高温还原区喷氨脱硝试验研究

建立了高温喷氨脱硝机理模型,研究了反应温度、氧体积分数、氨氮物质的量比和停留时间等参数对脱硝效率的影响,并在一维煤粉炉上开展了试验。结果表明:高温喷氨脱硝反应的温度窗口为1 200～1 600℃,氧体积分数应小于1%,氨氮物质的量比的范围为1.0～1.3,停留时间应大于0.4 s,CO体积分数对脱硝效率没有影响;燃用烟煤时,高温喷氨脱硝效率可达48%。     

基于碳酸氢铵的SNCR低温脱硝实验研究

为考察反应温度、氨氮摩尔比（NSR）、氧气体积分数及停留时间对选择性非催化还原（SNCR）脱硝效率的影响规律,并探究乙醇、碳酸钠和氯化铁添加剂的低温SNCR脱硝增效特性,深入分析其脱硝反应机理,在管式反应炉上进行了以碳酸氢铵为还原剂的SNCR脱硝实验及各添加剂的低温脱硝增效实验。实验结果表明：当氨氮摩尔比为1.7,氧气体积分数为4%时,以碳酸氢铵为还原剂的SNCR法在830~1 000 ℃下的脱硝效率高于60%;氧气体积分数为零时,不同温度下脱硝效率始终低于15%,氧气体积分数为2%~6%时,650~1 000 ℃下的脱硝效率随氧气体积分数增加而提高;SNCR反应速率随温度的升高而加快,反应达到平衡所需的停留时间变短;在模拟烟气中添加200 μl/L的乙醇可使650~800 ℃的低温范围内脱硝效率平均提升近30%,650 ℃的脱硝效率达到33.4%;添加少量碳酸钠（25 μl/L）或100 μl/L的氯化铁可使700~800 ℃下的脱硝效率平均提升超过25%;3种添加剂都能通过提高NH2自由基的生成量提高低温下SNCR法的脱硝效率。     

NO_xOUT工艺的试验研究及化学动力学模拟计算

在自行研制的试验台上对NOxOUT工艺进行了试验研究,结合化学反应动力学模拟研究了CO(NH2)2还原NO过程中的关键影响因素。试验中最佳的尿素溶液喷入温度为850～900℃,NO的还原率最高可达到83%。利用Chemkin 4.1均相反应模型,模拟NOxOUT工艺所得的最佳反应温度窗口及其在各温度下的NOx去除率与试验数据进行对比,结果基本吻合。NSR的增加和停留时间的加长都有利于NO的脱除;但随着NSR的增加,烟气中N2O的生成量也随之增加而影响脱硝效率。试验中检测到烟气尾气中的碱性随着NSR的增加而增大,随着温度的增大而降低,模拟结果与试验结果基本吻合。     

NH_3选择性非催化还原NO的实验研究

在电加热的管式反应炉上进行了NH3选择性非催化还原(SNCR)NO气相均相反应的实验研究,结果表明:最佳脱硝温度约为925℃,最大脱硝效率约为83%。综合考虑脱硝效率、NH3漏失和运行成本,最佳氨氮摩尔比为1.5。NO初始浓度从300μL/L降到100μL/L,脱硝效率由83%降到57%,但是脱硝后NO的排放浓度几乎不变,约为50μL/L。当O2浓度从1%增加到10%,脱硝效率由91%降到75%,反应后剩余的NH3由43μL/L减少到10μL/L。925℃时SNCR反应完全进行需要1s以上的停留时间,而1000℃时只需0.4s。     

高温条件下NH3还原NO实验研究

利用固定床实验系统,在800～1 500℃的反应温度范围内进行了NH_3还原NO实验,分析不同气氛条件下反应温度、氨氮摩尔比以及组分浓度对脱硝效率的影响。实验结果表明:氧化性气氛下最佳脱硝温度约为950℃,温度继续升高时脱硝效率开始下降,而还原性气氛下NH_3对NO的还原存在一个临界温度(约1 000℃),低于临界温度时,NH_3对NO没有脱除效果,反而会额外生成NO,超过临界温度后,脱硝效率随着温度的升高迅速跃升至最大,氨氮摩尔比为2.0时最大脱硝效率可达95%,且在1 200℃以上的高温条件下保持稳定;修正后的GADM98模型对NO浓度的预测与实验结果符合较好,活性基团对NH_2的消耗是高温氧化性气氛下脱硝效率下降的重要原因。     

选择性非催化还原（SNCR）脱硝反应影响因素的探索与研究

以氨气作为还原剂,在管壳式反应器中考察了温度、一氧化氮起始质量浓度、氧气质量分数及氨氮摩尔比对选择性非催化还原反应的脱硝效率以及氨逃逸的影响,为垃圾焚烧发电项目中脱硝工艺提供一定的参考依据。试验结果表明:在875～1 000℃,可得到最佳的反应温度窗口;一氧化氮起始质量浓度、氧气质量分数对脱硝反应的影响较小;当氨氮摩尔比为1.5:1时,脱硝反应效果较好。     

生物质炭再燃脱硝特性的试验研究

以木片炭和木屑混合物(WCC)、稻秆(RS)、桑树枝炭(MBC)和竹炭(BMC)为原料,利用携带流再燃脱硝试验装置,在NO初始体积分数为1×10-4～3×10-4条件下,研究了生物质炭再燃脱硝特性,分析了再燃燃料种类、再燃燃料粒径、再燃区反应温度t2、停留时间τ等因素对再燃脱硝效率的影响.结果表明:对于4种试验用生物质,WCC再燃脱硝效果最好,其脱硝效率为63.4%,RS和BMC次之,MBC没有脱硝效果;随着再燃燃料粒径的减小,再燃脱硝效果趋好;随着NO初始体积分数的减小,再燃脱硝效率降低,当NO初始体积分数低于1×10-4时,RS再燃脱硝效率反而升高;当t2=950～1 250℃时,WCC再燃脱硝效率随再燃区温度的升高而提高;在τ=0.4～0.8s时,随着τ的缩短,生物质再燃脱硝效率下降,当τ=0.4s时,再燃脱硝效率小于10%.为了保证一定的再燃脱硝效率,建议WCC再燃区反应温度和停留时间分别保持在1 150℃和0.8s.     

高级空气分级脱硝特性的实验研究

在一台20kW电加热多功能低Nox试验台上对高级空气分级--空气分级富燃料区喷氨脱除Nox进行了实验研究. 研究发现,主燃区过量空气系数SR1、温度T以及化学计量比NSR是影响氨剂对Nox还原的重要参数.1000℃时,较小SR1不利于氨剂对Nox的还原.增大SR1时,由于初始Nox水平较高,能一定程度上提高喷氨后的脱硝效率.主燃区温度为1300 ℃时,在SR1=0.75、SR1=0.85下喷氨都能提高10 %左右的脱硝效率,但在SR1=0.95、SR1=0.99时,较大NSR下,脱硝效率有一定回落.高温能促进较小SR1下喷氨后的脱硝效果,但在SR1较大时,高温对氨剂还原Nox不利.大部分试验工况下,NSR在1.5-2范围内,脱硝效率取得最佳值.     

基于410t/h Compact型流化床锅炉的SNCR影响因素探究

对1台以尿素为还原剂、配备Compact型旋风分离器的循环流化床锅炉的选择性非催化还原脱硝性能进行了数值模拟,重点研究了温度、氨氮摩尔比、NO初始浓度和O_2浓度对SNCR反应性能的影响规律。计算结果表明:最佳NSR在1.4左右,最佳温度在1 173 K附近;O_2浓度的变化对选择性非催化还原反应的影响和温度密切相关,当温度高于1 150 K时,O_2浓度的增加会导致还原剂的氧化反应加剧,使得脱硝效率随O_2浓度的上升而下降,温度越高,氧化反应越剧烈,脱硝效率下降趋势越明显;同时,O_2浓度的上升,有利于最佳脱硝温度向低温方向移动,综合考虑,认为烟气中O_2浓度不应高于3%。     

高温条件下氨还原剂脱硝特性试验研究

针对NH₃在高温区的脱硝特性进行研究，采用配气的方法在一维管式炉上进行实验，研究不同O₂浓度、反应温度、氨氮摩尔比等关键因素对高温区氨还原NO_x特性的影响．结果表明：氧浓度的升高使NH₃/NO的最佳反应温度下降，脱硝效率出现下降趋势；近零氧工况下NH₃还原NO_x最佳反应温度窗口向高温偏移，反应温度为1 300℃时还原效率最高；随着氨氮摩尔比的增加，NO_x的还原效率随之增加，最佳氨氮摩尔比为1.5，无氧工况下脱硝效率可达95%以上，为进一步优化脱硝技术提供参考．     

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.