石墨化阴极炭块生产与应用初探

以优质煅后石油焦为主要原料,充分利用现有设施,通过对配方、混捏成型工艺、焙烧工艺、石墨化工艺进行研究改进,研制了石墨化阴极炭块,并进行工业性生产试验和在铝电解槽上应用试验。试验后的结果表明,各类产品的理化性能均达到预期目标,并优于法国沙瓦公司CH系列产品指标,达到了国际先进水平。在电解槽上进行产业化应用后与高石墨质阴极炭块相比,使用石墨化阴极炭块能降低炉底压70 mV左右,电流效率平均提高1%~2%。     

优质铝用阴极炭块的技术与市场开发

早在1985-1986年青铜峡铝厂引进日本江津铝厂技术和装备时，曾引进石墨化阴极块应用于砌筑铝电解槽。1987-1990年，我们曾在国家“七五”科技攻关项目中，被列为“高铝用炭素质量研究”课题，国家下达项目经费300万元，在安微合肥铝厂和青铜峡铝厂等进行工业试验并试验成功。“铝电解槽应用半石墨化和石墨化阴极块”试验情况如下：     

铝电解槽用石墨化阴极材料的研究

以4种国产焦炭、3种国产煤沥青为原材料，采用热模压成型、一次焙烧、高压浸渍、二次焙烧和石墨化等工艺开展了铝电解槽用石墨化阴极材料的研究。在对原材料结构和理化性能分析的基础上，考察了原材料种类和配比不同的15个试样在热处理过程中的收缩率和体积密度的变化，并对石墨化后的试样的各项理化性能与工业发达国家生产的石墨化阴极炭块的性能指标进行了对比分析。结果表明，以国产焦炭和煤沥青为原材料，经过适当的混配和热处理工艺得到的石墨化阴极材料试样，其综合性能指标已达到铝电解槽对高性能石墨化阴极材料的要求。     

钠及氟盐对铝电解槽中炭阴极石墨化过程的催化作用

模拟铝电解槽炭阴极低温石墨化过程，研究了NaF、Na3AlF6、Na2CO3和直流电对炭阴极的石墨化过程的催化作用。     

中国高品质阴极炭块的工业生产及应用

综述了近几年中国高品质阴极炭块的生产技术及现状,研究了石墨含量对阴极炭块各项理化指标的影响,随着石墨含量的增加,阴极炭块的导电、导热性提高,抗电解质侵蚀性能明显增强,耐压强度有所降低。成型技术对石墨化阴极炭块的各向异性有明显的影响,振动成型生产的石墨化阴极炭块的各向异性不明显。总结了高石墨质阴极炭块、石墨化阴极炭块、硼化钛可湿润阴极炭块在大型预焙铝电解槽上的工业试验结果,高品质阴极炭块使大型槽的生产更平稳,能够提高电流效率、降低电耗和延长电解槽寿命。并初步分析了其技术经济性。     

铝电解钠对阴极渗透膨胀的影响及解决方法

分析了在铝电解槽中,钠对阴极的渗透膨胀过程。介绍了改善钠对阴极渗透膨胀的两种方法:提高阴极炭块石墨含量或石墨化程度和使用TiB2涂层及复合材料,并对目前国内这两种方法的研究和应用现状进行总结。     

高石墨质铝用阴极冷捣糊的研制

为满足提高大型预焙电解槽筑炉质量及减少工作环境污染的需要,成功地开发出一种施工温度34-38℃,超过国家行业标准的铝用阴极高石墨质冷捣糊.该铝用阴极高石墨质冷捣糊在240 kA大型预焙电解槽上的筑炉应用、焙烧启动和电解槽的实际使用证明,效果良好,达到了预期目标.     

铝电解槽石墨化阴极和槽壳的变形分析

针对铝电解槽石墨化阴极和槽壳变形现状,进行科学合理的实验,获得工业铝电解槽焙烧完毕后的位移,希望能够给相关研究人员提供一定的参考与帮助。     

世界最大石墨化阴极生产线即将完工

新安电力集团实施的年产3万t石墨化阴极生产线扩建正在积极建设当中,石墨化阴极在世界铝行业被公认为是替代石墨质阴极的最佳产品,生产吨铝可节电500千瓦时,还可延长电解槽寿命一倍以上。我国是电解铝生产第一大国,但石墨化阴极生产技术却被德、美、日三国掌握。为了攻克这一世界性的技术难题,早在2002年,     

石墨化阴极铝电解槽电热场仿真研究

将工业试验测试与数值仿真方法相结合,以ANSYS软件为主要开发工具,建立有限元模型对300kA石墨化阴极铝电解槽的电-热场进行计算分析,并与测试结果进行了比较和讨论。研究表明,石墨化阴极炭块内温度梯度相对普通阴极更小,温度分布更加均匀;配合使用碳化硅侧块能增强电解槽散热能力,可以有效加强大型预焙槽的散热。     

Porous current collectors for passive direct methanol fuel cells

A passive direct methanol fuel cell (DMFC) with its cathode current collector made of porous metal foam was investigated experimentally. The measured polarization curves, constant-current discharging behavior and EIS spectra showed that the passive DMFC having the porous current collector yielded much higher and much more stable performance than did the cell having the conventional perforated-plate current collector with high methanol concentration operation. It was demonstrated that the improved performance for the porous current collector was attributed to: (i) the enhanced oxygen transport on the cathode as a result of a larger specific transport area, (ii) the increased operating temperature as a result of the lower effective thermal conductivity of the porous structure, and (iii) the faster water removal as a result of the capillary action in the porous structure, The experimental results also revealed that the porous current collector with a smaller pore size yielded higher performance as a result of the lower cell resistance.     

Thermal and Electrical Conductivity of Amorphous and Graphitized Carbide‐Derived Carbon Monoliths

The influence of graphitization and composition of carbide‐derived carbon (CDC) monoliths on the electrical and thermal conductivity was investigated. Carbon monoliths with varying porosities were synthesized employing biomorphous macroporous TiC and SiC as precursors. Graphitization was carried out in situ during high‐temperature chlorination with and without addition of nickel, iron, and cobalt chloride to the carbide. The graphitized monoliths showed improved properties. The results demonstrate that despite graphitic carbon also glass‐like carbon, stemming from the carbide synthesis, increases the thermal and electrical conductivity significantly.     

Experimental studies and model validation for the optimization of electrodes configuration in a molten salt electrorefiner

Molten salt electrorefining is a high-temperature electrochemical process for treating the spent metallic fuel from fast reactors and is aimed at the separation of U and Pu from fission products. Potential and current distribution analysis was carried out by experimental studies as well as modelling using COMSOL Multiphysics for various electrode configurations. A 2D/2D axisymmetric geometry model was used to evaluate the potential and current distributions. The effect of the following parameters was evaluated: (1) configuration having two pairs of electrodes in parallel/staggered arrangement; (2) centre-to-centre distance between the electrodes; (3) solid cathode with and without insulation at the bottom; (4) Cd cathode and (5) cathode surface area. The resistance of the electrorefiner was calculated using COMSOL model for various electrode configurations and compared with that obtained experimentally. There was very good agreement between the experimental values and the simulation results. The computed cell resistance was also validated with published data. A sensitivity analysis was also performed to determine the parameter that more significantly influences the cell resistance. The two parameters that were varied were the electrolyte conductivity and the cell voltage. It is observed that of the two parameters the cell resistance is most sensitive to the electrolyte conductivity and there is no change in cell resistance with cell voltage.     

中温固体氧化物燃料电池SmBaCo_2O_（5＋δ）–Sm_（0.2）Ce_（0.8）O_（1.9）复合阴极材料的电化学性能

采用柠檬酸–硝酸盐自蔓延燃烧法分别合成了双钙钛矿结构的SmBaCo2O5＋δ（SBCO）阴极粉体和萤石型Sm0.2Ce0.8O1.9（SDC）电解质粉体,按3：2的质量比混合上述粉体研磨后得到复合阴极。利用X射线衍射仪研究化学相容性,直流四端子法测量电导率,热膨胀仪测量热膨胀系数;构建阳极支撑型单电池（Ni-SDC｜SDC｜SBCO-SDC）并进行了性能测试,用扫描电子显微镜观察电池的断面微结构,交流阻抗谱记录界面极化。结果表明：SBCO与SDC在1 000℃无相互作用;450～800℃,复合阴极的电导率在369～234 S/cm之间;SDC的加入降低了复合阴极的热膨胀系数;单电池具有理想的微观结构,阳极｜电解质｜阴极各界面彼此接触良好,650℃时极化电阻仅为0.031.cm2;以H2为燃料气（含体积分数3%水蒸气）,空气为氧化剂,650℃时电池的开路电压为0.77 V,输出功率最大值为640 mW/cm2。预示着SBCO-SDC是中温固体氧化物燃料电池有潜力的阴极材料。     

Current distribution measurements in a PEFC with net flow geometry

A measurement system for current distribution mapping for a PEFC has been developed. The segmented anode is constructed so as to have high thermal conductivity in order to prevent the formation of large temperature gradients between the electrodes. The construction is therefore feasible for use at high current densities. Both segmented and unsegmented gas diffusion layers are used. The effect of inlet humidification and gas composition at the cathode side is studied. In addition, two different flow geometries are studied. The results show that the measurement system is able to distinguish between current distribution originating from differences in proton conductivity, species concentration and gas diffusion layer properties.     

Increasing the electrical conductivity of carbon nanotube/polymer composites by using weak nanotube-polymer interactions

A weak interaction between carbon nanotubes (CNTs) and polymers was found to reduce polymer-wrapping on CNT surface, decrease the contact resistance between CNTs, and increase the electrical conductivity of their composites. Thermodynamic properties such as surface energy of components, filler-polymer interactions, and wettability of carbon/polymer systems were analyzed. It was found that the graphitized CNTs filled polyoxymethylene (POM) system exhibits the weakest CNT-polymer interaction among all the investigated systems and a poor wettability. Consequently, the graphitized CNT/POM composites possess a high electrical conductivity and a low percolation threshold of 0.5 wt.% CNT loading, which is associated with the weak CNT-polymer interaction, low contact resistance between CNTs, good connectivity of CNT networks, and high crystallinity of POM in the composites. The results obtained imply that high-performance composites with optimal CNT-network structures can be designed and fabricated by fully considering the surface properties of components and CNT-polymer interactions.     

Synthesis of nitrogen-doped onion-like carbon and its use in carbon-based CoFe binary non-precious-metal catalysts for oxygen-reduction

Nitrogen-doped onion-like carbon-rich materials were synthesized by heat treatment of a “hybrid” containing hexamethylene diamine complex in the presence of Co and Fe species while preparing non-precious metal electrocatalyst for oxygen-reduction. As demonstrated by electrochemical rotating disk electrode and fuel cell tests, the binary CoFe-based catalyst containing graphitized onion-like carbon nanostructures provides for improved performance relative to the single Fe-based catalyst in which no such carbon structure was observed. In the binary catalysts, variation of the ratios of Co to Fe and the total metal loading during the synthesis leads to a markedly different activity and four-electron selectivity for oxygen reduction. The optimized binary catalyst was studied in fuel cell lifetime tests using both constant current and voltage models, showing a good combination of activity and durability. Possible reasons for the improved performance of the CoFe-based binary catalyst are discussed. The graphitized onion-like carbon structure exclusively derived from Co in this work may be providing a robust matrix to host non-precious metal active sites, which would prevent water flooding of them, and increase the resistance to oxidative attack in the oxygen cathode, thereby leading to an improvement in performance durability.