Sulfur segregation during the high-temperature oxidation of chromium

A TEM and STEM examination has been carried out of cross-sectioned specimens of convoluted chromia scale formed by oxidizing chromium at 950° C. Sulfur was detected at the oxide/metal interface and the oxide grain boundaries (apart from low-angle grain boundaries), but not within the oxide grains. These results are consistent with the sulfur effect theory.     

Sulfur solubility in NiO and CoO at 1000°C

The solubility of sulfur in NiO and CoO at 1000°C has been investigated over a wide range of oxygen and sulfur partial pressures using CO, CO₂, and SO₂ as input gases. The concentration of dissolved sulfur increases regularly with sulfur partial pressure but appears to be insensitive to oxygen partial pressure. Dissolution of sulfur did not affect the electrical conductivity of NiO samples. It was concluded that sulfur probably dissolves, in the range 10^–2 –10^–3%, either by exchange with O^–2 ions occuping O^–2 sites as S^–2 ions, or as neutral sulfur on interstitial sites. The scatter in results prevented a more definite conclusion being drawn.     

Growth behavior of oxide forming on a sputtered oxygen-enriched type 304 stainless steel

Type 304 stainless steel was deposited with and without added oxygen and then oxidized at 900 °C in 0.1 atm oxygen. The oxidation rate of the oxygen-enriched steel was lower than that of the steel without added oxygen, and the oxide adhesion was better. Line scans on cross-sectioned scale on the oxygen-enriched steel showed that inward oxygen diffusion had occurred; however, this was not shown by any of the line scans on the steel without added oxygen. The diffusion rate of cations through chromia scale was reduced by the oxygen enrichment. A secondary ion mass microscopy study showed that sulfur segregation to the oxide scale occurred during oxidation. The extent of this segregation for the oxygen-enriched steel was much lower than that for the steel without added oxygen. The results are explained in terms of the sulfur effect theory by postulating that impurity sulfur segregated to oxide particles in the oxygen-enriched steel, resulting in a reduced sulfur level in the scale and at the oxide/metal interface.     

Oxidation limited life times of chromia forming ferritic steels

Long term, cyclic oxidation studies of three high – Cr, ferritic steels were carried out at 800°C and 900°C in air. It was found that with decreasing sample thickness the life time of the mentioned alloys decreases due to breakaway phenomena. This effect is caused by faster exhaustion of the chromium reservoir from the bulk alloy in case of thinner components. The observed life time limits can be predicted with reasonable accuracy by a theoretical model, using oxide growth rate parameters, initial alloy Cr content and critical Cr content required for protective chromia scale formation. In the calculation it has, however, to be taken into account that the oxidation rates of the steels increase with decreasing specimen thickness.     

应用WS-S600型全自动测硫仪测定磁铁矿全硫

从实验原理、方法等入手,介绍了WS-S600型全自动测硫仪在准确测定磁铁矿中全硫含量的应用,通过数据分析,发现测得的全硫含量与高频红外碳硫法对比无明显差异,且该法可以达到快速分析以及准确度的要求,解决了炼铁生产的实际需要.     

Diffusion of cations in chromia layers grown on iron-base alloys

Diffusion of the cations Cr, Fe, Mn, and Ni in Cr₂O₃ has been investigated at 1173 K. The diffusion measurements were performed on chromia layers grown on the model alloys Fe-20Cr and Fe-20Cr-12Ni in order to consider effects of small amounts of dissolved alien cations in Cr₂O₃. The samples were diffusion annealed in H₂-H₂O at an oxygen partial pressure close to the Cr₂O₃/Cr equilibrium. For all tracers the lattice-diffusion coefficients are 3–5 orders of magnitude smaller than the grain-boundary diffusion coefficients. The lattice diffusivity of Mn is about two orders of magnitude greater than the other lattice-diffusion coefficients, especially in Cr₂O₃ grown on Fe-20Cr-12Ni. The values of the diffusion coefficients for Cr, Fe, and Ni are in the same range. Diffusion of the tracers in Cr₂O₃ grown on different alloys did not show significant differences with the exception of Mn.     

An Investigation of the Growth Mechanism of Scale Formed on Chromium Containing Low Amounts of Sulfur,Chlorine, and Phosphorus

The growth mechanism of the flat and adherent scale formed at 900°C in 0.1 atm oxygen on chromium, which contained 1 ppm (wt) sulfur, 0.08 ppm (wt) chlorine, and 0.2 ppm (wt) phosphorus, has been found to be very different in adjacent parts of the scale, consistent with the results of previous tracer studies of the growth mechanism of chromia formed on chromium. In some places, it grew primarily by chromium transport, while in others it grew primarily by oxygen transport and in still others it grew by a mixture of both. New oxide formed within the outer part of the scale and, in some cases, throughout the scale. A tentative hypothesis is proposed to explain why growth mechanisms were different in different parts of the scale on the same specimen. The scale formed at 950°C on Fe–20%Cr–0.11%Si, which contained 15 ppm sulfur, grew predominantly by cation transport, with only a small amount of oxygen transport. In this case also, new oxide formed within the outer part of the scale.     

高硫铝土矿溶出过程中硫的行为研究

本文研究了高硫型高品位铝土矿溶出过程中硫的行为,考查了石灰添加量、溶出温度、苛性碱浓度和溶出时间对铝土矿中硫溶出率的影响。实验结果表明,在溶出高硫铝土矿时,硫溶出率最小的最佳条件是：温度240℃,碱浓度195g/l,时间50min,石灰添加量CaO16%。此时,硫的溶出率仅为7.05%,同时又能保证氧化铝溶出率不低于81%。处理高硫型高品位铝土矿时,需要综合考虑影响氧化铝溶出率的各方面因素,既要保证高的氧化铝溶出率,又要取得较低的硫溶出率。从而减轻硫进入溶液所导致的除硫负担,减少脱硫剂用量,降低除硫费用。     

脱磷剂中硫的检定

以纯铁、氧化铜、锡粒、钨粒和少量的五氧化二钒为助熔剂,采用高频红外碳硫仪测定脱磷剂中的硫含量。将测试结果与联测的碳含量结果相结合,提高分析的准确性。     

Corrosion of iron in sulfur dioxide at 0.1 MPa

The reaction of iron with sulfur dioxide at 0.1 MPa and 1073 K was studied. The composition and morphology of the scales, transport phenomena occurring in the growing scales, and kinetics of the process were investigated. Scanning electron microscopy and various techniques of X-ray analysis were used. The transport phenomena were studied by marker and by radiotracer techniques. The scales were composed of sulfide and oxides and grew by the outward diffusion of metal. It was concluded that the process initially took place through the reaction of iron with sulfur dioxide molecules. During the next stage of the process the reaction with sulfur dioxide molecules as well as with oxygen molecules is possible.     

硫磺成型及储运设施的腐蚀状况

采用现场检查和实验室微观分析等方法,分析评价了普光高含硫天然气净化厂硫磺成型及储运设施的腐蚀状况。结果表明,硫磺成型及储运系统存在含硫工业大气环境腐蚀、湿硫磺沉积或浸泡水中形成的强酸性环境腐蚀和硫磺料仓内部特定H2S及硫蒸汽气氛环境的腐蚀。     

高频燃烧红外吸收法分析高碳铬铁中碳、硫

通过对板流、助熔剂的选择及加入方式、称样量、分析时间等方面进行改进,解决了高碳铬铁中碳、硫元素分析经常出现燃烧释放慢、分析时间长、拖尾及数据不稳定等问题,提高了测定的准确性和稳定性.改进后的分析方法对标准样品进行准确度和精密度试验,分析结果与认定值相符,碳测定的相对标准偏差小于0.5％,硫测定的相对标准偏差为0.74％～2.80％,能够满足实验室快速分析高碳铬铁中碳、硫的需要.     

Sulfur activation-related extracellular proteins of Acidithiobacillus ferrooxidans

The fractions of the extracellular proteins of Acidithiobacillus ferrooxidans grown on two different energy substrates, elemental sulfur and ferrous sulfate,were selectively prepared with hot water treatment and distinctly shown by two-dimensional gel electrophoresis.Some protein spots with apparently higher abundance in sulfur energy substrate than in ferrous sulfate energy substrate were identified by using MALDI-TOF/TOE Based on peptide mass fingerprints and bioinformatical analysis,the extracellular ...     

高硫铝土矿生产过程粗液脱硫的研究

采用贵州某地的一水硬铝石高硫铝土矿为原料,进行了氧化铝生产过程粗液脱硫试验研究,考察了反应温度、反应时间及脱硫剂用量对脱硫效果的影响程度,并通过单因素及正交设计确定了粗液脱硫的试验条件,试验结果表明:利用铝酸钡进行粗液脱硫仅在溶液中碳酸钠浓度较低的情况下适用。     

高频红外吸收法测定银中的碳硫

作者采用高频红外吸收法同时测定Ag中的C和S,对试样的制备、助熔剂的选择、分析条件等进行了较详细的研究.方法快速、简便、灵敏度高,C、S的测定范围分别为0.002%～1%和0.002%～0.1%,对自己配制的合成样进行6次平行测定,其RSD分别为:C = 0.34%和S = 2.01%,C、S的回收率都在95%～105%,获得了满意的结果.     

Sulfur effects on the internal carburization of Fe-Ni-Cr alloys

Several commercial and laboratory-cast model austenitic alloys have been exposed in both sulfur-free carburizing environments and also in carburizing atmospheres to which additions of H₂S have been made. These studies were concentrated over the temperature range 1223–1323 K at a fixed carbon activity (a_c=0.8) with sulfur activities ranging from 2.2×10^–12 bar to 1.4×10^–9 bar. Under conditions of sulfur adsorption, e.g., 5.5 × 10^–11 bar at 1273 K, the blocking of adsorption sites for methane resulted in a transition from the parabolic kinetics observed during sulfur-free carburization to surface controlled linear kinetics. Higher levels of H₂S promoted the formation of a surface layer of chromium sulfide which reduced internal carburization but became a problem itself. The role of minor alloying elements has been established and the use of thermodynamic phase stability diagrams in defining the optimum conditions for sulfur inhibition of carburization evaluated.     

高频红外吸收法测定贵金属催化剂中的碳、硫

采用HCS－140型红外吸收碳硫分析仪同时测定贵金属催化剂中的碳、硫含量。试验了助熔剂种类、用量、样品量对测定的影响,用异标校正测定了多种类型贵金属催化剂中的碳、硫。取得了满意结果,方法的相对标准偏差为0．2％－7．7％。     

大牛地气田含硫气井腐蚀监测

根据大牛地含硫气井生产特点,室内采用化学分析方法分别对D1、D2两口气井的气样、水样、天然气中H2S含量、腐蚀产物等进行取样检测分析,现场采用挂片腐蚀失重法对试验井进行离线监测,计算油管腐蚀速率.结合两种常用气井腐蚀监测技术确定出试验井主要存在腐蚀类型为H2S气体引起的酸性腐蚀及高矿化度腐蚀.     

高硫铝土矿中硫的赋存状态及除硫(英文)

采用X射线衍射分析和化学物相定量法研究高硫铝土矿中硫的赋存状态,并对不同形态的硫的脱除方法进行研究。结果表明:高硫铝土矿中硫的存在形态有的以硫化物为主(主要是黄铁矿),有的以硫酸盐为主,不同产地的铝土矿中硫的主要存在形态是不同的,进一步补充了铝土矿中硫的物相存在的规律性。采用X射线衍射结合化学物相定量法能更准确确定高硫铝土矿中硫的存在形态。确定高硫铝土矿中硫的主要存在形态对除硫方法的选择具有理论指导意义。不同形态的硫可以采用不同的除硫方法。采用氧化焙烧能有效脱除高硫铝土矿中硫化物型硫,原矿溶出液中S2-的含量均在1.7g/L以上,而焙烧矿的溶出液中S2-的含量均在0.18g/L以下。通过N2CO3溶液洗涤可以有效脱除矿石中硫酸盐型硫,原矿中全硫含量下降到0.2%以下,符合生产中对矿石中硫含量的要求。     

球墨铸铁碳硫含量检测试样制备方法的研究

用红外分析仪检测球墨铸铁中碳、硫含量的试样制备方法有多种,其中切割成块状试样的取样方法具有无游离石墨脱离等优点。试验表明,以2.0 g钨粒作助熔剂,称样量为0.25（±0.05）g,采用切割的块状试样检测碳、硫含量,准确度高,重现性好,因此这种取样方法适合于检测球墨铸铁碳、硫含量的试样。