90t电弧炉底吹工艺效果分析

介绍了90 t电弧炉底吹系统,统计了底吹系统541炉冶炼数据与使用底吹前的生产数据进行比较,表明底吹系统能够均匀钢液温度和成分,增加搅拌能,使氧气消耗从49 m3/t(标准)降低到47.568 m3/t(标准),钢铁料消耗从1 160.586 kg/t降低到1 128.624 kg/t,渣中(FeO)从31.23%降低到25.24%,渣中(MgO)从7.65%降低到4.95%。     

底吹搅拌在Consteel电炉中的应用

通过对电弧炉底吹搅拌工艺技术原理的研究,分析了电弧炉底吹搅拌工艺对炼钢冶金过程的影响,进而制定了合理可行的底吹工艺参数。在通钢第一炼钢厂在70tConsteel电弧炉上安装了电弧炉底吹搅拌系统,冶炼结果表明：电弧炉底吹工艺能有效加强熔池搅拌强度,从而提高电弧炉熔池脱碳速度、脱磷率,降低终渣FeO含量,降低氧气消耗,缩短熔炼周期,为电弧炉高效冶炼提供帮助;冶炼成本分析表明,电弧炉底吹搅拌能有效降低冶炼成本,为电弧炉高效化炼钢提供了廉价而有效的途径。     

长炉龄高氧化性条件下转炉稳定生产实践

高废钢比、长炉龄和降低生产成本是钢铁企业转炉冶炼的重要发展方向。为解决生产过程中提高废钢比例造成终点过吹问题，某钢厂针对提升复吹效果进行了经济炉龄推进的可行性研究和分析，通过不断的摸索和完善，形成了一套具有日钢特色的转炉经济炉龄控制模式。首先，将原有毛细管式的底吹透气砖改为环缝式透气砖，采用梅花桩底吹布局并增长底吹透气砖长度的装置改进，并结合碳氧积动态调整底吹强度工艺制度来延长底吹透气砖寿命；然后通过数值模拟方法，研究了顶吹氧气和底吹空气下的熔池流场的变化，并分析了措施实施前后炉衬侵蚀变化情况；最后通过溅渣方式的优化，将原溅渣模式加轻烧镁球+生白云石改为加焦粉+轻烧白云石，并采用高枪位逐步压枪的方式溅渣，有效减少了溅渣时长和熔池侵蚀。将改进后的生产工艺应用在该钢厂实际生产中，采集炉衬侵蚀、钢铁料消耗和炉渣全铁数据。工业实践结果表明，实施优化后生产工艺后，钢水质量提升，其静态脱磷率由前炉役的66.3%提高至70.7%;冶炼和溅渣时间缩短，冶炼周期由44 min/炉降低至35 min/炉；优化后炉役的耐材成本降低1.17元/t,废钢消耗量提升4%,炼钢成本降低11.94元/t。     

Armco公司电弧炉吹氩搅拌的经验

美国Armco新材料公司在其三台150t电弧炉上,采用奥地利Radex公司开发的多孔定向塞在炉底吹氩,取得良好技术和经济效益。电耗下降7.5％,电极消耗     

提高电炉炉龄工艺实践

某炼钢分厂90 t UHP电弧炉自2009年电炉兑铁水以来,一次性炉龄一直徘徊在400～500炉,使用周期20～25天。经过对电炉耐材侵蚀机理的分析,结合冶炼工艺的现状,并通过优化耐材材质、改变炉底捣打方式、摸索炉衬耐材砌筑工艺、优化冶炼操作工艺等措施,在不挖修、不中途打结炉底及少喷补的条件下,2018年的一次性炉龄平均达到850炉,最高炉龄达到951炉,取得了显著的经济效益。     

45 t电弧炉转炉化改造与生产实践

电弧炉炼钢具有能量效率高、可调节性能好等优点,然而相比于转炉炼钢其冶炼时间较长,电弧炉转炉化操作能够有效降低电弧炉冶炼电耗,缩短冶炼时间,是实现电弧炉高效冶炼的重要途径之一。针对某钢厂45 t电弧炉转炉化过程,基于理论计算分析电炉转炉化中合理的铁水比例及高铁水比下冶炼操作工艺特点,并结合实际铁水温度与成分数据,确定铁水比应当控制在78%～88%范围内。通过设备改造、生产组织优化、工艺操作调节等方式优化电弧炉转炉化改造后的生产过程,最终确定有利于电弧炉冶炼的最佳兑入铁水比例为83%左右。此时45 t电弧炉完全实现转炉化操作,冶炼周期缩短了6.84 min,吨钢冶炼成本节约107.26元/吨坯,设备故障与热停时间缩短5 min/炉,同时减小了员工的劳动强度,取得了明显的经济效益。     

铁水捞渣机在电弧炉炼钢中应用实践

对铁水捞渣机的使用情况及铁水捞渣后的电弧炉操作进行了分析,从操作实践及统计分析看,电弧炉入炉铁水经过捞渣后,石灰消耗吨钢下降5．12kg,电弧炉操作得到很好改善,冶炼后期炉内大沸腾现象得到有效遏制。     

降低电弧炉冶炼电耗的实践

电弧炉炼钢是以电能转化为热能来熔化废钢去完成炼钢任务的。因此,在冶炼过程中要消耗大量的电能。对冶金企业来说,电弧炉是能耗大户,俗称“电老虎”。目前,由于我国的能源紧缺,电力不足,降低电弧炉冶炼电耗已成为我们国家,特别是冶金行业节能降耗的重点。西钢炼钢厂是60年代建成的老厂,有3吨电弧炉两座,变压器为2200kVA,平均出钢量6.39t,年产1.9万吨。从投产以来,由于种种原因,电炉冶炼电耗一直居高不下,1991年为708kWh/t(详见表1),成为公司节能降耗的一大。难题1992年开始做了一些尝试,从抓节能降耗人手,强化了科学管理,不断改进操作工艺,进行技术改造,取得了较好的效果。电炉冶炼电耗1992年为579kWh/t,1993年1～8月份为509kWh/t,工序能耗由原来的415kg标煤/t降到293kg标煤/t。     

65t电弧炉复合吹炼的水模拟研究

本文在相似原理的基础上利用1:4的水力学模型对某钢厂65t电弧炉各吹炼参数进行模拟研究,重点研究不同侧吹、底吹流量以及不同底吹位置布置方案对熔池搅拌效果的影响。在此基础上,分别研究底吹流量、侧吹流量和底吹位置布置对熔池混匀时间的影响。实验结果表明,侧吹、底吹流量对熔池混匀时间均有显著影响,侧吹流量较底吹流量影响更显著,底吹位置分布对熔池混匀时间影响较小。工业试验结果表明,与无底吹条件相比,复合吹炼能更好的搅拌熔池,提高脱碳速率,降低钢铁料消耗。     

45t电弧炉高比例铁水冶炼实践

某45t电弧炉在兑人60％铁水条件下,针对矮胖型炉型电弧炉对供电曲线、供氧制度和造渣制度进行了优化,解决了高比例铁水带来的炉墙炉盖粘钢、炉内大沸腾和炉门口跑钢等问题,使冶炼操作平稳,缩短了冶炼时间,降低了电耗和电极消耗。     

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%.     

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.     

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.     

Contents in Volume 23,2014

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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。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.     

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.