华能玉环电厂1000MW超超临界锅炉水冷壁超温分析与应对方案

高参数大容量燃煤锅炉水冷壁超温的主要原因是煤水比失调,水冷壁结焦、火焰偏斜以及水冷壁节流孔圈被金属氧化皮堵塞或异物堵塞造成流经该水冷壁管的给水量减少也是造成水冷壁超温的原因。从运行调整的角度主要采用调整配风、稳定燃烧、降低升降负荷的速率、防止燃烧剧烈变化等多种手段来控制水冷壁超温。     

350MW超临界锅炉水冷壁超温解决措施

近年来,350 MW超临界墙式切圆锅炉得到逐步推广,该炉型燃烧工况稳定,经济性较好,但是不少锅炉存在比较严重的水冷壁超温问题。基于大连开发区热电厂350 MW超临界墙式切圆锅炉水冷壁超温问题及调整解决措施,提出解决该问题的主要应对思路,可供出现同类问题参考。     

负荷变化对900 MW超临界锅炉炉内燃烧影响的数值模拟

利用Fluent软件对1台900 MW四角切圆燃烧锅炉在不同负荷下炉内燃烧过程进行了数值模拟,分析了负荷变化对炉内流动和传热的影响规律.结果表明:在高负荷工况下运行时,炉内燃烧充分且稳定,但是炉内火焰更容易冲刷水冷壁,可能发生局部结渣现象;在低负荷工况下运行时,炉内火焰充满度较差,切圆燃烧的稳定性显著下降,炉膛水冷壁灰污表面温度也相应降低,水冷壁表面结渣的倾向弱化,沿高度方向水冷壁吸热不均匀性增大.由于该锅炉的低NOx燃烧器采用了分离燃尽风,使得高温区扩展,火焰中心高度比采用有关标准推荐的方法计算所得结果高4~5 m.     

超临界压力W火焰锅炉运行方式对炉内热负荷影响的试验研究

对某600 MW超临界压力W火焰锅炉炉膛水冷壁壁温进行了测量,获得了炉膛水冷壁热负荷分布,调整锅炉运行方式(如磨煤机投运方式、前后墙的总风门挡板开度、煤粉细度和三次风风门挡板开度等),测量并计算炉内热负荷.结果表明:煤粉细度对炉内热负荷几乎没有影响;前后墙总风门挡板开度会影响炉内火焰行程,应该采用"前墙压后墙"的运行方式;三次风风门挡板开度变化会改变上、下炉膛热负荷的分布;不投运的磨煤机所对应区域的热负荷明显下降.     

300MW机组W型火焰锅炉燃烧调整试验研究

针对山西阳泉第二发电厂３００ＭＷ机组Ｗ型火焰锅炉存在的过热器超温、飞灰含碳量高、结渣等问题。进行了以二次风配风试验为主要内容的锅炉燃烧调整,通过在不同工况下检测炉内火焰温度分布等锅炉运行参数,分析了各主要二次风对锅炉炉内燃烧工况的影响及其调节规律,并讨论了锅炉负荷变化时对炉内温度分布和配风的影响。     

1000MW超超临界锅炉水冷壁壁温计算

采用分区计算简化大容量高参数超超临界锅炉炉内辐射、对流传热模型,研究炉膛水冷壁热负荷及壁温的空间分布情况,并与试验数据进行了对比,计算结果与试验值之间的偏差较小,最大为5.72%.该模型与算法可给出不同锅炉负荷条件下,水冷壁壁面热负荷与壁温沿炉膛宽度方向的分布规律.结果表明,水冷壁热负荷与壁温均呈现出中间高两端低的弧形分布.四角切圆燃烧锅炉火焰位置对炉内传热有很大影响.模拟计算可为超超临界锅炉的运行提供参考,预测了在材料允许温度范围内,火焰中心偏斜最大不超过2 m.     

660 MW超超临界锅炉火焰偏斜调整方法浅析

某公司超超临界660 MW机组四角切圆锅炉由于设计、安装等原因,运行中出现燃烧火焰偏斜问题,水冷壁壁温左右侧偏差达到80℃,后屏出口蒸汽温度左右侧偏差达到60℃,主、再汽温左右侧偏差达到15℃,严重影响机组运行的安全性、经济性。基于对660 MW四角切圆锅炉燃烧调整方法的分析与总结,纠正了火焰中心偏斜,消除了水冷壁壁温偏差和汽温偏差,优于设计值,确保了锅炉安全运行。     

600MW超临界W火焰锅炉前墙上炉膛水冷壁撕裂原因分析及处理

针对某超临界W火焰锅炉投产初期出现的前墙上炉膛水冷壁变形撕裂问题,分析了现场实测汽温数据,进行了炉内数值模拟计算和水动力校核计算,得出汽温偏差过大的原因.结果表明:各管出口汽温偏差太大导致上炉膛水冷壁的变形撕裂;通过运行调整、检修和技术改造,水冷壁的变形撕裂问题得到解决,满足了锅炉安全稳定运行的需要.     

黄埔发电厂1025t/h直流锅炉改进成一次风微量反偏转燃烧

黄埔发电厂1025t/h UP型直流炉改用一次风微量反偏转燃烧方式取得了令人满意的效果,炉内热负荷分布均匀,水平烟道两侧烟温基本一致。对防止水冷壁管超温爆漏方面起到了重要作用。     

600MW超临界循环流化床锅炉运行优化试验研究

在600 MW超临界循环流化床(CFB)锅炉上完成了一系列试验。试验包括60 m高CFB冷模试验、600 MW超临界CFB锅炉炉内(包括外循环系统)燃烧与传热均匀性试验以及水冷壁传热特性试验,分别研究了60 m高CFB冷模试验提升管内气固浓度分布、给煤均匀性对600 MW超临界CFB锅炉炉膛出口烟气成分均匀性的影响、二次风射程随负荷变化规律;分析了100%负荷下600 MW超临界CFB锅炉水冷壁汽水温度分布特性,并通过水冷壁背火侧壁温分析了水冷壁壁面气固流动特性、热流密度特性。通过这些试验研究发现炉膛上部(距布风板40 m以上)气固浓度随着炉膛高度的增加仅轻微增加;炉膛底部风煤混合对炉膛出口的烟气成分有强烈影响;通过测量水冷壁背火侧壁温可以分析获得炉内水冷壁壁面附近多项热力参数。     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

Contents in Volume 23,2014

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Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.     

汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.