铝电解阳极CO2气泡传质速率及其对电流效率影响的模拟研究
首发时间:2015-05-14
摘要:构建铝电解阳极CO2气泡生长、脱离阳极后在电解质熔液内上浮与CO2传质过程耦合模型,研究CO2气泡传质速率及其对二次铝损失反应的影响。计算结果表明,气泡长大过程CO2传质速率(10-6 mol/s)远大于气泡上浮中数值(10-8~10-9 mol/s)。当CO2气泡传质速率与铝损失速率相近时,减少电解槽极距对电流效率影响并不明显。电流密度i对气泡传质速率影响较大,当i从0.15 A/cm2增至0.75 A/cm2时,CO2气泡在电解质熔液中传质速率可增大至1.96×10-6 mol/s,但电流密度越高铝生成量越大,CO2气泡传质引起的电流效率降低趋势反而减小。在阳极加载超声可使气泡脱离阳极时粒径变小,同时亦使CO2气体在阳极底部停留时间减少,其综合作用使电流效率升高。正常电解条件下实验结果与模拟研究基本一致。
关键词: 有色金属冶金 气泡生长 传质速率 铝损失 电流效率
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Simulation study on CO2 mass transfer rate of anodic bubbles and its effect on current efficiency in aluminum electrolysis
Abstract:The coupled mass transfer model for CO2 bubbles growth at the aluminum electrolytic anode and floating of the bubbles which escaped from the bottom of the anode was constructed. The mass transfer rate of CO2 bubbles and its effect on the secondary aluminum loss reaction was investigated. The calculated results show that mass transfer rate in bubbles’ growing process about 10-6 mol/s is more than floating process about 10-8-10-9 mol/s. When mass transfer rate of gases is close to loss rate of aluminum, current efficiency (CE)doesn’t change remarkably with the anode and cathode distance (ACD) descending. But current density (i) has pronounced influence on the mass transfer rate in growing process. When i increases from 0.15 to 0.75 A/cm2, mass transfer rate is up to 1.96×10-6 mol/s, but i is bigger, aluminum generates more, so loss of CE caused by CO2 mass transfer decreases. When ultrasound is loaded on the anode, the size of the bubbles escaping from the anode is smaller, but the residence time for CO2 bubbles underneath the anode is shortened, and CE is improved about 2% by the combined effects. The calculated results are consistent with experimental results in giving condition.
Keywords: nonferrous metallurgy bubble growth mass transfer rate aluminum loss current efficiency
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