基于空气分级的主燃区喷氨技术降低锅炉NO_x的热态工业试验研究

基于空气分级主燃区喷氨技术降低NO_x,在一台240 t/h煤粉炉上进行了热态工业试验,并对主燃区的喷氨位置、化学氨氮比(NSR)、OFA运行方式、锅炉负荷等因素对NO_x还原效果的影响进行了试验研究。结果表明:锅炉中下磨满负荷运行时,主燃区四角的喷氨降低NO_x的效果优于侧墙,并且随着化学氨氮比的增加而增加,在NSR=1.6时取得35%的脱硝效率,当OFA的阀门开度维持在60%以下,锅炉运行时的脱硝效果较好,降低锅炉的负荷,相应地提高了主燃区喷氨的脱硝率,中上磨运行时,主燃区喷氨脱硝效果不佳,空气分级结合主燃区喷氨技术可以取得75%的脱硝率。     

富燃料区喷氨降低NO_x排放浓度的热态试验研究

对某热电厂75 t/h煤粉锅炉进行了富燃料区喷氨技术改造,以降低NO_x排放浓度。在改造后的实际运行的煤粉锅炉上进行了热态试验,研究了氨氮比、O_2浓度和温度对脱硝效率的影响。试验结果表明:当氨氮比为1.5时,采用富燃区喷氨技术可在空气分级技术改造的基础上,将NO_x排放浓度降低至50%左右;当氨剂喷入位置处的温度超过1200℃时,会引起NO_x排放浓度的增加;当氨氮比为1.5、4角位置处喷射尿素时,空气分级联合富燃料区喷氨可以达到约70%的脱硝率。     

高温主燃区还原性氛围下喷氨脱硝的试验研究

为研究煤粉燃烧过程中高温主燃区NH_3对NO_x还原效果的影响,采用尿素溶液为氨基还原剂,利用一维管式电加热沉降炉分析了氨剂对NO_x在不同反应条件下的还原特性。实验结果表明:主燃区温度为1 573 K时,在过量空气系数α≤0.95条件下,尿素溶液可有效的将主燃区烟气中NO_x还原为N_2,且脱硝效率都随氨氮比n增大而快速升高,当n1.75时,脱硝效率升高速度变缓;在还原性氛围中,相同n时,温度越高,脱硝效率越高,且高挥发分烟煤的脱硝效率大于低挥发分无烟煤所对应脱硝效率;试验条件下,神华烟煤的整体脱硝效率最高可达95%;单独喷水可降低NO_x浓度,但与喷氨工况相比,其降低幅度不明显。     

煤粉炉高温还原性氛围下NH_3还原NO_x

在一台75,t/h煤粉炉上采用炉内空气分级和低氮燃烧器进行改造,在主燃区创造高温强还原性氛围,在该区域喷入氨还原剂,通过实验研究在高温强还原性气氛下NH_3还原NO_x的影响因素及效果,结果表明:当主燃区过量空气系数(37)11时,喷入尿素溶液后,NO_x体积分数明显低于仅采用空气分级时的工况,当(37)11.15时,则得到相反结果,在富氧条件下NH_3易生成NO_x;在(37)1=0.9时,四角处和侧墙处沿喷枪轴线方向氧体积分数均小于0.4%,,温度在1,200~1,300,℃,该氛围下NH_3可有效降低NO_x;喷射位置在炉膛四角时NO_x排放浓度明显低于在侧墙处,最佳氨氮摩尔比为1.73,且在侧墙处喷入尿素溶液,随着氨氮摩尔比的增加NO_x排放有明显上升趋势;在主燃烧区喷入尿素溶液((37)1=0.9,氨氮摩尔比为1.73)NO_x还原效率为66.5%,,比单独采用空气分级高35.27%,,零氨逃逸.     

流化床流动和燃烧特性对SNCR脱硝的影响研究

为研究循环流化床炉内流动和燃烧产生的NO_x的不均匀性对SNCR(选择性非催化还原)脱硝效率的影响,针对炉内燃烧、喷氨和SNCR脱硝反应等一系列过程,建立了稠密气固流动耦合化学反应的数学模型,全面模拟了CFB(循环流化床)锅炉的气固流动、燃烧反应、NO_x生成和脱硝反应过程,重点研究了非均匀入口时不同喷氨方式对脱硝效率和氨逃逸率的影响。结果表明:CFB锅炉燃烧后在水平烟道出口存在明显的NO_x通量不均匀;通过改变喷氨点结构参数和操作参数,能显著提高脱硝效率,当采用第一列喷氨、垂直入射等措施且氨氮比为1.2时,脱硝效率能达到68%以上。     

富燃料区喷氨降低无烟煤NO_x排放的实验研究

在一维电加热管式沉降炉上对富燃料区喷氨——空气分级基础上向主燃料区喷氨还原NOx进行了实验研究。研究发现:主燃区过量空气系数、主燃区温度、化学计量比NSR对脱硝效率有着重要影响。主燃区过量空气系数越小,脱硝效率越高。主燃区过量空气系数SR=0.75时,喷氨不能明显提高脱硝效率。在1100℃下,当主燃区过量空气系数SR=0.95和0.90时,喷氨能进一步提高近20%的脱硝效率。在一定范围过量空气系数SR下,温度越高脱硝效率越高。但高温对较大主燃区过量空气系数SR下喷氨是不利的。绝大部分实验工况下,当NSR处于1.5~2.0时能取得最佳的脱硝效率。     

SNCR技术及其发展

SNCR技术作为一种建设周期短、投资少、脱硝效率中等的烟气脱硝技术,其性能受多种因素影响,主要有温度窗口、停留时间、氨氮比NSR、反应剂与烟气的混合程度、温度梯度、添加剂、烟气氛围以及还原剂种类等。反应窗口的选择、混合均匀性、化学动力学模拟为SNCR技术最关键工艺,对于大型电站锅炉,脱硝效率一般低于40％,大型炉型的低脱硝率、混合的均匀性、高氨逃逸是限制SNCR技术发展的制约因素,针对这些制约因素,国内外采用了多种手段,如与OFA、SCR、再燃技术联合,以促进SNCR技术的发展。     

330 MW电站煤粉锅炉高温主燃区喷氨脱硝的试验研究

在一台330 MW四角切圆煤粉锅炉上进行试验,研究各因素对高温主燃区喷氨脱硝的影响。结果表明：向高温主燃区喷入尿素溶液可有效脱除NO_x,且脱硝效率受锅炉负荷、配风方式和O₂体积分数等因素的影响;在锅炉常规运行的基础上进行主燃区喷氨,随着负荷的增加,最佳R_NSR增大,脱硝效率降低;相对于基准配风方式,在极限配风方式下进行喷氨可以提高脱硝效率,使最佳R_NSR减小;降低锅炉出口O₂体积分数可进一步提高主燃区喷氨的脱硝效率;主燃区喷氨与高速燃尽风协同控制可以在减小NO_x质量浓度的同时对飞灰含碳量和CO体积分数进行有效控制。     

煤粉炉内燃烧过程还原区强化脱硝试验研究

提出一种新型脱硝技术——多级强化还原煤粉燃烧技术,并在东方锅炉股份有限公司一台可实现煤粉自持燃烧的50 kW下行燃烧试验炉上开展了该技术的脱硝试验研究。采用再循环烟气携带还原抑制剂(尿素溶液或氨气)喷入强化还原区的方式进行强化脱硝。在空气分级的基础上,对两级燃尽风位置、还原抑制剂喷入位置、还原抑制剂的载气种类、还原抑制剂与烟气混合程度和氨氮比等影响脱硝效率的因素进行了研究。结果表明:在第一级燃尽风之前的还原区喷入尿素溶液,氨氮比为2时,脱硝效率可达20%左右;当在两级燃尽风之间的强化还原区喷入尿素溶液,氨氮比为2时,脱硝效率可达70%左右;氨气作为还原抑制剂时,随着氨氮比的增大,脱硝效率逐渐提高,当氨氮比在1.2～1.6时,脱硝效率稳定在70%左右,当氨氮比为2.5以上时脱硝效率达到80%以上。     

SCR烟气脱硝系统喷氨适应性调整的试验分析

在选择性催化还原烟气脱硝技术中,为了使还原剂与NO_x充分混合,最理想的状况是使还原剂的质量浓度分布与NO_x的质量浓度分布相一致。主要介绍了锅炉SCR脱硝系统喷氨适应性调整试验的测点布置、测量方法、试验结果与分析等,通过实验可知,调整各喷氨支管手动阀开度可有效提高SCR喷氨适应性,降低氨逃逸量,降低出口NO_x质量浓度。     

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.     

Contents in Volume 23,2014

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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.