基于偏最小二乘回归的氨法烟气脱硫效率预测

以影响氨法烟气脱硫效率的主要参数作为输入变量,以脱硫效率作为输出变量,采用偏最小二乘回归法建立了氨法烟气脱硫效率计算模型并对电厂脱硫效率进行了预测.结果表明:采用氨法烟气脱硫效率计算模型得出的预测值与实际运行数据的最大相对误差小于4.0%,模型的平均误差为0.53%,说明该烟气脱硫效率计算模型的预测精度较高,能够满足烟气脱硫效率预测的工程需要.     

氨法烟气脱硫模型的研究

以建立的填料塔氨法脱硫实验系统为例,研究了氨法脱硫的气液传质和化学反应过程,并建立了数学模型.利用该模型对填料塔氨法脱硫过程进行了数值模拟,分析了吸收液pH值、液气比、初始SO2浓度和烟气流速等因素对脱硫效率的影响,并与实验结果进行了对比.结果表明:在运行过程中,将pH值控制在5.5～6.5、液气比控制在2.0～2.7 L/m3、烟气流速控制在1.5～2.0m/s范围内较为合适;模型计算值和实验数据吻合良好,证明了该模型的合理性,为氨法烟气脱硫的工艺设计提供了理论参考.     

烟气脱硫吸收塔反应过程的数值模拟及试验研究

以鼓泡式脱硫塔为例,采用双膜模型对烟气脱硫过程进行了数值模拟,并与试验结果进行了比较。结果表明:影响鼓泡式脱硫反应过程的主要因素有烟气中SO2含量、吸收液浓度、气体温度、pH值及喷管浸入深度等;在运行中应保持pH值>8和浸管深度>200mm,且吸收液浓度4.5%左右较为合适.同时,脱硫效率对入口烟气温度变化敏感,入口烟气温度越低,脱硫效率越高.通过对这些因素的分析,有助于脱硫装置的运行优化.     

基于自适应粒子群优化BP神经网络的氨法烟气脱硫效率预测

针对氨法烟气脱硫效率的预测问题,建立了以脱硫系统运行中8个主要参数作为输入变量的BP神经网络模型,采用粒子群优化算法(PSO)对建立的BP神经网络模型的权值进行优化,提出基于粒子群优化算法的BP神经网络(PSO-BP)预测新模型,并利用某电厂脱硫系统20组运行数据对该模型进行了验证.结果表明:采用PSO算法对BP神经网络的权值和阈值进行寻优,避免了网络局部极小值的出现,提高了网络的泛化能力,采用PSO-BP预测模型可以对氨法烟气脱硫效率进行较高精度的预测.     

基于FOA和LS-SVM的风电场风速预测研究

针对目前最小二乘支持向量机选取核参数和惩罚因子的各种方法尚存在着一定的局限性,文章采用果蝇优化算法对参数进行优化选择,提出了基于果蝇优化算法与最小二乘支持向量机结合的风速混合预测方法。对新疆某风电场为期5天的240个(采样间隔0.5 h)实测风速值进行了仿真测试,利用建立的预测模型,对第5天的风速值进行预测,预测结果的平均绝对百分比误差仅为8.32%。将其与单纯的LS-SVM模型和基于网格搜索优化的LS-SVM模型的预测结果作了对比,仿真结果验证了基于果蝇优化算法和最小二乘支持向量机混合预测模型的可行性和果蝇算法对最小二乘支持向量机参数优化的有效性。     

烟气脱硫添加增效剂的试验分析

针对湿法烟气脱硫(FGD)装置在运行中存在承受高硫烟气能力较弱、脱硫效率较低、吸收塔浆液pH值偏高等问题,进行了添加DSA-5060型脱硫增效剂与脱硫效率、浆液pH值等关键参数之间的试验。结果表明:添加增效剂后,提高了脱硫效率、降低了吸收塔浆液pH值,FGD设备结垢现象得到了改善。     

3种软测量技术在预测湿法烟气脱硫效率上应用的比较

由于影响脱硫效率的因素较多,且都具有关联性,造成脱硫效率测量困难。就该问题提出了软测量技术,分别运用了偏最小二乘法(PLS)、模糊神经网络法(FNN)和支持向量机法(SVM)3种软测量方法建立了脱硫效率的预测模型。3个模型均基于江西某电厂DCS采集的脱硫系统原始数据,并在MATLAB平台上得到训练与检验,得到较精准的预测模型。最后对3种模型的预测效果进行了比对,得出以下结论:3个模型均能有效的实现预测功能,但在预测效果方面,支持向量机法不仅算法简洁,且精确度更高,在电厂实时测量中更具可行性。     

湿法脱硫系统托盘提效计算模型研究

通过托盘提效的湿法脱硫系统,构建脱硫提效计算模型,探索不同参数对脱硫效率的影响规律,并采用运行数据进行模型有效性验证。结果显示,当开孔率、入口 SO₂浓度、烟气流量降低时,脱硫效率均逐渐增加;当浆液 pH 值和浆液循环量增加时,脱硫效率增加。 在参数设计范围内,开孔率、入口 SO₂浓度、烟气流量和浆液循环量变化时,脱硫效率均在 99%左右。 浆液 pH 值从5.0 变化到 6.0,脱硫效率从 94.60%提高到 99.43%。 与某电厂脱硫系统运行的 4 个典型工况相比较,模型计算与电厂实测的脱硫效率绝对误差在 0.008%～0.091%之间。 该湿法脱硫提效计算模型相对准确可靠。     

亚硫酸钠循环法烟气脱硫工艺实验研究

以处理量为1800m3/h的亚硫酸钠循环法烟气脱硫装置为实验对象,着重研究吸收液pH值、液气比L/G、吸收液成份和脱硫剂初始浓度等因素对脱硫效率的影响,并对脱硫剂再生过程和再生清液的脱硫特性进行研究。结果表明:吸收液pH值决定硫成份在溶液中的状态,从而影响脱硫效率,当pH>6时,脱硫效率高且随pH增大变化平缓;当pH<6时,脱硫效率随pH减少急剧降低;该工艺可以在较低的液气比(L/G=0.25~1.25L/m3)下保持较高的脱硫效率(η>90%);同等条件下,与NaOH和Na2CO3相比较,Na2SO3的脱硫能力稍低;吸收液Na2SO3浓度在5%~10%范围内脱硫效率大于90%;脱硫剂再生反应过程能很快完成,再生脱硫剂脱硫效率稳定,与新鲜脱硫剂相比脱硫效率略低。     

基于模糊LS-SVM算法的大坝变形预测模型

在大坝工程变形分析和预测方面,研究了一种基于支持向量度的模糊最小二乘支持向量机(LS-SVM)算法,结合具体实例进行对比分析,结果表明模糊LS-SVM模型的预测精度要高于LSSVM模型,且支持向量机(SVM)的稀疏性也优于LS-SVM模型,可以很好地应用于大坝变形监测分析.     

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.