低溫電解膨脹性能的影響
(中南大學 冶金科學與工程學院，長沙 410083)
摘 要: 采用改進型陰極電解膨脹率測試儀，研究低溫電解質[K3AlF6/Na3AlF6]-AlF3-Al2O3中電流密度和過熱度對半石墨質陰極電解膨脹性能的影響，并對陰極的電解膨脹性能進行數(shù)值化表征。結果表明：金屬K和Na由表及里滲透進入陰極內部；隨著過熱度和電流密度的增大，陰極電解膨脹率均呈增大趨勢；當電解質過熱度由10 ℃升高至50 ℃時，陰極電解膨脹率由1.41%增大至2.10%；隨電流密度的增大陰極電解膨脹率呈現(xiàn)出不同的增幅；當電流密度小于0.4 A/cm2或大于0.7 A/cm2時，陰極電解膨脹率均明顯增大；而當電流密度在0.4 A/cm2到0.7 A/cm2之間變化時，陰極電解膨脹率相對恒定、增幅最小；數(shù)學模型中引入的參數(shù)可用于表征陰極的電解膨脹及低溫電解質中陰極抗K和Na滲透性能；低溫電解時，降低熔體過熱度、選擇合適的陰極電流密度均可減小金屬K和Na對陰極的破壞作用。
關鍵字: 鋁電解；半石墨質陰極；電解膨脹；電流密度；過熱度；低溫電解
（School of Metallurgical Science and Engineering, Central South University, Changsha 410083, China）
Abstract:The effects of current density and superheat of potassium and sodium penetration in [K3AlF6/Na3AlF6]-AlF3- Al2O3 on the electrolysis expansion of semi-graphitic cathode melts were studied with a modified laboratory Rapoport apparatus. A mathematical model was introduced to numerically character the electrolysis expansion performance of the semi-graphitic cathode. The results show that potassium and sodium penetrate into the semi-graphitic cathode from exterior to interior. The electrolysis expansion of semi-graphitic cathode increases with increasing current density and superheat. When the superheat increases from 10 ℃ to 50 ℃, the electrolysis expansion increases gradually from 1.41% to 2.10%. However, as the current density rises, the electrolysis expansion increases obviously before 0.4 A/cm2, and after 0.7 A/cm2 the electrolysis expansion increases obviously again. When the current density ranges in 0.4−0.7 A/cm2, the electrolysis expansion keeps constant relatively, and its increase is the least. In addition, the parameters introduced in the mathematical model can reflect the same information with the curve of electrolysis expansion, and sequentially character the resistance performance to K and Na penetration accurately at low temperature. At low temperature the destructive effect resulted from potassium and sodium penetration can be reduced by reducing superheat and choosing proper current density.
Key words: aluminum electrolysis; semi-graphitic cathode; electrolysis expansion; current density; superheat; low temperature electrolysis
