能源动力系统除灰新技术的机理及应用

我国能源动力系统尤其是电站锅炉燃用大量高灰煤,致使系统局部受热面严重积灰,影响锅炉的效率和出力,中国科学院力学研究所采用了可燃气体快速燃烧,产生燃气脉冲清除积灰的原理,研究发展了一种适用于我国大型电站锅炉的新一代除灰技术.目前,燃烧气脉冲除灰技术已在全国几十台125MW～600MW机组上成功应用.图9参4     

能源动力系统除灰新技术的机理及应用

我国能源动力系统尤其是电站锅炉燃用大量高灰煤,致使系统尾部受热面严重积灰,影响锅炉的效率和出力,中国科学院力学研究所采用了可燃气体快速燃烧,产生燃气脉冲清除积灰的原理,研究发展了一种适用于我国大型电站锅炉的新一代除灰技术,目前,燃气脉冲除灰技术已在全国几十台125MW-600MW机组上获得成功应用。图9参4     

气脉冲除灰技术应用研究

在我国能源动力系统中，大都存在着较严重的受热面积灰问题，燃烧气脉冲除灰技术，具有除灰效果好，使用维护简便等优点，已成功应用于各种大中型锅炉的受热面除灰，从气脉冲原理出发，系统地分析了混合气的流动和混合比对燃烧压力的影响，测量了气脉冲的作用范围，并对伴随输出的声波进行了声频谱分析，结果表明：在8m的范围内，气脉冲冲击波能清除中等粘合强度的灰渣，气脉冲的声频谱基本覆盖了声波除灰的频谱范围。     

电站锅炉燃气脉冲除灰过程研究

中国电站锅炉燃用大量的未经洗选的劣质煤,导致严重的锅炉积灰。积灰不仅使锅炉热效率下降,而且堵塞烟气通道,影响了锅炉的正常运行。燃气脉冲除灰技术是中国科学院力学研究所燃烧实验室开发的,并在30多台大型电站锅炉应用,取得了很好的效果。本文工作研究了该项技术中燃烧室结构和燃料对火焰传播和压力脉冲的影响;用压力传感器测量燃气脉冲在出口外流场中的压力分布,观察燃气脉冲的作用强度和作用范围;用振动传感器测量积灰板的振动,以及在不同空间位置振动加速度的变化情况,由此推论了除灰作用的机理。     

300MW煤粉锅炉燃烧产物中汞的分布特征研究

在对某300MW燃煤电站锅炉的煤，渣，底灰，飞灰进行取样后，通过煤样，灰样，渣样中的汞进行定量测量，并借助于质量平衡分析方法计算烟气中汞的浓度，获得了煤在大型电站锅炉中燃烧时汞污染物的分布特征及其排放特性，图5表1参9。     

爆炸波除灰器中火焰传播及压力波形研究

燃烧气脉冲发生器应用于电站锅炉除灰。其工作原理是预混可燃气体在右端部分开口,内部有障碍物的容器中快速燃烧。形成一定的压力脉冲。并产生作用于积灰表面的射流和冲击波。火焰在湍流扰动装置的作用下不断加速。容器中的压力不断上升。火焰传播愈快,压力波形愈陡。压力锋值愈高。针对这些现象。主要研究了乙块、水煤气、液化石油气和甲烷四种燃料,在不同燃料浓度、不同阻塞比时对火焰传播的影响,分析了不同燃料浓度下对压力波形的影响。     

煤粉超细化对炉内受热面积灰与结渣的影响

煤粉颗粒温度、环境气氛和惯性沉积是电站四角切圆煤粉燃烧锅炉炉内受热面积灰与结渣的主要外在因素，以此为依据采用超细化煤粉燃烧技术对炉内受热面积灰和结渣的影响进行了理论分析与实验研究，阐述了煤粉超细化对于减轻电站有四角切圆煤粉燃烧锅炉炉内受热面积灰与结渣具有优越性。     

燃用低热值煤气锅炉燃烧系统节能改造的技术分析

本文介绍了钝体缝隙式燃烧器在燃用低热值煤气锅炉中的应用，讨论了低热值煤气强化燃烧的技术，认为提高可燃成分的浓度及煤气的初始温度，有利于低热值煤气的燃烧。     

ACFB与PCFB灰特性的比较研究

流休床燃烧技术的出现为解决因各种化石燃料的利用而带来的环境问题提供了很好的途径。在不久的将来，增压循环流化床（ＰＣＦＢ）燃烧技术将具有广阔的市场前景。这里须弄清ＰＣＦＢ燃烧产物中灰的特性与常压循环流化床（ＡＣＦＢ）燃烧产物中灰的特性的异同。不过，燃烧产物中灰的各组成成份将随加入的脱硫剂量和机组运行工况的不同而有很大的变化。在燃料中硫含量一定和同种脱硫剂的情况下，ＰＣＦＢ锅炉燃烧产生的灰量通常较ＡＣＦＢ锅炉燃烧产生的灰量要少，这主要是由于在增压锅炉中仅需较少的脱硫剂。上述两种锅炉中因脱硫产生的灰量之所以有差异，同时又是由于在常压和增压条件下脱硫反应机理的不同。本文所用到的灰样来自于商用ＡＣＦＢ电站和ＦＷ公司在芬兰卡弗莱的１０ＭＷ ＰＣＦＢ中试电站。文中叙述的灰特性和文中提供的ＡＣＦＢ灰样或ＰＣＦＢ灰样较其它地方所     

锅炉防磨涂料的导热性能测试

锅炉防磨涂料的导热性能测试哈尔滨理工大学吕薇华东工业大学孙家庆，徐开义哈尔滨理工大学刘伟军，刘兴家１前言在电站燃煤锅炉中，燃烧产物形成食灰的气固双相流，当含灰的气流以一定速度流过对流受热面时，将发生对流受热面的灰冲刷磨损。当燃煤中含灰量较高时，严重的...     

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.     

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.     

Decomposition of limestone in a solar reactor

The thermal decomposition of limestone has been selected as a model reaction for developing and testing an atmospheric open solar reactor. The reactor consists of a cyclone gas/particle separator which has been modified to let the concentrated solar energy enter through a windowless aperture. The reacting particles are directly exposed to the solar irradiation. Experimentation with a 60 kW reactor prototype was conducted at PSI's 90m² parabolic solar concentrator, in a continuous mode of operation. A counter-current flow heat exchanger was employed to preheat the reactants. Eighty five percent degree of calcination was obtained for cement raw material and 15% of the solar input was converted into chemical energy (enthalpy).The technical feasibility of the solar thermal decomposition of limestone was experimentally demonstrated. The use of solar energy as a source for high-temperature process heat offers the potential of reducing significantly the CO₂ emissions from lime producing plants. Such a solar thermochemical process can find application in sunny rural areas for avoiding deforestation.     

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.     

Biohydrogen production by Anabaena sp. PCC 7120 wild-type and mutants under different conditions: Light, nickel, propane, carbon dioxide and nitrogen

Increasing awareness of environmental problems caused by the current use of fossil fuel-based energy, has led to the search for alternatives. Hydrogen is a good alternative and the cyanobacterium Anabaena sp. PCC 7120 is naturally able to produce molecular hydrogen, photosynthetically from water and light. However, this H₂ is rapidly consumed by the uptake hydrogenase.This study evaluated the hydrogen production of Anabaena sp. PCC 7120 wild-type and mutants: hupL⁻ (deficient in the uptake hydrogenase), hoxH⁻ (deficient in the bidirectional hydrogenase) and hupL⁻/hoxH⁻ (deficient in both hydrogenases) on several experimental conditions, such as gas atmosphere (argon and propane with or without N₂ and/or CO₂ addition), light intensity (54 and 152 ??Em⁻²s⁻¹), light regime (continuous and light/dark cycles 16 h/8 h) and nickel concentrations in the culture medium.In every assay, the hupL⁻ and hupL⁻/hoxH⁻ mutants stood out over wild-type cells and the hoxH⁻ mutant. Nevertheless, the hupL⁻ mutant showed the best hydrogen production except in an argon atmosphere under 16 h light/8 h dark cycles at 54 ??Em⁻²s⁻¹ in the light period, with 1 ??M of NiCl₂ supplementation in the culture medium, and under a propane atmosphere.In all strains, higher light intensity leads to higher hydrogen production and if there is a daily 1% of CO₂ addition in the gas atmosphere, hydrogen production could increase 5.8 times, related to the great increase in heterocysts differentiation (5 times more, approximately), whereas nickel supplementation in the culture medium was not shown to increase hydrogen production. The daily incorporation of 1% of CO₂ plus 1% of N₂ did not affect positively hydrogen production rate.     

Investigation of the thermodynamic and kinetic properties of La–Fe–B system hydrogen-storage alloys

La–Fe–B hydrogen-storage alloys were prepared using a vacuum induction-quenching furnace with a rotating copper wheel. The thermodynamic and kinetic properties of the La–Fe–B hydrogen-storage alloys were investigated in this work. The P–C–I curves of the La–Fe–B alloys were measured over a H₂ pressure range of 10⁻³ MPa to 2.0 MPa at temperatures of 313, 328, 343 and 353 K. The P–C–I curves revealed that the maximum hydrogen-storage capacity of the alloys exceeded 1.23 wt% at a pressure of approximately 1.0 MPa and temperature of 313 K. The standard enthalpy of formation ΔH and standard entropy of formation ΔS for the alloys' hydrides, obtained according to the van't Hoff equation, were consistent with their application as anode materials in alkaline media. The alloys also exhibited good absorption/desorption kinetics at room temperature.     

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.     

The Solar Office in context

The goal of sustainability in buildings can only hope to be realised if buildings are designed to both conserve and generate energy. The Solar Office at Doxford International is designed to minimise the use of energy while its external fabric is designed to replace such energy that is used. The recently completed building is now subject of a comprehensive monitoring programme. The programme covers both the performance of the 73 kW_p photovoltaic installation and the environmental conditions within the building as a whole. Hour by hour findings are posted on a dedicated web site. Photovoltaics could have the same impact on building form and layout as the invention of the passenger lift at the end of the last century.     

液压系统常见的故障诊断及处理

任何工程机械式液压设备使用时出现故障是不可避免的。但是怎样确定故障的原因及找到好的解决方法，这是使用者最关心的问题。讲述了液压系统常见的故障及其排除方法。     

Hydrogen recovery from the photovoltaic electroflocculation-flotation process for harvesting Chlorella pyrenoidosa microalgae

In this paper, an integrated process using photovoltaic power to harvest microalgae by electro-flocculation (EF) and hydrogen recovery is presented. It is mainly favorable in regions with high solar radiation. The electro-flocculation efficiency (EFE) of Chlorella pyrenoidosa microalgae was investigated using various types of electrodes (aluminum, iron, zinc, copper and a non-sacrificial electrode of carbon). The best results regarding the EFE, and biomass contamination were achieved with aluminum and carbon electrodes where the electrical energy demand of the process for harvesting 1 kg of algae biomass was 0.28 and 0.34 kWh, respectively, while the energy yield of harvested hydrogen was 0.052 and 0.005 kWh kg^?1, respectively. The highest harvesting efficiency of 95.83 ± 0.87% was obtained with the aluminum electrode.The experimental hydrogen yields obtained were comparable with those calculated from theory. With a low net energy demand, microalgae EF may be a useful and low-cost technology.