锅炉运行氧量对锅炉效率影响的定量分析

在锅炉参数耗差分析中,计算运行氧量偏离基准值引起的煤耗偏差时,一般是根据反平衡法中的热损失计算模型来求解得到,但由分析可知运行氧量除了直接影响锅炉效率外,还通过影响排烟温度、飞灰含碳量等参数间接影响锅炉效率.借助神经网络较强的非线性拟合能力、网络泛化及容错能力,构建了基于BP神经网络的排烟损失和机械未完全燃烧损失两项之和的网络模型,利用该模型定量分析了运行氧量变化对锅炉效率的影响.计算结果表明该模型具有较高的准确性,运行氧量对锅炉效率影响的曲线走向符合物理规律,为运行氧量的耗差分析提供了一种新方法.     

锅炉运行氧量基准值确定方法的研究

电站锅炉炉膛出口运行氧量是锅炉运行中的重要参数.不仅对锅炉效率有重要的影响,而且还将引起其他运行参数的变化,进而影响机组的供电煤耗率.借助神经网络较强的非线性拟合能力、网络泛化及容错能力,根据锅炉运行氧量的特性进行建模,获得了运行氧量、机组供电煤耗率与机组各运行参数之间关系的网络模型,并且以机组的供电煤耗率为优化目标函数,利用遗传算法对输入参数进行全局寻优,得到了各运行工况下最优氧量的预测值.研究结果表明该模型具有较高的准确性,通过全局寻优得到的运行氧量值具有可操作性,为锅炉运行氧量基准值的确定提供了一种新方法.     

基于多项式拟合的锅炉运行参数对燃煤机组发电煤耗影响研究

为精确计算锅炉运行参数对燃煤发电机组发电煤耗的影响,以发电煤耗的数学模型为基础,采用微积分理论,忽略管道效率和汽轮机热耗率的影响,建立发电煤耗与锅炉效率的微分关系。以某电厂330 MW亚临界燃煤发电机组为例,利用机组历史运行数据和设备厂家提供的设计资料,基于拉格朗日多项式拟合分别建立排烟温度、锅炉效率、发电煤耗与机组负荷率的拟合关系,从而得到任意工况下排烟温度与发电煤耗目标值的数学模型。依据锅炉排烟热损失的简易算法,建立锅炉排烟温度和运行氧量对发电煤耗影响耗差分析模型,最后对采样周期内锅炉运行参数进行聚类划分,计算排烟温度和运行氧量对发电煤耗影响的数值。该方法计算结果准确,方便实用,为电厂节能改造、优化运行、检修决策和节能技术监督提供参考。     

基于GB标准电站锅炉运行参数变化对供电煤耗影响研究

拟采用VC++软件编程计算供电煤耗,基于GB10184-88标准,通过定量分析电站锅炉运行参数中的排烟温度、排烟氧量及飞灰含碳量的变化对供电煤耗的影响,提出影响供电煤耗的主次因素:排烟温度、飞灰含碳量及排烟氧量,并提出降低煤耗的合理化建议,以提高火电厂的热经济性指标,指导电厂安全经济运行。     

600MW超超临界锅炉最佳运行氧量试验研究

以国内某电厂600MW超超临界锅炉为研究对象,对其进行了变氧量试验研究,通过测量不同工况下锅炉运行各项热损失并计算热效率,进而结合辅机电耗计算供电煤耗,分析运行氧量对锅炉热效率、辅机电耗及供电煤耗的影响,得到最佳运行氧量值以使机组经济运行。结果表明,在600MW、500MW、360MW电负荷下,最佳运行氧量分别是将锅炉表盘氧量值偏置1.0(即3.82%附近)、偏置0.4(即4.16%附近)、偏置0.4(即5.49%附近)。研究结果可为运行人员调整运行方式提供参考。     

电站锅炉运行氧量基准值确定方法的比较分析

合理确定在不同工况下的运行氧量基准值是实现电站锅炉高效经济运行的关键。炉膛出口运行氧量的改变会导致锅炉热损失以及送风机电耗的改变,从而影响电站经济性。以供电煤耗率作为机组经济性评价准则来确定机组运行氧量基准值的研究取得了一定的成果,本文对其中四种确定锅炉运行氧量基准值的方法进行了比较分析。     

锅炉经济性分析及最优氧量的确定

在锅炉送风及炉膛压力控制系统中,氧量设定值的改变会导致锅炉热损失及送风机电耗的改变,从而影响电站经济性.针对机组运行状态发生改变后的氧量最优值更新问题,提出了改进的增量式模糊数值型关联规则挖掘算法,并以 1 台300 MW 机组为例进行了分析.结果表明:这种新的挖掘算法与传统的数据挖掘方法相比,具有良好的快速性,效率可提高4～16倍,大大减少了候选项集的数目,因而大量减少了重复计算的费用.该方法确定的氧量最优值可有效降低机组供电煤耗效率,并可提高机组运行经济性.     

锅炉在线氧量测点安装常见错误浅析

锅炉炉膛出口氧量参数是锅炉运行中的重要参数,不仅对锅炉效率有着重要的影响,而且还将引起其他参数的变化,进而影响机组供电煤耗。针对目前大量电厂存在运行氧量显示失真的问题,提出了对在线氧量测点安装的整改建议,进而为火电厂优化氧量测量提供参考。     

主蒸汽压力变化对机组煤耗率的影响分析

主蒸汽压力是机组实际运行中必须密切监视和调节的主要参数之一,在机组实际运行中会不可避免的偏离设计值,从而影响机组的发电标准煤耗率,影响机组的热经济性和安全性.在火电厂热经济性统一物理模型和数学模型的基础上,根据多元扰动下的热力系统能效分析模型得到主汽压变化对煤耗率影响的计算模型,并以某电厂660 MW机组为例进行验证,并计算了此机组不同工况下主汽压变化对机组煤耗的影响,并绘制成图,对其规律进行了分析.此计算模型得到的计算结果误差较小,足以满足工程实际的需要.     

加热器上端差对煤耗率影响的通用强度矩阵计算模型

定量计算分析加热器上端差变化对火电机组发电煤耗率的影响对节能降耗具有重要的现实意义,为解决以前计算方法的局限性,提出了一种计算上端差改变对煤耗率影响的新方法.以火电机组热经济性分析的统一物理模型和数学模型为基础,借助梯度算子,建立了基于强度矩阵的上端差改变对煤耗率影响的通用计算模型,并对某600MW机组的典型工况进行了计算.结果表明：该模型推导简单、计算量小、精度高且通用性强;强度矩阵可直接用于定性和定量地分析各个加热器上端差改变对机组煤耗率的影响;端差对经济性的影响除了其本身的大小外,还与加热器所处的位置和结构有关,在运行或检修中,更应关注强度系数大的加热器端差变化对经济性的影响.     

火电厂节能工作浅析

本文探讨了火电厂节能基本程序和工作方法,分析节能工作要从基础工作、技术创新、设备整治、燃烧管理等方面入手的论述.     

浅析磨合期汽车的使用

如何合理使用磨合期的汽车，使其摩擦机件的磨损量能够平稳、均匀地磨合而不至于过度磨损，对汽车实际使用寿命有着重要的意义。从机器磨合期的特点和磨损机理出发，对汽车磨合期如何正确使用进行了有实际意义的探讨。     

Geothermal energy in agriculture in Yugoslavia

SFR Yugoslavia has natural hot water springs practically all over its territory, indicating the presence of geothermal reservoirs underground. There is no final estimate of how much energy can be expected from this new resource, except for figures based on the results of studies and investigations.The first use of geothermal energy in Yugoslavia in numerous spas dates back to the 19th century. Some remarkable examples of central heating are known, but the most widespread use is in agriculture (in greenhouse heating, farm heating and drying of agricultural products).     

Energy conservation measures in an institutional building in sub-tropical climate in Australia

In this study, various energy conservation measures (ECMs) on heating, ventilating and air conditioning (HVAC) and lighting systems for a four-storied institutional building in sub-tropical (hot and humid climate) Queensland, Australia are evaluated using the simulation software called DesignBuilder (DB). Base case scenario of energy consumption profiles of existing systems are analysed and simulated first then, the simulated results are verified by on-site measured data. Three categories of ECMs, namely major investment ECMs (variable air volume (VAV) systems against constant air volume (CAV); and low coefficient of performance (COP) chillers against high COP chillers); minor investment ECMs (photo electric dimming control system against general lighting, and double glazed low emittance windows against single-glazed windows) and zero investment ECMs (reset heating and cooling set point temperatures) are evaluated. It is found that the building considered in this study can save up to 41.87% energy without compromising occupancies thermal comfort by implementing the above mentioned ECMs into the existing system.     

Leading-edge Technologies in Hydropower Development in China

After the implementation of the Reform and Opening-up Policy for a period of 40 years, the exploitation of China’s hydropower resources developed significantly. Through vast amounts of scientific and technological research and construction practices, China has accumulated abundant engineering experience with respect to the construction technologies required for 300-meter-high concrete arch dams, 200-meter-high roller-compacted concrete gravity dams, 200-meter-high concrete face rockfill dams, and 250-meter-high earth core rockfill dams, large-flow discharge and energy dissipation, huge underground cavern group constructions, complicated foundation treatments for high earth and rockfill dams and high and steep slope reinforcements. These series of technologies have now reached an international leading level. In the near future, these technical improvements will likely have broader application prospects and make greater contributions toward hydropower development both in China and across the world.     

Uncertainties in decarbonising heat in the UK

Heating is arguably one of the most difficult sectors to decarbonise in the UK's energy system. Meeting the 80% greenhouse gas emission reduction target by 2050 is likely to require that heat related emissions of CO₂ from buildings are near zero by 2050, and there is a 70% reduction in emissions from industry (from 1990 levels). Though it is clear that the use of the natural gas network will reduce over time, recent modelling suggests a limited residual role for gas by 2050 to help meet peaks in heat demand. High levels of uncertainty about the way in which heat will be decarbonised present a number of challenges to policy makers. This paper will explore the risks and uncertainties associated with the transition to a low carbon heat system in the UK as outlined by the 4th carbon budget review. The potential impact of key uncertainties on the levelised costs of heat technologies and the development of energy networks are explored using a sensitivity analysis approach. Policy changes required to decarbonise the heat sector are also examined.     

Solar drying in sludge management in Turkey

Two main wastewater treatment plants in Bursa city in Turkey will start to operate and produce at least 27,000 tons of dry solids per year by the end of 2006. The purpose of this study was to investigate an economical solution to the sludge management problem that Bursa city would encounter. The general trend in Turkey is mechanical dewatering to obtain a dry solid (DS) content of 20%, and liming the mechanically dewatered sludge to reach the legal landfilling requirement, 35% DS content. This study recommends limited liming & solar drying as an alternative to only-liming the mechanically dewatered sludge. Open and covered solar sludge drying plants were constructed in pilot scale for experimental purposes. Dry solids and climatic conditions were constantly measured. Faecal coliform reduction was also monitored. The specially designed covered solar drying plant proved to be more efficient than the open plant in terms of drying and faecal coliform reduction. It was found that, if the limited liming & solar drying method was applied after mechanical dewatering instead of only-liming method, the total amount of the sludge to be disposed would be reduced by approximately 40%. This would lead to a reduction in the transportation, handling, and landfilling costs. The covered drying system would amortize itself in 4 years.     

Viscous heating in liquid flows in micro-channels

Many experimental works on forced convection through micro-channels evidenced that when the hydraulic diameter is less than 1 mm, conventional theory can no longer be considered as suitable to predict the pressure drop and convective heat transfer coefficients. This conclusion seemed valid for both gas and liquid flows. Sometimes the authors justified this claim by invoking “new” micro-effects. On the contrary, in this paper the explanation of the experimental results obtained for micro-channels in terms of friction factors will be researched inside the conventional theory (Navier-Stokes equations). In particular, this paper will focus on the role of viscous heating in fluids flowing through micro-channels. A criterion will be presented to draw the limit of significance for viscous dissipation effects in micro-channel flows. The role of the cross-sectional geometry on viscous dissipation will be highlighted and the minimum Reynolds number for which viscous dissipation effects can no longer be neglected will be calculated as a function of the hydraulic diameter and of the micro-channel geometry for different fluids. It will be demonstrated how viscous effects can explain some experimental results on the Poiseuille numbers in micro-channels, which recently appeared in the open literature.     

Electoral cycles in electricity losses in India

A third of electricity in India is lost each year, where losses refer to power that is supplied but not billed. Utilizing data from the power corporation of Uttar Pradesh, India's most populous state, we study the politics of electricity losses. Examining annual data over four decades, we document that UP's electricity losses tend to increase in periods immediately prior to state assembly elections. Drawing upon geographically disaggregated data for the period 2000–09, we observe higher line losses just prior to the 2002 and 2007 state elections. Our analysis shows that the incumbent party was more likely to retain the assembly seat as line losses in the locality increased. We interpret these results as corroboration that political parties deliberately redirect electricity to flat rate and unbilled users in a context of chronically inadequate supply. Political factors appear to affect line losses in ways that technical and economic factors alone cannot explain.