燃用非设计煤种链条炉排锅炉过热蒸汽超温改造

DHL 35—450/3.82—AⅡ型链条炉排锅炉因燃用非设计煤种,导致炉内燃烧恶化,炉膛出口出现大量炽热粒子冲刷过热器,使得过热蒸汽超温,锅炉出力下降。针对上述问题,提出了评价粒子流冲刷过热器所引起的传热影响的计算方法和炉拱改造方案,并采用CFD技术,对炉拱改造前后的炉内流场进行了模拟与对比。研究结果表明,通过改造炉拱,改善了炉内燃烧工况,炉内火焰充满度高,形成了"α"火焰,消除粒子流,使锅炉性能得到优化。     

流态粒子炉的热交换

综述了流态粒子炉的传热模型，探讨影响传热因素。根据笔者和有关学者的实验研究，得知流态粒子炉中温加热能力为气氛炉的三倍，最佳流化状态及合理的粒子筛分组成是提高其加热能力的主要手段。     

大容量高热值垃圾焚烧炉炉内流场的模拟研究

为优化大容量高热值垃圾焚烧炉的燃烧工况,利用数值模拟手段对不同炉膛结构下的焚烧炉内部流场进行对比分析。结果表明,烟道位置对焚烧炉内的流场分布具有明显影响,烟道入口的最佳位置为垃圾料层燃烧段的上方;前拱二次风会在烟道入口处形成涡流,涡流随后拱倾斜角的增大而增长;前拱对气相燃烧的影响大于后拱;当前拱倾斜角为21°、后拱倾斜角为35°时,炉内挥发分燃烧的效率较高,流场分布较为理想。     

小型农村固体废弃物焚烧炉炉拱结构的研究

对处理农村固体废弃物的小型L型火焰焚烧炉炉拱的结构参数进行研究。提出一种用于L型火焰焚烧炉的新型炉拱结构。采用正交试验设计方法,确定了8种不同的试验条件。炉拱的最佳无量纲准则为:H/L=0.333,H/L=0.12,前拱角度为45°。通过热态试验验证以农村固体废弃物为燃料的L型火焰焚烧炉的炉拱结构的有效性。     

锅炉炉拱的优化设计

１．动量合成法的提出为了加强炉内气流混合，合理组织炉内的热辐射和烟气流动，减少锅炉的热损失，提高锅炉的燃烧效率，在层燃炉中要布置合适的炉拱。锅炉炉拱设计方法很多，如覆盖率法、辐射源法、经验查表法等，这些方法均未反应出烟气在炉内的流动状况和前拱几何尺寸...     

900t/d高热值生活垃圾焚烧炉炉体结构的数值模拟研究

采用数值模拟的方法,针对某台900 t/d高热值垃圾焚烧炉,研究前后拱角度、烟道位置对炉内燃烧过程、温度场、速度场、烟气主要组分分布及污染物排放特性的影响。结果表明:适当降低前拱角度有利于气流扰动和混合,强化传热和提高燃料燃尽率,提高后拱角度有利于增加烟气停留时间,促使热解后的可燃气体燃烧充分,提高热效率。前拱角度为21°,后拱角度为35°时炉内获得最佳的流场分布。烟道上移将增大炉膛容积,降低容积热负荷,出口烟气温度降低。烟道下移,炉膛容积减小,烟气在炉膛内的停留时间降低,烟道温度升高。烟道左右偏移容易造成温度场分布不均、水冷壁高温腐蚀等现象。从烟道模型中得到了最佳气流分布场和低的排放值。     

移动火床炉消烟炉拱的模拟试验研究

火床炉冒黑烟是一个混合不良的问题，而混俣的关键在于炉拱。对移动火床炉拱区气体混合特性进行了模拟试验研究，比较了不同拱型条件下拱区气体的混合性能，证明由Ｍ形前拱和高覆盖率后拱组成的拱组具有最佳的混合性能。最后，给出了一个典型的拱区混合模拟浓度场，以展示拱区气体混合全貌。     

链条锅炉复合燃烧及其优化的数值模拟研究

以某化工厂一台35 t/h链条锅炉为物理模型,借助Fluent软件对链条锅炉采用复合燃烧技术改造前后炉内燃烧特性以及优化送粉速度进行数值模拟计算。计算结果表明:链条锅炉采用复合燃烧改造后,炉内温度分布更加均匀,炉内高温区达到1500~2000 K,整体烟气平均温度升高了100~200 K;随着送粉速度的提高,炉内高温区呈现从左到右的偏斜趋势,且后拱上方的回流区逐渐变小,当送粉速度为20 m/s时,炉内温度场和速度场最为合理。     

关于防止火床炉炉膛冒正压的若干措施

根据流体力学和炉内空气动力学的基本原理,分析了炉内冒正压的机理,提出对大空间,小炉拱的炉膛,只要保证炉膛出口在０－２０Ｐａ的负压时不会出现冒正压;对极低,长炉拱小空间炉膛是否出现冒正压现象的关键在于炉膛,炉拱结构和炉内的空气动力参数是否合理。同时提出防止措施。     

新型碳化硅节能炉拱

1 前言 锅炉炉拱是指锅炉炉膛下部直接遮蔽炉排的蓄热反应墙,即炉墙向炉膛内突出的部分.炉拱的作用是储蓄热量、调整燃烧中心、提高炉膛温度、加速新煤着火以及延长烟气流程,从而促进充分燃烧.因此炉拱在锅炉经济运行中的作用是很大的.     

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.