降低大型火力发电机组厂用电率的探讨

厂用电率是衡量火力发电机组经济性能的主要经济技术指标之一,分析了华能德州电厂6#机组(660MW)存在的节电潜力以及在降低机组厂用电率方面所采取的一系列措施.通过优化辅机运行方式、进行技术改造、加强运行管理等方法,使6#机组厂用电率得到了较大幅度的降低,达到了节电降耗的目的.     

循环流化床锅炉发电机组的节电措施

现役循环流化床锅炉汽轮发电机组厂用电率高达10％～13％．明显地抵消了循环流化床锅炉燃烧效率高、排放污染低、煤种适应性强等诸多优势，厂用电率高的问题已成为制约循环流化床锅炉大型化快速发展的瓶颈．其中锅炉辅机的耗电率占了很大的比例，是降低机组厂用电率的主攻方向，本文针对广东梅县发电厂三期5、6号循环流化床锅炉从运行调整、辅机系统改造等方面提出了降低循环流化床锅炉机组厂用电率的各项措施进行了分析．使循环流化床锅炉发电机组的厂用电率降到接近同类型煤粉炉发电机组的程度。     

600 MW供热机组汽动给水泵开机经验介绍

某热电厂2×600 MW机组自投产以来,由于机组启动时间长、电动给水泵运行成本高、耗电量大、设备的潜力没得到充分发挥;为有效减小发电量与供电量差值,节省厂用电、降低厂用电率、尽可能的减少发供电煤耗,有效提高机组经济性。     

基于流态重构的循环流化床锅炉节能燃烧技术的应用实践

针对循环流化床锅炉辅机电耗普遍偏高的问题,先后在燃烧劣质无烟煤的135 MW机组和300MW机组循环流化床锅炉上进行了降低床料存量实现流态重构的燃烧试验,分析了基于流态重构的循环流化床锅炉节能燃烧技术对改善锅炉机组性能的影响.运行实践表明:流态重构后,循环流化床锅炉辅机电耗明显下降,在风机具备变频条件下电耗可降低更多;135 MW机组锅炉运行厂用电率从8.2%降低为6.9%,300MW机组锅炉厂用电率约为4.3%,锅炉主要受热面的磨损明显减轻,飞灰可燃物含量降低3%～5%.     

单机运行循泵节能优化运行策略探讨

基于2017年循泵运行数据报表的分析,发现全年循泵对标运行情况不佳,存在循泵厂用电率偏高的现象。专家小组经对相关数据的全面分析、调查和比对,发现在单机组运行工况下,运行方式不经济,循泵叶角调节不合理。通过讨论分析并经试验验证,采用单机组运行单循泵方式、循泵叶角精益化调节等手段,达到单机运行工况下循泵的节能优化运行,实现了降低循泵厂用电率的目标。     

620℃超超临界煤电机组能耗指标动态计算与分析

为分析再热汽温620℃超超临界机组的日常连续运行实际能耗,以某电厂设计蒸汽参数为28 MPa/600℃/620℃的1 000 MW超超临界湿冷机组为研究对象,基于机组运行大数据,开展了长周期的能耗指标动态计算与分析。研究表明:额定负荷下,锅炉热效率达到了保证值,汽轮机组热耗率比设计值高32 kJ/(kW·h),厂用电率优于设计值,修正后的机组供电标准煤耗率基本达到设计值;随着负荷率的降低,锅炉热效率降低,汽轮机组热耗率升高,厂用电率升高,机组发、供电标准煤耗率增加,机组发、供电效率降低;当负荷率由100%降低至50%时,修正后锅炉热效率降低1.09%,汽轮机组热耗率升高380 kJ/(kW·h),厂用电率升高1.84%,机组供电标准煤耗率增加23.63 g/(kW·h),机组供电效率降低3.53%。     

#9机组循泵变频改造

循环水泵电机作为火力发电厂的重要一次电气设备,与机组同步长周期运行,是电厂最重要和最关键的设备之一。对火电厂技术经济指标"厂用电率"的影响较大。原循环水泵电机采用工频运行的方式工作,不能根据用水需求而调节,厂用电率高。根据多年的学习及对电机的使用的了解,决定改造其运行方式,将工频运行改造为变频运行。改造后循环水泵电机启动电流下降,厂用电率也同比下降,实现了电机的节能、增效。     

厂用电不平衡影响发电机组进相能力案例分析

针对南网某700 MW火电机组厂用电率不平衡而导致的进相运行能力不足问题进行了案例分析和计算。围绕厂用电压水平给出了厂用电调整优化策略,在手算和PSCAD仿真中对优化后的厂用电水平进行了进相仿真模拟,验证了厂用电调整措施的正确性,并针对类似问题提出评价策略和防范措施。     

燃煤发电机组超低排放改造增加能耗模型研究

随着国内环境压力加大,火电环保要求逐步提高,全国范围燃煤机组进行超低改造,超低改造实现减排的同时增加了机组能耗,给火电节能工作带来更大压力。通过对超低改造脱硫、脱硝、除尘增加厂用电率的设计值和实际运行值进行数据分析,归纳出超低改造系统增加厂用电率计算模型,为测算超低改造系统对机组能耗水平的影响提供理论依据,为下一步环保系统节能奠定基础。     

电动给水泵运行方式优化探讨

针对350MW超临界机组2台给水泵运行方式耗用大量厂用电的实际问题,进行了不同工况参数下的电泵出力试验,提出了低负荷阶段单电泵运行的优化方案.运行结果表明:单电泵运行方式可满足机组73％以下负荷工况的安全运行需求,降低厂用电耗效果明显,对火电厂的经济运行具有重要意义.     

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.