Análisis térmico del proceso de oxidación sulfidación de aceros usados en la refinación de crudos pesados mediante la técnica micro raman confocal.
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Bedoya Moreno, María Isabel
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Trabajo de grado - Maestría
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EspañolFecha de publicación
2019-09-12
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Aceros ferríticos especializados T91 y T92 sometidos a temperaturas elevadas y a condiciones específicas de operación en atmósferas oxidantes compuestas por H2S, O2, suelen formar en su superficie capas de óxido y productos sulfurosos. Estas capas podrían ser termodinámicamente estables con un carácter altamente protector o con baja estabilidad termodinámica, susceptibles a la corrosión; la corrosión generada por este fenómeno, afecta significativamente la vida útil de los equipos de procesos petroquímicos construidos en este tipo de materiales especializados. En este estudio se ha realizado la caracterización de las propiedades morfológicas, composicionales, térmicas, químicas y mecánicas de estas capas, evaluando los mecanismos de su crecimiento a nivel experimental, en los aceros inoxidables ferríticos modificados Fe-9Cr-1Mo T91, Fe-9Cr-0.5Mo T92, comparados con el acero inoxidable austenítico AISI 316L y el acero de bajo carbono ferrítico-perlítico AISI 1020, con el objetivo de analizar a partir de las propiedades térmicas obtenidas por la técnica Raman y la tendencia en cada material a generar pérdidas térmicas en los procesos petroquímicos. Para el crecimiento de capas de óxido-sulfidación en estos aceros se empleó un montaje de hornos de tipo tubular, el cual permitió simular experimentalmente las atmósferas de gases que se producen en el procesamiento de crudos pesados. Técnicas de microscopía electrónica de barrido, espectroscopia Raman Confocal térmico, AFM en modo Kelvin, AFM en modo de Modulación de fuerza, y simulación termodinámica con el software HSC Chemistry 6.0, permitió comparar el crecimiento de las diferentes capas y su estabilidad. La cinética de crecimiento de estas capas se determinó mediante mediciones de pérdida/ganancia de peso; variando temperatura, tipo de acero y tiempos de exposición. Los resultados obtenidos permitieron determinar que el acero austenítico AISI 316L presentó mayor conductividad térmica y mayor estabilidad estructural y termodinámica ante ambientes óxido-sulfidantes, hasta 400°C-36 horas de permanencia.
Abstract: Specialized ferritic steels T91 and T92 subjected to high temperatures and specific operating conditions in oxidative atmospheres composed of H2S, O2, usually form oxide layers and sulphurous products on their surface. These layers could be thermodynamically stable with a highly protective character or with low thermodynamic stability, susceptible to corrosion; The corrosion generated by this phenomenon significantly affects the useful life of the petrochemical process equipment built in this type of specialized materials. In this study, the characterization of the morphological, compositional, thermal, chemical and mechanical properties of these layers was evaluated, evaluating the mechanisms of growth of the layers produced at experimental level, in ferritic stainless steels modified Fe-9Cr-1Mo T91, Fe-9Cr-0.5Mo T92, compared with austenitic stainless steel AISI 316L and ferritic-pearlitic low carbon steel AISI 1020, with the objective of analizyng thermal properties obtained by the Raman technique and the tendency in each material to generate thermal losses in petrochemical processes. For the growth of oxide-sulphidation layers in these steels, an assembly of tubular type furnaces was used, which allowed to simulate experimentally the atmospheres of gases that are produced in the processing of heavy crude oil. Scanning electron microscopy techniques, thermal Confocal Raman spectroscopy, AFM in Kelvin mode, AFM in Force Modulation mode, and thermodynamic simulation with HSC Chemistry 6.0 software, allowed to compare the growth of the different layers and their stability. The growth kinetics of these layers was determined by weight loss / gain measurements; varying temperature, type of steel and exposure times. The results obtained allowed to determine that the Austenitic steels 316L showed greater thermal conductivity and greater structural and thermodynamic stability in oxide-sulfur environments up to 400°C-36 hours of permanence.
Abstract: Specialized ferritic steels T91 and T92 subjected to high temperatures and specific operating conditions in oxidative atmospheres composed of H2S, O2, usually form oxide layers and sulphurous products on their surface. These layers could be thermodynamically stable with a highly protective character or with low thermodynamic stability, susceptible to corrosion; The corrosion generated by this phenomenon significantly affects the useful life of the petrochemical process equipment built in this type of specialized materials. In this study, the characterization of the morphological, compositional, thermal, chemical and mechanical properties of these layers was evaluated, evaluating the mechanisms of growth of the layers produced at experimental level, in ferritic stainless steels modified Fe-9Cr-1Mo T91, Fe-9Cr-0.5Mo T92, compared with austenitic stainless steel AISI 316L and ferritic-pearlitic low carbon steel AISI 1020, with the objective of analizyng thermal properties obtained by the Raman technique and the tendency in each material to generate thermal losses in petrochemical processes. For the growth of oxide-sulphidation layers in these steels, an assembly of tubular type furnaces was used, which allowed to simulate experimentally the atmospheres of gases that are produced in the processing of heavy crude oil. Scanning electron microscopy techniques, thermal Confocal Raman spectroscopy, AFM in Kelvin mode, AFM in Force Modulation mode, and thermodynamic simulation with HSC Chemistry 6.0 software, allowed to compare the growth of the different layers and their stability. The growth kinetics of these layers was determined by weight loss / gain measurements; varying temperature, type of steel and exposure times. The results obtained allowed to determine that the Austenitic steels 316L showed greater thermal conductivity and greater structural and thermodynamic stability in oxide-sulfur environments up to 400°C-36 hours of permanence.