Abstract

The dynamic behavior (formation/dissolution) of the ledge, depending on the electrolyte overheating temperature, thermal resistance of the lining material, and composite of the cryolite–alumina electrolyte, is studied experimentally using a model installation mimicking the actual conditions of the electrolytic aluminum production. A window that enabled the change of the lining material is mounted into the front wall of the installation case. The ledge formation occurs due to a heat flow formed due to the temperature difference of the electrolyte and electrolyzer walls. The electrolyte cryolite ratio (CR) is varied in a range of 2.1–2.5. The alumina concentration in the electrolyte does not exceed 4.5 wt %. The change in the shape of the working space in the electrolyzer during the electrolysis is determined by the ledge thickness. The active ledge formation in the experimental cell starts upon overheating by 3–4 K. It is shown that a thicker ledge is formed at the same overheating temperature with a decrease in the thermal resistance of the lining material from 16 to 14 m²/W, but a decrease in the thermal resistance in the already formed ledge almost does not affect its thickness. Similarly to the industrial electrolyzer, the ledge profile formed in the experimental cell can be conditionally divided into three zones, notably, bottom ledge, ledge at the metal/electrode interface, and side ledge. The dynamic behavior of the side ledge differs from the bottom ledge; notably, the side ledge is thicker at a high electrolyte CR, while the bottom ledge is thinner. The chemical analysis of components in the dry knock out shows that the CR and Al₂O₃ concentrations increase over the cell height from top to bottom. It is concluded that the side ledge has a heterogeneous composition that depends on the electrolyte composition and cooling rate.

中文翻译：

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铝电解槽中侧缘和底部缘的形成

摘要

壁架的动态行为（形成/溶解）取决于电解质的过热温度，衬里材料的热阻以及冰晶石-氧化铝电解质的复合材料，并通过模拟模拟电解铝实际条件的模型装置进行了实验研究生产。可以更换衬里材料的窗口安装在安装箱的前壁。壁架的形成是由于由于电解质和电解槽壁的温度差而形成的热流而发生的。电解质冰晶石比率（CR）在2.1-2.5范围内变化。电解质中的氧化铝浓度不超过4.5重量％。电解过程中电解槽中工作空间的形状变化由壁架厚度决定。² / W，但是已经形成的凸缘的热阻降低几乎不会影响其厚度。与工业电解槽类似，在实验单元中形成的壁架轮廓可以有条件地分为三个区域，特别是底部壁架，金属/电极界面处的壁架和侧面壁架。侧窗台的动态行为不同于底窗台；值得注意的是，在高电解质CR下，侧凸缘更厚，而底部凸缘更薄。干敲除中各成分的化学分析表明，CR和Al ₂ O ₃浓度从上到下随电池高度的增加而增加。结论是，侧凸缘具有取决于电解质组成和冷却速率的异质组成。