Efecto de la relación de aspecto (H/D) en la distribución de partículas en tanques de agitados mineros
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Fecha
2021
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es
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Universidad Andrés Bello
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Licencia CC
Licencia CC
Resumen
En la industria minera, el transporte y procesamiento de mezcla mineral más agua, conocida como pulpa mineral, es un proceso continuo que incluye múltiples equipos los cuales tienen un determinado tiempo de operación, razón por la cual es necesario tener tanques de agitados que permitan mantener la pulpa de forma homogénea mientras se realizan las demás fases de la operación. Es importante avanzar en el entendimiento de estos indispensables equipos para así poder entender cómo se distribuyen las partículas y las velocidades, según los parámetros geométricos que se utilizan en la actualidad. Para este propósito, se realizó un estudio numérico de un tanque de mezcla de 2 m de diámetro y 2 m de altura el cual corresponde al caso base. Dos casos adicionales fueron considerados con relaciones de aspecto altura vs diámetrode1,1 y 1,2respectivamente. Las demás variables se mantuvieron contantes; esto es la velocidad de giro del agitador de 190 rpm; la velocidad de entrada del flujo de 1 m/s y el número de baffles. Los tres modelos fueron implementados utilizando las ecuaciones promediadas de Reynolds (URANS)y considerando un fluido no-Newtoniano. Respecto a la ubicación de las partículas se observa de los resultados numéricos que existe una distribución más homogénea a medida que disminuye la relación de aspecto. Además, hay un efecto interesante en las zonas cercanas a los baffles donde el flujo se acelera al llegar a ellos y se produce un flujo re circulatorio luego de sobrepasarlos. También se validó el tipo de flujo generado por un agitador de tipo radial. Respecto a las velocidad es medias, se pudo comprobar que, si bien la relación de aspecto influye en las velocidades dentro del tanque, generando zonas de mayor velocidad cerca de las paredes en los tanques con mayor relación de aspecto, éstas nunca sobrepasaron los0,8m/s. Por otra parte, la cantidad de partículas que escapa del tanque no se ve significativamente afectada por la relación de aspecto, ya que, si bien había un mayor número de partículas que escapaban al comienzo de la simulación del caso con relación de aspecto 1,1,este número se equiparaba al final de la simulación. De las líneas de flujo se desprende que las mayores velocidades se ubican en las regiones bajo el agitador y estas disminuyen en las regiones sobre el agitador.
The mining industry in Chile is fundamental to the country's economy. For transportation and processing a mixture of mineral plus water is used, which forms a mineral pulp. This is a continuous process in which multiple teams come into play, which have an operating time, for which it is necessary to have stirred tanks that allowthe pulp to be kept homogeneously while the other phases of the operation are carried out. It is important to advance in the understanding of these essential equipment in order to understand how the particles are distributed, according to the geometric parameters that are used today. For this reason, a numerical study was carried out of a mixing tank of 2 m in diameter and 2 m in height, which is the base model and of two more cases. In which the aspect ratio height vs diameter is varied, obtaining aspect ratios of 1,1 and 1,2 to see the behavior of the flow, leaving all the other variables constant, such as the rotation speed of the stirrer of 190 rpm, the inflow velocity of the flow of 1,0m/s and the number of baffles. These models were implemented usingReynolds' averaged equations (RANS) and considering a non-Newtonian fluid. It was found that, although the aspect ratio influences the velocities inside the tank, generating zones of higher speed near the walls in the tanks with a higher aspect ratio, these were never greater than 0,8 m / s. On the other hand, the amount that manages to escape is not affected to a great extent by the aspect ratio, since although there were a greater number of particles that escaped at the beginning of the simulation of thecase with aspect ratio 1,1, this number was equated at the end of this one. In relation to the flow lines, it can be seen that there are higher speeds in the regions under the shaker and these decrease in the regions above the shaker. Regarding the location of the particles, a more homogeneous distribution is generated as the aspect ratio decreases. In addition, there is an interesting effect in the areas near the baffles in which the flow accelerates when it reaches the baffles and recirculation occurs after exceeding them. The type of flow generated by a radial type agitator was also validated.
The mining industry in Chile is fundamental to the country's economy. For transportation and processing a mixture of mineral plus water is used, which forms a mineral pulp. This is a continuous process in which multiple teams come into play, which have an operating time, for which it is necessary to have stirred tanks that allowthe pulp to be kept homogeneously while the other phases of the operation are carried out. It is important to advance in the understanding of these essential equipment in order to understand how the particles are distributed, according to the geometric parameters that are used today. For this reason, a numerical study was carried out of a mixing tank of 2 m in diameter and 2 m in height, which is the base model and of two more cases. In which the aspect ratio height vs diameter is varied, obtaining aspect ratios of 1,1 and 1,2 to see the behavior of the flow, leaving all the other variables constant, such as the rotation speed of the stirrer of 190 rpm, the inflow velocity of the flow of 1,0m/s and the number of baffles. These models were implemented usingReynolds' averaged equations (RANS) and considering a non-Newtonian fluid. It was found that, although the aspect ratio influences the velocities inside the tank, generating zones of higher speed near the walls in the tanks with a higher aspect ratio, these were never greater than 0,8 m / s. On the other hand, the amount that manages to escape is not affected to a great extent by the aspect ratio, since although there were a greater number of particles that escaped at the beginning of the simulation of thecase with aspect ratio 1,1, this number was equated at the end of this one. In relation to the flow lines, it can be seen that there are higher speeds in the regions under the shaker and these decrease in the regions above the shaker. Regarding the location of the particles, a more homogeneous distribution is generated as the aspect ratio decreases. In addition, there is an interesting effect in the areas near the baffles in which the flow accelerates when it reaches the baffles and recirculation occurs after exceeding them. The type of flow generated by a radial type agitator was also validated.
Notas
Memoria (Ingeniero Civil)
Palabras clave
Minería, Equipos y Accesorios, Investigaciones, Tanques de Almacenamiento, Métodos de Simulación