铝电解预焙阳极原料配方对阳极过电位的影响

Effect of raw material recipe on anodic overvoltage of pre-baked carbon anode in aluminum electrolysis

铝电解碳素阳极过电位高达400～600mV,导致吨铝电耗和原铝的生产成本增加.作者通过不同原料配方(沥青量和残极添加量)工业试验预焙阳极取样,在实验室用"改进断电流法"进行阳极过电位测试,考察了铝用碳素阳极生产中粘结剂沥青含量和残极添加量对阳极过电位的影响.研究结果表明:随着沥青量的增加,试验阳极的过电位变化不大,但略有降低;添加残极时带入的Na3AlF6,AlF3,Al2O3和NaF等杂质,可加速阳极过程的电化学和表面转化步骤,从而降低阳极过电位;阳极孔隙度过高可导致阳极过电位增大.

As an important part of cell voltage, the anodic overvoltage of carbon anode is as high as 400～600 mV, which directly influences the electric energy consumption per ton of aluminum and the production cost of primary aluminum. In this paper, the anode samples are drilled from the industrial testing prebaked anodes with different recipe respecting to the pitch content and butt addition. Their anodic overvoltage is measured with the so called modified current interruption technique in laboratory, and the effect of pitch content and butt addition on anodic overvoltage of prebaked carbon anode in aluminum electrolysis is studied. The results show that the anodic overvoltage decrease a little with the pitch content increase. The impurities such as Na3AlF6, AlF3, Al2O3 and NaF are introduced into the prebaked carbon anodes when butts are added, much of which may accelerate the electrochemical step or surface transform steps of the anodic process, so the anodic overvoltage decreases; exorbitant porosity of carbon anode may result in the increase of anodic overvoltage.