气体扩散阳极在湿法炼锌上的应用

介绍了气体扩散阳极(氢扩散阳极)在湿法炼锌上的节能降耗原理,用气体扩散阳极代替普通阳极将降低50%左右的能耗;与此同时,介绍了氢扩散阳极的结构并对它在冶金上的应用进行了展望。     

湿法炼锌节能新工艺研究

研究了湿法炼锌工艺中电解时用ＳＯ２的阳极氧化代替传统炼锌工艺中的阳极反应，以降低电解的槽电压并达到节能目的。同时考察了各种因素对槽电压的影响。     

电解锰节能措施的研究现状

金属锰主要通过湿法冶金获得的,而金属锰的电解能耗非常高,如何降低金属锰的电解能耗成为了研究热点。本文主要介绍了电解锰所用阳极材料、阳极结构、添加剂、阴离子交换膜等四个方面的研究进展,其中对阳极材料及其结构改性进行了重点阐述,并对目前电沉积锰阳极存在的缺陷,提出了相应的解决策略。最后,对电解锰节能的发展方向进行了展望。     

金属氧化物电极在湿法冶金中的应用

<正> 水溶液电解制取金属是湿法冶金的一个重要组成部分,用以制备锌、铜、锰、镉等多种有色金属。电解中要求阳极材料具有较高的耐蚀性和较低的电位。目前在湿法冶金中大量采用的不溶性阳极是石墨和铅银合     

电解铜过程中阳极钝化的研究

阳极钝化会降低生产效率和产品质量,并增加铜电解的成本.阳极钝化是因为在阳极上形成了氧化薄膜,钝化前电势会产生波动,这是杂质、硫酸铜和氧化铜共同作用造成的.阳极泥可以减小孔隙和抑制扩散,导致生成硫酸铜沉淀,从而减小了阳极的电解面积.     

新型酸雾抑制剂FC-1100的应用研究

介绍一种新型酸雾抑制剂FC-1100,通过该试剂在我国某湿法炼铜厂的试验结果表明:FC-1100酸雾抑制剂可以有效地降低电解液的表面张力,使电解时阳极析出的氧气能顺利溢出,不把硫酸酸雾带出到空气中,达到降低空气中硫酸酸雾的效果。     

降低200 kA铝电解槽阳极效应系数的实践

本文论述了通过对电解相关设备的改进和工艺技术条件的优化,实现降低电解阳极效应系数和效应发生时间,达到降低电解能耗的目的,原铝交流电耗降低了150 kWh/t.Al,节能效果显著.     

从氯化铅和氯化亚铁混合溶液中电解提取铅

采用隔膜袋电解法从氯化铅和氯化亚铁的混合溶液中电解提取铅。通过维持隔膜袋里混合溶液小的静压头,避免含有三价铁离子的阳极液扩散进入阴极室。试验结果表明,在电流密度500 A/m2、阴极液中Pb2+质量浓度50 g/L、电解温度90℃、电解时间1.5 h的条件下,阴、阳极的电流效率分别达到95%、80%。     

锌电解能耗分析及节能对策

从理论上分析了影响锌电解过程电能消耗的各种因素—Zn 与 H_2SO_4浓度、液温、极距、阳极电位与过电压、电解液电阻、阳极膜电阻、接触电阻、电流密度以及电流效率等.并引入理论式进行计算,指出现行锌电解工艺节电极限为14～15%。同时提出了锌电解工序的节能对策以及今后的展望。     

国外湿法冶炼车间通风方式探讨

锌湿法冶炼浸出、净液及电解生产过程中有大量的酸雾、水蒸气等产生,车间工作环境恶劣,污染严重.作者考察了国外冶炼厂湿法车间,通过本文进行介绍,同时分析探讨反应槽废气处理及锌电解车间的通风方式与国内不同之处,提出改善工作环境、节能减排的设想.     

质子交换膜电解制氢氢气渗透研究进展

由于膜的吸水特性,高压质子交换膜(PEM)制氢（尤其是差压式,氢侧高压/氧侧常压）存在氢气渗透问题,影响电解堆的运行安全与效率。基于菲克定律描述的渗透通量与渗透率、分压差的关系,综述了温度/压力、膜水合程度、氢气分压差对氢气渗透的影响规律。在常规运行压力范围（3.5 MPa）内,扩散系数与溶解度主要受温度影响,温度升高则渗透率增大;氢气渗透率随膜水合程度的增加而增大;氢气分压差对渗透的影响表现出线性（渗透池环境）与非线性（电解制氢环境）两种关系,非线性可能源于膜透水性提升与水通道结构改变引起的对流渗透。考虑到电解制氢实际工况存在电流,综述了电流密度对氢渗透的影响,氢气渗透率随运行电流密度的升高而增大,氢过饱和是可能的影响机理,高电流密度下氢过饱和度升高,导致氢气通过膜的渗透增加。      

Electrochemical Characterization of a Solid Oxide Membrane Electrolyzer for Production of High-Purity Hydrogen

A laboratory-scale solid oxide membrane (SOM) steam electrolyzer that can potentially use energy value in waste or any source of carbon or hydrocarbon to produce high-purity hydrogen has been fabricated and evaluated. The SOM electrolyzer comprises an oxygen-ion-conducting yttria-stabilized zirconia (YSZ) electrolyte with a Ni-YSZ cermet cathode coated on one side and liquid-metal anode on the other side. The SOM electrolyzer is operated at 1000 °C by providing a steam-rich gas feed to the Ni-YSZ cermet cathode and feeding a reductant source into the liquid-metal anode. The steam is reduced over the cathode, and oxygen ions are transported through the YSZ electrolyte and are oxidized at the molten metal electrode by the reductant feed. The advantage of SOM electrolyzer over the state-of-the-art solid oxide electrolyzer is its ability to use solid, liquid, and gaseous reductant feed in the liquid-metal anode to reduce the oxygen chemical potential and drive the reaction for hydrogen production. In this study, an electrochemical process model for a SOM electrolyzer was developed. The condition of the liquid-metal anode with reductant was simulated by bubbling humidified hydrogen (3 pct H₂O) in the liquid metal, and the electrochemical performance of the SOM electrolyzer was modeled. The experimental data were curve-fitted into the model to identify the various polarization losses. It showed that the performance of the SOM electrolyzer was dominated by the ohmic resistance of the YSZ membrane. Based on the results of this study, future work is needed toward increasing the performance efficiency of the SOM electrolyzer.     

Grain boundary diffusion of hydrogen in nickel

Grain boundary diffusion of hydrogen in nickel was quantified through permeation measurements performed on fine-grained foils produced by electrodeposition. The permeation data were analyzed with a modified version of the Hart equation. The grain boundary diffusion coefficient at 30°C is at least 3 × 10⁻¹² m²/s, which is a factor of 40 greater than the lattice diffusion coefficient; however, the analysis indicates that a 1000-fold increase may not be unreasonable. The activation energy for grain boundary diffusion in this system is 30 kJ/mole, which is approximately three-fourths of the activation energy for hydrogen diffusion in single-crystal nickel. These results indicate that grain boundary diffusion should be considered in models of hydrogen transport during hydrogen-induced cracking of nickel and nickel-based alloys. Formerly Graduate Student, Department of Materials Science and Engineering, Massachusetts Institute of Technology     

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.     

A Comparative Study on Hydrogen Diffusion in Amorphous and Crystalline Metals Using a Molecular Dynamics Simulation

A comparative study on hydrogen diffusion in amorphous and simple crystalline structures has been carried out using molecular dynamics simulations. The Cu-Zr bulk metallic glass (BMG) system is selected as the model material and a modified embedded-atom method (MEAM) interatomic potential for the Cu-Zr-H ternary system is developed for the atomistic simulation. It is found that the diffusivity of hydrogen in amorphous alloys is lower than that in open structured crystals but higher than that in close-packed crystals. The hydrogen diffusion in amorphous alloys is strongly hydrogen concentration dependent compared to crystals, increasing as the hydrogen content increases, and the Arrhenius plot of hydrogen diffusion in amorphous alloys shows an upward curvature. The reasons to rationalize all the findings are discussed based on the variety of energy state and migration energy barrier for interstitial sites in amorphous alloys.     

A Computational Study of the Mass Transport Behavior of Hydrogen in In-Service Carbon Steel Pipeline Fillet Welds During Deposition and Desorption

Numerical calculations were used to study the diffusion and thermotransport of hydrogen during deposition and diffusion of hydrogen during desorption of in-service carbon steel pipeline fillet welds prone to hydrogen cracking. During deposition, only a small amount of hydrogen migrates into the HAZ and little migrates into the pipe. Thermotransport decreases the hydrogen concentration in the HAZ and regions of the weld closer to the HAZ, and increases the concentration toward the outer edge of the weld. This effect increases the rate of desorption of hydrogen from the weld, which increases with weld size/pipe wall thickness. The activation energy for desorption varies with the fraction of hydrogen removed and appears to be a function of the activation energy for diffusion and mass fraction of hydrogen in the weld, HAZ, and pipe. The differences in the desorption rate due to thermotransport appear to be due to differences in the activation energy for desorption and hydrogen concentration gradients. Maintaining a 121 °C preheat/interpass temperature during welding significantly reduces post-weld heating times necessary to reach hydrogen levels considered to be safe from hydrogen cracking. Calculated results and experimental results from another study show good agreement for desorption at 132 °C for up to 30 minutes.

     

钢中氢热脱附谱线影响因素的数值模拟

热脱附谱线分析已广泛用于研究高强钢中氢原子的吸收与扩散行为,以及氢原子与氢陷阱之间的反应动力学参数等。通过分析热脱附谱线峰值温度可获取氢陷阱的最重要参数：氢陷阱与氢原子之间的结合能。采用McNabb-Foster模型系统模拟研究钢中氢的热脱附谱线的影响因素。结果表明：除氢原子与氢陷阱之间的结合能之外,热脱附实验加热速率以及初始实验温度,样品尺寸、形状,氢原子在氢陷阱中的初始占有率,以及在样品中的分布等均能影响热脱附谱线的峰值温度以及形状,从而对氢陷阱与氢原子之间的结合能分析产生影响。同时基于局域平衡模型的模拟结果发现热脱附过程中氢原子从低结合能氢陷阱解析后可再次被高结合能陷阱捕获。     

La0.8Mg0.2(Ni2.7Co0.6Al0.1Mn0.1)x贮氢合金的电化学性能分析

采用恒电位法、EIS分析及双电极系统对La0.8Mg0.2(Ni2.7Co0.6Al0.1Mn0.1)x(x=0.9～1.10)系列合金进行电化学性能分析。结果表明,x=1.05的合金具有较好的自放电性能(CR=97.3%),而x=1.10的合金有较高的电化学容量(369 mAh.g-1)。合金电极的电化学阻抗谱(EIS)表明,随着化学计量比x的增大,合金电极的电荷迁移电阻先减小后增大,动力学性能先增强后减弱。线性极化测试表明,随着化学计量比x的增大,合金电极表面的电化学反应速率先增大后减小。通过合金电极阳极电流对时间响应的半对数曲线计算的氢扩散系数D随着化学计量比x的增大先增大后降低,说明合金内部的氢扩散能力先增强后降低。