铝电解槽内阳极气泡运动的冷态模拟

采用硫酸铜作电解质、石墨作阳极的电解实验模拟研究工业铝电解槽的阳极气体运动规律,以及气泡运动对电解质运动影响的规律。当阳极倾斜度小于6°时,倾角的变化对速度影响较大,阳极倾斜角的增加会加速气泡运动速度但减小气泡尺寸;阳极倾斜度达到6°以上时,几乎不存在气泡合并现象,且倾角变化对气泡速度的影响变小;气泡运动对电解质的推动作用主要体现在阳极底部气泡所在的薄层内,同时在电解质的底部存在回流现象,但流速甚小,约为5 mm/s。     

铝电解中二氧化锡基（氢气）气体阳极

开发一种在低温电解质（850℃）铝电解中应用的新型二氧化锡基气体阳极以降低铝电解能耗和二氧化碳排放。在此种气体阳极中,氢气通入阳极后参与阳极反应,分别用石墨和铝作阴极和参比电极。采用循环伏安法研究此体系中铂和二氧化锡基电极上氧离子的电化学行为,并确定氧气的析出电势。然后,采用气体电极进行恒电流电解实验,相对于未通入气体和通入氩气,通入氢气后阳极出现明显的去极化现象（阳极电势约下降0.8 V）。实验结果表明,氢气已参与阳极三相界面（气体-电解质-电极）反应,为还原性气体阳极在铝电解上的应用提供了可行性。     

铝电解槽电解质与内衬换热系数的数值计算

铝电解槽内电解质与内衬界面传热系数直接决定电解槽热平衡。基于多相流理论及壁函数方法,建立了铝电解槽电解质与内衬界面的换热系数计算数学模型,在商业数值计算软件上实现对传热推动力、传热系数分布的计算。研究结果表明:阳极气泡的作用处于主导地位,但电磁力的作用也不能被忽略,在进行换热系数计算时,需同时考虑二者的共同影响;在电解槽的大面及小面槽帮处,换热系数的分布主要受电解质流动的影响,而对于阳极底部则由于气泡层的阻碍使得此区域的传热系数较小;阳极开槽会增大电解质与阳极的换热系数,但会一定程度上减小电解质与槽帮的换热系数。     

稀土电解槽流场的数值模拟

采用雷诺应力模型(RSM)对上插式阴极结构稀土熔盐电解槽内部流场进行模拟研究,得到电解槽内部含气率和流场分布规律。计算结果表明:电解产生的气体主要集中在阳极内表面附近,且在电解槽上端靠近阳极处,含气率达到最大值;阳极内表面附近的最大上升流速为0.9 m/s;电解槽底部大部分区域电解质的流动速度均小于0.01 m/s,基本上属于流动死区;在底吹气体搅拌模型下,电解槽底部出现逆时针涡流,该区域电解质的流动速度较未通气体时的相比增加10倍以上,这能够在一定程度上改善电解槽底部的流动性,减轻底部"结瘤"现象。     

铝电解槽的多层板式阳极

本专利提出的阳极,是由一束预焙碳板組成,也即多层板式阳极。其在电解槽中的配置是,碳板下端向下延伸入熔融电解质中,碳板的露出面至少要稍离碳板下部一定距离,以便由阳极底部向上形成很深的沟梢。这些沟槽由阳极的一侧延伸至另一側,阳极顶部是密閉的,以免起噴烟口作用。在阳极底掌产生的气泡,向上流經沟柵而在阳极侧部排出,这样,可使阳极底掌不为气体所遮蔽。由于有沟槽,气体可均勻地排出。也由于气泡可由短小的通道横过,不太会扰动电解质,也不太会使气体     

铝电解金属阳极上的气泡析出行为

利用双室透明石英电解槽研究了铝电解金属阳极上气泡的析出行为.实验发现,在低电流密度下,电解开始的一段时间内,新生的氧用于氧化金属阳极表面以形成氧化物膜,此时阳极室没有氧气析出,而阴极室有铝雾扩散; 当形成足够厚的氧化膜后,阳极的氧化速度减慢,阳极表面才析出氧气.在高电流密度下,由于单位时间内在阳极上产生的氧量高于用于氧化金属阳极表面所需的氧量,电解一开始阳极上就有氧气析出.对低电流密度下气泡的生长过程观察发现,气泡先在阳极表面长大,再汇聚成一个或几个大气泡从阳极底部析出,析出前的气泡平均直径随电流密度的增加而减小.     

影响铝电解槽稳定运行的因素分析及改进措施

大型预焙阳极电解槽的生产稳定性好坏，对保证正常电解生产和取得良好经济指标和经济效益具有重要意义。本文结合实际，讨论分析了电流强度，电解质水平，铝水平技术条件，阳极质量及出铝，熄灭阳极效应，更换阳极作业质量等因素对铝电解槽稳定运行的影响，总结了几年来，为保证生产稳定进行，通过加强改造，优化工艺技术条件，提高阳极质量，规范各项操作及限电期间电解生产几个方面的改进措施。     

大型铝电解槽电解质流场涡结构的数值模拟

针对铝电解槽内熔体旋转流动的特点,提出使用涡量和旋转强度来对其涡结构进行定量解析,并以某300kA槽电解质流场为研究对象,使用CFX12软件平台进行数值模拟。结果表明:极间水平截面和阳极间缝垂直截面的旋转强度最大值分别为1.611和1.961 s 1,其绝对涡量最大值分别为4.002和3.391 s 1;阳极气泡的搅动使阳极周围电解质中成对出现反向对称小涡;而电磁力的不均匀性导致部分阳极底部出现不对称大涡;阳极中缝和间缝相交位置的绝对涡量超过4 s 1,在该位置布置下料点有利于氧化铝的分散。故运用涡分析法能得到更为丰富和精确的流场信息,为槽结构的设计提供理论指导。     

Ni-Fe-Cu惰性金属阳极的抗氧化和耐蚀性能

对Ni-Fe-Cu合金的抗氧化和耐熔盐腐蚀性能进行了研究.结果显示, 该合金的氧化动力学曲线符合抛物线规则.静态电解质中的溶解腐蚀速率随温度的增高和NaF与AlF3的摩尔分子比的降低而增大.在不同电解条件下, 组成为NaF-AlF3-NaCl-CaF2-Al2O3的电解质体系中电解时, 该阳极周围产生大量气泡, 槽电压在3.6～4.2之间波动, 阳极的电解极化腐蚀速率随电解质中氧化铝浓度的增高、温度的降低而减小, 产品铝的纯度达到97%～98%.     

铝电解槽阳极气泡行为研究新动态

本文介绍了铝电解槽阳极气泡行为研究的新进展。大部分研究停留在水溶液模拟试验及基于这些试验数据的模拟计算上,对于工业铝电解槽阳极气泡行为的研究还应该继续。     

Physical modeling of gas induced bath flow in drained aluminum reduction cell

A room temperature physical model was used to study the bubble behavior and gas induced bath circulation in a drained aluminum reduction cell. By passing compressed argon through the penetrated Plexiglas box bottom plate immersed in water, gas evolution at the anode bottom surface was simulated. Bubble behavior and liquid flow field were studied and analysis was presented. Bath secondary recirculation was observed in the interpolar gap not the net rising flow as expected. Liquid driven by the bubbles forms small vortices along the interpolar gap with small mean and turbulent velocities and accordingly poor mass transfer. Secondary recirculation also exists between the slot and interpolar gap, part of the flow in the interpolar gap go to the slot with the bubbles and fluid at the bottom of the slot enters the interpolar gap directly without going to the center channel. The existence of the fluid secondary recirculation is very unfavorable to the alumina dissolution and dispersion. Increasing the anode tilt or gas flow rate, or decreasing the anode-cathode distance can make the secondary recirculation in the interpolar gap weak, however, will intensify the secondary recirculation between the slot and interpolar gap.     

A Nonlinear Shallow-Water Model Combined with Gas Bubble Effect for Melt Flows and Interface Instability in Aluminum Reduction Cells

A nonlinear shallow-water model combined with the effect of anode gas bubbles was derived for the melt flows and interface instability in aluminum reduction cells. Both the electromagnetic forces and the drag forces between the bath and gas bubbles, as the main driven forces for the melt flows, were taken into account in this model. A comparative numerical study was carried out using both the model considering the bubble and the model without considering the bubble. The results show the effect of the bubble cannot be neglected in a fluid dynamics analysis for the aluminum reduction cell. The bath flow, induced by the motion of bubbles, presents a series of small eddies rather than large eddies as the metal flow pattern shows. The horizontal drag forces between the bath and the bubbles in the bath layer enlarge the deformation of the metal–bath interface, to some extent, but have a positive influence on stabilizing the metal–bath interface perturbations.     

Impact of operations at low anode-cathode distance on energy consumption and greenhouse gas emissions at Aluminerie Alouette

The energy consumption for aluminum production by the Hall-Héroult process has been significantly improved during the last few decades. This has been achieved mainly as a result of improved cell design and suitable process control strategies that have allowed higher cell currents and smaller anode-cathode distance (ACD). Without taking suitable corrective actions, operations at lower ACD conditions can negatively impact aluminum re-oxidation, by-pass current, alumina dissolution and anode effect rates. Superior operational practices are therefore required to maintain acceptably low instability levels along with lower specific energy consumption. This paper discusses anode effect fundamentals and greenhouse gas emissions in relation with industrial cells operating at low ACD at the Aluminerie Alouette plant in Quebec.     

Mathematical simulation of gas induced bath flow in drained aluminum reduction cell

A mathematical model describing the bubble driven bath flow in a drained cell with a center sump was presented, which spanned the fluid around half an anode and was developed to simulate the flow fields. The calculated results show reasonable agreement with the experiment. Then the model was developed to a full cell model, and bath flow pattern in the whole cell was predicted and analyzed. The flow pattern variation with the changes of the ACD, anode slope, anode immersion depth and current density, especially the fluid secondary recirculation, was modeled. According to the results, side channel or slots feeding technique was recommended in such a drained cell.     

Numerical Simulation of Alumina-Mixing Process with a Multicomponent Flow Model Coupled with Electromagnetic Forces in Aluminum Reduction Cells

An extended computational fluid dynamics model combined with the driving forces of anode gas bubbles and electromagnetic forces (EMFs) was developed for the alumina-mixing process in aluminum reduction cells. A practical feeding scheme and the consuming rate of alumina depending on the local current intensity of the bath–metal interface were considered in the simulation. A comparative numerical study was carried out using the models with and without considering the EMFs. The results show that considering different driving forces in modeling can lead to different results for alumina mixing in the cell. The existence of the bubble movement makes alumina disperse more quickly in local areas, and it greatly contributes to the vertical dispersion in the early stage of mixing. The EMF plays a more important role in the long-range transportation of alumina in the cell. Both forces should be taken into consideration in the modeling because they have a positive influence on distribution uniformity and the dispersion rate of alumina.     

300 kA预焙铝电解槽温度和初晶温度的自适应模糊控制

采用自适应模糊技术,设计了300kA预焙槽电解质温度和初晶温度的控制系统.该系统包括参数采集,参数网络传输和参数预处理,专家知识规则库、模糊逻辑决策,参数辨识、模糊规则自适应,人机界面和执行机构等模块.通过调整氟化铝添加量、出铝量和设定电压,以及氧化铝下料间隔的自修正,实现对电解槽温度、初晶温度、效应系数的控制.该系统在常规模糊控制基础上,通过变化在线辨识参数,得到系统自适应不同的电解槽.系统的输入参数除传统的电压、温度和分子比外,还采用初晶温度、过热度和阴极压降等作为系统的输入参数.控制系统在我国某厂300 kA铝电解槽上运行9个月,电流效率达94.3%,效应系数为0.08,每吨铝的直流电耗13 000kW·h.     

立式高压电机转子铸造模具排气方案的探讨

结合铸铝转子形状特点与工艺特点,阐述了立式高压铸造模具排气系统的设计方案.排气方案在型腔内采用排气塞排气为主,排气槽向四周排气为辅的排气方案.该方案成功地解决了转子短路环铸件内存在大而多气孔的问题.     

葡萄糖对铝合金电极电化学活性及自腐蚀的影响

针对铝-空气电池放电时铝合金阳极自腐蚀严重的问题,利用失重法、线性扫描伏安法等电化学方法研究了葡萄糖作为铝合金阳极缓蚀剂的缓蚀效果,以及葡萄糖对铝合金阳极电化学性能、空气电极电化学性能的影响,并利用XRD及金相组织形貌对放电后的铝合金阳极表面进行葡萄糖的缓蚀机理分析。结果表明,添加葡萄糖能够使铝合金阳极利用率由45%提高至90%,能适当提高铝合金阳极的电流密度约12 mA/cm2,且几乎不影响空气阴极的电化学性能。XRD及金相组织表明,添加葡萄糖能够促使铝合金阳极表面放电过程中产生的氢氧化铝脱落而使铝合金表面光滑平整。     

高效喷气精炼过程中的机械搅拌

在喷气精炼过程中,气泡的分散和细化是提高精炼效率的必要条件。在水模型实验中应用了单向的偏心搅拌模式来寻找最佳的气泡微细化条件。影响气泡微细化的因素有：搅拌模式、偏心度、搅拌转速、喷嘴结构、喷嘴的浸入深度以及气体流量。气体的喷入方式包括两种,一是从搅拌桨下方的喷嘴中直接喷入,二是从一个位于搅拌桨下方的弯管中喷入。在偏心搅拌模式下,漩涡远离了搅拌桨的轴心,小气泡产生于搅拌桨附近的强湍流或高剪切应力场中,随着机械搅拌产生的宏观流向漩涡方向移动。因此,单向的偏心搅拌模式能促进气泡在溶池内的细化和分散。