Thesis ANÁLISIS COMPUTACIONAL DE LA INYECCIÓN DE MEZCLAS GAS NATURAL - VAPOR PARA REDUCCIÓN EN HORNO DE REFINO RAF
Date
2016
Authors
PAVEZ MUÑOZ, JAVIER ANDRÉS
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Abstract
El presente trabajo realiza un estudio sobre la posibilidad inyección de una mezcla gas natural– vapor para el proceso de reducción del cobre blíster en un horno de refinación de unaimportante fundición del norte de Chile. El suministro de combustible se encuentra limitado a2 toberas siendo el combustible actual gas natural y se desea cambiar a esta mezcla vapor – gasnatural con la finalidad de reformar el contenido de metano presente en el GN, aprovechandolas altas temperaturas que desarrolla el horno en su interior. Producto de la reformación demetano se obtendría principalmente monóxido de carbono e hidrógeno que, al reducir eloxígeno disuelto en el cobre, generarían una combustión más limpia generando en gran partedióxido de carbono y vapor de agua, disminuyendo así la producción de hollín o carbóndepositado en los gases de escape del horno que se producen al reducir el oxígeno con GN. Serealiza un análisis sobre las reacciones globales que podrían ocurrir utilizando la constante deequilibrio químico, determinándose en base a su valor las reacciones que tienen posibilidadesde llevarse a cabo a la temperatura de reducción del horno (1200 °C). En base a estas reaccionesse determinan los flujos requeridos para el proceso, además de aplicar un factor de eficienciapara adaptarse a las necesidades de distintas condiciones, utilizándose una cota inferiorreportada de 75%. Debido a que los gases se encuentran afectos a la compresibilidad, se empleala teoría de flujo compresible en tuberías con fricción de pared y transferencia de calor paracaracterizar el problema en términos matemáticos asumiendo flujo turbulento, para luego serresuelto utilizando el método de diferencias finitas regresivas implementando para ello unprograma en lenguaje Fortran. Para caracterizar el comportamiento de la mezcla de gases seutiliza la ecuación de estado de Benedict – Webb – Rubin que considera la compresibilidad delos gases a alta presión. Las variables de interés a lo largo de la tobera corresponden a lapresión, la temperatura, la densidad y la velocidad, siendo ésta última una variable de controldado que el flujo se encontrará estrangulado al alcanzarse la barrera sónica. De los resultadosde las simulaciones computacionales para temperaturas de inyección en el rango de 400 – 600K y relación vapor – gas natural molar en el rango 3 – 5, se observa que no es posible lainyección por las dos toberas disponibles, por lo que sería necesario tener una 3a o una 4a toberapara adecuarse a los requerimientos operacionales. Se establecen además, en base a lascondiciones de transferencia de calor y dimensiones de la tobera, los flujos máximos admisiblesdentro del rango estudiado de temperatura y relación vapor – gas natural.
The present work carries out a study about the possibility of a natural gas (NG) – steam mixinjection for the process of blister copper’s reduction in a refining furnace of an importantfoundry of the north of Chile. The fuel supply is limited to two nozzles being the current fuelnatural gas which is to be replaced with a natural gas – steam mixture in order to reform themethane content present in the NG, taking the advantage of the high temperatures inside thefurnace. The methane reforming mostly produces carbon monoxide and hydrogen that, byreducing the oxygen dissolved in the copper, would yield a cleaner combustion producing insignificant proportion carbon dioxide and water vapor, decreasing the production of soot ordeposited carbon in the exhaust gas of the furnace that’s produced at reducing the oxygen withNG. An analysis is made about the global reactions that might happen using the chemicalequilibrium constant, getting based on its value which reactions have possibilities of being heldat the temperature of reduction furnace (1200 °C). According to these reactions the requiredflow is stablished for the process, applying besides an efficiency factor to account for differentconditions, using a lower level reported of 75%. The theory of compressible flow in pipes isused since the gases are affected to compressibility-related effects with wall-friction and heattransfer to characterize the problem in mathematic terms, assuming turbulent flow and solvingusing the backward difference method which is implemented in Fortran language. For thepurpose of characterizing the behavior of gases is used the Benedict – Webb – Rubin equationof state that considers the compressibility of gases at high pressure. The variables of interestalong the nozzle are the mean values of pressure, temperature, density and velocity, the latterbeing the control variable since the flow will choke when the sound barrier is reached. Fromthe numerical results for temperature of injection in the range of 400 – 600 K and vapor –natural gas molar ratio of 3 – 5, it is observed that is not possible to inject for the two availablenozzles therefore it would be necessary to have a 3rd or a 4th nozzle to adjust to the operationalrequirements. In addition, the maximum admissible flows within the range studied oftemperature and vapor – natural gas ratio are stablished based on the conditions of heat transferand nozzle dimensions.
The present work carries out a study about the possibility of a natural gas (NG) – steam mixinjection for the process of blister copper’s reduction in a refining furnace of an importantfoundry of the north of Chile. The fuel supply is limited to two nozzles being the current fuelnatural gas which is to be replaced with a natural gas – steam mixture in order to reform themethane content present in the NG, taking the advantage of the high temperatures inside thefurnace. The methane reforming mostly produces carbon monoxide and hydrogen that, byreducing the oxygen dissolved in the copper, would yield a cleaner combustion producing insignificant proportion carbon dioxide and water vapor, decreasing the production of soot ordeposited carbon in the exhaust gas of the furnace that’s produced at reducing the oxygen withNG. An analysis is made about the global reactions that might happen using the chemicalequilibrium constant, getting based on its value which reactions have possibilities of being heldat the temperature of reduction furnace (1200 °C). According to these reactions the requiredflow is stablished for the process, applying besides an efficiency factor to account for differentconditions, using a lower level reported of 75%. The theory of compressible flow in pipes isused since the gases are affected to compressibility-related effects with wall-friction and heattransfer to characterize the problem in mathematic terms, assuming turbulent flow and solvingusing the backward difference method which is implemented in Fortran language. For thepurpose of characterizing the behavior of gases is used the Benedict – Webb – Rubin equationof state that considers the compressibility of gases at high pressure. The variables of interestalong the nozzle are the mean values of pressure, temperature, density and velocity, the latterbeing the control variable since the flow will choke when the sound barrier is reached. Fromthe numerical results for temperature of injection in the range of 400 – 600 K and vapor –natural gas molar ratio of 3 – 5, it is observed that is not possible to inject for the two availablenozzles therefore it would be necessary to have a 3rd or a 4th nozzle to adjust to the operationalrequirements. In addition, the maximum admissible flows within the range studied oftemperature and vapor – natural gas ratio are stablished based on the conditions of heat transferand nozzle dimensions.
Description
Catalogado desde la version PDF de la tesis.
Keywords
FLUJO COMPRESIBLE , GAS NATURAL , REFINACION COBRE