Studies on the corrosion and the behavior of inert anodes in aluminum electrolysis

The corrosion rates of inert anodes based on tin oxide and nickel ferrite cermet materials were studied as a function of some operating parameters. To reach a better understanding of the corrosion mechanism, the behavior of the anodes was observed under some specific conditions, such as in pure cryolite, at high current densities, at different potentials, and at varying cathode surface areas. It was confirmed that low alumina concentrations led to catastrophic corrosion of the anodes and that high current densities and high as well as low NaF/AlF₃ molar ratios were also detrimental. The corrosion rate of tin oxide based anodes showed a minimum (so-called “normal corrosion”) at anodic potentials of 2.2 to 2.4 V with respect to aluminum. The normal corrosion is due to chemical dissolution of the anode material and reduction of the corrosion products into the cathode metal. The corrosion rate increased with increasing cathode surface area. At potentials higher than ～2.5 V, the anodes showed catastrophic corrosion. Catastrophic corrosion can be ascribed to decomposition of the anode material by depletion of alumina at the anode surface provoked by low bulk concentration of alumina and/or high current density.     

新型铝电解槽控制系统

通过工业试验研究,摸索出了铝电解槽表观电阻与氧化铝浓度之间的关系曲线。在此基础上,通过对试验数据的解析,建立了氧化铝浓度模糊控制模型,实现了名电解槽按需下料,极大地降低了阳极效应系数。同时开发出槽况自诊断,极距调整,设定电压自修正,阳极效应预报等模型,并成功地应用于基于ＰＬＣ控制的一种新型铝电解槽控箱中。     

Heat transfer and fluid flow in the welding arc

Through the numerical solution of the Navier/Stokes equation, the energy transport equation, and the magnetic diffusion equation, a mathematical model has been developed to predict the velocity, temperature, and current density distributions in inert gas welding arcs. Although the model has one adjustable parameter, the cathode current density, it was found that a single value of this variable was sufficient to provide internally consistent results for a range of arc lengths and arc currents representative of welding. The computed temperature distributions in the arc were found to be in good agreement with spectroscopically measured temperatures taken from the literature, and similar agreement was obtained between the predicted and measured current density distributions at the surface of water cooled copper anodes. The mechanisms of heat and momentum transfer to the anode were investigated in the light of recent findings concerning the anode boundary layer and the presence of negative anode fall voltages. The predicted convective heat fluxes to the anode were found to be generally consistent with experimental data.     

Corrosion of Zinc Ferrite Based Inert Anodes in AlF3-NaF-Al2O3 Melts Under Conditions of Anodic Polarization

ZnFe2O4-based inert anodes were made to conduct the aluminum electrolysis tests. The corrosion behaviors of the inert anodes were examined and discussed. Experiment results prove that: (1) ZnFe2O4-based inert anodes are good corrosion resistant to AlF3-NaF-Al2O3 melts under the conditions of anodic polarization; (2) High anodic current density(＞1.5 A·cm-2), high alumina concentration and low ratio of NaF/AlF3 in the molten salts will be the most important conditions for using inert anode.     

湿法提铜电积工程实践及添加剂优化探讨

总结了国内外铜电积的工程实践,对铜电积过程添加剂进行优化。结果表明,铜电积液添加Co2+有利于减缓阳极腐蚀速度和降低阳极电位,合适的Co2+浓度为100mg/L;古尔胶有利于生成表面光滑、平整的阴极铜,适宜用量为每吨铜50g;硫脲在不同的电流密度下对阴极铜质量影响不同;铜电积液不适宜添加盐酸。     

Motion dynamics of anodic gas in the cryolite melt–alumina high-temperature slurry

The results of physical simulation of the behavior of bubbles formed due to the electrochemical evolution of oxygen on an inert anode during the high-temperature electrolysis of alumina slurry in the fluoride melt are presented. Similarity criteria are calculated, the experiments for a water model with vertically oriented electrodes are performed, and the data on the behavior of bubbles in the slurry are found with the help of video recording. The 20% aqueous solution of sulfuric acid with an alumina content of 30 vol % was used as the model electrolyte. The experiments were performed in a range of current densities from 0.05 to 0.25 A/cm². Video was recorded using a Nikon D3100 camera with a recording frequency of 30 frames/s. The data on the motion dynamics of the bubbles, the quantitative data that characterize coalescence, and the bubble lifting velocity are found. To determine the average lifting velocity, 125 bubbles were analyzed. They were 0.8–2.3 mm thick. The bubble motion is performed in the slug regime with lifting velocity of 1.0–2.3 cm/s. The bubble layer thickness was about 5 mm. Further investigations will be directed to finding new data on the behavior of bubbles for various solid phase contents, current density, electrode slope angle, and granulometric composition.     

Electrochemical anodic dissolution of FeCuNiCoMn alloy in ammonium solutions containing clorine ions

The effect of chlorine ion concentration, temperature and current density on metal distribution among the electrolyte, cathode deposit and mud in the process of electrochemical dissolution of FeCuNiCoMn alloy in an ammonium medium is examined. High iron content (65.90%) compared to that of non-ferrous metals (12.07% Cu, 12.81% Ni, 1.30% Co) and Mn 5.33% is a specific feature of the alloy. The alloy was produced by means of high-temperature reduction smelting of manganese nodules from the Clarion Cliperrton area in the Pacific Ocean. It was found that electrochemical dissolution of the alloy is accompanied by formation of a CuNiCo-cathodic deposit and two types of mud: one tightly clinging to the anode surface, and another, finely suspended in the electrolyte. The highest-purity cathode deposit in mass %: 40.28 Cu, 50.27 Ni, 1.21 Co, 7.63 Fe and 0.61 Mn was obtained at ion ratio in the solution NH₄⁺: Cl⁻ = 2.5: 0.5, temperature 323 K, anodic current density 350 A/m², separation of the anode and cathode spaces by a shielding screen, continuous removal of the anodic mud and maintaining of a constant pH in the electrolyte (10 ± 0.2). In these conditions, >99% of Fe and Mn, 25% Cu, 54% Ni and 52% of Co is transferred into the mud.     

降低大型预焙铝电解槽阳极效应的实践

本文总结了某公司300 kA预焙铝电解槽降低阳极效应的管理及生产实践,提出控制工艺技术条件和氧化铝浓度、提高现场操作质量和改进设备管理是有效降低阳极效应系数的保证,同时深入分析了提高效应管理的途径。     

基于分布式感知的氧化铝浓度动态仿真

氧化铝浓度的分布与电解过程的电流效率、温室气体排放及运行稳定性等参数都息息相关。针对传统铝电解多相多场的离线仿真速度响应不及时、对硬件要求高、仿真结果无法在线或直接用于指导生产实践等问题，将离线仿真数据与检测数据有效融合，开展铝电解动态仿真的研究，即基于实时阳极电流信号及未来预测值，结合动态U型曲线关系，在CFD氧化铝浓度的离线仿真结果库的基础上，对氧化铝浓度进行了动态仿真。为最终实现铝电解数字孪生体分布式信号采集-电流预测-氧化铝浓度动态仿真的一体化提供先进思路与技术方法。     

双向平行流铜电解生产实践

从电解液温度、电解液中铜和酸的浓度、阳极泥沉降、结垢清洗等方面对顶侧双向平行流和底侧双向平行流铜电解槽生产情况及条件进行比较。结果表明,顶侧双向平行流有利于阳极泥沉降,可降低阴极铜含银,阳极泥清洗时间短;底侧双向平行流电解液流动更为简单,循环条件好,但不利于阳极泥沉降、不便于清洗。高银阳极宜采用顶侧双向平行流,利于提高银回收率;低砷高锑高杂阳极,阳极中摩尔比As/(Sb+Bi)<2,阳极泥沉降差,宜采用顶侧双向平行流,提高阳极泥沉降;高电流密度(大于400 A/m²),阳极中摩尔比As/(Sb+Bi)>2,阳极泥沉降好,宜采用底侧双向平行流,循环条件更好。     

Electrochemical Reduction of 2,4-Dinitrotoluene in a Continuous Flow Laboratory Scale Reactor

An electrochemical laboratory scale reactor was used to treat 2,4-dinitrotoluene (DNT). Experiments were conducted by using a graphite carbon cylinder impregnated with glassy carbon (zero porosity) as the cathode and a platinum wire as the anode. All experiments were conducted under anoxic conditions. Initially, experiments simulating batch conditions were conducted to obtain the optimum operating conditions for the reactor. During this batch-mode study, the effect of various parameters such as applied current, electrolyte concentration, and type of electrolyte on the reduction of DNT were evaluated. Results showed that the rates of DNT reduction increased with an increase in current or concentration of electrolyte. Based on the results obtained from the batch simulation experiments, continuous flow experiments were conducted at three different currents and one electrolyte concentration. The ionic strength of the feed solution was maintained at 0.027 M. A current of 200 mA (current density 0.088 mA/cm2) provided a stable reduction of DNT at the 80% level for a period of 14 days after which reactor cleaning was necessary for removal of suspended solids that were formed within the reactor. End products determined for the experiments showed 80–100% molar balance closure.     

电解法制备高纯钛的研究

以海绵钛为可溶阳极,纯钛板为阴极,NaCl-KCl-TiClx混合熔盐作电解质,在900～980℃温度范围内进行熔盐电解,研究了加料温度、电解温度、可溶钛浓度以及阴极电流密度等因素对阴极产品杂质含量的影响。结果表明,在较高温度下加料并电解可获得杂质含量低的产品,通过控制可溶钛浓度和阴极电流密度可获得不同形貌和纯度的阴极产品。     

铝电解槽氧化铝浓度的模糊控制

应用模糊控制理论，对铝电解槽氧化铝浓度的控制方法进行研究，首先对电压和电流采样，滤波，解析得到氧化铝浓度，控制器以氧化铝浓度的偏差为输入，氧化铝加料间隔为输出，然后通过考察氧化铝浓度曲线，总结前人控制经验得出模糊控制规则，并以物料平衡作为辅助校验，最后通过C语言编程实现控制过程。     

硅钛负极储锂过程交流阻抗分析

为研究钛含量对硅钛负极电化学储锂反应动力学过程的影响,通过交流阻抗分析法测试了硅钛摩尔比分别为50和25时,硅钛负极在200mA/g电流密度下充放电100圈后的电阻值。结果表明,降低硅在复合材料中的含量有利于减少SEI(Solid Electrolyte Interphase,固体电解质膜)的生成量、降低电荷转移电阻值。当硅钛摩尔比为25时,负极具有更好的电极反应动力学过程,电荷转移阻抗从初始阶段142Ω增加至212Ω。     

钕电解相关物质理论分解电压的计算

本文计算了NdF3-LiF-Nd2O3体系各物质的理论分解电压。结果表明,采用惰性阳极,理论分解电压按Nd2O3、NdF3、LiF顺序依次增大,温度升高,理论分解电压降低;采用活性阳极(石墨)时,Nd2O3与石墨反应生成CO和CO2,其理论分解电压较小,反应较易发生,尤以生成CO的反应更易发生。但当电流密度较高或Nd2O3浓度较低时,可能生成碳氧氟化合物及氟碳化合物,并发生阳极效应,各物质的理论分解电压也随温度的升高而降低。     

Simulation of the Fluid Flow-Related Phenomena in the Electrolyte of an Aluminum Electrolysis Cell

A full-scale water model and mathematical simulation were used to study the fluid flow-related phenomena in a water model of an aluminum electrolysis cell. The time-dependent, multiphase fluid flow model was developed to represent the complex transient flow in the electrolysis bath. The accuracy of the mathematical model was validated by the ink dispersion and laser doppler velocimetry measurements in the water model. The shape, motion, release frequency of large-size bubbles, the fluid flow pattern, and the electrolyte–metal interface were predicted by the mathematical simulation. The design and operation of the anode were discussed, including the effect of the anode edge corner shape, the presence of a tilted bottom angle, and the magnitude of applied current density. The results indicated that coupling using a curved corner, with slot and with tilted angle at the anode, is effective for the release of bubbles and for the stability of the electrolyte–metal interface.     

一次电解生产4N5精铟的试验研究

本工艺是通过系列试验,考察了在低电流密度下,采用不同的阴极材料,调整电解液中铟离子和氯化钠浓度以及粗铟阳极中铅锡含量的变化对精铟质量的影响。通过试验数据分析,确定各种技术条件和各类杂质对精铟质量的影响,提出提高精铟直产率的措施,确定了铟电解精炼最佳技术操作条件,确保一次电解生产4N5合格精铟,从而实现降低生产成本,提高生产效率。     

铝电解槽阳极极距构成模型及工艺能耗

计算了普通电解槽生产中通常的阳极极距,提出了阳极极距“三层构成模型”及“极限阳极极距”概念,用此理论对目前研究中的低槽电压生产仍能获得较好生产指标进行了解释,并展望了铝电解工艺能耗能达到的可能范围：在阳极电流密度为0．8A／cm^2左右时,电解直流电耗可达到9500kWh／t—Al左右．     

硫酸体系中Ni-MnO2同时电沉积的研究

研究了温度、电流密度和电解液pH值等对硫酸体系中Ni MnO2 同时电解过程的影响 ,通过正交试验确定了电解过程的最佳工艺条件为 :[Ni2 +] 90 g/L ;[Mn2 +] 30 g/L ;pH 3 5;90℃ ;电流密度 16 5A/m2 ;[H3 BO3 ] =15g/L ,槽电压 2 86V ,此时阴极电效为 99 88% ,阳极电效接近 10 0 % ,得到的阴极镍纯度为 99 87% ,阳极MnO2 品位为 87 85%。     

Modeling of fluid flow and heat transfer in the plasma region of the dc electric arc furnace

A mathematical model describing the transport processes in the plasma arc in dc electric arc furnaces has been developed. The equations of conservation of mass, momentum, and energy are solved numerically in conjunction with Maxwell's equations of the electromagnetic field to calculate the velocity and temperature distributions in the plasma region. The heat transfer from the arc to a rigid anode surface is calculated. The model is applied to obtain quantitative results on the relative importance of the various modes of heat transfer from the electric arc to the anode surface. Computational results were obtained for varying arc current magnitudes and anode-cathode distances. The model predicts higher arc jet velocity and a broader arc core at higher arc current. The shorter arc length is more efficient for transferring heat to the anode.