Mathematical modeling of aluminum degassing by the impeller injector technique validated by a physical modeling
- PDF / 389,584 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 3 Downloads / 196 Views
Mathematical modeling of aluminum degassing by the impeller injector technique validated by a physical modeling M. Hernández-Hernández1, W. F. Cruz-Mendez1, C. Gonzalez-Rivera1, M. A. Ramírez-Argáez1 1 Facultad de Química, UNAM, Departamento de Ingeniería Metalúrgica. Edificio “D” Circuito de los Institutos s/n, Cd. Universitaria, C.P. 04510 México D.F., México.
ABSTRACT A mathematical model is developed to describe deoxidation of water in a physical model of a batch aluminum degassing reactor equipped with the rotor-injector technique, assuming that deoxidation kinetics of water is similar to dehydrogenization of liquid aluminum. Degassing kinetics is described by using mass transport and mass balance principles by assuming that degassing kinetics can be characterized by a mass transfer coefficient, which depends on the process variables. The transport coefficient and the average bubble diameter are estimated with correlations reported in the literature for similar gas-injection systems. The water physical model helped to validate the mathematical model and to perform a process analysis by varying: 1) Gas flow rate (20 and 40 l/min); and 2) Impeller’s angular velocity (290 and 573 rpm). Results from the model agree well with measurements of deoxidation kinetics at low impeller rotating speeds. At high rotating speeds the model is still valid but less reliable because it does not take into account the formation of the vortex at the free surface. Nevertheless, the model provides predictions of the influence of every operating parameter and it can be used as a good approximation for real systems. INTRODUCTION There are several technologies for degassing aluminum, being the rotating impeller technology the most employed for last two decades. Then, several research works have been carried out looking for a complete understanding of the kinetics and fluid dynamics of this process. For such a purpose, mathematical and physical models have been developed as affordable tools for analysis. With these tools, the process can be understood and optimized in terms of quality production, lowering the costs and diminishing the environmental impact. There are available mathematical models describing the removal of hydrogen from liquid aluminum based on the oxygen-water system (water acting as liquid aluminum, oxygen replacing hydrogen and nitrogen purge instead of argon) [1-3]. Those mathematical models have been easily validated with the aid of water physical models, which are experimentally simpler and easier to handle than experiments with molten aluminum [3-6]. Deoxidation in water physical models can be used to study aluminum degasification because both systems present similar firstorder exponential decay degassing kinetics [7-9]. In this study, a mathematical model based on oxygen-water system has been developed and it has been validated with water physical model experiments. EXPERIMENTAL PROCEDURE Physical modeling
49
A full-scale physical model of a real degassing furnace is built of acrylic equipped with the impeller-in
Data Loading...
