350 kA电解槽富Li、K电解质体系选择

Selection of Li/K-rich Electrolyte System for 350 kA Electrolytic Cell

国内某350 kA电解系列使用高Li、K氧化铝生产,Li、K在电解质中富集,形成了Na_(3)AlF_(6)-Al_(2)O_(3)-AlF_(3)-CaF_(2)-MgF_(2)-LiF-KF电解质体系。随着Li、K富集,生产不稳定,指标恶化。通过实验室和现场测定电解质相关性质,采用试错法进行工业试验,统计分析电解质成分对电流效率、初晶温度、电导率和氧化铝溶解性能的影响,确定适宜的电解质成分,即分子比2.50±0.05、CaF_(2)≤4.77%、MgF_(2)≤0.68%、LiF≤5%和KF≤3%。将其进行工业应用,并配合工艺和操作管理,取得了较好效果,实现噪声值下降、阳极效应受控和炉膛状况好转,电流效率提高2.91%,直流电耗较应用前降低326 kWh/t。

The 350 kA electrolysis series in a Chinese plant adopted high Li-K alumina for production.As the enrichment of Li and K in the electrolyte,an electrolyte system of Na_(3)AlF_(6)-Al_(2)O_(3)-AlF_(3)-CaF_(2)-MgF_(2)-LiF-KF was formed,meanwhile,the production became unstable and indicators were deteriorated.Against this background,laboratory and field tests were carried out to measure the properties of the electrolyte,and industrial tests were conducted using the trial-and-error method to analyze the impact of electrolyte compositions on current efficiency,liquidus temperature,conductivity and alumina solubility,and finally proper electrolyte compositions were determined,that is,molecular ratio of 2.50±0.05,CaF_(2)≤4.77%,MgF_(2)≤0.68%,LiF≤5%and KF≤3%.The test results were further put into industrial application,and good effects have been obtained by combining process and operation management,which were reflected by reduced noise level,anode effect within control,improved hearth condition,current efficiency improved by 2.91%and DC power consumption reduced by 326 kWh/t.