【作者】 黄有国；

【导师】 刘业翔； 赖延清；

【作者基本信息】 中南大学 ， 电化学工程， 2009， 博士

【摘要】 采用惰性阳极和可润湿性阴极的新型铝电解槽技术,是铝电解工业实现节能、减排与增效的重要途径。惰性阳极经长期研究已取得较大进展,但仍然无法满足现行铝电解质体系与电解工艺条件下的耐腐蚀要求。低温电解可改善惰性阳极服役环境,降低阳极腐蚀速率,促进惰性阳极铝电解技术的工业化实现。论文在国家973计划课题(2005CB623703)及863计划课题(2008AA030503)的资助下,以开发NiFe2O4基金属陶瓷惰性阳极低温电解工艺为目标,以5Cu/(NiFe2O4-10NiO)金属陶瓷惰性阳极为代表,针对Na3AlF6-K3AlF6-AlF3低温电解质体系,系统研究了熔体组成与过热度对该种阳极电解腐蚀行为的影响,确定有利于改善惰性阳极服役环境的低温电解质组成与工艺；同时,系统研究了Na3AlF6-K3AlF6-AlF3熔体的导电性能,在此基础上研究了LiF添加剂对Na3AlF6-K3AlF6-AlF3熔体初晶温度、溶解A12O3能力(溶解度与溶解速度)及导电性能的影响规律,为开发具有“低温、高A1203溶解度和高电导”新型电解质提供理论依据。主要研究结果如下：(1)揭示了Na3AlF6-K3AlF6-AlF3低温电解质熔体组成及过热度对5Cu/(NiFe2O4-10NiO)金属陶瓷惰性阳极腐蚀速率的影响规律,确定最有利于降低阳极腐蚀速率的熔体组成为KR值(K3AlF6/(K3AlF6+Na3AlF6)质量百分比)为20%-40%、A1F3含量为23%-28%(初晶温度为830℃-850℃)。在此组成范围的电解质熔体中,过热度为20℃、阳极电流密度为0.95A／cm2(按阳极底部面积计算)条件下,5Cu/(NiFe2O4-10NiO)惰性阳极的腐蚀速率可降低到0.80cm／y,与传统Na3AlF6-AlF3电解质(CR=2.3,初晶温度为951℃,过热15℃)中的5.27cm／y相比,降低85%。(2)揭示了熔体温度、A1F3含量及KR值对Na3AlF6-K3AlF6-AlF3熔体电导率的影响规律,建立了熔体电导率与熔体组成及温度之间的回归关系式,绘制了Na3AlF6-K3AlF6-AlF3熔体在20℃过热度时的等电导率图。熔体电导率与熔体组成及温度之间回归关系式为该回归公式拟合相关系数为0.99,标准偏差为0.027Ω-1·cm-1。从电导率的经验公式及等电导率图可以获取不同成分电解质的电导率值及不同电导率值的电解质组成范围,为获得“低温、高Al2O3浓度、高电导”的电解质提供了应用基础。(3)揭示了LiF添加对Na3AlF6-K3AlF6-AlF3熔体初晶温度、溶解Al2O3能力及电导率的影响规律,研究设计了“低温、高Al2O3浓度、高电导率”电解质。LiF的添加降低了熔体初晶温度,降低了熔体的Al2O3溶解度,提高了熔体的电导率。800℃、850℃和900℃电解温度下,具有“低温、高Al2O3浓度、高电导”特征的低温铝电解质的组成分别是：KR值为30%-40%,AlF3含量为25.1%-27.6%,LiF含量为2%,过热度为20℃-40℃；KR值为10%-30%,AlF3含量为24.5%-27.7%,LiF含量为2%,过热度为40℃；KR值为10%-20%,AlF3含量为16.7%-21.3%,LiF含量为2%,过热度为20℃-40℃。更多还原

【Abstract】 Aluminum reduction cells with inert anodes and wettable cathodes have been proved to be of great significance in saving energy, reducing pollution, and increasing efficiency in the process of aluminum electrolysis. While the research on inert anode has achieved great improvement through efforts of researchers, it still cannot meet the demand of corrosion resistance in recent electrolyte system and technological conditions. Aluminum electrolysis at low temperature can improve the working condition of inert anode, reduce the corrosion rate of inert anode, and then bring about the industrialization of inert anode.Funded by the State Key Project of Fundamental Research (973 project:2005CB623703) and National High Technology Research and Development Project (863 project:2008AA030503), and with the aim to explore electrolytic process of NiFe2O4 based inert anode at low temperature, represented by 5Cu/(NiFe2O4-10NiO) cermet inert anode, and based on Na3AlF6-K3AlF6-AlF3 system, the effects of composition and superheat of melts on electrolytic corrosion behavior of this anode are studied systematically. The composition and electrolytic parameters which are beneficial to improve the working condition of inert anodes is pointed out. Meanwhile, the electrical conductance of Na3AlF6-K3AlF6-AlF3 melts is studied systematically. In addition, the effects of LiF on liquidus temperature, dissolving ability of Al2O3(solubility and dissolution), and electrical conductance of melts are studied, which provides theoretical foundation for exploring novel electrolyte with "Low liquidus temperature, Favorable Al2O3 solubility and High electrical conductivity". The main results of the thesis can be summarized as follows:(1) The influence of melt components of Na3AlF6-K3AlF6-AlF3 low temperature electrolyte and superheat of melts on corrosion rate of 5Cu/(NiFe2O4-10NiO) cermet inert anode is indicated. The melt component which is beneficial to reduce the anode corrosion rate is that KR(the weight percent of K3AlF6 in (Na3AlF6+K3AlF6)) is ranging from 20% to 40%, and AlF3 content is ranging from 23% to 28% (correspondingly, liquidus temperature ranging from 830℃to 850℃). In this composition range, the corrosion rate of inert anode is 0.8cm/y while the superheat is 20℃and anode current density is 0.95 A/cm2(Calculation according to all the bottom area of anode), which is significantly decreased by 85%, compared with 5.27cm/y in Na3AlF6-AlF3 electrolyte(the cryolite ratio is 2.3, the liquidus temperature is 951℃, and the superheat is 15℃).(2) The influence of melt temperature, AlF3 content, and KR on electrical conductivity of Na3AlF6-K3AlF6-AlF3 melts is indicated. A regression equation showing the relationship between electrical conductivity of melts and melts composition and temperature is built. The ternary isotherm diagram of Na3AlF6-K3AlF6-AlF3 melts at 20℃superheat is drawn, too. The regression equation is as follow. The correlation coefficient of regression equation is 0.99 and its standard deviation is 0.027Ω-1·cm-1.The electrical conductivity with various compositions can be obtained in regression equation and ternary isotherm diagram, and the compositions range with various electrical conductivity can be obtained, which provides application basis for obtaining an electrolyte with low liquidus temperature, favorable Al2O3 solubility, and high electrical conductivity.(3) The influence of addition of LiF on the liquidus temperature, dissolve ability of Al2O3, and electrical conductivity of melts is indicated. An electrolyte of low liquidus temperature, favorable Al2O3 solubility, and high electrical conductivity are studied and designed. The addition of LiF reduces the liquidus temperature of melts and the solubility of Al2O3 in melts but increases the electrical conductivity of melts. For this low temperature electrolyte, which has low liquidus temperature, favorable Al2O3 solubility, and high electrical conductivity, its compositions at 800 ℃,850℃and 900℃can be described respectively as follows:KR, ranging from 30％to 40％and AlF3 content,ranging from 25.1％to 27.6％,with 2％of LiF(the superheat is ranging from 20℃to 40℃)；KR,ranging from 10％to 30％and AlF3 content,ranging from 24.5％to 27.7％,with 2％of LiF(the superheat is 40℃)；KR,ranging from 10％to 20％and AlF3 content,ranging from 16.7％to 21.3％,with 2％of LiF(the superheat is ranging from 20℃to 40℃).更多还原