天然气压力能透平回收分析与联合循环研究

从热力学第二定律角度分析透平膨胀过程中降的构成,对管输天然气做功能力进行理论分析,得出了温度、压力、化学的计算方法和透平膨胀输出轴功极限能力的评价因子。在理论分析的基础上,进一步给出了现有的基于冷电联产的联合循环方式,从机电一体化角度提出了该领域基于总能系统理论的多学科的研究思路。     

天然气压力能回收装置热力学分析

高压天然气调压过程中存在着巨大的可供回收的压力能,节流阀、透平膨胀机、气波制冷机、涡流管是典型的能量回收设备。在对上述四种能量回收装置进行简要介绍之后,以[火用]概念为基础,以[火用]平衡为工具,对其进行了全面的热力学分析。结果表明：透平膨胀机的火用效率最高,其次是气波制冷机、涡流管、节流阀,且当膨胀比变化时,透平膨胀机的性能较稳定。涡流管、气波制冷机具有分离效果,可用于天然气脱水预冷。研究结果对于压力能回收装置的选用和调压流程的优化具有一定的指导意义。     

价值因子在热经济学分析中的应用

本文在热力学分析和火用效率分析的基础上，将火用价值因子应用于热经济分析。从动态价值角度及能级角度对用能过程的合理性，方案的可行性及系统的最优性进行分析。通过理论分析和实例研究，指出火用价值因子方法进一步完善了热经济学分析，有推广使用价值。     

天然气余压发电制冰系统设计及实际产能模拟

针对天然气分输站目前无法对管输天然气压力能进行有效回收的问题,以及传统的制冰行业电力消耗较大,而冰需求市场又逐年扩大等问题,本文提出一种天然气余压发电制冰一体化系统。系统主要包括膨胀发电系统、冷能利用系统两部分,利用膨胀机回收天然气压力能并同轴带动发电机发电,再利用换热器对膨胀机出口的低温天然气冷能进行回收。然后结合某天然气分输站供气参数和膨胀机特性曲线,用Aspen软件对整个工艺流程进行模拟,以估算系统的实际发电量、产冰量。系统既得到了高品位的电能,同时也能缓解冰需求市场的压力,降低了制冰行业的高电力消耗。     

热分离技术与压力能的回收利用

探讨了过程工业中气体压力能的回收利用途径 ,对节流阀、透平膨胀机、热分离器的工作原理、性能、特点、能量回收型式进行了比较与分析 ,讨论了这些膨胀装置的应用场合。结合 30× 1 0 4m3/d处理规模的天然气脱水流程的工程实例 ,介绍了热分离技术在压力能利用方面的优势和节能、降耗效果     

大型CFB锅炉天然气点火系统应用问题研究

针对大型循环流化床(CFB)锅炉应用天然气点火系统存在燃烧不稳定火焰脱火的问题,以某电厂350 MW超临界循环流化床机组天然气点火系统为研究对象,探讨了天然气层流扩散和紊流扩散燃烧的机理,从燃烧学理论出发研究了天然气火焰脱火的主要原因是燃烧器喷口燃气流速与火焰传播速度不匹配。基于一元定常可压缩气体流动的基本特性,将天然气燃烧器气枪喷口简化为一元流体的喷管,计算出CFB锅炉天然气点火系统燃烧器出口的最大流速,以此为基础提出天然气系统燃气压力的调整措施和燃烧器喷口结构的优化方案。通过理论分析计算和设备的结构优化,解决了大型CFB锅炉天然气点火系统燃烧器火焰脱火的问题,可为同类型的机组提供借鉴的依据。     

直接膨胀式太阳能热泵系统的理论分析

简述了直接膨胀式太阳能热泵的基本工作原理,从热力学理论出发,对直接膨胀式太阳能热泵的循环进行了理论热力分析,提出了系统各主要部件的能量平衡和火用平衡方程,分析了系统的性能系数COP和火用效率Eη。     

湿蒸汽临界参数的研究计算及其在蒸汽透平设计中的应用

本文对进口为饱和蒸汽和湿蒸汽热力平衡膨胀流动过程中的最大流量及临界参数进行了深入的探讨和分析;用最大流量法编制了计算机程序,对进口滞止压力为0.002～15MPa,进口湿度为0～20％参数范围的最大流量、临界参数进行了计算,并将计算结果绘制成能方便应用于工程设计中的曲线图;对最大流量、临界压比拟合了便于计算机及工程设计应用的计算公式。本文所计算的参数范围包括了一般火电站透平与核电站透平中可能遇到的压力和湿度值。所得到的计算结果既为有关方面的研究工作提供了基础,也为蒸汽透平的设计提供了实用数据,填补了长期以来湿蒸汽流动过程中临界参数无准确、系统数据的空白。     

初参数对超临界CO2塔式光热发电系统■效率的影响

初参数对塔式光热发电系统热力性能有着重要影响。基于国内外研究现状,文章建立了超临界二氧化碳(S-CO₂)再压缩塔式光热发电系统,研究了不同辐射强度下,该系统不同设备、各子系统和整个系统的(火用)效率,以及吸热器散热损失随透平进口温度和进口压力的变化情况。研究表明：透平进口温度从500℃上升到800℃时,低温回热器(火用)效率最大值为90.21%,对应温度560℃;当辐射强度从95%THA增加到105%THA时,集热子系统(火用)效率最大值点往温度升高的方向偏移且最大值增大,最大为27.88%,对应温度700℃。透平进口压力从20 MPa增加到34 MPa时,循环子系统(火用)效率先增后减,当辐射强度从95%THA增加到105%THA时,其最大值点往压力升高的方向偏移且最大值减小,最大为74.9%,对应压力24 MPa。透平进口压力对吸热器散热损失的影响较小,而进口温度对其影响较大。研究结果可为S-CO₂塔式光热发电系统优化设计提供参考。     

液化天然气冷量火用特性研究

在建立了精确的预测液化天然气密度及汽液相平衡算法的基础上，考虑了真实流体效应影响，推导了液化天然气（ＬＮＧ）低温火用、压力火用及冷量火用分析数学模型，运用上述模型计算了各种火用的大小，并讨论了环境温度、系统压力、混合物组分对ＬＮＧ冷量火用特性的影响，提出应根据实际ＬＮＧ流体的低温火用、压力火用大小，综合考虑气体供给压力等因素，通过热力循环优化，确定ＬＮＧ冷量火用动力回收的利用方案     

Comparative exergoeconomic analyses of the integration of biomass gasification and a gas turbine power plant with and without fogging inlet cooling

Inlet cooling is effective for mitigating the decrease in gas turbine performance during hot and humid summer periods when electrical power demands peak, and steam injection, using steam raised from the turbine exhaust gases in a heat recovery steam generator, is an effective technique for utilizing the hot turbine exhaust gases. Biomass gasification can be integrated with a gas turbine cycle to provide efficient, clean power generation. In the present paper, a gas turbine cycle with fog cooling and steam injection, and integrated with biomass gasification, is proposed and analyzed with energy, exergy and exergoeconomic analyses. The thermodynamic analyses show that increasing the compressor pressure ratio and the gas turbine inlet temperature raises the energy and exergy efficiencies. On the component level, the gas turbine is determined to have the highest exergy efficiency and the combustor the lowest. The exergoeconomic analysis reveals that the proposed cycle has a lower total unit product cost than a similar plant fired by natural gas. However, the relative cost difference and exergoeconomic factor is higher for the proposed cycle than the natural gas fired plant, indicating that the proposed cycle is more costly for producing electricity despite its lower product cost and environmental impact.     

Study of humid air turbine cycle with external heat source for air humidification

In this paper, through introducing an external heat source to the conventional humid air turbine (HAT) cycle, we have studied the performances of the improved humid air gas turbine cycle mainly by exergy analysis method. In order to attain the performance of the humid air gas turbine with external heat source, we compare it with the conventional HAT cycle in detail with different factors such as the pressure ratio, turbine inlet temperature (TIT) and the external circulating water mass flow. The results showed that the specific work of the new system and the humidity ratio of saturator are all increased in some degree. For example, in the same pressure ratio and TIT, when the ratio of the external circulating water mass flow rate with that of the internal water is 0.2, the specific work increases more than 15.2 kJ kg⁻¹a, and the humidity raises at least 2.0 percent points. By introducing the external circulating water into the system, though thermal efficiency of the new HAT cycle is lower than that of the conventional HAT cycle, the exergy efficiency exhibits different results. Generally, when the pressure ratio is over 8, the exergy efficiency for the proposed HAT cycle is higher than the conventional HAT cycle; while less than 8, whether or not the exergy efficiency increases will mainly depend on TIT. In addition, the exergy destructions of components in systems were investigated. Through the comparison of the new system with the conventional HAT cycle, it was found that the exergy loss proportion in combustion declines for the new system, and the proportion of exhaust loss increases. From the viewpoint of total energy system, the HAT cycle with utilization of external heat source is a beneficial way to improve the overall performances of energy utilization. Copyright © 2009 John Wiley & Sons, Ltd.     

Energy,exergy and thermoeconomic analysis of a combined cooling,heating and power (CCHP) system with gas turbine prime mover

In this paper energy, exergy and thermoeconomic analysis of a combined cooling, heating and power (CCHP) system has been performed. Applying the first and second laws of thermodynamics and economic analysis, simultaneously, has made a powerful tool for the analysis of energy systems such as CCHP systems. The system integrates air compressor, combustion chamber, gas turbine, dual pressure heat recovery steam generator (HRSG) and absorption chiller to produce cooling, heating and power. In fact, the first and second laws of thermodynamics are combined with thermoeconomic approaches. Next, computational analysis is performed to investigate the effects of below items on the fuel consumption, values of cooling, heating and net power output, the first and second laws efficiencies, exergy destruction in each of the components and total cost of the system. These items include the following: air compressor pressure ratio, turbine inlet temperature, pinch temperatures in dual pressure HRSG, pressure of steam that enters the generator of absorption chiller and process steam pressure. Decision makers may find the methodology explained in this paper very useful for comparison and selection of CCHP systems. Copyright © 2010 John Wiley & Sons, Ltd.     

Energy and exergy analyses of a CFB‐based indirectly fired combined cycle power generation system

Combined cycle configuration has the ability to use the waste heat from the gas turbine exhaust gas using the heat recovery steam generator for the bottoming steam cycle. In the current study, a natural gas‐fired combined cycle with indirectly fired heating for additional work output is investigated for configurations with and without reheat combustor (RHC) in the gas turbine. The mass flow rate of coal for the indirect‐firing mode in circulating fluidized bed (CFB) combustor is estimated based on fixed natural gas input for the gas turbine combustion chamber (GTCC). The effects of pressure ratio, gas turbine inlet temperature, inlet temperatures to the air compressor and to the GTCC on the overall cycle performance of the combined cycle configuration are analysed. The combined cycle efficiency increases with pressure ratio up to the optimum value. Both efficiency and net work output for the combined cycle increase with gas turbine inlet temperature. The efficiency decreases with increase in the air compressor inlet temperature. The indirect firing of coal shows reduced use with increase in the turbine inlet temperature due to increase in the use of natural gas. There is little variation in the efficiency with increase in GTCC inlet temperature resulting in increased use of coal. The combined cycle having the two‐stage gas turbine with RHC has significantly higher efficiency and net work output compared with the cycle without RHC. The exergetic efficiency also increases with increase in the gas turbine inlet temperature. The exergy destruction is highest for the CFB combustor followed by the GTCC. The analyses show that the indirectly fired mode of the combined cycle offers better performance and opportunities for additional net work output by using solid fuels (coal in this case). Copyright © 2009 John Wiley & Sons, Ltd.     

氢能燃气轮机循环低温能有效利用及热力学分析

为了充分利用液氢的低温Ｙｏｎｇ,在气能燃气轮机循环中附加了一个空气预冷器和氢气透平。该循环的比功,热效率,Ｙｏｎｇ效率均较简单循环燃气轮机有很大提高。本文对液氢－燃气动力循环进行了热力学分析,指出它的优越的动力性能。     

Proposal and thermodynamic performance study of a novel LNG-fueled SOFC-HAT-CCHP system with near-zero CO2 emissions

The cold energy in many liquefied natural gas (LNG) satellite stations is directly carried away by air or seawater. This causes cold energy waste and environmental cold pollution. To solve this problem, a combined power, heating and cooling system (CCHP) driven by LNG is established based on solid oxide fuel cell (SOFC) and humid air turbine (HAT), namely SOFC-HAT-CCHP system, in which, not only can the waste cold energy cool compressor inlet air to decrease power consumption, but supply cold energy for the cold storage and CO₂ recovery. Based on FORTRAN and Aspen Plus, the thermodynamic performance calculation models and the simulation work of the new system are carried out, such as the exergy and energy analysis, as well as the effects of the selected important variables. The results indicate that total exergy efficiency and total power efficiency are 64.7% and 54.4%, and the total thermal efficiency is 79.1%. Besides, the capture rate and purity of the CO₂ are 98.7% and 98.9% respectively. The novel system is environmental protective, energy-saving and efficient, which may provide a new direction to reasonably utilize the waste cold energy in LNG satellite stations.     

Energy and exergy analysis of steam cooled reheat gas–steam combined cycle

This paper deals with parametric energy and exergy analysis of reheat gas–steam combined cycle using closed-loop-steam-cooling. Of the blade cooling techniques, closed-loop-steam-cooling has been found to be superior to air-film cooling. The reheat gas–steam combined cycle plant with closed-loop-steam-cooling exhibits enhanced thermal efficiency (around 62%) and plant specific work as compared to basic steam–gas combined cycle with air-film cooling as well as closed-loop-steam cooling. Further, with closed-loop-steam-cooling, the plant efficiency, reaches an optimum value in higher range of compressor pressure ratio as compared to that in film air-cooling. It has also been concluded that reheat pressure is an important design parameter and its optimum value gives maximum plant efficiency.Component-wise inefficiencies of steam cooled-reheat gas–steam combined cycle based on the second-law-model (exergy analysis) have been found to be the maximum in combustion-chamber (≈30%), followed by that in gas turbine (≈4%).     

Exergy analysis of liquefied natural gas cold energy recovering cycles

Liquefied natural gas (LNG) is known as ‘green fuel’ used in power plant, automobile and so forth due to its higher energy density and environmentally friendly advantages. LNG, besides its high quality chemical exergy, has plenty of physical exergy such as cold exergy and pressure exergy, which could be utilized further. Analysis of physical exergy and its affected factors has been conducted. Based on the analysis, several cycles used for recovering and applying the physical exergy of LNG, such as combined power cycle, gas turbine power generation cycle and automobile air‐conditioning system have been proposed. The parameters affecting the performance of the cycles are discussed. The recovery and utilization of physical exergy of LNG are the important measures to save energy and protect the environment. Copyright © 2005 John Wiley & Sons, Ltd.     

Parametric analysis of a coal based combined cycle power plant

In the present paper thermodynamic analyses, i.e. both energy and exergy analyses have been conducted for a coal based combined cycle power plant, which consists of pressurized circulating fluidized bed (PCFB) partial gasification unit and an atmospheric circulating fluidized bed (ACFB) char combustion unit. Dual pressure steam cycle is considered for the bottoming cycle to reduce irreversibilities during heat transfer from gas to water/steam. The effect of operating variables such as pressure ratio, gas turbine inlet temperature on the performance of combined cycle power plant has been investigated. The pressure ratio and maximum temperature (gas turbine inlet temperature) are identified as the dominant parameters having impact on the combined cycle plant performance. The work output of the topping cycle is found to increase with pressure ratio, while for the bottoming cycle it decreases. However, for the same gas turbine inlet temperature the overall work output of the combined cycle plant increases up to a certain pressure ratio, and thereafter not much increase is observed. The entropy generation, the irreversibilities in each component of the combined cycle and the exergy destruction/losses are also estimated. Copyright © 2005 John Wiley & Sons, Ltd.