| Rare earth metal as a "rising star" in metal materials shows an unprecedentedmomentum and speed development in application because of unique chemical andphysical properties. China has a lot of rare earth resources in the world. And China'srare earth content accounted for40%of the world, production accounts for90%of theworld. But there are significantly different development levels between China and theworld in rare earth deep processing and preparation techniques. The problem of smallerscale equipment is widespread. Although, the small cell has the advantage of easyoperation and easy to adjust, but the large cell showing unparalleled advantages on itscapacity, size, stability and long-term development prospects. And, the large cell iseasy to realize a higher degree of automation, improved equipment and better upgradesfor intensive, large-scale production, which has a great significance to stable theproduction process and product quality. So the design optimization of large-scale rareearth electrolytic cell has important practical significance and potential fordevelopment. The design of large-scale electrolytic cell still follow the simpleexpansion method currently. The electrolytic cell test can only rely on the reliability ofproduction practices. And lack of appropriate theoretical basis. The main research isused the widely used ANSYS at present to simulate the distribution of electric field andtemperature field, etc. In addition, the actual presence of molten salt electrolysisproduction of tungsten cathode surface rapid loss of local issues on-site investigation,theoretical analysis, simulation tests revealed the injury mechanism analysis and presentation of technical means of protection and this is another important task of thispaper.The main conclusions as follow.?1?Traverse a variety of cell structure, with the use of commercial softwareANSYS finite element simulation of temperature and electric field. Combined resultsthat the outer contour of20kA rare earth electrolytic cell as a racetrack. Tungstencathodes are evenly distributed in the electrolytic cell, and be surrounded by graphiteanodes. And the inter-electrode distance ranges7cm~14cm, the effective depth of theanode ranges25cm~30cm, anodic current density is1.5A/cm2. The simulation resultsshow that the melt voltage of5cathodes electrolytic cell ranged6.530V~6.789V; themelt voltage of6cathodes electrolytic cell ranged5.028V~5.279V. And the potentialline evenly distributed, uniform current strength in the electrolytic cell.?2?Calculated the heat balance of different unit electrolytic cell structures. Theheat balance of6cathodes double rows electrolytic cell with anode inner radius11.8cm, inter-electrode distance8.8cm, melt voltage5.279V, and cathode currentdensity1.128A/cm2is perfect. The temperature field of electrolytic cell determined issimulated using the ANSYS Thermal Electric field module. Simulation results showthat the maximum temperature of the cell structure temperature field is1088?. Afterconsidering the overall thermal radiation on the outside of the electrolytic cell, theoverall temperature can be maintained to meet the needs of production at1050?.?3?Consideration the difficult position of the middle anode and inconvenienceof operating problems, and investigated the influence of electric field and temperaturefield on20kA6cathodes double rows electrolytic cell when removed the middle anode.The results show that The results show that the former has a melt voltage5.279V, thecathode current density is1.128A/cm2, the maximum furnace temperature is1088?,and the temperature distribution of the electric field and radiate symmetrical axis; thelatter melt voltage is5.279V cathode current density is1.104A/cm2, the maximumtemperature of the furnace was1105?, but the electric field distribution is on longeruniform, appears to offset the lack of the anode side.?4?Measuring the department rapid damage of tungsten cathode above themolten salt in rare earth electrolysis and research that above the surface of molten saltat70mm~80mm, the corrosion rate is7.5mm/a?0.02mm/day? with purple loose salt sediments on the surface. The result of department rapid damage is not only the simpleconsumption of high-temperature oxidation, but also rare earth oxide molten saltelectrolyte volatiles attached to the surface of the tungsten cathode, and promote thedestruction of its high-temperature oxidation. Oxygen in the air supplied to the moltentungsten cathode through closed steam, and Cathode contact it under high temperatureresulting in the department vigorous oxidation. Coupled with the presence of moltensalt deposition attachments occupy the leading cause of injury involved in hotcorrosion to occur. |
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