塑料协同高温铜渣气化的实验研究

基于环境保护和能源资源优化利用的视角,城市生活垃圾气化备受国内外学者的关注,旨在找到一条高效的垃圾能源化利用途径。鉴于生活垃圾组分复杂,而塑料作为生活垃圾的重要组成部分,本课题选取塑料为研究对象,以空气为气化介质、铜渣为催化剂,进行相关研究。在自行搭建的气化试验台上开展塑料的气化试验研究,主要研究气化比(即空气消耗系数)、温度和催化剂对塑料气化的影响。实验结果表明:气化实验比、温度对催化气化产气品位有很明显的影响;在气化温度为750~900℃,随着气化温度升高,产气品位明显提高;铜渣催化剂的使用使得塑料能够进一步催化重整,可提高气化产气CO、H2、CH4等可燃组分,有较好的催化效果。     

垃圾循环流化床低温气化试验研究及模拟

在一台自行研制的循环流化床气化炉上进行了模拟城市生活垃圾低温气化试验.结果表明,随气化温度升高,气化气体低位热值明显增高,可燃组分含量也随之增大,尤其是当气化温度从500℃升高到600℃时,气化气体中CO、H2和CH4含量显著增加;随着过量空气系数的增大,气化气体中可燃组分含量和气化气体低位热值均减小;垃圾中适当保持一定水分含量有利于提高其气化气体中可燃组分含苗和气化气体低位热值.同时采用ASPENPLUS软件建立了垃圾流化床气化模型,通过改变气化温度、过量空气系数和垃圾全水分含量进行模拟计算,结果显示,各工况下生成气化气体低位热值的模拟值和试验值符合较好,证明该模型可用于城市生活垃圾气化特性的预涮和分析.     

基于炉排炉的气化燃烧技术实验研究

为了更深入地研究生活垃圾气化工艺技术,本文基于我司逆推式生活垃圾机械炉排炉,发展了新型的垃圾气化燃烧技术,设计了新型的两段式垃圾气化炉,对生活垃圾气化燃烧过程进行了试验研究。研究结果表明:低位热值相对较高的生活垃圾可以实现长时间持续稳定的气化燃烧;可燃性合成气体的比例一直处于波动状态;实现了SO_2和NO_X的达标排放,并实现了CO的零排放,充分验证气化燃烧工艺的低排放的环保优势;一定的上料速度下,气化炉炉膛出口烟气温度越高,合成气燃烧热越低,实验时需要控制炉膛出口烟气温度这一重要指标。作为新一代垃圾处理技术,气化燃烧技术在环保方面更具优势,但为了维持整个系统的平衡及安全稳定运行,需要较高的垃圾热值。     

城市生活垃圾气化熔融焚烧技术

近年来，为防止全球气候变暖，社会上对环境保护的要求日益严格。尤其是要求城市生活垃圾处理最大限度地采用无害化技术，抑制二恶英的排放。能够遏制二恶英产生和排放的无害化城市生活垃圾气化熔融焚烧技术被提出。本技术一般分两类，一类为垃圾气化 灰渣熔融焚烧技术，该技术的工艺流程为：先将城市生活垃圾在500-600℃温度下的热解气化制得可燃气体，制得的气体再根据用途进一步精制，垃圾中95%以上的含氯物质经济去所后所剩下的含碳灰渣在温度为1300℃以上的熔融燃烧设备中进行熔融处理，原垃圾中99.8%以上二恶英可被分解掉，无害化熔融渣可以多种用途；另一类为垃圾直接气化熔融焚烧技术，该技术的工艺流程为：交垃圾在温度1350-1500℃的熔融燃烧设备中进行熔融处理，原垃圾中的99.8%以上的二恶英可被分解掉。文章介绍新型城市生活垃圾气化熔融焚烧技术。     

城市生活垃圾中废弃木料流化床热解气化试验研究

为开发适合我国城市生活垃圾处理的低污染气化熔融技术，对城市生活垃圾中广泛存在的废弃木料组分进行了流化床热解与气化试验。流化床中，在反应温度400～700℃、过量空气系数0～0．8的范围内，对木料进行了系统的热解气化试验，分析了反应产物特性及其产量变化规律。结果表明，热解温度5000℃，热解油产量最大，可占原料质量的38％，热解气产量随温度增加而增大；气化温度600℃、过量空气系数0．4时，气化效率最高，达到73％，此时每标准立方米气化气热值为5800kJ，气化气产率为2．01m^3／kg；并进行相关的反应特性及机理分析。     

城市生活垃圾直接气化熔融焚烧炉模糊自适应控制系统模型研究

城市生活垃圾直接气化熔融焚烧炉的运行过程受许多不确定性因素的影响,城市生活垃圾直接气化熔融焚烧过程的不稳定将会产生二恶英等新的有害物质,随着人们对城市生活垃圾焚烧过程可能造成二次污染的日益关注,如何改善和控制城市生活垃圾焚烧过程的稳定以减少二次污染的发生已经成为一个重要的研究方向。所以应用模糊自适应控制策略对城市生活垃圾直接气化熔融焚烧炉的气化过程和二次燃烧过程进行控制,并对所有的控制策略进行了仿真。仿真结果表明:模糊自适应方法具有良好的控制效果,是解决城市生活垃圾直接气化熔融焚烧过程熔融区温度和第2燃烧室温度不稳定的有效方法。     

城市生活垃圾气化发电的技术经济性评价

随着人们对生存环境要求的不断提高和土地资源价值的日益提升,城市生活垃圾热转化处理已逐渐取代填埋处理,成为垃圾处理的主要选择。垃圾熔融气化技术是近年兴起的处理方式,参考日本一座处理量为400 t/d的城市生活垃圾熔融气化发电工程,运用生命周期评价和投入产出分析方法分析其环境影响和经济性,结果显示,垃圾气化熔融的烟气污染和二噁英排放的环境影响均低于传统的直燃工程;工程投资和垃圾处理补贴是垃圾热转化工程经济性的重要影响因素,垃圾气化熔融工程经济性略低于直燃工程。未来如在我国推广垃圾熔融气化技术,需适当提高垃圾处理补贴,并进一步加强垃圾分类以提高入炉垃圾的热值和成分稳定性。     

垃圾熔融处理中鼓风条件对炉温影响的计算分析

以重庆市生活垃圾在直接气化熔融炉内的燃烧熔融过程为研究对象,计算了在不同鼓风条件下处理生活垃圾时气化熔融炉炉温的变化,分析了鼓风条件对直接气化熔融处理炉炉温的影响规律,计算结果为气化熔融炉鼓风参数的合理选择提供了理论依据.     

25t/d城市生活垃圾上吸式气化炉的产气特性分析

对浙江省某地25 t/d的生活垃圾气化炉进行了检测研究,通过分析得到原生垃圾气化实际工况下,洁净合成气热值为1947 kJ/m3,干合成气的产量为1969 m3/t;焦油热量占气化炉出口合成气热量比例为29.5%;合成气中含水率为28.17%,对入炉垃圾进行脱水提质有助于提高合成气产量和品质;垃圾气化联合燃烧系统污染物排放浓度较低,在未使用烟气净化系统时CO、NOx和SO2已能实现达标排放。分析认为,气化技术能实现生活垃圾能源化清洁利用,未来应用前景广阔。     

城市生活垃圾能源化技术的发展动态

简述了城市生活垃圾能源化的可行性,介绍了焚烧、垃圾衍生燃料、熔融、气化、液化等主要技术。     

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

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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.     

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.     

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.     

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.