纳米级二氧化钛硫脱及再生性能的试验研究

以纳米级二氧化钛粉末为基料，采用溶胶－凝胶法（sol-gel)制备了四种实验样品，在低温下进行动态吸附试验，结果表明二氧化钛用于烟气脱硫的机理主要是物理吸附，再生后重复使用是可行的。低温烧结的纳米级TiO2的脱硫性能良好，具有工程应用前景。在440℃和540℃上烧结的TiO2脱硫剂对SO2的吸附性能最佳。TiO2脱硫剂的晶态是影响脱硫性能的重要因素之一。     

利用改性TiO_2光催化同时脱硫脱硝的试验及其反应机理的研究

通过在活性炭纤维(ACF)上负载锐钛矿型二氧化钛和混晶型二氧化钛,制备了TiO2/ACF1和TiO2/ACF2 2种可用于烟气同时脱硫脱硝的光催化剂,并分别在不同试验条件下考察了2种光催化剂同时脱硫脱硝的效率.同时,利用扫描电镜(SEM)和X-射线电子能谱(EDS)分析了反应前后光催化剂的微观性质,对其尾气吸收液的成分进行了离子色谱分析,探讨了TiO2/ACF2光催化剂同时脱硫脱硝的反应机理.结果表明:TiO2/ACF2光催化荆的催化活性较高,在最佳试验条件下,TiO2/ACF2光催化剂脱除SO2和NO的效率可分别达到97.5%和49.6%;烟气中SO2和NO的脱除经历了吸附、催化氧化和溶解3个过程,在本试验条件下,负载型TiO2/ACF2光催化剂对SO2和NO的催化氧化占主导地位.     

纳米TiO_2催化煤燃烧的实验研究

研究了纳米TiO2在有、无CaO脱硫的工况下,对汶南褐煤和内蒙烟煤的催化燃烧效果.通过热重曲线,从着火温度、失重量、放热量等燃烧特性方面,对实验结果进行了分析.结果表明:在无CaO脱硫时,纳米TiO2使烟煤的着火温度下降15 ℃,褐煤的燃尽温度降低了32 ℃;在有CaO脱硫时,纳米TiO2使褐煤的着火温度下降17 ℃,烟煤的燃尽温度降低了8 ℃,同时褐煤、烟煤的燃烧反应活化能分别降低了5.9 kJ/mol和1.3 kJ/mol,褐煤的发热量升高.XRD图谱中没有新物质生成也证明了纳米TiO2的催化燃烧作用.这一结果为燃烧脱硫的同时,提高煤的燃烧效率,节约用煤量提供了理论依据.     

椰壳活性炭担载Cu脱硫剂烟气脱硫试验研究

建立了固定床烟气脱硫反应器,采用椰壳活性炭（AC）担载Cu制备脱硫剂CuO/AC,研究了煅烧温度、Cu担载量、脱硫反应温度及烟气成分对脱硫剂脱硫性能的影响.结果表明：CuO/AC脱硫剂煅烧温度为250℃时较适宜;Cu担载量为5%~7.5%、脱硫反应温度为200~250℃、烟气中有适量的O2时,CuO/AC脱硫剂具有较好的脱硫能力;再生温度为300℃时得到的再生脱硫剂的脱硫效果最好,但脱硫能力与新的脱硫剂相比有所下降.     

蒸汽活化器设计方案比较和分析

在中温(400℃~800℃)干法循环流化床烟气脱硫工艺中,由于反应产物CaSO4的比摩尔容积大于脱硫剂CaO的比摩尔容积,进而使得SO2气体在脱硫剂颗粒内的扩散变得非常困难,从而影响了脱硫反应的进行和脱硫剂的利用率。为了提高钙利用率,采用中高温(800℃)硫化、低温(150℃)蒸汽活化的方法来处理乏脱硫剂。在文中提出了移动床式蒸汽活化器和流动床式蒸汽活化器两种方案,并进行了计算和分析。     

火焰合成Cu基催化剂在甲烷催化燃烧中的烧结行为

在高温催化燃烧中烧结对催化剂的活性影响巨大,而火焰合成的纳米催化剂的烧结行为鲜有研究.通过火焰喷雾热解合成了以TiO2、ZrO2、Si O2为载体的一系列Cu基负载型纳米催化剂,并将所合成的纳米颗粒用于低浓度CH4催化燃烧以评价其性能.对比反应前后催化剂的BET、XRD及TEM表征,研究了不同催化剂材料在高温催化过程中晶相转变与烧结之间的竞争关系,并发现了CuO-ZrO2的表面扩散主导以及Cu O-TiO2的晶界扩散主导的烧结机制.从催化燃烧测试分析发现,CuO-ZrO2在600℃对甲烷的催化转化率达到了90%,Cu O-TiO2由于其抗烧结性能较差在800℃才达到88%转化率,而Cu O-Si O2反应性最差,在600℃只有30%转化率.结果表明,ZrO2负载型Cu基纳米催化剂活性较高兼具抗烧结性能.     

微波合成载铂二氧化钛纳米管光催化剂及其光催化性能

以自制二氧化钛纳米颗粒为原料,利用微波反应器合成二氧化钛纳米管(Titania nanotubes,TNTs),然后利用微波助乙二醇还原法得到负载Pt的二氧化钛纳米管(Pt/TNTs)。利用高分辨率透射电镜(HRTEM)、X射线衍射(XRD)和紫外可见吸收光谱(UV-Vis)对该催化剂进行表征,并重点研究Pt/TNTs的光催化分解水性能。结果表明:Pt颗粒均匀分散在二氧化钛纳米管表面,微波助乙二醇还原法制备的Pt/TNTs较Pt负载TiO2颗粒在可见光区域表现出较强的吸收,并且其起始吸收带边发生明显红移,通过模拟太阳光分解纯水制氢实验可知,用微波助多元醇制备Pt改性的TiO2纳米管光催化剂具有更高催化剂活性,其在全波段下氢气产量优于Pt负载的TiO2纳米颗粒催化剂,且在可见光区能分解纯水产氢,产氢量为0.86L/(m2.h.g)。     

应用X射线衍射仪分析铝基氧化铜吸附剂的硫化性能

介绍了制备DS01型铝基氧化铜脱硫剂的方法。对脱硫剂进行了烟气循环脱硫-再生的实验，采用X射线衍射分析了铝基氧化铜对硫氧化物的吸附性能。热态实验和测试分析表明，DS01型铝基氧化铜吸附剂硫化性能稳定；含量6．2％CuO的吸附剂在X-射线衍射图谱上没有发现CuO晶相，表明吸附剂表面出现单层分散；使用该脱硫剂进行烟气多次循环脱硫，CuO微晶粒并没有发生明显的团聚现象，表明吸附剂多次循环使用其活性不减。图2参5     

添加钢渣的碱式碳酸镁脱硫剂脱硫性能的研究

脱硫剂的选用是影响燃煤锅炉烟气脱硫效率的重要影响因素之一。实验采用了实验室规模的鼓泡反应装置模拟烟气湿法脱硫过程,分别以碳酸钙、氧化镁、碱式碳酸镁以及添加钢渣的碱式碳酸镁作为脱硫剂进行了烟气脱硫实验,研究反应温度、鼓泡深度以及搅拌速度对脱硫剂脱硫性能的影响。结果表明,在模拟的烟气湿法脱硫反应过程中,几种脱硫剂的脱硫效率随着鼓泡深度与搅拌速度的增加而显著提高,反应温度对脱硫剂脱硫效率的影响并不明显。结合实验现象进行推断,SO2在气液两相界面的传质扩散和其水解产物在液相的扩散直接影响镁基脱硫剂的脱硫过程。     

含碱工业废弃物用作流化床燃煤脱硫剂的实验研究

基于以废治污、保护环境的目的,选取了7种含碱固体废弃物作为流化床燃煤脱硫剂,利用热重分析技术对含碱工业废弃物及其复合脱硫剂的硫化反应特性进行了实验研究.结果表明,碱渣、盐泥、赤泥在850℃左右具有较好的脱硫特性;白泥和电石渣,最佳脱硫反应温度介于900℃～1 000℃之间,具有较好的高温脱硫性能;白泥、电石渣和石灰石中...     

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%.     

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.     

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.     

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.     

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.     

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.     

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.     

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。