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Corrosion Behavior of Hastelloy® C-2000® Ni-Cr-Mo-Fe Alloys in the Entrained-Flow Coal Gasification Syngas Plants

Lee Sungkyu, Kim Min-Jung, Choi Nuri, Hwang Sang Yeon, Chung Seok-Woo, Lee Seung-Kong, Yun Yongseung

Archives of Metallurgy and Materials

2020

Vol. 65, iss. 2

869--878

A mechanistic exposure experiment was performed on the commercially available and welded Ni-Cr-Mo-Fe alloy samples used in the piping materials of the coal gasification pilot plant. Thermodynamic Ellingham-Pourbaix stability diagrams were constructed to provide insight into the mechanism of the observed corrosion behavior. The thermodynamic inference on the corrosion mechanism was supplemented with the morphological, compositional and microstructural analyses of the exposed samples using scanning electron microscopy, X-ray diffraction and energy-dispersive X-ray spectroscopy analyses. X-ray diffraction result revealed stable corrosion products of NiO, MoNi4 and Cr4.6 MoNi2.1 after accumulated total exposure duration of 139 h to the corrosive atmosphere. Scanning electron microscopy and energy-dispersive X-ray spectroscopy positively identified formation of rather continuous and adherent pre-oxidation corrosion products although extensively peeled-off oxides were finally observed as corrosion scales on the post-exposure alloy samples, which were attributed to the chlorination/oxidation into thin (spalled) oxides.

Effect of NF3 Gas on Stabilization of Alkaline Earth Metal-Cu Mordenite Catalysts During N2O Decomposition Reaction

Seo Minhye, Lee Soo-Young, Cho Sung-Su, Song Hyoung Woon, Kim Hyun-Kyung, Kim Dong Soo, Lee Sungkyu

Archives of Metallurgy and Materials

2019

Vol. 64, iss. 2

695--700

Mordenite-zeolite supported Ca-Cu and Ba-Cu catalysts (Ca-Cu/MOR and Ba-Cu MOR) were successfully fabricated for direct decomposition of both NF3 and N2O gases contained in waste gas stream of (semiconductor) electronics industry. N2O conversion rates of Ca-Cu and Ba-Cu catalysts were 79 and 86%, respectively, at 700°C and 1 atm under space velocity of 5000 h-1. The Ca-Cu catalyst was especially noteworthy in that its capability of converting N2O could be maintained even after its exposure to co-feeding NF3 gas constituent in the waste gas stream. Compositional and surface morphological analyses of the Ca-Cu and Ba-Cu catalysts were made before and after exposure to the waste gas stream to examine any noticeable degradation or change of the catalysts. Unlike Ba-Cu catalyst, SiO2 constituent of the Ca-Cu catalyst was found to remain immune to the NF3-cofeeding waste gas stream, casting a positive prospect for superior and steady N2O decomposition performance via maintenance of its structural integrity.