堰板对氯碱电解槽阳极室温度场的影响

采用流体力学计算软件对阳极室单个隔栅进行了数值模拟,考察了堰板高度对离子膜表面温度分布的影响,研究堰板对氯碱工业离子膜电解槽阳极室温度场特性的影响。模拟结果表明:安装堰板后的阳极室内,电解槽内温度分布更加均匀,特别是在电解槽中部更加明显;膜面的温度分布比较均匀,在83~88℃之间,膜面最高温度出现在顶部个别区域。安装堰板后,膜面顶部高温区域明显减小,当循环板高度为700 mm时,膜表面最高温度最低,为92.3℃。     

基于CFD的塑料薄膜冷却性能分析

为了研究塑料薄膜的冷却成型过程,利用计算流体动力学(CFD)软件对塑料薄膜在平行流道流延辊上冷却过程进行数值模拟,得到了不同冷却水雷诺数和温度条件下薄膜的温度场。结果表明,薄膜温度分布为中间高两端低,且靠近冷却水入口一侧的温度低于另外一侧。薄膜冷却效率和宽度方向温度分布均匀性随冷却水雷诺数的增大而提高。薄膜冷却效率随冷却水温度的升高而降低,冷却水温度的升高有利于提高薄膜宽度方向的温度分布均匀性。     

如何提高金属阳极电解槽的电流效率(节选)

我国自78年金属阳极电解槽工业化至今已运转七年多了。金属阳极电解槽与石墨阳极电解槽相比,在很多方面充分显示了它的优越性,但是金属阳极电解槽电流效率不如石墨阳极电解槽高,石墨阳极电解槽国内阴极(总管)电流效率一般只有93～94％。国外金属阳极电解槽阴极(总管)电流效率一     

阳极孔隙率对固体氧化物燃料电池性能影响的数值分析

基于商用计算流体动力学软件及开发的燃料电池多孔介质内多组分流动和扩散、传热传质、电化学反应、电流场等复杂的物理过程的计算程序,对采用不同孔隙率阳极的平板式阳极支撑固体氧化物燃料电池(planar-electrode-support solid oxide fuel cell,PES-SOFC)的性能进行数值计算,得到不同阳极孔隙率下单电池内部各气体组分浓度、温度、电势、电流、电流密度等参数的分布。由计算结果可知,在阳极孔隙率为0.3～0.4之间时,以氢气为燃料的该类型SOFC单电池表现出较好的气体扩散和电流传导特性,相应输出电压也较高。     

电流密度对氯碱工业离子膜电解槽传递特性影响

为考察电流密度对氯碱工业中离子膜电解槽内流体传递特性的影响,利用流体力学计算软件,对不同电流密度下电解槽阳极室进行了数值模拟,得到了阳极室单个格栅内流体的速度、温度和浓度分布。以液体循环量、膜附近处速度的最大值、膜表面温度和浓度为指标,考察了不同电流密度下电解槽的运行情况。结果表明:随着电流密度的增加,电解槽内液体循环量增大,膜表面温度升高,盐水浓度降低;在电流密度为4.5 kA·m^-2的典型工况下,电解槽内平均温度为86.39℃,膜表面平均温度为87.40℃;当电流密度提高时,可以通过降低进口溶液温度,获得与典型工况相近的电解槽内平均温度和膜表面平均温度。     

微型直接甲醇燃料电池阳极传质分析

针对微型直接甲醇燃料电池,将阳极流场板简化为规则结构的多孔介质,运用多孔介质理论建立了包括流场板在内的阳极传输模型。模型考虑了阳极流道内液体饱和度沿流动方向的变化、催化层的厚度以及甲醇渗透,计算并讨论了阳极流道内液体饱和度的分布和流量对电池电流密度的影响,分析了阳极过电位对甲醇浓度分布和电池性能的影响以及质子交换膜内的传质特性。     

水银电解槽的改进

美国奥林·麦添逊化学公司最近对水银电解槽的设计作了一些改进。改进后的电解槽侧面如附图所示。这种新的水银电解槽的型号是E-11。它是从这个公司原来长期沿用的E-8型发展起来的。这次改进旨在加宽电槽,提高效率。要达到这个目的,必须同时考虑到放大阳极厚度,考虑到水银的分布情况以及分解室(水银电解槽的主要组成部分之一,另一主要组成部分是电解室)的容量等问题。在阳极的设计上,曾经进行过不少试验。先是从小型电解槽开始研究,据计算:6时厚的阳极比3时厚的要多出百分之之十的有效石墨。这一情况说明放大     

隔膜电槽的分布电压测量方法及探讨

通过对国内隔膜法金属阳极电解槽的调查,实感对现有隔膜电槽分布电压进行测量之必要。为加快金属阳极电解槽的推广、了解、掌握槽电压的分布规律,特向读者推荐关于隔膜电解槽分布电压的测量方法,供选择、设计金属阳极电解槽槽型,提供有关参考数据。     

循环板对氯碱电解槽阳极室浓度场的影响

为弄清氯碱工业离子膜电解槽阳极室内浓度场特性及电解槽几何结构对其影响规律,采用计算流体力学方法对阳极室单个隔栅进行了数值模拟,得到了单个隔栅内流体浓度分布。结果表明,循环板长度取800mm时,膜面浓度平均偏差可低至0.0194。     

金属阳极电解槽的维护及管理

金属阳极钌钛涂层自1968年问世以来,由于优点突出,迅速地被各国广泛应用于氯碱工业。金属阳极电解槽在我国已有十多年的历史。国内已有不少厂家陆续将金属阳极电解槽取代石墨电解槽。根据我厂金属阳极电解槽几年来的使用情况。谈谈对金属阳极电解槽的维护及管理。一、金属阳极电解槽使用前的准备金属阳极电解槽组装前,必须进行认真检查:(1)首先检查阳极网片的制作质量,     

离子膜法烧碱扩能后电解槽温度的控制

介绍离子膜电解槽槽温控制的重要性。介绍了扩能后槽温对电流效率、槽压和碱中含盐量的影响。提出采用蒸汽预热盐水、降低阳极液温度、降低原水加热温度等方式,将槽温控制在合理范围。     

Sensitivity Analysis for a Planar SOFC: Size Effects of the Porous Gas Diffusion Layer Underneath the Channel Rib

This paper investigates the size effects of the gas diffusion layer underneath the channel rib on the performance of a planar solid oxide fuel cell (SOFC). Based on 3‐dimensional numerical simulations, the sensitivities of the electrical performance parameters (Nernst potential and current density) and the thermal performance parameters (heat generation and temperature) are examined as a function of variations in the channel rib width and anode thickness. The sensitivity values of the Nernst potential and current density are calculated to guide the design of a cell in a planar SOFC. In particular, the changes in ohmic losses for the interconnectors and anode are analyzed as a function of the variations of the channel rib width and anode thickness. The variations of the mole fractions of hydrogen, oxygen, and water in the active areas of the channel rib and the channel are presented, which provide sensitivity profiles for gas diffusion with respect to changes in the anode thickness.     

浅议影响离子膜电解槽电流效率的因素

保持最佳的离子膜电解工艺操作条件是离子膜电解槽的操作关键,它能使离子膜长期稳定地保持较高的电流效率和较低的槽电压,进而稳定直流电耗,延长离子膜的使用寿命。本文详细分析了影响离子膜电解槽电流效率的因素,认为电解槽在运行过程中,要保持高的电流效率应做到:高质量的入槽盐水;适宜的阴极液浓度、阳极液浓度和适宜的电流密度;严格控制阳极液PH值;保持适宜的电解槽温度、电解液流量和稳定的高质量的无离子水供应。     

Characterization of an electrochemical reactor for the ozone production in electrolyte-free water

The filter-press electrochemical ozonizer is characterized as a function of the applied electric current, temperature, and linear velocity of the electrolyte-free water. Lead dioxide electroformed on surface of a non-platinized fine mesh stainless steel support was used as anode. Electrolysis of the electrolyte-free water was carried out using the membrane electrode assembly (MEA) adequately compressed by means of a specially designed clamping system. Electrochemical characterization studies were carried out galvanostatically as a function of temperature and linear velocity of the circulating water. It was verified that the electrochemical ozone production (EOP) taking place at the reacting zones formed at the solid polymer electrolyte (SPE)/mesh electrode interface is not considerably affected by circulating water when the linear velocity inside the distribution channels is higher than 1.20 cm s⁻¹. A current efficiency for the EOP of 13% and a specific electric energy consumption of 70 Wh g⁻¹ were obtained when an electric current of 130 A was applied at 30 °C. The reactor service life test revealed that the MEA using the lead dioxide fine mesh electrode as anode and a fine mesh stainless steel electrode as cathode, pressed against the SPE, is stable for the ozone production.     

Three-dimensional numerical simulation of straight channel PEM fuel cells

The need to model three-dimensional flow in polymer electrolyte membrane (PEM) fuel cells is discussed by developing an integrated flow and current density model to predict current density distributions in two dimensions on the membrane in a straight channel PEM fuel cell. The geometrical model includes diffusion layers on both the anode and cathode sides and the numerical model solves the same primary flow related variables in the main flow channel and the diffusion layer. A control volume approach is used and source terms for transport equations are presented to facilitate their incorporation in commercial flow solvers. Predictions reveal that the inclusion of a diffusion layer creates a lower and more uniform current density compared to cases without diffusion layers. The results also show that the membrane thickness and cell voltage have a significant effect on the axial distribution of the current density and net rate of water transport. The predictions of the water transport between cathode and anode across the width of the flow channel show the delicate balance of diffusion and electroosmosis and their effect on the current distribution along channel.     

The physical–chemical properties and electrocatalytic performance of iridium oxide in oxygen evolution

An IrO₂ anode catalyst was prepared by using the Adams method for the application of a solid polymer electrolyte (SPE) water electrolyzer. The effect of calcination temperature on the physical–chemical properties and the electrochemical performance of IrO₂ were examined to obtain a low loading and a high catalytic activity of oxygen evolution at the electrode. The physical–chemical properties were studied via thermogravimetry–differential scanning calorimetry (TG–DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The electrochemical activity was investigated by using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronopotentiometry in 0.1 mol L⁻¹ H₂SO₄ at room temperature. The optimum condition was found to be at the calcination temperature of 500 °C, where the total polarization reached a minimum at high current densities (>200 mA cm⁻²). The optimized catalyst was also applied to a membrane electrode assembly (MEA) and stationary current–potential relationships were investigated. With an optimized catalytic IrO₂ loading of 1.5 mg cm⁻² and a 40% Pt/C loading of 0.5 mg cm⁻², the terminal applied potential difference was 1.72 V at 2 A cm⁻² and 80 °C in a SPE water electrolysis cell.     

Optimal temperature for DMFC stack operation

We report a model of heat transport in a fragment of DMFC stack consisting of a bipolar plate with the linear anode channel. The model takes into account fragment heating due to reactions and cooling by the flow in the anode channel and by water evaporation. The resulting system of equations is solved using asymptotic technique. The solution yields optimal inlet temperature of the anode flow, which provides uniform distribution of stack temperature. Physically, in this regime stack and flow temperatures are equal and local rate of stack heating is exactly compensated for by the local rate of cooling due to evaporation.     

Dissolution of hydrogen and the ratio of the dissolved hydrogen content to the produced hydrogen in electrolyzed water using SPE water electrolyzer

Concentration of dissolved hydrogen in electrolyzed water using a solid polymer electrolyte (SPE) water electrolyzer was investigated using a DH-meter. A ratio of the dissolved hydrogen content to an amount of hydrogen concentration calculated from charge passed during electrolysis was estimated. The ratio increased from 10 to 20% with a decrease in current density from 3.0 to 0.3 A dm⁻². The effect of the linear velocity of water on the ratio of dissolved hydrogen was studied. The cross-sectional area of the water channel was changed to change the linear velocity of water. The ratio of dissolved hydrogen increased with increasing the velocity. Due to the fast mass transport by high velocity, the small hydrogen bubbles are fast transferred by the diffusion into the bulk water and dissolved. The population density of the small hydrogen bubbles is found to have an effect on the ratio of the dissolving hydrogen.     

V–I characteristics of solid polymer electrolytic (SPE) dehumidifier

Measurements of the V–I characteristics of a solid polymer electrolytic (SPE) dehumidifier were done using a modified SPE dehumidifier with four electrodes which included two electrodes to carry the main current and the other two electrodes to measure the voltages applied to the electrical double layer, which are the boundary voltages between the electrodes and the SPE membrane. The measured results were analyzed using the Butler-Volmer equation to examine the validity of the measurements. The current flowing in the dehumidifier is produced by the decomposition of water near the anode. Therefore, under a steady-state condition, the current should be proportional to the supply rate of water to the anode. On the other hand, a two-layer model for the SPE dehumidifier presented in our previous article showed that the current flowing in the dehumidifier was roughly proportional to the water content in the vicinity of the anode. These results were introduced for interpretation of the V–I measurements of the SPE dehumidifier. It was concluded that the dehumidifier current was expressed in the form of a Butler-Volmer equation as a function of the electrode boundary voltages which were the voltages across the boundary between the electrodes and the SPE membrane. An experimental formula for the current under a steady-state condition was developed as a function of the water content near the anode and the boundary voltages.     

Preparation and evaluation of RuO2–IrO2, IrO2–Pt and IrO2–Ta2O5 catalysts for the oxygen evolution reaction in an SPE electrolyzer

IrO₂–RuO₂, IrO₂–Pt and IrO₂–Ta₂O₅ electrocatalysts were synthesized and characterized for the oxygen evolution in a Solid Polymer Electrolyte (SPE) electrolyzer. These mixtures were characterized by XRD and SEM. The anode catalyst powders were sprayed onto Nafion 117 membrane (catalyst coated membrane, CCM), using Pt catalyst at the cathode. The CCM procedure was extended to different in-house prepared catalyst formulations to evaluate if such a method could be applied to electrolyzers containing durable titanium backings. The catalyst loading at the anode was about 6 mg cm⁻², whereas 1 mg cm⁻² Pt was used at the cathode. The electrochemical activity for water electrolysis was investigated in a single cell SPE electrolyzer at 80 °C. It was found that the terminal voltage obtained with Ir–Ta oxide was slightly lower than that obtained with IrO₂–Pt and IrO₂–RuO₂ at low current density (lower than 0.15 A cm⁻²). At higher current density, the IrO₂–Pt and IrO₂–RuO₂ catalysts performed better than Ir–Ta oxide.