垃圾水分对焚烧炉热力性能的影响

我国目前的垃圾具有水分高、热值低等现状,直接焚烧时,会降低燃烧温度,增加排烟热损失,降低焚烧炉效率,热值过低还需要添加煤粉稳燃。研究了垃圾水分对燃料热值、焚烧炉烟气量、炉膛温度、焚烧炉排烟热损失、焚烧炉效率、垃圾耗量及煤耗量等的影响规律。计算表明:水分增加时,燃料热值、焚烧炉效率、理论燃烧温度降低,而排烟热损失、总烟气量、燃料消耗量增加。但是排除垃圾的水分,而实际垃圾的消耗量不变。以某垃圾焚烧发电厂的垃圾样品为例,得到了焚烧炉几个主要热力参数的变化。     

1t／h医疗垃圾焚烧炉热力性能研究

本文介绍了处理量为1t／h的医疗垃圾焚烧炉的结构和参数。得到了混合燃料热值和成分、助燃燃料量、烟气停留时间、焚烧炉蒸发量的计算公式。采用校核方法,对垃圾热值变化、水分变化和垃圾处理量变化时焚烧炉的热力特性进行了计算,分析了各参数的变化规律。计算表明,垃圾热值提高,蒸发量、焚烧炉效率提高,理论燃烧温度、管束出口烟温、排烟温度和热空气温度也提高,但提高幅度不同;垃圾水分增加时,焚烧炉蒸发量、效率、理论燃烧温度、管束出lz？烟温、排烟温度和热空气温度降低;蒸发量、焚烧炉效率随垃圾处理量的增加而增加,绝热燃烧温度基本不变,管柬出口烟温、排烟温度和热空气温度略有增加。     

空气预热器进风温度变化时基于燃料高位和低位热值的锅炉排烟热损失计算

锅炉排烟热损失是评价燃煤火力发电厂技术经济性的关键,详细分析了利用烟气余热来提高空预器进风温度对锅炉排烟热损失的影响,给出了以燃料高位热值和低位热值为基准的各项排烟热损失计算公式。计算结果表明,空预器进风温度提高时,锅炉热效率增加,且以高位热值为基准和以低位热值为基准计算的排烟热损失与锅炉主机厂的性能计算结果一致,为空气预热器进风温度变化时锅炉排烟热损失的计算提供了可行的方法。     

褐煤预干燥对锅炉传热特性及运行经济性的影响

以某300MW褐煤燃烧机组为研究对象,计算和分析褐煤干燥程度(即水分质量分数分别为34.1%、30.0%、25.0%、20.0%和18.0%)对锅炉运行中炉膛燃烧及各受热面传热特性的影响,研究了褐煤干燥前后锅炉热经济性的变化.结果表明:随着褐煤干燥程度的加深,理论燃烧温度比水分质量分数为34.1%的原褐煤分别提高了50.19K、101.51K、134.82K和148.13K,最大升高幅度达8.18%,炉膛内燃烧加剧,辐射放热量增加,烟气流速降低,各受热面的对流传热系数和辐射传热系数减小,但单位燃料的对流传热量却有所增加,锅炉排烟温度下降,锅炉热效率和运行经济性提高.     

天然气烟气冷凝式余热利用技术

介绍天然气冷凝式余热回收原理,分析天然气燃烧产物的组成,对排烟热损失、节能量、冷凝率进行了计算和分析。结果显示,烟气中可回收的蒸气潜热达到烟气低位热值的11.2%。排烟热损失随排烟温度的升高而增加,当排烟温度低于露点温度时,排烟热损失随排烟温度的升高急剧增加,水蒸气冷凝率随排烟温度的升高而降低。此外,对这种方法降低烟气中NOX排放的环保特性也进行了探讨。     

降低排烟温度,提高锅炉热效率

在锅炉改造时,有些单位往往仅注意炉膛的改造,而忽视尾部对流受热面的增加,而且改造都是以增容方式出现的,结果将导致锅炉排烟温度的升高和排烟量的增加。使得改造效果不十分显著。由于技术经济条件的限制,烟气离开锅炉排入大气时,烟气温度比冷空气温度要高很多。排烟温度对锅炉热效率有着直接的影响,排烟温度越高,排烟热损失就越大,锅炉热效率就越低（见图1）。图1排烟温区对排烟热损失的影响通常在过量空气系数一定时排烟温度每升高或降低13－18℃时,排烟热损失就升高或降低1％。我们知道,进入省煤器的给水温度一般都不高,仅3…     

生物质电厂锅炉燃烧调整试验研究

分析了生物质发电现状,针对某生物质电厂秸秆锅炉,进行了燃烧调整试验研究,考察了一次风、二次风、燃料性质和锅炉漏风对燃烧的影响.结果表明,加强燃烧中心区通风,协调一、二次风量,可降低锅炉不完全燃烧损失和排烟损失,提高锅炉效率;控制人厂燃料含土量与水分,减少杂物,可提高燃烧安全性;降低锅炉漏风量、调整锅炉配风、可保证锅炉正常运行.为生物质锅炉设计、改造和运行提供了参考.     

Consteel电炉余热锅炉的热平衡计算方法研究

针对Consteel电炉余热锅炉烟气入口参数不稳定的特点,得到了余热锅炉的各项热损失、锅炉效率、有效利用热量和蒸发量的计算公式。对65t Consteel电炉炼钢设备余热锅炉进行了热平衡计算,计算表明,锅炉的排烟热损失随烟气入口温度的降低而增加,而锅炉效率、有效利用热量和蒸发量随烟气入口温度的降低而降低,锅炉的平均蒸发量为23．1t／h。     

增氧燃烧型冷凝式燃气锅炉节能特性的研究

指出了冷凝式燃气锅炉在实际应用中存在的问题,给出了增氧燃烧型冷凝式燃气锅炉的概念。以陕北天然气作为燃料,对增氧燃烧型冷凝式燃气锅炉的节能特性进行的研究表明:采用增氧燃烧技术的冷凝式燃气锅炉,热烟气中水蒸气的露点温度和理论冷凝率、锅炉的供暖季节效率随着增氧体积份额的增加而增加;锅炉排烟热损失和引风机的能耗随着增氧体积份额的增加而减少。     

600MW亚临界锅炉富氧改造热力学性能及?分析

利用锅炉热力计算和?分析的方法对某600 MW燃煤锅炉在不同O_2/CO_2气氛下进行锅炉热力特性和?效率计算,并与空气气氛下锅炉热力特性和?进行比较。结果显示:在富氧燃烧条件下,锅炉排烟量和排烟热损失有所减少,锅炉效率有所增加,同时锅炉的辐射和半辐射受热面的烟气侧换热系数增加。O_2/CO_2中氧气分压处于25%～30%之间时,锅炉的理论燃烧温度和炉膛出口温度与空气气氛相似。富氧条件下锅炉?效率提高1%左右,且?损失大部分发生在传热和燃烧过程中。     

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%.     

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。     

Contents in Volume 23,2014

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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.     

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.