| Aluminum industry develops rapidly in China, and the annual production of aluminum has ranked first in the world for13consecutive years. However, high energy consumption restricts the development of aluminum industry. Current efficiency is an important indicator of energy consumption, and liquid aluminum dissolved diffusion loss is one of the main factors. Few researches on aluminum dissolved diffusion loss can be found at home and abroad, which mainly stays in an experimental stage. Therefore, studying liquid aluminum diffusion transfer process and establishing a numerical model of the liquid aluminum diffusion have a great significance to decreasing energy consumption of electrolytic aluminum industrial.This paper is based on the project cooperating with Guiyang Aluminium Magnesium Design&Research Institute of double diffusion model research. In this paper, the multiphase flow law and aluminum diffusion transfer mechanism in electrolytic bath have been studied. The flow field model and liquid aluminum turbulent diffusion model of350kA and420kA cells have been established. The relationship between interphase force and flow field and aluminum diffusion have been analyzed. The effect of magnetic field to flow field and aluminum concentration field have been calculated and analyzed, and the optimization scheme or effective energy-saving measures of cells have been listed out. The main results of this paper are as follows:(1) Considered the complex phase interaction in cell, chose the right turbulence model with turbulent viscosity correction, a three-phase flow model with bubble and magnetic force of350kA and420kA cells were established on CFX computing platform and the flow characteristics and the impact of bubble behavior to flow field were analyzed.(2) Studied the mechanism of aluminum diffusion transfer, considered the effect of concentration boundary layer and turbulent mass transfer to aluminum diffusion process, a model of liquid aluminum diffusion transfer was established. The aluminum concentration distribution between ACD (anode-cathode distance) was analyzed. The calculation results show that there are closely association between aluminum dissolved diffusion and flow field. The concentration boundary layer of high velocity region is thin, of which the diffusion rate is high. The analysis of aluminum concentration between ACD shows that aluminum concentration decreases to10-5rapidly in concentration boundary layer, and is almost unchanged in turbulent zone, while decreases significantly in reaction zoon for the oxidation by anode gas. The numerical results of aluminum concentration distribution in ACD are excellently consistent with the test results(3) The calculation results of flow field and concentration field in different magnetic field conditions show that aluminum diffusion process is affected by electromagnetic force and bubble force. It is determined by bubble force when the magnetic field is limited to a certain extent. The bus configuration is different in different cells, and the effect of magnetic field to aluminum diffusion is different in different direction.(4) Y axis magnetic field has a greater impact on the current efficiency than X axis in350kA series cells. Optimization of Y axis magnetic field would have a better effect. But the aluminum loss increases significantly when X axis magnetic field increases more than10%. So the increase of X axis magnetic field should be below10%when Y axis magnetic field is optimized. The bus configurations of420kA series cells are more reasonable, so there is less space for magnetic field optimization. Because of a relatively low ACD, slotted or perforated anodes will facilitate gas escaping, decrease the bubble effect to flow field and diffusion, and are more conducive to improve current efficiency. |
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