Effect of electromagnetic force and anode gas on electrolyte flow in aluminum electrolysis cell

1 INTRODUCTIONThe movement of electrolyte has a veryi mpor-tant influence on the process of aluminumelectrol-ysis[1]. On one hand,the movement of electrolytecan help anode gas release ,accelerate the dissolu-tion and diffusion of alumina and eli minate temper-ature gradient of electrolyte ,and enhances the heattransfer between electrolyte and the freeze . Ontheother hand,the movement of electrolyte can makealuminumfluid fluctuate , causing aluminum cellsto unstably operate and re-oxidation…     

固体氧化物燃料电池阳极材料La0.8Mg0.2Cr0.8M0.2O3-δ（M=Zn,Al,Zr）的研究

采用Sm0.2Ce0.8O1.9(SDC)作为电解质材料,La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF)作为阴极材料,以溶胶—凝胶法制备的La0.8Mg0.2Cr0.8Zn0.2O3-δ,La0.8Mg0.2Cr0.8Al0.2O3-δ,La0.8Mg0.2Cr0.8Zr0.2O3-δ粉体作为阳极材料,组装硫氧固体氧化物燃料电池。分别以硫蒸汽和二氧化硫气体为燃料气,测试电池阳极材料性能。结果表明:以硫蒸汽为燃料,La0.8Mg0.2Cr0.8Zn0.2O3-δ在750℃达到最大开路电压420 mV,此时最大功率密度为23 mW/cm2;以二氧化硫为燃料,La0.8Mg0.2Cr0.8Zn0.2O3-δ在650℃获得最大开路电压162 mV,最大功率密度为2 mW/cm2。催化效果顺序为La0.8Mg0.2Cr0.8Zn0.2O3-δ>La0.8Mg0.2Cr0.8Al0.2O3-δ>La0.8Mg0.2Cr0.8Zr0.2O3-δ。     

新型中温SOFC阴极Ba_(0.6)Sr_(0.4)Co_(0.9)Nb_(0.1)O_(3-δ)的制备与性能研究

采用固相反应法合成了中温固体氧化物燃料电池(IT-SOFCs)阴极材料Ba0.6Sr0.4Co0.9Nb0.1O3-δ(BSCN)。利用XRD对该材料的结构进行了表征。研究表明,室温下阴极材料BSCN成立方相结构(Pm-3m);将该阴极材料与电解质Ce0.9Gd0.1O1.95(GDC)混合,并在1 000℃煅烧10h后,它们之间无化学反应发生。在SOFCs的操作温度(600～800℃)下,BSCN阴极的电导率可达21～27S/cm。热膨胀测试表明,BSCN的热膨胀系数为17.0×10-6/K,明显低于SrCo0.9Nb0.1O3-δ(SCN)的热膨胀系数,这有利于提高阴极与电解质GDC间的热匹配性。以BSCN作电极,GDC作电解质,制备对称电池BSCN/GDC/BSCN,研究电极与电解质间的极化阻抗。750℃时,极化阻抗仅为0.026Ω.cm2。以BSCN作阴极,NiO-SDC(NiO-Ce0.8Sm0.2O1.9)作阳极,300μm厚的GDC作电解质,制备单电池BSCN/GDC/NiO-SDC。800℃时,单电池的最大功率密度可达782mW/cm2。以上结果表明,BSCN有望成为中温固体氧化物燃料电池阴极的候选材料。     

Effect of working condition on thermal stress of NiFe2O4-based cermet inert anode in aluminum electrolysis

Based on the FEA software ANSYS,a model was developed to simulate the thermal stress distribution of inert anode.In order to reduce its thermal stress,the effect of some parameters on thermal stress distribution was investigated,including the temperature of electrolyte,the current,the anode cathode distance,the anode immersion depth,the surrounding temperature and the convection coefficient between anode and circumstance.The results show that there exists a large axial tensile stress near the tangent interface between the anode and bath,which is the major cause of anode breaking.Increasing the temperature of electrolyte or the anode immersion depth will deteriorate the stress distribution of inert anode.When the bath temperature increases from 750 to 970 ℃,the maximal value and absolute minimal value of the 1st principal stress increase by 29.7% and 29.6%,respectively.When the anode immersion depth is changed from 1 to 10 cm,the maximal value and absolute minimal value of the 1st principal stress increase by 52.1% and 65.0%,respectively.The effects of other parameters on stress distribution are not significant.     

Simulation of the influence of the baffle on flowing field in the anode baking ring furnace

In an anode baking horizontal flue ring furnace, the temperature distribution is one of the key factors influencing the quality of baked anode and is closely correlated with the gas flow. To understand the gas flow distribution in the flue, Navier-Stokes equation with “k-ε“ two-equation turbulence model was adopted and the simulation on the gas flow was performed. The numerical simulation results showed that the even direction of gas flow should be considered in the design of flue baffles and the gas flow distribution was really uneven in the flue in practical use. By adjusting the number and location of flue baffles rationally, the even distribution of gas flow can be improved obviously.     

变截面异型螺旋型腔电解加工流场分析

针对闭式整体构件电解加工间隙流场分布不均匀的,基于电解加工间隙流场,设计了阴极过水孔工作端面,比较了不同背压条件下电解加工间隙流场,分析了间隙流场空穴、涡流现象.研究结果表明,通过改变过水孔分的疏密,孔径的大小和形状,增加背压,消除了间隙流场中低流速区域,电解液较低流速区域的速度由0.239 7m/s提升至0.508 5m/s,减少了空穴和涡流现象的发生,优化了阴极结构.     

交指状流场质子交换膜燃料电池的数值分析

为研究流场结构设计对电池内的流动、组分传递和电池性能等的影响,建立了一个稳态的三维非等温质子交换膜燃料电池数学模型,应用此模型对一个交指状流场设计的电池单体（电极面积为64 cm ×65 cm）进行了数值研究.数值计算得到了电池的温度、组分质量浓度和局部电流密度等的空间分布,分析了不同电池反应物湿度等对电池特性的影响.结果表明,受传质的影响,沟道下方阴极催化层的温度大于相应沟脊下方的区域;与饱和气流进气的基本工况相比,降低阴极的进气湿度能提高电池的性能,而降低阳极的进气湿度则会导致电池性能的下降.     

虚火花放电初始过程的PIC模拟

比较了两种计算气体放电的模型——流体模型和PIC模型。利用PIC方法对虚火花放电初始放电过程进行了计算机模拟,揭示了三个放电阶段电离增长的特点。对不同的气压和阴极孔径下虚阳极的形成时间和传播速度进行了模拟计算。较高的气压和较大的阴极孔径能够加速虚阳极的形成,并加快向空心阴极扩展速度。研究了较高气压和低气压下空心阴极效应在形成虚阳极过程中的作用。在低气压下,空心阴极效应在起始放电过程中具有重要作用。     

阴极流道对PEM燃料电池性能影响

目的研究阴极流道变化对PEM燃料电池性能的影响,比较不同阴极流道下的PEM燃料电池的性能和稳定性,优化阴极流道,找出阴阳极流道的最佳组合.方法运用燃料电池测试系统测量了PEM燃料电池的性能参数,比较在相同操作参数,相同阳极流道,不同的阴极流道对电池性能的影响.结果阳极交指/阴极交指流场燃料电池性能最好,阳极交指/阴极蛇形流场燃料电池性能其次,阳极交指/阴极平行流场燃料电池性能最低.阳极流道与阴极流道的最佳组合为阳极交指流道、阴极交指流道组成的流场为最佳组合流场.结论实验结果对PEM燃料电池的流道优化组合具有重要的参考作用,为其推广应用提供了参考依据.     

A method of determining and designing the drained slope in drained aluminum reduction cells

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Preparation and electrochemical properties of polymer Li-ion battery reinforced by non-woven fabric

A polymer electrolyte based on poly(vinylidene) fluoride-hexafluoropropylene was prepared by evaporating the solvent of dimethyl formamide, and non-woven fabric was used to reinforce the mechanical strength of polymer electrolyte and maintain a good interfacial property between the polymer electrolyte and electrodes. Polymer lithium batteries were assembled by using LiCoO2 as cathode material and lithium foil as anode material. Scanning electron microscopy, alternating current impedance, linear sweep voltammetry and charge-discharge tests were used to study the properties of polymer membrane and polymer Li-ion batteries. The results show that the technics of preparing polymer electrolyte by directly evaporating solvent is simple. The polymer membrane has rich micro-porous structure on both sides and exhibits 280% uptake of electrolyte solution. The electrochemical stability window of this polymer electrolyte is about 5.5 V, and its ionic conductivity at room temperature reaches 0.151 S/m. The polymer lithium battery displays an initial discharge capacity of 138 mA·h/g and discharge plateau of about 3.9 V at 0.2 current rate. After 30 cycles, its loss of discharge capacity is only 2%. When the battery discharges at 0.5 current rate, the voltage plateau is still 3.7 V. The discharge capacities of 0.5 and 1.0 current rates are 96% and 93% of that of 0.1 current rate, respectively.     

电解质掺杂Na2SO4对固体氧化物燃料电池性能的影响

以不同含量的Na2SO4掺杂YSZ（Y2O3稳定的ZrO2,Y2O3的摩尔分数为8％）为复合电解质,Co3O4为阳极催化剂,La0.7Sr0.3MnO3为阴极催化剂,组装固体氧化物燃料电池,以二氧化硫气体为燃料气,测试复合电解质材料电池的电化学性能.结果表明：以质量分数为25％的Na2SO4＋YSZ为复合电解质的电池在700℃时,获得最大开路电压372mV,功率密度7.87mW·cm-2.以不同含量的Na2SO4掺杂YSZ作为复合电解质时,电池的电流密度和功率密度的高低顺序均为：质量分数25％的Na2SO4＋YSZ＞质量分数16％的Na2SO4＋YSZ＞质量分数8％的Na2SO4＋YSZ＞质量分数50％的Na2SO4＋YSZ＞YSZ.     

电解法合成高铁酸钠的实验研究

通过改变传统电极设置位置,评定影响电解效率的各因素以实现电流效率的最大化.在简化电解装置的同时,不影响电流效率的提高.实验结果表明,将传统左右式设置电极改为上下式设置电极,阴极距液面2cm,阳极距底面4cm,电流密度2mA/cm2,NaOH浓度14mol/L,温度60℃,电解1.5h,并加入搅拌的情况下电流效率最大达到58%.     

埋地燃气管道牺牲阳极阴极保护法的改进

分析我国城镇埋地燃气管道的腐蚀原理,介绍阴极保护在城镇燃气管道防腐中的应用,从测试桩结构的改进、阳极布局原则的调整和测试桩布局原则的调整三个方面阐述了对牺牲阳极阴极保护法的改进。对埋地燃气管道的腐蚀防护有一定的借鉴作用。     

单室空气阴极微生物燃料电池性能

以石墨毡为阳极、Pt/C为阴极、葡萄糖模拟废水为基质构建了一个单室空气阴极微生物燃料电池(air-cathode microbial fuel cell,ACMFC),研究了电池内流体、不同葡萄糖底物质量浓度等条件对电池产电性能及污水处理效果的影响.研究结果表明:水流流量为15 mL/min、葡萄糖底物的质量浓度为1.0 g/L时,电池的最大功率为85.9 mW/m2,ACMFC运行48 h,对模拟废水的COD去除率可达81.6%.     

Removal of nickel from spent electroless nickel-plating bath with nickel foam cathode

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电动修复技术处理铬污染黏土试验研究

利用电动修复技术对红星化工厂铬渣污染黏土进行修复,试验电压分别为20,30,40,50,60V,以0.1mol/L KCl为两极电解液,阴极采用乙酸控制pH值在6左右,试验周期为5d.结果表明：电动修复能够去除土样中的铬,最高去除率可达58.26%;本试验50V即1.25V/cm电压梯度为经济有效的去除电压;Cr（Ⅵ）以含氧阴离子的形式向阳极迁移,Cr（Ⅲ）迁移较复杂,在沉淀态和游离态之间转换;阳极电解液中Cr（Ⅵ）的浓度易达到饱和,对Cr（Ⅵ）的去除产生抑制.     

Effect of atomization gas pressure variation on gas flow field in supersonic gas atomization

In this paper, a computational fluid flow model was adopted to investigate the effect of varying atomization gas pressure (P0) on the gas flow field in supersonic gas atomization. The influence of P0 on static pressure and velocity magnitude of the central axis of the flow field was also examined. The numerical results indicate that the maximum gas velocity within the gas field increases with increasing P0. The aspiration pressure (ΔP) is found to decrease as P0 increases at a lower atomization gas pressure...     

Performance of a thermally regenerative ammonia-based battery using gradient-porous copper foam electrodes

Gradient-porous copper foam electrodes were applied to alleviate the adverse effects of the uneven current distribution of electrodes along the electrolyte flow direction in thermally regenerative ammonia-based batteries(TRABs). The results indicated that gradient-porous copper foam with a decreasing pore size(TRAB-LMS) provided the most uniform current distribution and generated the highest power density(15.5 W/m~2), total charge(1800 C) and energy density(1224 W h/m~3). With the increase in flow rate, the power density of the TRAB-LMS increased considerably within a certain range and then decreased slightly, with the optimal flowrate at 15 mL/min. Under the optimal flow rate, the performance of TRAB-LMS increased when the ammonia concentration rose from 0.5 to 2 M(1 M=1 mol L~(-1)); however, it decreased slightly when the ammonia concentration further increased to 3 M. The slight decrease in the cathode potential suggested that the flow and ammonia concentration beyond the optional values facilitated not only the transfer of ammonia into the porous anode, but also the crossover of ammonia from the anode to the cathode.     

Mechanism of Capacity Fading Caused by Mn(Ⅱ) Deposition on Anodes for Spinel Lithium Manganese Oxide Cell

The capacity fade of spinel lithium manganese oxide in lithium-ion batteries is a bottleneck challenge for the large-scale application.The traditional opinion is that Mn(Ⅱ) ions in the anode are reduced to the metallic manganese that helps for catalyzing electrolyte decomposition.This could poison and damage the solid electrolyte interface(SEI) film,leading to the the capacity fade in Li-ion batteries.We propose a new mechanism that Mn(Ⅱ) deposites at the anode hinders and/or blocks the intercalation/de-intercalation of lithium ions,which leads to the capacity fade in Li-ion batteries.Based on the new mechanism assumption,a kind of new structure with core-shell characteristic is designed to inhabit manganese ion dissolution,thus improving electrochemical cycle performance of the cell.By the way,this mechanism hypothesis is also supported by the results of these experiments.The LiMn_(2-x)Ti_xO_4 shell layer enhances cathode resistance to corrosion attack and effectively suppresses dissolution of Mn,then improves battery cycle performance with LiMn_2O_4 cathode,even at high rate and elevated temperature.