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。     

超临界循环流化床锅炉SNCR脱硝特性研究

在实验室和Fluent软件模拟条件下研究温度和氨氮摩尔比（NSR）变化对选择性非催化还原技术（SNCR）脱硝效率的影响，同时关注氨气逃逸现象。结果显示：温度是SNCR的控制因素，低温情况下，SNCR脱硝效率很低，温度从750℃提升至1 000℃，脱硝效率先提高并在950℃达到峰值，因为NH3的还原作用出现拐点。在低温下提高NSR对脱硝效率的影响不大，温度提高至SNCR反应温度时，提高NSR可以有效促进脱硝反应，但是过高的NSR因为竞争反应会使脱硝效率的增加放缓，NSR=1.5较为合适。低温下，NSR越大，氨气逃逸现象越严重，随着温度增加，SNCR反应提升，氨气逃逸得到明显改善。     

选择性非催化脱硝不同还原剂的比较试验研究

SNCR(选择性非催化还原)过程试验是在CRF(Combustjon Research Facility)试验装置上进行的.使用尿素、氨水、(NH4)2CO3、NH4HCO3还原烟气中的NOx,通过雾化喷嘴在CRF炉膛内喷入还原剂.试验结果表明,对于所使用的还原剂随着NH3/NO摩尔比的增加,NO还原效率逐渐提高;对于尿素、氨水、(NH4)2CO3等还原剂,氨氮比为1～2.5,脱硝效率分别为65％～89％、62％～86％、45％～84％;对于NH4HCO3,氨氮摩尔比0.8～1.5,脱硝效率为46％～73％.不同还原剂的温度窗口不同,适宜尿素进行SNCR过程的反应温度最高,氨水最低.     

SNCR脱硝过程中固体聚合脱硝剂的性能研究

由于以尿素或氨水为还原剂的传统非催化还原脱硝(SNCR)技术存在还原剂分解不充分、反应温度高、脱硝效率低等问题,固体脱硝剂可用于克服上述问题。以三聚氰胺、尿素、甲醛为基体,制备了一种固体聚合脱硝剂,并分析反应温度、O₂体积分数、H₂O体积分数、停留时间和氨氮比等对其反应活性的影响。结果表明：固体聚合脱硝剂的活性温度窗口与常规还原剂相比较低;当O₂体积分数为1.2%时,脱硝效率最高,为84.2%;H₂O体积分数为1.4%时,脱硝效率最高,为91.4%;而停留时间对脱硝剂反应活性的影响不明显,氨氮比的影响更为明显,当氨氮比为1.5时脱硝效率最高。     

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。     

一维火焰燃烧过程过程中SNCR脱硝试验研究

试验研究了一维火焰燃烧炉内不同条件下选择性非催化还原法(SNCE)的脱硝特性,探讨了结构参数和运行参数对脱硝的影响,在试验基础上得出了SNCR的脱硝规律。试验表明:液氨与尿素作为还原剂时,液氨的脱硝效率稍高,温度窗口的选择至关重要,试验中适宜的窗口温度在900℃～1 000℃之间,NH3/NOx的最佳比例在1.0～1.6之间,停留时间在1s左右。     

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%。     

660 MW燃煤电厂SNCR脱硝数值模拟

研究选择性非催化还原脱硝法(SNCR)在大型燃煤电厂运行的影响因素,使用计算流体力学软件CFD模拟炉内喷入以尿素为还原剂的脱硝过程。模拟结果发现锅炉处于满负荷运行时,炉膛顶部满足SCNR脱硝温度窗口的高度为57 m以上,因此使用三区、五区、六区的尿素溶液喷枪。随着氨氮比的增加,脱硝率从25.9%增大到32.2%的同时,烟道出口氨气泄漏量从5μmol/mol增加到46μmol/mol。在氨氮比为1.5时有最理想的脱硝效果,脱硝率为28.3%,烟道出口氨气泄漏量为11.2μmol/mol。     

气态氨作还原剂的SNCR脱硝工艺的试验研究与模拟

在自行研制的试验台上对氨气作还原剂的SNCR脱硝工艺进行了实验研究,并利用化学反应动力学软件Chemkin 4.1进行了模拟.通过试验发现,采用自制改进型槽缝式TB系列喷嘴内部喷入的方式明显优于侧喷,提高了NO_x的去除率.以NO_x去除率高于50%为标准,试验所得温度窗口为863～937 ℃.随着氨氮比的增大,NO_x的去除率和氨的泄漏量增大,当氨氮比大于1.0后,NO_x去除率的随氨氮比增大的幅度减小,而氨的泄漏量增大幅度增大.利用Chemkin 4.1的模拟所得的温度窗口和NO_x去除率与实验基本相符,通过对详细机理中重要基元的分析,得出了各温度下的主要反应途径.     

基于低氮燃烧的循环流化床低温增效脱硝实验研究

为探究循环流化床（CFB）锅炉的低NOx排放性能,在热输入功率为81.3 kW的CFB热态实验台上研究了燃煤平均粒径与二次风对NOx原始生成量的影响,考察了以碳酸氢铵为还原剂,以碳酸钠和乙醇为添加剂的选择性非催化还原（SNCR）低温脱硝增效性能。结果表明：随燃煤平均粒径的减小,NOx生成量降低;提高二次风比例及二次风口位置可降低NOx生成量;以碳酸氢铵为还原剂的SNCR法在氨氮摩尔比为1.7时脱硝效率达到65.2%,还原剂利用率达到峰值;在650~800 ℃的低温范围内,添加碳酸钠较无添加剂工况的脱硝效率平均提升24.5个百分点,750 ℃时的脱硝效率提升34.8个百分点;添加乙醇后的低温区效率平均提升28.2个百分点,温度低于700 ℃时增效性能优于添加碳酸钠工况;添加剂主要通过自由基链式反应提升SNCR法的低温脱硝性能。     

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。     

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.