福建省垃圾焚烧飞灰的理化特性分析

以福建省3个地区垃圾焚烧厂的飞灰样品为研究对象,对飞灰的微观形貌、元素组成、重金属浸出特性等进行分析。结果表明：这些飞灰由大量的结晶态和一些不规则状颗粒,呈球状、椭球状、片状层叠或立方体组成,颗粒松散,粒径在5～50μm之间不等;3种飞灰的元素组成以Ca和O为主,2类元素占比在85%以上,其余部分元素有Cl、S、Mg、Si等。3种飞灰中的重金属含量与土壤平均值范围相比较,Cr、Ni的含量在参考范围内,Pb、Cu、Zn的含量远超参考值,3种飞灰均为高浸出毒性的危险废弃物,需要经过安全处理后才可以进行填埋等处置。     

城市污泥流化床焚烧炉飞灰中重金属迁移特性

对120 t/d城市污泥循环流化床焚烧炉飞灰中重金属迁移富集特性进行试验研究,对污泥、飞灰及不同温度、取样点的飞灰中Cr、Mn、Ni、Cu、Zn、As、Cd和Pb 8种重金属迁移富集特性进行了分析。试验结果表明:飞灰、底渣及入炉污泥中主要化学成分为Si O_2、Fe_2O_3、Ca O、Al_2O_3和P_2O_5,"Si0_2-Ca O-Al_2O_3-金属氧化物"体系构成了重金属吸附的载体,也为不同形态重金属的吸附提供了活性空间。Cd、As为易挥发性重金属,在炉膛内挥发的Cd、As及其化合物蒸气在503℃和475℃时几乎全部富集于飞灰颗粒;Cr、Mn、Cu、Zn主要通过夹带富集于飞灰颗粒,它们在尾部烟道不同温度区域飞灰颗粒上的富集程度相当,为难挥发性重金属。     

电厂煤飞灰颗粒物的物理化学特征

对某台300MW燃煤电站锅炉电除尘器前后的飞灰进行取样,使用激光粒度仪测定粒度分布,使用X射线衍射仪(XRD)和扫描电镜(SEM)研究颗粒中的矿物成分及其微观形貌特征,同时使用电子探针对电除尘器后飞灰的单颗粒进行成分分析．结果表明：通过电除尘装置排入大气的颗粒物平均粒径为2．5μm左右;飞灰粗颗粒中有较多硅铝氧化物和粘土矿物,而细颗粒中则含有较多金属氧化物,且粗颗粒中石英所占矿物相比例相当高;电除尘器前的飞灰形貌类型种类较多,电除尘器后飞灰形貌类型简单,主要是圆球或圆形的颗粒;电除尘器后飞灰单个颗粒间组分随粒径变化的有Si、Al、Ca和S,而元素Fe和Ti的含量较恒定．     

粒径对燃煤电站飞灰元素质量分数分布的影响

对燃煤电站不同粒径飞灰样品进行了扫描电镜、X射线衍射、电子探针和离子色谱分析,研究了燃煤飞灰中元素质量分数随飞灰粒径的变化规律,分析了过量空气系数对飞灰中元素质量分数分布的影响,并将其与电加热沉降炉的试验结果进行了比较.结果表明:Na、S、Ca和Cl元素的质量分数分布随粒径改变整体上呈负相关变化;Al、Si、K和Fe的质量分数分布随粒径改变整体上呈正相关变化;粒径为25～45 μm飞灰中元素的质量分数分布随过量空气系数的变化呈现明显的规律性,而粒径＞45～75 μm飞灰中元素的质量分数分布随过量空气系数变化的规律不明显;在200～350℃时,加热温度对飞灰中Cl和S元素的质量分数分布无影响.     

无烟煤燃烧中的重金属排放及分布特性

为得到无烟煤燃烧中的重金属排放及分布特性,采用3.5 MW燃烧实验台进行中试实验,对无烟煤燃烧过程中的Pb、Cd、Cu、Zn、Ni和Cr等6种重金属的排放及分布特性进行了测试。实验结果表明:6种元素在飞灰中的质量分数均高于底渣,且富集于超细颗粒中,富集程度的顺序为:Pb,CdCu,ZnNi,Cr。其中,Pb和Cd在粒径约为1μm的飞灰中富集因子达到17~22。在燃烧产物中,重金属大部分分布在飞灰中,底渣和烟气中的比例很低。其中,Cd、Cu、Ni等元素全部分布在飞灰和底渣中,而Pb、Zn和Cr则少量分布在烟气中,以气态形式存在,Pb的质量分数最高、达到13.4%。     

部分痕量元素在煤粉炉中赋存特性

定量测定了1台220t/h煤粉炉进口煤样、底渣、飞灰中Mn、Cr、Pb、As、Se、Zn、Cd、Hg8种痕量元素的含量,分析了飞灰粒径、炉膛温度、含氧量以及痕量元素自身性质对痕量元素赋存、挥发特性的影响。根据痕量元素的赋存、挥发特性,将元素分成3类：第一类元素为Hg;第二类元素为Pb、Zn和Cd;第三类元素为Mn,Se介于第一类元素和第二类元素之间;Cr同时表现出第一类和第三类元素性质。研究发现,除Mn外,其它元素在飞灰中的富集程度随飞灰粒径的减小而增加;飞灰对各痕量元素吸附机理不同;炉膛温度升高能促进部分痕量元素的挥发;除Mn和Cr外,其它元素在飞灰中相对富集系数大于底渣;含氧量低并非促进所有痕量元素挥发;痕量元素分类应视具体情况而定。     

不同添加剂/吸附剂对循环流化床燃烧痕量元素迁移的影响规律

在6,k Wth流化床实验装置上进行了贵州烟煤的燃烧实验,采用电感耦合等离子体质谱仪(ICP-MS)研究不同添加剂/吸附剂对11种痕量元素(Be、Cr、Mn、Co、Cu、As、Mo、Cd、Sb、Ba、Pb)在燃烧产物中的富集规律.结果表明:活性炭和稻壳焦对痕量元素都有一定的吸附作用,稻壳焦可增加Be、Mn、Co、Cu、As、Mo、Cd、Sb、Ba、Pb这些元素在飞灰中的富集程度,降低了Cr在飞灰中的富集程度;活性炭对Cr、Mn、Cu、Mo、Cd、Sb、Pb的富集都有一定的促进作用.原煤中掺混Ca Cl2能提高Mn、Sb和Ba在飞灰中的富集程度,同时抑制了其他元素在飞灰中的富集;掺混NH4Cl对Co和Cu在飞灰中的富集有抑制作用,但作用很小,对其他的痕量元素在飞灰中的富集都有一定的促进作用,其中对Mo、Cd和Sb的促进最为明显.     

煤燃烧过程中矿物质气化与亚微米颗粒物形成的研究

应用热重分析仪研究了煤中矿物质的气化,同时通过沉降炉试验台架研究了燃煤过程中亚微米颗粒的形成和排放特性,并对亚微米颗粒的形成机理进行了探讨.结果表明:矿物质的气化量随着温度的升高而增大;在1400℃时,各个元素的气化能力由大到小依次为S、Cu、Pb、Zn、Na、K、Ca、Fe、Mg、Cr和Mn;温度越高,煤粉粒径越小,氧气含量越高,形成的PM1.0的浓度越大,并富集了易气化元素S、P和Na等,PM1.0可能是由气化-凝结机理形成的.     

不同工况飞灰重金属和PAHs特性试验研究

针对220t/h燃煤循环流化床电站锅炉研究锅炉负荷和钙硫比对电除尘器 飞灰的粒径分布、常量化学成分、微量元素和多环芳烃的影响。结果表明：60％以上飞灰粒径小于100μm，负荷增大，粒径和当量粒径增大。Ca/S比对飞灰粒径分布影响较小，锅炉负荷和Ca/S比增大，飞灰化学成分SiO2、Al2O3减少，CaO和SO3增加，各微量元素含量分布规律为：Hg＜Cd＜Pb＜Cu＜Ni＜Cr。随着锅炉负荷和钙硫比升高，多环芳烃各类和含量减少。     

煤粉炉中痕量元素迁移影响因素的研究

采用Z-8200型原子吸收分光光度计和VF-320型X射线荧光光谱仪,定量测定了1台220t/h煤粉炉中原煤、底渣、飞灰中8种痕量元素的含量。基于改进的Meij相对富集系数,从底渣和飞灰两个方面,系统分析了温度、含氧量、飞灰粒径、痕量元素自身性质以及煤种特性迁移规律的影响。研究结果表明：炉膛温度升高能加快部分痕量元素的挥发;Cr和Mn在飞灰、废渣中含量相当,但两者相对富集系数明显不同;含氧量低并非促进所有痕量元素挥发;Pb、Cd、Zn、Cr在底渣和飞灰中含量并不一定都与各自的沸点成单一的关系;飞灰粒径越小,痕量元素富集系数越大,各痕量元素随飞灰粒径减小的变化趋势并不相同等。     

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.     

Contents in Volume 23,2014

<正>~~     

Performance assessment of some ice TES systems

In this paper, a performance assessment of four main types of ice storage techniques for space cooling purposes, namely ice slurry systems, ice-on-coil systems (both internal and external melt), and encapsulated ice systems is conducted. A detailed analysis, coupled with a case study based on the literature data, follows. The ice making techniques are compared on the basis of energy and exergy performance criteria including charging, discharging and storage efficiencies, which make up the ice storage and retrieval process. Losses due to heat leakage and irreversibilities from entropy generation are included. A vapor-compression refrigeration cycle with R134a as the working fluid provides the cooling load, while the analysis is performed in both a full storage and partial storage process, with comparisons between these two. In the case of full storage, the energy efficiencies associated with the charging and discharging processes are well over 98% in all cases, while the exergy efficiencies ranged from 46% to 76% for the charging cycle and 18% to 24% for the discharging cycle. For the partial storage systems, all energy and exergy efficiencies were slightly less than that for full storage, due to the increasing effect wall heat leakage has on the decreased storage volume and load. The results show that energy analyses alone do not provide much useful insight into system behavior, since the vast majority of losses in all processes are a result of entropy generation which results from system irreversibilities.     

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%.     

Effect of co-cultivation of Chlamydomonas reinhardtii with Azotobacter chroococcum on hydrogen production

Chlamydomonas reinhardtii cc124 and Azotobacter chroococcum bacteria were co-cultured with a series of volume ratios and under a variety of light densities to determine the optimal culture conditions and to investigate the mechanism by which co-cultivation improves H₂ yield. The results demonstrated that the optimal culture conditions for the highest H₂ production of the combined system were a 1:40 vol ratio of bacterial cultures to algal cultures under 200 μE m^?2 s^?1. Under these conditions, the maximal H₂ yield was 255 μmol mg^?1 Chl, which was approximately 15.9-fold of the control. The reasons for the improvement in H₂ yield included decreased O₂ content, enhanced algal growth, and increased H₂ase activity and starch content of the combined system.     

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.     

Natural-gas fueled spark-ignition (SI) and compression-ignition (CI) engine performance and emissions

Natural gas is a fossil fuel that has been used and investigated extensively for use in spark-ignition (SI) and compression-ignition (CI) engines. Compared with conventional gasoline engines, SI engines using natural gas can run at higher compression ratios, thus producing higher thermal efficiencies but also increased nitrogen oxide (NO_x) emissions, while producing lower emissions of carbon dioxide (CO₂), unburned hydrocarbons (HC) and carbon monoxide (CO). These engines also produce relatively less power than gasoline-fueled engines because of the convergence of one or more of three factors: a reduction in volumetric efficiency due to natural-gas injection in the intake manifold; the lower stoichiometric fuel/air ratio of natural gas compared to gasoline; and the lower equivalence ratio at which these engines may be run in order to reduce NO_x emissions. High NO_x emissions, especially at high loads, reduce with exhaust gas recirculation (EGR). However, EGR rates above a maximum value result in misfire and erratic engine operation. Hydrogen gas addition increases this EGR threshold significantly. In addition, hydrogen increases the flame speed of the natural gas-hydrogen mixture. Power levels can be increased with supercharging or turbocharging and intercooling. Natural gas is used to power CI engines via the dual-fuel mode, where a high-cetane fuel is injected along with the natural gas in order to provide a source of ignition for the charge. Thermal efficiency levels compared with normal diesel-fueled CI-engine operation are generally maintained with dual-fuel operation, and smoke levels are reduced significantly. At the same time, lower NO_x and CO₂ emissions, as well as higher HC and CO emissions compared with normal CI-engine operation at low and intermediate loads are recorded. These trends are caused by the low charge temperature and increased ignition delay, resulting in low combustion temperatures. Another factor is insufficient penetration and distribution of the pilot fuel in the charge, resulting in a lack of ignition centers. EGR admission at low and intermediate loads increases combustion temperatures, lowering unburned HC and CO emissions. Larger pilot fuel quantities at these load levels and hydrogen gas addition can also help increase combustion efficiency. Power output is lower at certain conditions than diesel-fueled engines, for reasons similar to those affecting power output of SI engines. In both cases the power output can be maintained with direct injection. Overall, natural gas can be used in both engine types; however further refinement and optimization of engines and fuel-injection systems is needed.     

Exergetic evaluation of 5 biowastes-to-biofuels routes via gasification

This paper presents the exergy analysis results for the production of several biofuels, i.e., SNG (synthetic natural gas), methanol, Fischer–Tropsch fuels, hydrogen, as well as heat and electricity, from several biowastes generated in the Dutch province of Friesland, selected as one of the typical European regions. Biowastes have been classified in 5 virtual streams according to their ultimate and proximate analysis. All production chains have been modeled in Aspen Plus in order to analyze their technical performance. The common steps for all the production chains are: pre-treatment, gasification, gas cleaning, water–gas-shift reactions, catalytic reactors, final gas separation and upgrading. Optionally a gas turbine and steam turbines are used to produce heat and electricity from unconverted gas and heat removal, respectively. The results show that, in terms of mass conversion, methanol production seems to be the most efficient process for all the biowastes. SNG synthesis is preferred when exergetic efficiency is the objective parameter, but hydrogen process is more efficient when the performance is analyzed by means of the 1st Law of Thermodynamics. The main exergy losses account for the gasification section, except in the electricity and heat production chain, where the combined cycle is less efficient.     

Controls on the Karaha–Telaga Bodas geothermal reservoir,Indonesia

Karaha–Telaga Bodas is a partially vapor-dominated, fracture-controlled geothermal system located adjacent to Galunggung Volcano in western Java, Indonesia. The geothermal system consists of: (1) a caprock, ranging from several hundred to 1600 m in thickness, and characterized by a steep, conductive temperature gradient and low permeability; (2) an underlying vapor-dominated zone that extends below sea level; and (3) a deep liquid-dominated zone with measured temperatures up to 353 °C. Heat is provided by a tabular granodiorite stock encountered at about 3 km depth. A structural analysis of the geothermal system shows that the effective base of the reservoir is controlled either by the boundary between brittle and ductile deformational regimes or by the closure and collapse of fractures within volcanic rocks located above the brittle/ductile transition. The base of the caprock is determined by the distribution of initially low-permeability lithologies above the reservoir; the extent of pervasive clay alteration that has significantly reduced primary rock permeabilities; the distribution of secondary minerals deposited by descending waters; and, locally, by a downward change from a strike-slip to an extensional stress regime. Fluid-producing zones are controlled by both matrix and fracture permeabilities. High matrix permeabilities are associated with lacustrine, pyroclastic, and epiclastic deposits. Productive fractures are those showing the greatest tendency to slip and dilate under the present-day stress conditions. Although the reservoir appears to be in pressure communication across its length, fluid, and gas chemistries vary laterally, suggesting the presence of isolated convection cells.     

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.