液化气混空气燃气与天然气的互换性

燃气互换性问题存在于城市燃气供应的始终，在供气气源的性质发生较大变化时问题尤为突出。在液化气混空气为主要气源的城市燃气供气系统中，将来引进天然气时，所遇到的问题中最重要的就是液化气混空气燃气与天然气之间的互换性问题。作者采用美国燃气协会(A．G．A．)互换性判定方法，对这两种燃气的互换性进行了判定分析，并根据燃气用具的运行特性，分析了以液化气混空气燃气作为基准气设计和进行初调整的燃气用具，使用天然气后可能出现的问题。为将来天然气能顺利地与液化气混空气置换提出了合适的液化气混空气比例。     

民用燃气燃烧器适应燃气性质变化的调整

１燃气互换性的考虑１．１华白数对燃气互换性的影响华白数是在互换性问题产生初期采用的一个互换性判定指数，各国一般规定在两种燃气互换时华白数的变化不大于±５％～１０％。在互换性问题产生的初期，由于置换气和基准气的化学、物理性质相差不大，燃烧特性比较接近，...     

天然气气源变化对燃气内燃机性能影响及对策

分析燃气内燃机用天然气互换性判定指数,应选取华白数、甲烷值。针对多气源并存的局面,从国家及行业标准、燃气内燃机生产厂家、用户端等角度出发,提出稳定燃气内燃机性能的对策。     

美国燃气协会燃气互换性公式评述（第四部分）

6评述 （1）美国的燃气互换性研究始于不同燃气的混合需要。美国燃气协会36号公告法的命题就是《其他燃气与天然气的互换性》。其他燃气的组成都是已知的、互换性研究主要解决作为补充燃气的其他燃气与毖础负荷天然气互换时的定量比例,     

天然气互换性判别方法研究

综述了欧美等国家和地区在天然气互换性方面的研究进展,归纳、总结和评述了现在国际上应用较多的天然气互换性判别法,分别是美国的AGA 36号公告方法、韦弗指数法,法国德尔布互换法、英国的达顿互换性判别方法等,这些方法都是针对大气式燃烧方式提出的,具备各自的适用性和限制性。我国于1982年借鉴了法国德尔布互换性法,针对我国城镇燃气进行了分类和组分定义。对近年来我国在燃气互换性方面的研究和进展进行了总结,指出随着燃气利用终端设备的多样化,要根据具体燃气燃烧利用设备,基于设备燃烧时燃气和空气混合方式的不同,研究选取适应要求的、科学的燃气互换性指标和配气控制参数。     

美国燃气协会燃气互换性公式评述(第一部分)

美国燃气协会(A.G.A)的燃气互换性公式即美国燃气协会36号研究公报发表的公式,在我国的许多参考书中早已有所介绍,但至今未看到这些公式的理论基础、假设和形成的详细资料。根据计算结果,判定两种燃气能否互换时,公告原文本分成两类,即最佳值(Preferable)和不良值(Objectionable),无中间挡。我国有的文献中(9)分成合适、勉强和不合适3挡,但未说明"勉强"挡的出处和准确的内涵。范围的判定标准对这一方法的应用关系极大。从原文看,"中间挡"已突破了最初的理论假设条件,是在做燃具应用试验中出现的一些可允许情况,与原始的调定方法有关,是专对补充燃气而言,且并无"勉强"之意。本文引用了原文中的论述,可作进一步的研究。在已知所有的燃气互换性方法中,只有美国燃气协会的36号公告和韦弗法采用了数学公式分析的方法,曾做了大量的试验,内容十分丰富,可看到的资料也比较完整。本文尽可能的对36号公告法的试验结果作介绍,以加深对其研究思路的理解。对认识当前新形势下燃气互换性的问题也会有所帮助。     

第一族燃气互换性的研究

一、前言 第一族燃气互换性的研究在欧洲已基本结束,现在它们的城市燃气主要是天然气。但我国天然气产量不高,人工燃气在相当长一段时间内将会是城市燃气的主要气源。因此,研究第一族燃气的互换性问题,在我国是有现实意义的。 法国是研究燃气互换性较早,也较成功的国家之一。法国规定:为保证燃具正常工     

燃气质量管理方法与实践——当今液化天然气质量与瓦换性研究进展论述之三

本刊前两期讨论了当前终端用户对燃气质量的要求和燃气互换性研究的方法和进展。最后应讨论保证燃气互换性要求的质量调节方法与实践，回答怎么办的问题。     

燃气质量变化对终端用户的影响——当今液化天然气质量与互换性研究进展论述之一

从本期起,我刊将连续3期刊登我国燃气行业资深专家——中国工程院院士李猷嘉先生的论述"当今液化天然气质量与互换性研究进展"。国际燃气联盟(IGU)和英国BP集团于2010年发表了《燃气质量和互换性手册》,该手册是国际燃气联盟对互换性问题的系统的最新阶段成果。笔者通过学习和研究,认为我国在燃气互换性问题研究上与发达国家存在差距,并且还未意识到差距的所在,和应该怎么去做,而习惯于老的思维方式,希望国内燃气行业能认识、研究和借鉴该成果。我国燃气行业的现状是主要着眼于生活用气,而生活用气在世界范围内的比例已很小,同时对燃气质量问题的处理很粗放,此问题一直未得到解决,一直延续到今天,而沿海各省LNG的质量与原管道燃气的互换问题已迫在眉睫。应对气候的变化首先要着眼于改变我国的能源结构,"十二五"规划已开始有了转变,今后无论国内或进口天然气将必然有较大的发展,世界上燃气行业出现的发展趋势在我国迟早会到来。论述分成3部分,之一:"燃气质量变化对终端用户的影响",解决当今世界燃气的终端用户对燃气质量的要求,从中提炼出燃气互换性的共同参数(基础部分)。之二:"液化天然气互换性和质量的研究进展",介绍和分析发达国家的研究思路:在民用燃烧设备互换性研究成果的基础上,增加一些限制条件以满足当前发展的需要(原理部分)。之三:"燃气质量管理方法与实践",解决不能互换时的措施(对策部分)。为了完成此篇论述,李猷嘉院士花了整整半年以上的时间,写稿时还做了大量的计算工作。由衷感谢李猷嘉院士对国际上燃气互换性问题研究的持续关注、介绍和系统阐述,感谢他对本刊的支持和信任。《城市燃气》杂志社     

关于开展天然气互换性研究的建议

燃气互换性是城市燃气行业较熟悉的问题,但这里提出的天然气互换性研究不仅对我国是新课题,也是欧美等国当前重点研究的课题,是当今国际天然气工业关注的热点问题.     

Isotopically exchangeable phosphate in freshwater sediments: Effects of u.v.-irradiation,formaldehyde, solid/solution ratio,and pH on its experimental determination

The influence of bioactivities, solid/solution ratio and the pH on the isotopic exchangeability of phosphate in a freshwater sediment was investigated. From the comparison of the results obtained for the same sample in the presence or absence of formaldehyde, it is concluded that microorganisms can effect the analysis for isotopically exchangeable phosphate. Irradiation with u.v.-light caused a sharp rise in isotopic exchangeability. In the pH-range 6.6–8.4 isotopic exchangeability of phosphate increases with decreasing pH-value which is attributed to an easier exchange of H₂PO₄⁻ than of HPO₄²⁻. The influence of the solid/solution ratio on the isotopic exchangeability of phosphate in the solid phase is small or nil. However, because of the relatively large amount of phosphate that goes into solution, the total isotopic exchangeability E_i of phosphate in the solid and liquid phase together is strongly increased at a low solid/solution ratio. From these results it is concluded that in order to make a meaningful comparison of isotopically exchangeable phosphate in different soils or sediments it is essential to work at a nearly constant pH and solid/solution ratio. Such a comparison was made for 26 freshwater sediments from the Rhine/Meuse delta, in the presence and absence of 0.17 mol l⁻¹ formaldehyde as a biological inhibitor and it is concluded that addition of the latter is essential. The lowest total isotopic exchangeabilities of phosphate, (15–25) were measured in the sediments collected from the Haringvliet, whereas higher values (40–80) were found in the sediments from the Brielse Meer and the Grote Rug. This could well be indicative of a similar variance in the biological availability of the phosphate in the investigated sediments.     

Probability,exchangeability and extremes: with discussion of iceberg loading

The basic concepts of probability and utility, as well as their interrelationship, are reviewed. The duality embodied in the definitions of these quantities is emphasized. The assumptions of exchangeability as an alternative to independence, in assessing the implications of data sets and in problems of inference, is shown to offer the opportunity for considerable improvement in statistical analysis. Exchangeability implies that the order of a sequence of random events or quantities is not of significance. The use of a basic urn model in formulating problems involving exchangeability is demonstrated. The extension of the analysis to continuous random quantities as well as to problems of extremes is summarized. An example of the analysis of arrival of icebergs at discrete points in time at the location of an offshore structure is included and it is shown that the results include the uncertainty resulting from short data bases. The added risk associated with this uncertainty is acknowledged implicitly in the methodology.     

CB10新型钢模板施工技术的应用

通过对CB10新型钢模板体系在多个工程中的应用表明,该模板体系具有自重轻、强度大、刚性好、易拆装、互换性强、成本低,浇筑混凝土平整度高、接缝严密、无错台、不漏浆、综合效益高、可充分满足清水混凝土施工要求等特点。做到既环保又节能,从技术和措施上为绿色建筑的建成创造条件。     

材料燃烧过程中的毒性气体分析

本文通过分析不同材料燃烧产生的烟及毒性气体的特征，提出了烟气毒性浓度指数的概念，并以烟气毒性浓度指数划分材料燃烧后的毒性等级。     

Species Transport from Post-Flashover Fires

A study was performed to determine the use of an equivalence ratio to predict gas levels (CO, CO₂, O₂, and unburned hydrocarbons) transported to locations remote from a post-flashover compartment fire. A series of tests were conducted in a reduced-scale facility to measure the evolution of post-flashover compartment fire gases flowing down a hallway. Test variables included air entrainment into gases in the hallway, stoichiometry of the compartment fire gases entering the hallway, mass flow rate of compartment fire gases, and the presence of a vitiated smoke layer accumulated in the hallway. In cases with no layer accumulated in the hallway, species yields in the hallway were found to correlate with a control volume equivalence ratio. The control volume equivalence ratio is the ratio of the mass loss rate of fuel inside the compartment to the air flow into the compartment plus the air entrained into compartment fire gases flowing along the hallway. Layers that accumulate in the hallway were determined to limit oxidation, which in some cases resulted in CO yields transported to remote locations being 20% higher than those inside the compartment. Based on the experimental data, a methodology was developed for predicting species levels transported to remote locations.     

Comparing in situ distribution coefficients and exchangeability of radiocaesium in freshwater sediments with laboratory predictions

Two short-term (24 h) laboratory procedures, based on measurement of the affinity and capacity of the specific binding sites for radiocaesium on illitic clay minerals, are used to predict the in situ 137Cs distribution coefficients (KD) in two Dutch freshwater sediments. Differences in the measured amount of specific binding sites between the sediments are shown to be related to differences in the particle size and illite content. A procedure based on measurement of the combined parameter KD[NH4+] predicts the measured in situ 137Cs distribution in both sediments very well. This is remarkable because the in situ data are based on 137Cs/sediment contact times of > 1 year, while previous experiments have shown that increasing contact times between Cs+ and sediments decreases the short-term exchangeability of caesium, as measured by extraction with a high ammonium concentration. The good predictions of the 37Cs solid/water distribution by short-term ion-exchange experiments, therefore, indicate that more 137Cs in the sediments is exchangeable than is measured by the commonly used extraction with high ammonium concentrations.     

Microscopic analysis of the engineering geological behavior of soft clay in Shanghai, China

The upper 75 m of the alluvium beneath Shanghai can be divided into three clay layers. Consolidation of the upper soft clay contributes to the average 3 mm/year land subsidence which occurs in the Shanghai region, despite mitigation measures including reduction in groundwater exploitation from the underlying aquifer and groundwater recharge. Data indicate that the soft clay is semi-dispersed, marginally stable, and susceptible to compaction. The study reports an analysis of the granulometric characteristics and aggregate components, pore-size distribution, microstructure, pore solution composition and cation exchangeability of the soft clay. The results indicate the deformation/consolidation of the soft clay is related to its microscopic physical and chemical characteristics rather than the fluctuation of the groundwater level in the underlying aquifer.     

Effects of atmospheric wind on flows through natural convection roof vents

Natural convection roof vents are widely used in industrial and other buildings for clearing smoke and toxic gases produced by fires and explosions. In the design of such vents where hot gases are driven out by pressure differences, it has been a common practice to ignore the effects of outside wind. Buoyancy is assumed to be the only driving force. This paper shows that under certain wind conditions the effects of wind can completely override buoyancy, causing either flow reversal or inefficient extraction. A new design method, based on wind tunnel measurements, is proposed by which the effects of wind can be taken into account. A worked example is presented to illustrate the method.     

工业燃气互换性的分析

本文在对不同工艺所要求的燃气互换性条件进行分析的基础上，结合低热值煤气的燃烧特点，提出了一组适合于锅炉和加热炉的燃气互换准则数。并通过理论计算和工程实例分析，得出了当混合煤气为置换气，焦炉煤气为被置换气时，互换准则数允许波动的范围。     

连续墙抓斗通用工装设计

介绍地下连续墙抓斗设备重要零部件——抓斗合件制造过程的改进及抓斗体通用工装的设计方案.抓斗体通用工装的设计思想主要是从连续墙抓斗的装配要求出发,结合产品特性,努力改善产品的制造条件,并满足通用化的制作要求.通过设计壁板单片工装和抓斗体通用工装,加强抓斗体系列产品的焊接过程控制,为连续墙抓斗体的后续加工打下良好的基础,进而从根本上解决抓斗装配中反映出来的各种问题,最终达到保证产品质量,提高工作效率的目的.