process with LTGC, and the Blaue Turm gasification process with HTGC. All systems include further processing of the cleaned gas from biomass gasification into almost pure hydrogen. The calculated exergy efficiencies are, respectively, 50.69%, 45.95%, and 50.52% for the systems without heat recovery. The exergy efficiencies of the systems with heat recovery are, respectively, 62.79%, 64.41%, and 66.31%. The calculated hydrogen yields of the three processes do not differ very much. The hydrogen yield of the Battelle LTGC process appeared to be 0.097 kg (kg_{(dry biomass)})⁻¹, for the FICFB LTGC process a yield of 0.096 kg (kg_{(dry biomass)})⁻¹ was found, and for the Blaue Turm HTGC 0.106 kg (kg_{(dry biomass)})⁻¹.