Observations on the effect of low sulfur activity on the oxidation of chromium-depleted zones in a stainless steel

Coupon specimens of 20% Cr-25% Ni-Nb-stabilized steel have been oxidized in an atmosphere of CO ₂-2%CO-670 vppb COS at 0.1 MPa pressure for periods up to 500 hr at 1123 K. Standard specimens, annealed at 1203 K prior to testing, showed an enhancement of iron in the surface scale and a much increased propensity to spall compared with control tests in a sulfur-free atmosphere. The main purpose of the work was to examine the effect of sulfur on the ease of formation of a healing layer under duplex attack produced by depleting specimens in chromium by prior vacuum annealing. It is shown that although a chromium-rich layer had formed, extensive breakdown occurred in the sulphidizing atmosphere leading to continued internal oxidation. Sulfur was found to partition at the base of this attack and to be associated with a large concentration of nickel. Spaliation was also enhanced in the depleted specimens, the favored site being the interface between the spinel and outer iron-rich oxide of the duplex structure. Partitioning of both sulfur and carbon was observed at this interface in those regions of the specimen showing healing layer breakdown.     

High-temperature sulfidation of Mo-50 Wt.% Re

Mo-50Re was sulfidized over the range of 1000–1100°C in sulfur vapor at pressures of 10^–4 and 10^–2 atm. The reaction kinetics followed the parabolic rate law with an activation energy of 55.4 kcal/mole for and 48.2 kcal/mole for atm. The pressure dependence varied between +1/4 to +1/6 for the slope of a plot of log K_p vs log .Analysis of the diffusional processes occurring in both the scale and the alloy substrate gave an expression for the ratio of the thickness of the scale and of the -phase as a function of the corresponding rate constants for the growth of each layer. Finally, the conditions required for the formation of the -phase layer between the outer scale and the alloy substrate were obtained in terms of the ratio between the diffusion coefficients of the two metals in the intermetallic compound.     

一种新型Ni-Fe-Cr基合金在模拟锅炉烟气中的腐蚀行为研究

应用X射线衍射仪、扫描电子显微镜、能谱仪等分析方法研究一种新型Ni-Fe-Cr基高温合金在700℃/750℃煤灰/烟气中的腐蚀行为。结果表明:750℃的腐蚀速率明显高于700℃,其腐蚀层的厚度由700℃的3μm增加到20μm。腐蚀1 000h后,SEM观察到Ni-Fe-Cr高温合金在700℃下表面有少量"瘤状"凸起产物,XRD结合EDS表明其腐蚀产物由表向里依次是结构疏松的NiO、Fe_2O_3和Fe3O4,内层为相对致密的Cr_2O_3、Al_2O_3和TiO2,基体和腐蚀层界面靠近基体一侧是多孔的硫化物。提高腐蚀温度到750℃表面出现更多凸起,并且出现了破裂。Cr_2O_3保护性氧化膜局部开裂或者剥落而形成"瘤状"凸起产物。氧化膜生长过程中的内应力以及温度降低产生的热应力共同作用,导致氧化膜开裂甚至与基体剥离。温度升高同样加剧熔融盐破坏氧化膜从而加快腐蚀进程。     

模拟烟灰/气腐蚀对Super304H钢高温持久性能的影响

本工作采用烟灰/气腐蚀-载荷协同作用试验装置,研究了模拟煤粉锅炉燃烧环境中烟灰/气腐蚀对Super304H钢650℃持久性能的影响,同时对比研究了相同温度下Super304H钢在静态空气中的持久性能。结果表明:在腐蚀环境中,不同应力下钢的持久寿命缩短,腐蚀效应对其持久寿命的影响随时间延长会更加显著;通过双对数法推算出Super304H钢在模拟烟灰/气腐蚀环境中的持久强度为80MPa,相比静态空气环境(140MPa)降幅约43%。静态空气中钢表面氧化膜表面较平整,而模拟烟灰/气腐蚀环境中钢表面腐蚀产物相疏松多孔,并出现大量"瘤状"凸起产物。XRD结合EDS表明,模拟烟灰/气腐蚀环境中试样表面除富含Fe、Cr、Ni的氧化物以外,还分布着硫化物以及复合硫酸盐的腐蚀产物。在载荷作用下,腐蚀介质引起腐蚀层/金属界面孔洞形核速率加快,这是Super304H钢持久强度降低的主要原因。     

Hydrocracking ofn-heptane on a sulfided NiMo-Y zeolite catalyst: effect of the sulfidation method

The activity and the selectivity of a bifunctional NiMo sulfides-Y zeolite catalyst forn-heptane hydrocracking depend very much on the sulfidation agent, namely hydrogen sulfide, or dimethyldisulfide in solution inn-heptane orn-decane. The presence of a hydrocarbon during the sulfidation lowers the acid activity of the catalyst because of coking of the zeolite acid sites, and also decreases the hydrogenating activity, due to a poorer sulfidation of the catalyst.     

Study of intrinsic sulfidation behavior of Fe2O3 for high temperature H2S removal

Iron-based sorbent was preferable for desulfurization from coal-derived gas due to economic consideration and favorable dynamic property. The intrinsic behavior of Fe-based sorbent should be primarily understood in the sulfidation process for improving its performance. A series of tests were carried out with Fe₂O₃, Fe and other compounds containing-Fe (FO) made from the same precursor FeC₂O₄·2H₂O in H₂S-N₂ mixture in this study. The formation of H₂ was observed with Fe and FO as sorbents. While SO₂ was detected with FO and Fe₂O₃ as sorbents, its concentration in outlet was gradually decreased. The crystal phase and surface chemical state of fresh and sulfided Fe₂O₃ with different reaction times were characterized by XRD and XPS measurements. The result suggested that the intrinsic H₂S removal by Fe₂O₃ would produce multi-phase of sulfides. The possible mechanism of sulfidation reaction was discussed.     

硫化时间对电沉积制备FeS2薄膜组织与结构的影响

利用电沉积及热硫化法制备了FeS2 多晶薄膜,研究了不同硫化时间对FeS2 薄膜形成过程的影响。结果表明采用Na2S2O3 和FeSO4 水溶液电沉积和150~ 200℃处理可以制备多孔Fe3O4 薄膜,再经400℃、80kPa硫化处理,Fe3O4 可转变成FeS2 多晶薄膜。随硫化时间延长到10h,FeS2 的晶格常数减小而晶粒粗化,再继续延长硫化时间,FeS2 的晶格常数增大而晶粒尺寸下降。可以用点缺陷浓度、相变应力及亚晶界运动等因素分析Fe3O4 向FeS2 转变过程中的微观组织参数变化规律。     

含硫纤维素的合成及其吸附性能的研究

以甘蔗渣为原料,对其进行碱化处理,然后在碱性条件下与CS2反应制备得到吸附能力强,成本低廉的含硫纤维素吸附剂。研究表明,含硫纤维素吸附剂的最佳制备工艺条件为:3g甘蔗渣,20%Na OH溶液,碱化时间24h,CS26m L,反应温度25℃,反应时间为1.5h。同时对100m L 50 mg·L-1的铜离子溶液进行吸附研究,得到最佳的吸附条件为:吸附剂用量0.1g、p H值为8、吸附温度为40℃、吸附时间1h,最大的吸附容量为49.48mg·g-1,吸附率为98.96%。     

5-溴-2-甲基苯并噻唑的合成研究

以2,4-二溴硝基苯为原料,在相转移催化剂条件下,经过硫代、还原、酸化、酰化和环合等5步反应制备得到目标化合物,产物收率≥59.1%。考察了Na2S2滴加时间、还原反应时间、酸化时间和酰化产物中水分含量对产物收率的影响。适宜的反应条件分别是:Na2S2滴加时间为5 h,还原反应时间为4 h,酸化时间为35 min,酰化产物含水量≤4%。     

等离子喷涂Al-Mo涂层的高温硫化和氧化行为研究

烧嘴是水煤浆气化系统的重要部件。运行过程中的高温硫化经常导致烧嘴提前失效,进而影响设备的安全稳定运行。本文采用等离子喷涂方法制备了Mo为粘结层的Al-Mo涂层,测量其在973 K, 1073 K and 1173 K的硫化和氧化行为,并与Mo涂层和Inconel合金进行比较。结果表明Al-Mo涂层的高温硫化抗力和氧化抗力均优于Mo涂层,高温硫化抗力优于Inconel合金。该涂层的提出为喷嘴失效问题的解决提供了便捷、有效的技术方案。