预焙铝电解槽阳极底部开排气沟对电解质流场的影响

Influences of gas discharging grooves at bottom of prebaked carbon anodes on bath flow pattern in aluminum reduction cells

对预焙铝电解槽阳极底部开排气沟时周围电解质流场进行计算,发现部分阳极气体可以通过排气沟向外排放,减少气泡在阳极底部停留时间和阳极底掌气泡覆盖率,从而有利于降低极间电阻压降和阳极效应系数,减少电解能耗;另一方面气体带动电解质进入排气沟,然后进入电解槽侧部通道,扩大了电解质循环通道,促进了阳极周围电解质流动和槽内的传质传热,有利于保持电解正常进行,相比之下排气沟为通沟时较非通沟更有利于保持电解质流动稳定;同时由于排气沟促进了阳极气体排放,使铝液与阳极气体发生“二次反应”(即电解还原的铝卷入电解质中被阳极气体重新氧化)的机会减少,有利于提高铝电解电流效率。

Simulations on the bath flow fields around a prebaked carbon anode with gas discharging grooves at the bottom which could be applied on aluminum reduction cell was conducted. The results reveal that with the help of the grooves, anode gas discharging is facilitated, residence time of bubbles in the interpolar gap（ or ACD） and the bubbles coverage of the anode bottom can be reduced, which greatly contributes to the decrease of the voltage drop in ACD and anode effects, so the energy consumption of the aluminum production can be lowered. On the other hand electrolyte dragged by gas bubbles goes into the grooves, then to the side channel of the cell, passageway for the bath circulation is widened, a relatively smooth bath circulation around the anode will be formed, which enhances the heat and mass transmission, therefore a good electrolysis operation can be obtained. Compared the grooves which extend through the whole length of the anode bottom with those do not, the former are more propitious to the stability of the bath flow, meanwhile as the grooves facilitate the gas venting, the so called ＂second reaction＂, i.e. the aluminum reduced diffuse into the bath and react with the anode gas again, could be restrained to some extent, which would be beneficial to the improvement of the current efficiency.