Molecular dynamic simulation of aluminum-water reactions using the ReaxFF reactive force field

In this study we employed the ReaxFF reactive force field to examine the dynamics associated with the dissociation of adsorbed water molecules on an aluminum nanocluster surface. We have investigated several different concentrations of water on an Al₁₀₀ cluster to elucidate the dynamics of the dissociation phenomena. Our results indicate that the dissociation of an isolated water molecule on the surface requires significant activation energy, and that an assisted dissociation by a neighboring, non-adsorbed, water molecule is more energetically favorable. The dynamics of this reaction pathway are discussed and compared to recent quantum studies along with a further investigation of the role inert gases and oxide layers have on these processes. Our results shed light on this atomic scale behavior and increase the potential for reactive metal/water systems to be used as lightweight, portable, and on-demand energy sources via fast hydrogen gas production.     

Exergy analysis of Illinois No. 6 coal

The projected increase in coal utilization in utility power plants makes it desirable to refine customary evaluations of coal which are based on the First Law of Thermodynamics. Presented in this paper is a Second Law or exergy analysis of Illinois No. 6 coal. A theoretical analysis is carried out and the quality of coal is calculated. The methodology, although applied to Illinois No. 6 coal, should be applicable to other coals or non-homogeneous fuels.     

Effect of CO2 and steam gasification reactions on the oxy-combustion of pulverized coal char

For oxy-combustion with flue gas recirculation, elevated levels of CO₂ and steam affect the heat capacity of the gas, radiant transport, and other gas transport properties. A topic of widespread speculation has concerned the effect of gasification reactions of coal char on the char burning rate. To asses the impact of these reactions on the oxy-fuel combustion of pulverized coal char, we computed the char consumption characteristics for a range of CO₂ and H₂O reaction rate coefficients for a 100 μm coal char particle reacting in environments of varying O₂, H₂O, and CO₂ concentrations using the kinetics code SKIPPY (Surface Kinetics in Porous Particles). Results indicate that gasification reactions reduce the char particle temperature significantly (because of the reaction endothermicity) and thereby reduce the rate of char oxidation and the radiant emission from burning char particles. However, the overall effect of the combined steam and CO₂ gasification reactions is to increase the carbon consumption rate by approximately 10% in typical oxy-fuel combustion environments. The gasification reactions have a greater influence on char combustion in oxygen-enriched environments, due to the higher char combustion temperature under these conditions. In addition, the gasification reactions have increasing influence as the gas temperature increases (for a given O₂ concentration) and as the particle size increases. Gasification reactions account for roughly 20% of the carbon consumption in low oxygen conditions, and for about 30% under oxygen-enriched conditions. An increase in the carbon consumption rate and a decrease in particle temperature are also evident under conventional air-blown combustion conditions when the gasification reactions are included in the model.     

花生壳与煤共燃的燃烧特性研究

用热重分析法,对花生壳与煤以相同比例掺混后在不同升温速率下进行了共燃试验。研究表明,生物质的加入改善了煤的燃烧性能,且随升温速率的升高,着火温度呈下降趋势;各试样的挥发分最大释放速率、固定炭最大燃烧速率、燃尽温度均呈增加趋势,它们的燃烧特性均随升温速率的升高而变好。     

煤质变化对锅炉燃烧的影响及应对措施

通过分析煤炭的燃烧过程、链条炉排的燃烧特点及其对煤质的要求以及煤质不同成分对锅炉燃烧的影响,提出了在煤质发生变化时的应对措施,来保证供热质量达标和安全平稳运行.     

GEF子项-6样机锅炉介绍

郑州锅炉厂与德国BAY公司和BABCOCK公司联合开发设计的DZL10—1．25—AⅡ前置炉膛水火管锅炉已生产、安装、测试完毕,各项指标均已达到或超过CEF要求。文章对该样机锅炉作出全面介绍。     

Kinetic study for the reduction of residual char particles using oxygen and air

This study characterizes the chemical kinetics for the reduction and elimination of char particles using air and pure oxygen as the oxidants. Commercial carbon black was used as char for the experimental studies reported here. Different oxidant injection flow rates have been examined at various injection temperatures between 400 and 700 °C under atmospheric pressure conditions to obtain the intrinsic kinetic parameters. The char conversion rates have been measured in a laminar flow hot stream using 0.2 g and 0.3 g mass of initial char samples. The kinetic parameters are obtained by fitting the available experimental data into the derived one-film model. The proposed one-film model is compared and analyzed for consistency and reliability for the calculated intrinsic kinetic parameters.     

Process for the concurrent production of hydrogen,carbon monoxide and low-volatile,low-sulfur char by flash carbonization of coal

Flash carbonization is being investigated to produce hydrogen and carbon monoxide with the concurrent production of low-sulfur, low-volatile char from bituminous coal. High temperatures (>1255 K) and short reaction times (<15 s) are used at atmospheric pressure. No tar is formed in the process and the gas is separated immediately from the hot char which is quenched to retain a volatile content of ca 10–20%. Results of thermodynamic equilibrium calculations using the free energy minimization method and the equilibrium constant method have been in good agreement and are compared with experimental results. Predesign capital and operating cost estimates have indicated that the cost of producing synthesis gas (hydrogen and carbon monoxide) by this process would be competitive with the cost of producing synthesis gas by the partial oxidation of methane when the by-product char is credited at the equivalent fuel value.     

柴油机燃用F-T柴油与0号柴油混合燃料的燃烧特性

根据实测的喷油器针阀升程和示功图,开展了直喷式柴油机燃用F-T柴油与0号柴油混合燃料时燃烧特性的研究．试验用燃料为0号柴油、含25%和50%F-T柴油的混合燃料以及100%F-T柴油．结果表明,在相同工况下,随着混合燃料中F-T柴油比例的增加,喷油延迟角增大,而喷油持续期变化不大．滞燃期随着F-T柴油比例的增加而缩短,其中当F-T柴油的比例由0增至25%时,滞燃期缩短最为明显,此后进一步增加F-T柴油的比例,滞燃期缩短幅度减小．随着混合燃料中F-T柴油比例的增加,预混燃烧放热峰值降低,扩散燃烧放热峰值增大,燃烧持续期略有延长,缸内最高燃烧压力和气体最高平均温度降低,最大压力升高率显著下降,发动机的燃烧噪音和机械损失减小,有效燃油消耗率和有效热效率得到改善．     

Improvement of Emissions and Burning Limits in Burner Combustion using an Injector on the Concept of Fuel-Water Internally Rapid Mixing

This study tried to apply biomass fuel to clean burner combustion under high load conditions by water addition. A newly developed injector mixes fuel rapidly with water inside of the injector with support of atomizing air. The mixture composed of three-fluid is injected as spray into a flame stabilizer of burner. Investigation of emission performance of this injector shows that the internally rapid mixing type of injector is hopeful technique to introduce water into burner combustion. Combustion by this injector emits exceedingly less particulate matters at high load. NOx emission is strongly dependent on water flow rate.     

The influence of pressure on the control of premixed turbulent flames using an electric field

Previous investigations of the effects of electric fields on flames have shown the potential for stabilizing flames and reducing emissions with comparatively little effort, but were restricted to atmospheric pressure. In the present work the influence of the electric field on premixed turbulent jet flames at increased pressure is investigated. Besides the question of whether field effects persist at elevated pressure, it is of interest to find physically based scaling laws. The current work describes experiments with premixed turbulent seven-hole Bunsen-jet flames for pressures between 1 and 10 bar, where the exit velocity was held constant, and where electric fields of varied strength and direction were applied to the flame. Concentrations of CO, NO, and NO₂ were measured in the exhaust gas section. Experiments show that the electric field influence is clearly visible for increased pressures, without any indication that 10 bar should be an upper limit. CO emissions could be reduced by about 95%, irrespective of pressure. The decrease of CO was accompanied by an increase of NO_x by about 25%. Both of these effects can be understood qualitatively within the framework of a one-dimensional model. For reduced voltages up to 3.5 kV/bar the model correctly describes the current-voltage characteristics and leads to the conclusion that high pressure should favor rather than hamper electric field effects on flames. The electric power required for a CO reduction of 95% amounted to 0.1% of the thermal power. The improvement of the lean blowoff limit upon application of an electric field observed so far ranges from 1 to 3% and increases with pressure.     

邹县发电厂6号锅炉再热器热偏差的改造措施

邹县发电厂6号锅炉是美国福斯特惠勒公司（F．W）设计和生产的600MW亚临界燃煤粉锅炉．由于再热器采用一级布置,热偏差大,在出口段炉外部分和出口垂直段部分出现较大范围超温,并有爆管现象发生．邹县发电厂联合上海发电设备成套设计研究院共同进行了技术攻关．通过试验研究和计算分析,找出了超温爆管的原因,提出了3个改造方案,并进行了比较,在实施改造中采用了第二个方案,取得了预期的效果,     

邹县发电厂6号锅炉再热偏差的改造措施

邹县发电厂6号锅炉是美国福斯特惠勒公司(F.W)设计和生产的600 MW亚临界燃煤粉锅炉.由于再热器采用一级布置,热偏差大,在出口段炉外部分和出口垂直段部分出现较大范围超温,并有爆管现象发生.邹县发电厂联合上海发电设备成套设计研究院共同进行了技术攻关.通过试验研究和计算分析,找出了超温爆管的原因,提出了3个改造方案,并进行了比较,在实施改造中采用了第二个方案,取得了预期的效果.     

凤滩电厂6号水轮机尾水锥管裂纹原因分析及处理

凤滩水电厂6号机组投产不到一年的时间,尾水锥管与基础环焊接处X-Y象限产生大范围的裂纹,已经严重影响到新机组的安全稳定运行。本文重点介绍凤滩6号机组尾水锥管裂纹的处理方案,并初步分析了裂纹产生的原因及预防措施,经处理该缺陷得到了有效解决。     

Adiabatic fixed-bed gasification of coal, dairy biomass, and feedlot biomass using an air–steam mixture as an oxidizing agent

Concentrated animal feeding operations, such as cattle feedlots and dairies, produce a large amount of manure, cattle biomass (CB), which can be included as renewable feedstock for locally based gasification for syngas (CO and H₂) production and subsequent use in power generation. Experimental results on effects of bed temperature and gas composition on the higher heating value (HHV) and energy recovery are presented for dairy biomass (DB) gasification using air and air–steam as oxidizers. Some experimental data are compared with adiabatic gasification modeling which includes atom balance conservation for assumed product species and chemical equilibrium analysis. Wyoming sub-bituminous coal (WYC) and Texas Lignite coal (TXL) are used as standard fuels for comparison purposes in modeling studies. Two main parameters are investigated in this study. One is the modified equivalence ratio (ER_M) defined as the ratio of stochiometric oxygen to total oxygen supplied in the oxidizing mixture of air and steam. The second is a measure of how much steam is in the oxidizer and is called the air steam ratio (ASTR), which is defined as the ratio of oxygen supplied in the air to the total oxygen supplied in the oxidizer. The results suggested that gasification of CB and coals under higher ER_M yield elevated concentrations of CO and CH₄, and low percentages of H₂ and CO₂, while higher ASTRs (less steam) produced mixtures poor in H₂, CO₂, and CH₄ and rich in CO with lower HHV. It was also found that FB and DB produced higher amounts of H₂ than WYC and TXL under the same ER_M and ASTR.     

A study of multi-phase flow through the cathode side of an interdigitated flow field using a multi-fluid model

This work presents a study of multi-phase flow through the cathode side of a polymer electrolyte membrane fuel cell employing an interdigitated flow field plate. A previously published model has been extended in order to account for phase change kinetics, and a comparison between the interdigitated flow field design and a conventional straight channel design has been conducted. It is found that the parasitic pressure drop in the interdigitated design is in the range of a few thousand Pa and could be reduced to a few hundred Pa by choosing diffusion media with high in-plane permeability. The additional compressor work due to the increased pressure loss will only slightly increase, and this may be offset by operating at lower stoichiometries as the interdigitated design is less mass transfer controlled, which means that the overall efficiency of the interdigitated arrangement will be higher. In the interdigitated design more product water is carried out of the cell in the vapor phase compared to the straight channel design which indicates that liquid water management might be less problematic. This effect also leads to the finding that in the interdigitated design more waste heat is carried out of the cell in the form of latent heat which reduces the load on the coolant. Finally we see that the micro-porous layer might help keep the gas diffusion layer substrate dry due to a potentially higher evaporation rate caused by a combination of the Kelvin effect and a larger specific surface area compared to the diffusion layer substrate.     

亚临界600MW汽轮机6瓦瓦温过高原因和检修工艺

台山电厂600MW汽轮机6瓦多次出现瓦温过高异常,危及汽轮机安全运行,降低了机组可靠性。通过技术人员分析,认为造成瓦温高的原因有轴系稳定性、轴瓦自位能力和轴颈表面损伤等原因,随后对6瓦的检修工艺进行了针对性改进,形成了一套较为可行的检修措施,从而使6瓦检修后的可靠性提高。     

Methane decomposition with some CO2 as co-feed: Co-production of syngas and carbon fibers/microspheres by using a hybrid of K2CO3 and coal char

Co-production of hydrogen and valuable carbonaceous materials by catalytic methane decomposition (CMD) is a promising process. However, nowadays it is still difficult for various carbon catalysts to make it. Here CMD with addition of some CO₂ as co-feed was proposed and evaluated by using a hybrid of K₂CO₃ and coal char (CC). Effect of the additional CO₂ as co-feed was investigated on methane conversion, the outlet gas composition, and the deposited carbon morphology. The results show that co-production of syngas (H₂ and CO) and carbon fibers/microspheres could be obtained along with high and stable methane (around 80%) and CO₂ conversion (up to about 100%) in the process. Stable molar ratios of H₂/CO (ranging from 0.6:1 to 5:1) as well as different carbon morphologies (amorphous, fibrous or microspherical) can be regulated and controlled by the molar ratio of CH₄/CO₂ (from 75:10 to 75:75) in the feedstock. Quantitative and qualitative analysis of the products show that there is probably a synergy between K₂CO₃ and CC during the reaction process.     

汽油/CNG混合燃料发动机的性能和燃烧特性研究

研究了汽油／CNG混合燃料的发动机性能和燃烧特性。在研制汽油／CNG发动机集中电子控制单元基础上,研究了不同汽油和天然气混合比例对发动机动力性能、排放性能的影响,结果表明,随着混合燃料中天然气比例的增加,发动机的功率和转矩下降,HC和NOx排放降低,在不同负荷下应供给发动机不同比例的汽油和天然气,这样既可以获得较好的发动机动力性能,又可以实现发动机低排污特性;对燃烧特性的研究结果表明,在天然气中混入汽油有利于改善天然气的燃烧特性,混合物的燃烧特性参数随两种燃料的混合比的不同而不同,其值界于天然气和汽油之间。