焙烧法回收阳极炭渣中电解质试验研究

Recovery of electrolytes from anode carbon residue by roasting method

阳极炭渣是铝电解过程产出的危废,主要成分是冰晶石、亚冰晶石和碳,目前主要以堆存的方式暂存,不但污染环境,而且造成资源浪费。本文以甘肃某电解铝厂提供的阳极炭渣为原料,对其进行了表征分析,并在焙烧温度范围内热力学分析和TG-DSC分析的基础上,进行了单因素焙烧试验,得到以下主要结论:阳极炭渣中电解质含量较低区域,电解质附着在颗粒的表面和间隙,较高区域则包裹碳质材料;化学反应吉布斯自由能变分析表明,焙烧法回收阳极炭渣中电解质可行;单因素试验得到的较佳焙烧工艺为温度800℃、升温速率5℃/min、保温时间1.5 h,此条件下,阳极炭渣的失重率为24.3%,电解质碳脱除率为96.32%,回收率为90.63%;回收电解质中出现K_(2)NaAlF_(6)和LiF新相,Na、Al、F、Mg、Ca、K元素分布均匀且含量增加,电解质初晶温度为921.5℃,可满足铝电解工业应用要求。

Anode carbon slag is a hazardous waste generated during the aluminum electrolysis process,mainly composed of cryolite,subglotite,and carbon.Currently,it is mainly stored in a temporary manner through stacking,which not only pollutes the environment but also causes resource waste.This article uses anode carbon slag provided by an electrolytic aluminum plant in Gansu as raw material,and conducts characterization analysis on it.Based on thermodynamic analysis and TG-DSC analysis within the calcination temperature range,a single factor calcination test is conducted,and the following main conclusions are obtained.In areas with low electrolyte content in anode carbon slag,electrolytes adhere to the surface and gaps of particles,while higher areas wrap around carbonaceous materials;The Gibbs free energy analysis of chemical reactions indicates that the roasting method is feasible for recovering electrolytes from anode carbon slag;The optimal roasting process obtained from the single factor experiment is a temperature of 800℃,a heating rate of 5℃/min,and a holding time of 1.5 hours.Under these conditions,the weight loss rate of anode carbon slag is 23.73%,the removal rate of electrolyte carbon is 96.17%,and the recovery rate is 91.32%;K_(2)NaAlF_(6)and LiF new phases appeared in the recovered electrolyte,with a uniform distribution and increased content of Na,Al,F,Mg,Ca,and K elements.The initial crystallization temperature of the electrolyte was 921.5℃,which can meet the industrial application requirements of aluminum electrolysis.