Experimental and Theoretical Study on Melting Kinetics of Spherical Aluminum Particles in Liquid Aluminum
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Experimental and Theoretical Study on Melting Kinetics of Spherical Aluminum Particles in Liquid Aluminum Marco Ramírez-Argáez, Enrique Jardón, Carlos González-Rivera Facultad de Química UNAM, Departamento de Ingeniería Metalúrgica, Edificio D, Circuito de los Institutos s/n, Coyoacán, México D.F. CP 04510 México. ABSTRACT In this study a process analysis of the melting process of solid particles in a bath of same composition is performed using both experimental information and theoretical computations. An experimental setup was used to measure the thermal histories and to follow the evolution with time of the size of solid metallic spherical particles being melted in a metallic bath of same composition. For such a purpose, pure aluminum was used during the experiments for both solid particles and liquid bath. A mathematical model was also developed based on first principles of heat transfer to simulate the melting kinetics of a cold metallic spherical particle immersed in a hot liquid bath of same composition. The mathematical model was reasonably validated when compared against the experimental results obtained in this work. A process analysis of the melting process was performed to determine the effect of the initial temperature and size of the solid particle, the bath temperature and the convective heat transfer coefficient on the melting time and on the energy consumption. The analysis showed that the variable presenting the most significant effect on both the melting time and the energy consumption is the convective heat transfer coefficient between the particle and the bath, since an increment in such a parameter accelerates the melting process and saves energy. Therefore, proper stirring of the bath is highly recommended to enhance the melting of metallic alloying additions in the metallic baths. INTRODUCTION Melting of solid metallic particles in liquid baths is an operation widely used in foundry industry to produce metallic components, and therefore a key economic factor is to understand the melting process in order to optimize it. This is why in the past several researchers have studied the kinetics of melting by both experimental systems and mathematical modeling. It is well-known that when a solid cold particle (in this case a sphere) is added to a hot bath, a solid layer is solidified from the liquid at the surface of the sphere, and consequently this grows, eventually reaching a maximum size and then gradually decreasing in its radius until fusion is completed [1]. Several works studied the kinetics of melting by performing experiments in real metallic baths [2]. Those works were able to track the size of the particles and to determine the fusion kinetics as a function of the stirring degree of the bath, initial bath and particle temperatures, and initial particle size. One of the important industrial cases is the melting of scrap steel or pellets of Direct Reduced Iron (DRI) added at the top of the steelmaking Electric Arc Furnaces (EAF), which consume a lot of energy (in the range of 500 – 600 KWh/
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