Resumo

LOPEZ C., Carlos Alberto. Study of the effect of a gaseous atmosphere of ammonia in a component of a catalytic reactor manufactured of an AISI type 304 stainless steel. Iteckne [online]. 2013, vol.10, n.1, pp.27-36. ISSN 1692-1798.

Some industrial processes are conducted under stringent conditions for the materials due to that in several opportunities, it is involved stressful states for materials like some work variables related to high temperatures and pressures and corrosive substances. Also, sometimes a combination of the above factors may lead to affect the integrity of the equipment, which can generate significant damage or catastrophic failure of equipment or its components, with consequent economic losses generated due to the replacement of these, to expensive repairs and lost profits for the stops on the production floor. This paper presents the study of AISI type 304 stainless steel which was built an internal capsule or basket that corresponds to two exchangers arranged in series where process gases circulate, which contains a catalyst, that give the reaction necessary to produce NH₃ (ammonia) in a catalytic reactor plant used in fertilizer production. This equipment operates quite demanding conditions such as temperatures in the range of 427 °C and 566 °C, an operating pressure of 4200 psi. Furthermore, it is in contact with synthesis gas as H₂, N₂, CH₄ and NH₃, among others. This equipment has been in service for about 30 years, from which sample was taken to assess their current status through various metallurgical and mechanical tests like chemical composition, metallography, optical microscopy (SEM), X-Ray and stereoscopy. The result of analysis led to the conclusions that the material suffered the phenomenon known as nitriding at a given thickness, also found the presence of numerous cracks and precipitation of carbides. It is done as part of the evaluation, a number of recommendations for the use of a particular type of material for the construction of new production equipment.

Palavras-chave : Stainless Steel; ammonia; nitrogen; nitriding; cracking; carbides precipitation.

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