Effect of TiB_2 content on resistance to sodium penetration of TiB_2/C cathode composites for aluminium electrolysis

1　INTRODUCTIONInrecent years ,therehavebeenincreasingeffortstoimprovetheHall Heroult processintheprimaryaluminiumindustry[1 ] .InordertoovercometheshortagesofHall Heroultprocess ,suchashighconsumptionofelectricalpower ,highconsumptionofcarbonanodeandserious pollutionduetocarbonanodemanufactureandconsumptionetc ,anoveltypeofaluminareducedcellsbasedoninertanodeandwettablecathodesystemwasdevelopedtoreplaceconventionalHall Heroultprocess[2 ,3 ] .Titaniumdiboride(TiB2 )appearstobethebestca…     

Effect of TiB2 content on resistance to sodium penetration of TiB2／C cathode composites for aluminium electrolysis

TiB2/C cathode composites with various contents of TiB2 were prepared and their characterizations were observed and compared. The expansion of samples due to sodium and bath penetration was tested with a modified laboratory Rapoport apparatus and the appearances of the cut sections of specimens after electrolysis were studied.The results show that the mass of TiB2/C cathode composites with mass fraction of TiB2 less than 70% appreciably increases, but that of the composites with mass fraction of TiB2 more than 70% decreases slightly after being baked.The resistance to sodium and bath penetration of TiB2/C cathode composites increases with the increase of TiB2 content, especially in the composites with high TiB2 content. TiB2/C cathode composites have high resistance to the penetration of sodium and bath as well as good wettability by molten aluminum, and keep integrality and have little change of appearance after electrolysis, which indicates that TiB2/C cathode composites can be used as inert wettable cathode for aluminum electrolysis.     

Electrical resistivity of TiB2/C composite cathode coating for aluminum electrolysis

1INTRODUCTIONThere are many disadvantages in the presentHall-Heroult electrolytic process[1],such as highenergy consumption,low unit productivity and se-rious environmental pollution and so on,especiallythe high energy consumption of per ton alumin-ium,which ranges from13MW·h to15MW·h,and the energy efficiency is less than50%[2].Therefore,low-energy consumption aluminumre-duction cell has been a research focus for interna-tional aluminum companies and institutes.Thedrained cathode cel…     

新型阴极结构电解槽铝电解试验

针对传统铝电解槽极距已经达到低限,槽电压不能大幅度降低的关键技术难题,提出一种新型阴极结构铝电解槽．介绍了这种新型阴极结构电解槽的特点和工艺技术特征,以及在重庆天泰铝业公司168kA电解槽上进行工业电解槽试验的结果．统计期内3台试验电解槽平均槽电压为3．803V,平均直流电耗比同系列其他127台传统电解槽低1250kW·h／tAl,达到12101kW·h／tAl．     

Effect of carbon fibre on properties of TiB2/C composite cathode coating for aluminum electrolysis

The tensile strength, compressive strength and electrical resistivity of TiB2/C composite cathode coating were measured with a hydraulic pressure universal test machine and an electrical resistivity test device, and the effects of carbon fibre content and carbon fibre length on tensile strength, compressive strength and electrical resistivity were investigated. The results show that the tensile strength of coating increases at the beginning and then reduces with the increase of carbon fibre content when the carbon fibre (length of 3 mm) content ranges from 0 to 4.0%; at the carbon fibre content of 1.5%, the tensile strength of coating reaches the maximum, 25.6 MPa. For the coating with carbon fibre content of 1.5%, the carbon fibre length has a great influence on tensile strength and compressive strength of coating; when the carbon fibre length is 6 mm, the tensile strength and compressive strength of coating reach the maximum, 27.6 MPa and 39.2 MPa, respectively. The electrical resistivity of coating reduces with the rise of temperature and the length of carbon fibre, and the influence of carbon fibre length on electrical resistivity of coating at low temperature (30-200℃) is more obvious than that at high temperature (960℃).     

Simulation of thermal and sodium expansion stress in aluminum reduction cells

Two finite element（FE） models were built up for analysis of stress field in the lining of aluminum electrolysis cells. Distribution of sodium concentration in cathode carbon blocks was calculated by one FE model of a cathode block. Thermal stress field was calculated by the other slice model of the cell at the end of the heating-up. Then stresses coupling thermal and sodium expansion were considered after 30 d start-up. The results indicate that sodium penetrates to the bottom of the cathode block after 30 d start-up. The semi-graphitic carbon block has the largest stress at the thermal stage. After 30 d start-up the anthracitic carbon has the greatest sodium expansion stress and the graphitized carbon has the lowest sodium expansion stress. Sodium penetration can cause larger deformation and stress in the cathode carbon block than thermal expansion.     

Electrode selection of electrolysis with membrane for sodium tungstate solution

Abstrac By measuring the electrode polarization curves of many kinds of materials and life spans of electrodes through intensifying electrolysis in the process, the appropriate electrode materials for different stages of electrolysis of sodium tungstate solution with membrane have been selected The effects of the electrodes with different shapes on electrolysis have been investigated. The result shows that network electrode is more suitable to electrolysis of sodium tungstate solution. Project supported by the Key Program of the 9th Five-year Plan of China Synopsis of the first author Xiao Liansheng, associate professor, born in 1956, majoring in separation science and metallurgical engineering.     

Electrolysis expansion performance of semigraphitic cathode in [K3AlF6/Na3AlF6]-AlF3-Al2O3 bath system

The electrolysis expansion of semigraphitic cathode in [K₃AlF₆/Na₃AlF₆]-AlF₃-Al₂O₃ bath system was tested by self-made modified Rapoport apparatus. A mathematical model was introduced to discuss the effects of α _CR (cryolite ratio) and β _KR (elpasolite content divided by the total amount of elpasolite and sodium cryolite) on performance of cathode electrolysis expansion. The results show that K and Na (potassium and sodium) penetrate into the cathode together and have an obvious influence on the performance of cathode electrolysis expansion. The electrolysis expansion and K/Na penetration rate increase with the increase of α _CR. When α _CR=1.9 and β _KR=0.5, the electrolysis expansion is the highest, which is 3.95%; and when α _CR=1.4 and β _KR=0.1, the electrolysis expansion is the lowest, which is 1.28%. But the effect of β _KR is correlative with α _CR. When α _CR=1.6 and 1.9, with the increase of β _KR, the electrolysis expansion and K/Na penetration rate increase. However, when α _CR=1.4, the electrolysis expansion and K/Na penetration rate firstly increase and then decrease with the increase of β _KR. Foundation item: Project (2005CB623703) supported by the Major State Basic Research and Development Program of China; Project (2008AA030502) supported by the National High-Tech Research and Development Program of China     

Numerical simulation of busbar configuration in large aluminum electrolysis cell

Various busbar configurations were built and modeled by the custom code based on the commercial package ANSYS for the 500 kA aluminum electrolysis cell. The configuration parameters, such as side riser entry ratio, number of cathode bars connected to each riser, vertical location of side cathode busbar and short side cathode busbar, distance between rows of cells in potline, the number of neighboring cells, ratio of compensation busbar carried passing under cell and its horizontal location under cell along with large magnetohydrodynamic（MHD） computation based on the custom evaluation function were simulated and discussed. The results show that a cell with riser entry ratio of 11：9：8：9：11 and cathode busbar located at the level of aluminum solution, 50% upstream cathode current passing under cell for magnetic field compensation, the distance between rows of 50 m is more stable.     

Effect of carbon fibre on properties of TiB2/C composite cathode coating for aluminum electrolysis

The tensile strength, compressive strength and electrical resistivity of TiB₂/C composite cathode coating were measured with a hydraulic pressure universal test machine and an electrical resistivity test device, and the effects of carbon fibre content and carbon fibre length on tensile strength, compressive strength and electrical resistivity were investigated. The results show that the tensile strength of coating increases at the beginning and then reduces with the increase of carbon fibre content when the carbon fibre (length of 3 mm) content ranges from 0 to 4.0%; at the carbon fibre content of 1.5%, the tensile strength of coating reaches the maximum, 25.6 MPa. For the coating with carbon fibre content of 1.5%, the carbon fibre length has a great influence on tensile strength and compressive strength of coating; when the carbon fibre length is 6 mm, the tensile strength and compressive strength of coating reach the maximum, 27.6 MPa and 39.2 MPa, respectively. The electrical resistivity of coating reduces with the rise of temperature and the length of carbon fibre, and the influence of carbon fibre length on electrical resistivity of coating at low temperature (30–200 °C) is more obvious than that at high temperature (960 °C). Foundation item: Project(2005CB623703) supported by the Major State Basic Research Development Program of China     

基于Web的铝电解综合信息系统设计及其关键技术实现

在铝电解生产过程中,办公局域网和工业控制网采用Web技术集成,形成综合的Web管理信息系统,已成为当前及今后铝电解企业信息化发展的主要目标之一.所提出得基于Web的铝电解综合信息系统,基于SQLServer等大型关系型数据库、JSP技术、SOCKET传输技术和三层Web架构,实现了办公局域网与CAN网的集成.详细论述了系统实现的几个关键技术,如数据的采集与提取,实时数据传输、静态数据传输等.最后分析了本系统的应用前景.     

Laboratory study of property-modified prebaked carbon anode and application in large aluminum electrolysis cells

A kind of complex additive mainly containing Al, Mg, F, and O was prepared. The synthetical performances of the property-modified prebaked anodes containing additives were tested in laboratory. On the basis of ideal testing results obtained, a large number of industrial prebaked property-modified anodes are prepared in a large-scale aluminum company. Further more, they are all used in 160 kA prebaked anode aluminum electrolysis cells. The statistic result show that, compared with common anodes, the property-modified ones enhance current by 11.6 kg per ton aluminum averagely.     

Laboratory study of property-modified prebaked carbon anode and application in large aluminum electrolysis cells

A kind of complex additive mainly containing Al, Mg, F, and O was prepared. The synthetical performances of the property-modified prebaked anodes containing additives were tested in laboratory. On the basis of ideal testing results obtained, a large number of industrial prebaked property-modified anodes are prepared in a large-scale aluminum company. Further more, they are all used in 160 kA prebaked anode aluminum electrolysis cells. The statistic result show that, compared with common anodes, the property-modified ones enhance current efficiency by 0.78%, reduce energy consumption by 106.1 kW·h per ton aluminum and reduce carbon consumption by 11.6 kg per ton aluminum averagely. Foundation item: Project(G1999064903) supported by Major State Basic Research Development Program of China     

Effect of baking processes on properties of TiB2/C composite cathode material

Pitch and TiB₂/C green composite cathode material were respectively analyzed with simultaneous DSC-TGA, and effects of three baking processes of TiB₂/C composite cathode material, i.e. K25, K5 and M5, on properties of TiB₂/C composite cathode material were investigated. The results show that thermogravimetric behavior of pitch and TiB₂/C green composite cathode is similar, and appears the largest mass loss rate in the temperature range from 200 to 600°C. The bulk density variation of sample K5 before and after baking is the largest (11.9%), that of sample K25 is the second, and that of sample M5 is the smallest (6.7%). The crushing strength of sample M5 is the biggest (51.2 MPa), that of sample K25 is the next, and that of sample K5 is the smallest (32.8 MPa). But, the orders of the electrical resistivity and electrolysis expansion of samples are just opposite with the order of crushing strength. The heating rate has a great impact on the microstructure of sample. The faster the heating rate is, the bigger the pore size and porosity of sample are. Compared with the heating rate between 200 and 600° of samples K25 and K5, that of sample M5 is slower and suitable for baking process of TiB₂/C composite cathode material. Foundation item: Project (2005CB623703) supported by the Major State Basic Research and Development Program of China; Project (2008AA030502) supported by the National High-Tech Research and Development Program of China     

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…     

锂离子电池正极材料LiMgxMn2-xO4的合成及性能

利用相转移法合成了LiMgxMn2-xO4前驱体,在电炉中于一定温度下烧结一定时间,得到锂离子电池正极材料粉体,并利用XRD、SEM、IR等对材料粉体进行结构形态表征.考察焙烧温度、焙烧时间、Mg的掺杂含量等对产物结构和电化学性能的影响.实验结果表明:当Mg的掺杂量x=0.06,于750℃焙烧15 h时所制备的样品材料结构稳定且呈尖晶石型,样品电极的充放电性能良好,首次放电比容量达125 mAh/g,放电平稳,样品电极可逆循环性能良好.     

铝电解可湿润性阴极的研究开发与工业试验

介绍了侧衬为Si3N4-SiC与碳砖相复合的新型侧部内衬材料，底块为一体化成型TiB2-C复合的阴极材料整体结构完整优化的新型铝电解可湿润性阴极的研制与工业电解槽试验结果。     

Effect of electromagnetic force on turbulent flow of molten metal in aluminum electrolysis cells

The standard κ-ε model was adopted to simulate the flow field of molten metal in three aluminum electrolysis cells with different anode risers. The Hartman number, Reynolds number and the turbulent Reynolds number of molten metal were calculated quantitatively. The turbulent Reynolds number is in the order of 10^3 , and Reynolds number is in the order of 104 if taking the depth of molten metal as the characteristic length. The results show that the molten metal flow is the turbulence of high Reynolds number, the turbulent Reynolds number is more appropriate than Reynolds number to be used to describe the turbulent characteristic of molten metal, and Hartman number displays very well that electromagnetic force inhibits turbulent motion of molten metal.