Microfibrous entrapment of small catalyst particulates for high contacting efficiency removal of trace CO from practical reformates for PEM H2-O2 fuel cells

Preferential oxidation (PROX) of CO in H₂ is the most efficient way to remove CO from a practical reformate stream for PEM H₂-O₂ fuel cells. Pt/Al₂O₃ has long been known as a suitable catalyst for this purpose. Over the conventional Pt/Al₂O₃ catalyst, however, PROX of CO in H₂ has been known to occur at temperatures above 150°C, and the maximum CO conversion usually takes place at about 200°C. In this study, the promotion of Pt/Al₂O₃ with a transition metal results in significantly enhanced catalytic performance in the temperature range of 25 to 150°C. The active reaction temperature window is enlarged to 25 to 200°C compared with a narrow window at about 200°C over the conventional Pt/Al₂O₃. A high void and a tailorable sintered microfibrous carrier consisting of 5 vol.% of 4 and 8 μm diameter Ni fibers is used to entrap 15 vol.% 150 to 250 μm diameter Al₂O₃ particulates. The alumina support particulates are uniformly entrapped into a sinter-locked, three-dimensional network of 4 and 8 μm Ni fibers. Promoter and Pt are then dispersed onto the microfibrous entrapped alumina support particles by the incipient-wetness impregnation method. The composite catalysts possess 80 vol.% voidage. At equivalent bed volumes, microfibrous entrapped catalysts achieve complete CO reduction (GC detection limit ∼40 ppm CO) at five times the higher gas hourly space velocity value compared with packed beds of 1 to 2 mm catalyst particles demonstrating ultrahigh contacting efficiency provided by the microfibrous entrapped catalysts. This paper was presented at the ASM Materials Solutions Conference & Show held October 18–21, 2004 in Columbus, OH.     

Effect of flow velocity on pipeline steel corrosion behaviour in H2S/CO2 environment with sulphur deposition

The effect of element sulphur on the performance of corrosion inhibitor in H₂S/CO₂ gas field solution was investigated at different velocities. The morphology and composition of corrosion products were characterised by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) methods. The results indicated that L360 QS steel surface suffered from sulphur-induced pitting corrosion at a low velocity due to insufficient sulphur-carrying fluid power. At high flow velocities, the steel surface is likely to be suffered high fluid power which can remove the inhibitor film and corrosion scales by the mechanical erosion effect. The sulphur corrosion mechanism model and the flow-induced corrosion model due to the high wall shear force have been proposed in the study. This work suggested that the gas production rate should be controlled at an acceptable level to guarantee the service safety of pipeline system.     

Comparison of corrosion scales formed on KO8OSS and N8O steels in CO2/H2S environment

Abstract

Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) were applied to analyse the microstructure and composition of the corrosion scale formed on KO80SS and N80 tubes with carbon dioxide (CO₂) and hydrogen sulphide (SO₂). The corrosion scales of both KO80SS and N80 tubes were of the double layer structure, and not only uniform corrosion but also localised corrosion was observed. The crystal of the surface layer is laminar. The main phase in the outer layer is calcium carbonate (CaCO₃), and the inner scale consisted of iron carbonate (FeCO₃) for KO80SS steel and FeS_0·9 with a little amount of FeCO₃ for N80 steel respectively. Additionally, the electrochemical techniques were used to investigate the characteristics of the corrosion scales. The results indicated that the polarisation resistance R_p of KO80SS steel film was nobler than that of N80 steel film. Finally, the corrosion current I_corr of KO80SS steels was lower than that of N80 steels. Corrosion scale of KO80SS tube steels is more protective to the matrix than that of N80 tube steels.     

Regenerable sorbent for natural gas desulfurization

Sulfur-containing odorants are normally added to propane and natural gas supplies to facilitate leak detection. The sulfur in these fuels can poison the catalysts used in fuel-cell fuel-processing systems, thereby inactivating the surfaces of the fuel-cell anodes and resulting in degraded power generation performance. The sulfur content of natural gas or any hydrocarbon fuel needs to be reduced to very low levels to ensure long-term stable electrochemical performance for both high- and low-temperature fuel cells. This paper presents the development and test results of a new physical adsorbent for natural gas desulfurization. The sorbent effectively removes all sulfur-bearing compounds at ambient temperature with very high capacity. The new sorbent can also be fully regenerated by the temperature swing. In a series of tests, the sulfur adsorption capacity of the new material is compared with other commercially available and specially prepared sorbents. The results of the comparison tests are also summarized in this paper. This paper was presented at the ASM Materials Solutions Conference & Show held October 18–21, 2004 in Columbus, OH.     

油气管道CO2/H2 S腐蚀及防护技术研究进展

CO2和H2S是油气管道中主要的腐蚀介质,两者往往同时存在于原油和天然气之中,是造成油气输送管道内腐蚀发生的主要原因之一,甚至会导致管道失效、穿孔、泄漏、开裂等现象,严重威胁了管网的安全运行及正常生产。因此CO2和H2S引起的管道腐蚀问题,已成为当前研究的热点问题。针对油气管道日益严重的CO2和H2S腐蚀问题,综述了CO2单独存在、H2S单独存在以及CO2和H2S共同存在三种体系中油气管道的腐蚀过程,得出了在这三种腐蚀体系下油气管道出现的主要腐蚀行为规律以及腐蚀机理。阐述了CO2和H2S共同存在体系下,缓蚀剂、耐蚀性管材、电化学防腐技术、管道内涂层技术等先进的油气管道腐蚀防护技术,并剖析了这些防护措施各自的特点及在实际工程使用中的优势和局限性。最后,展望了CO2和H2S共存体系的进一步研究方向以及更经济、更有效的防腐措施发展前景。     

Study on the impact toughness and diffusible hydrogen of G105 drill pipe steel in wet H2S environment

In order to investigate the influence of wet H₂S environment on impact toughness of G105 drill pipe steel, the impact test of drill pipe exposed to NACE A solution for different time was carried out. Meanwhile, the diffusible hydrogen concentration was measured to study the relationship between diffusible hydrogen and impact toughness damage. The results suggest that with the increase of corrosion time, the impact energy of G105 drill pipes decreases from 107.7 to 88.4?J, and the dynamic fracture toughness decreases gradually. The impact toughness damage increases as the diffusion hydrogen concentration increases. However, the impact energy recovery happened after hydrogen releasing. The quasi-cleavage features occur with the increasing of hydrogen concentration.     

Corrosion of Three Commercial Steels Under ZnCl2 –KCl Deposits in a Reducing Atmosphere Containing HCl and H2S at 400–500°C

The corrosion of three commercial steels in a reducing atmosphere containing HCl plus H₂S in the presence of ZnCl₂–KCl deposits has been investigated at 400–500°C and compared with the corrosion of the same materials in a similar gas mixture free from H₂S. The presence of H₂S in the gas accelerated the corrosion of the three commercial steels beneath ZnCl₂–KCl deposits. All materials suffered from severe corrosion with partial detachment and spalling of the external scales. Degradation of the steels resulted from the penetration of chlorine-containing species through the scale formed initially down to the metal matrix, because chorine-rich species were detected close to the alloy/scale interface. Although the corrosion resistance generally increased with increasing Cr content, even the high-Cr stainless steel SS304 is still unable to provide good corrosion resistance against the ZnCl₂–KCl deposits in the presence of H₂S due to the bad adherence of the scales to the alloy. The mechanisms of attack are discussed on the basis of thermodynamic considerations and of the active-oxidation model.     

2205双相不锈钢在酸性H2S环境下的应力腐蚀行为及开裂机理研究

_{摘要:采用C型环实验研究了2205双相不锈钢在饱和H2S环境下的应力腐蚀行为及开裂机理。研究结果表明,2205双相不锈钢在NACE标准A溶液中有良好的抗应力腐蚀能力。通过OM}、_{SEM、EDS及电化学手段分析得出2205双相不锈钢的应力腐蚀开裂经历了表面点蚀,蚀坑形成,H2S解离,H原子吸附并从蚀坑位置扩散进入金属基体,在金属基体中聚集,通过氢致开裂机制导致裂纹萌生,并逐渐扩展。}