循环流化床锅炉冷渣器的调整与改造

冷渣器是循环流化床锅炉的重要辅机之一,其作用是采用水或空气将循环流化床锅炉排出的900℃左右的高温灰渣冷却至200℃以下,回收一部分灰渣的物理显热,提高锅炉效率,它的正常运行直接影响到循环流化床锅炉的安全可靠和经济连续运行,而冷渣器能否维持正常排渣与冷渣器结构、设计有关外,也与运行人员的操作水平有关,故循环流化床锅炉的排渣系统运行不正常,故障率高是导致循环流化床锅炉不能带满负荷运行或被迫停炉的直接原因之一,针对梅县发电厂三期新投产的2台135 MW机组循环流化床锅炉排渣系统在运行中出现的问题进行分析及探讨,并提出了改造的实施方法。     

大型循环流化床锅炉灰渣冷却装置

作为循环流化床锅炉的重要辅机，灰渣冷却装置的正常运行至关重要，特别是随着循环流化床锅炉大型化的发展，已经直接关系到整个锅炉岛的安全经济运行，本文着重描述了非机械式冷渣器的原理，结构特点及其运行方式。     

流化移动叠置式冷渣器的发展与运行经验

针对流化床锅炉的热污染,浙江大学开发了一系列新型流化移动叠置式灰渣冷却器。在实验室理论与大量试验的基础上,设计开发制造了冷渣量为1.5t/h冷渣器示范装置和一系列冷渣器产品。1997年为日本一公司锅炉配用的大容量冷渣器（单台冷渣量达7.2t/h）目前已与锅炉一起投入试验生产,运行正常,介绍了流化床移动叠置式冷渣器在浙江大学的发展与运行经验。图6表1参8     

大型循环流化床锅炉冷渣器的运行故障及改进措施

循环流化床锅炉风水冷渣器运行存在主要问题及原因分析,并提出了改进措施。介绍和推选滚筒冷渣器,发展完善滚筒冷渣器有助于大型循环流化床锅炉安全可靠运行。     

220 t/h循环流化床锅炉排渣系统运行概况

循环流化床锅炉是80年代发展起来的高效率、低污染和可良好综合利用的燃煤技术,循环流化床锅炉的排渣方式也各有不同,而排渣系统的正常运行一直是循环流化床锅炉的一个重点、难点。此文较为详细地介绍了侯马晋田热电有限公司220t/h锅炉排渣系统改造后的运行情况。     

风水共冷式冷渣器及其经济性分析

采用冷渣器是降低流化床锅炉灰渣物理热损失的有效方法。本文在已有冷渣器的基础上,设计出一种适用于大容量流化床锅炉的新型冷渣器——风水共冷式冷渣器,并分析了这种冷渣器的经济性。     

滚筒冷渣器传热模型的研究

分析了携带翅片滚筒冷渣器内灰渣颗粒的流动过程和传热过程,提出了滚筒冷渣器一维轴向传热模型,模型中考虑了渣中未燃尽碳的残余燃烧,模型参数根据文献和实验室实验确定.利用该模型对一台300MW循环流化床锅炉上滚筒冷渣器的温度进行了预测,并与实际运行参数进行了比较.结果表明:该模型可以很好地预测滚筒冷渣器出口灰渣的温度和冷却水温度.     

流化床风冷式冷渣器的排渣温度及其分布

采用冷渣器可回收流化床锅炉的灰渣余热,便于干式除渣及灰渣的综合利用。本文给出了流化床风冷式冷渣器的排渣温度及其分布规律。     

410 t/h CFB锅炉风水联合冷渣器的改进

排渣系统运行故障是目前影响循环流化床锅炉运行可靠性的主要因素之一,特别是风水联合冷渣器的事故常导致机组降负荷运行甚至停运,给电厂造成很大的经济损失.结合永济发电厂的实际情况,针对运行中存在的问题,提出了防止冷渣器结焦堵塞的措施,以及堵塞后清理疏通方法.通过设备改进和燃烧调整等工作,经过一年多的运行考验,效果非常明显,冷渣器运行的可靠性大大提高.     

我国大型CFB锅炉现状分析及对福建省CFB锅炉大型化发展的启示

分析我国目前已投运以无烟煤为燃料的大型循环流化床锅炉特点、运行中存在的问题及其解决方案。指出目前已投运大型CFB锅炉出现的主要问题在于输煤系统、给煤系统、灰渣系统以及运行中的磨损等几方面,其中冷渣器的结焦、堵渣、排渣不畅等是主要的共性问题。认为对于燃烧福建无烟煤的大型CFB锅炉,宜于采用水冷或汽冷旋风分离器,炉膛应敷设卫燃带以防止磨损和提高燃尽度,应采用结合“T”型定向的风帽技术和采用水冷滚筒式冷渣器以利于解决灰渣系统问题。     

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.     

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.     

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.