微量元素铈对沥青热解过程的影响

利用热重分析仪(TG-DTG)研究了微量元素铈加入沥青前后的热解动力学模型,测定了铈元素加入的炭阳极CO2/空气残余率并进行了XRD衍射分析。结果表明,随着微量元素铈的加入,热解速度放慢,热解温度区间变宽,表观活化能降低,热解反应更容易发生,沥青产焦率增加4.79个百分点;炭阳极晶粒厚度变大,减少了活性质点数;可提高炭阳极在CO2和空气中的残余率,可降低炭阳极的额外消耗。     

The effect of quality of anodes on the process of electrolytic of manganese dioxide

During the electrosynthesis of manganese dioxide, the anode material and anode current density (i _a) exert the largest influence on the characteristics of electrolysis and the quality of the obtained material. The activation of anodes, which consists of the deposition of the titanium-manganese alloy on the titanium base of the electrode by the thermal-diffusion method, prevents passivation at i _a = 100 and 200 A/m². The electrochemical characteristics of electrolysis for NTMA (a built-up titanium-manganese activated anode) and ATDP (an experimental activated anode with thermodiffusion coating) anodes at i _a = 100 and 200 A/m² have close values. The voltage across the bath does not exceed 2.2–3.0 V, the current efficiency is 95–98%, and electrical power consumption is 1.33–1.80 (kW h)/kg. The chemical composition and the crystalline modification of electrical manganese dioxide corresponds to the requirements of GOST (State Standard) 25823-83. The activated ATDP anodes behave similarly to the known HTMA anodes. After electrolysis, no variations in the surface layer are found on them.     

石油焦煅烧程度对铝用炭阳极显微结构及电解消耗的影响

以不同煅烧程度石油焦为骨料,煤沥青为黏结剂制备铝用低煅焦炭阳极.通过激光共聚焦扫描显微镜和图像分析方法对炭阳极孔隙结构进行分析表征,并考察阳极反应性和电解消耗性能.在煅后焦微晶尺寸1.7~2.7 nm范围内降低石油焦煅烧程度,炭阳极小孔隙逐渐沿骨料-黏结剂界面演变为裂纹状大孔隙,炭阳极孔隙率、形状因子及连通率均先减小后增大,视孔隙比表面积呈减小趋势.煅后焦微晶尺寸降低至1.9 nm较为适宜,对应的炭阳极空气和CO₂反应质量损失率最少为9.6%和3.0%,每吨铝阳极碳耗为355.4 kg.低煅焦炭阳极过量消耗机制从以黏结剂选择性消耗转变为骨料与黏结剂共同消耗,使碳渣量减少.      

Anodic behaviour of the Pb–Co3O4 composite coating in copper electrowinning

The electrochemical and corrosion properties of Pb–Co₃O₄ (about 3% Co) composite anode for copper electrowinning without additives as well as in the presence of two combinations of organic additives in the electrolyte have been investigated and compared with those of Pb–Sb 5.85% anode. The formation of PbO₂ layer on the surface of these electrodes was traced by cyclic voltametric measurements using rotating disc electrode (RDE) method. The Pb–Co₃O₄ composite anode shows a depolarizing effect on the process of oxygen evolution as compared to Pb–Sb anode. The corrosion rate of Pb–Co₃O₄ anode during prolonged polarization is approximately 6.7 times lower than that of Pb–Sb anode. The influence of the tested organic additives on the anodic behaviour of both anodes is negligible.     

镍元素对炭阳极反应活性的影响

考察了煅后焦中微量元素镍对炭阳极反应活性的影响,并对炭阳极的二氧化碳反应性、空气反应性进行了测试。结果表明,适量的镍元素可以改善炭阳极在CO2中的残极率、粉化率和质量损失率;也能提高炭阳极在空气中的残极率、粉化率和质量损失率。镍元素的添加对炭阳极的CO2反应性和空气反应性均有抑制作用,可改善炭阳极质量,降低炭阳极的额外消耗。     

稀土元素铈对铝用炭阳极反应性的影响

煅后焦中添加稀土元素铈对炭阳极的二氧化碳反应性、空气反应性的影响进行了研究。结果表明,铈元素添加量在(60～1 060)×10-6范围内可改善和提高炭阳极在CO2和空气中的残极率和粉化率。添加铈元素可抑制炭阳极对炭阳极CO2/空气反应性,降低炭阳极的额外消耗。     

Solubility of oxygen in Fe–Co melts containing titanium

Solutions of oxygen in Fe–Co melts containing titanium are subjected to thermodynamic analysis. The first step is to determine the equilibrium reaction constants of titanium and oxygen, the activity coefficients at infinite dilution, and the interaction parameters in melts of different composition at 1873 K. With increase in cobalt content, the equilibrium reaction constants of titanium and oxygen decline from iron (logK(FeO · TiO₂) =–7.194; logK(TiO₂) =–6.125; logK(Ti₃O₅) =–16.793; logK(Ti₂O₃) =–10.224) to cobalt (logK(CoO · TiO₂) =–8.580; logK(TiO₅) =–7.625; logK(Ti₃O₅) =–20.073; logK(Ti₂O₃) =–12.005). The titanium concentrations at the equilibrium points between the oxide phases (Fe, Co)O · TiO₂, TiO₂, Ti₃O₅, and Ti₂O₃ are determined. The titanium content at the equilibrium point (Fe, Co)O · TiO₂ ? TiO₂ decreases from 1.0 × 10^–4% Ti in iron to 1.9 × 10^–6% Ti in cobalt. The titanium content at the equilibrium point TiO₂?Ti₃O₅ increases from 0.0011% Ti in iron to 0.0095% Ti in cobalt. The titanium content at the equilibrium point Ti₃O₅ ? Ti₂O₃ decreases from 0.181%Ti in iron to 1.570% Ti in cobalt. The solubility of oxygen in the given melts is calculated as a function of the cobalt and titanium content. The deoxidizing ability of titanium decline with increase in Co content to 20% and then rise at higher Co content. In iron and its alloys with 20% and 40% Co, the deoxidizing ability of titanium are practically the same. The solubility curves of oxygen in iron-cobalt melts containing titanium pass through a minimum, whose position shifts to lower Ti content with increase in the Co content. Further addition of titanium increases the oxygen content in the melt. With higher Co content in the melt, the oxygen content in the melt increases more sharply beyond the minimum, as further titanium is added.     

Properties of the coke-pitch composition of the soderberg anode

Specimens from the zone of the coke-pitch composition (CPC) of ??dry?? and ??colloid?? Soderberg anodes with pitch contents of 28.2 and 24.0%, respectively, are sampled. The relative elongation coefficient and viscosity of the specimens are measured, and the granulometric composition of the coke charge is determined. It is noted that the properties associated with composition fluidity provide the uniform filling of the anode case even at a lowered pitch content. The redistribution of the coke particles in the CPC zone of the operating electrolyzer is characteristic of the dry anode during the sedimentation of the particles. No such phenomenon is noted for the CPC of the colloid anode. This excludes the possibility of stratification of the anode mass and forms more favorable environmental conditions for the electrolyzer operation.     

Regularities of reactions of titanium carbonitrides and oxycarbides with nickel

Specific features and regularities of reactions of titanium carbide alloyed over the sublattice of nonmetals (N, O) with the nickel melt are analyzed. It is established that the partial substitution of carbon in TiC by nitrogen decreases its dissolution rate in nickel and increases the degree of process incongruence (the transfer of carbon into the melt is preferential compared with titanium). The concentration dependence of the dissolution rate of TiC_xN_z in nickel changes its sign to the opposite one compared with approaching the system to equilibrium. Titanium carbonitride is not recrystallized through the nickel solution as the only phase, and mainly its carbide component is subjected to recrystallization. It is revealed that the partial substitution of carbon in TiC to oxygen increases its dissolution rate in nickel. The dissolution of oxycarbide TiC_0.6O_0.4 in nickel is accompanied by the gradual loss of its carbon until titanium monoxide is formed and by its further disproportionation. The peculiarity of the interaction mechanism of titanium oxycarbides with the nickel melt is determined by reaction [C] + [O] = CO↑ in the liquid phase.     

Kinetics and contact interaction mechanism of titanium carbonitride with the Ni–Mo melt

Kinetic features and the contact interaction mechanism of hot-pressed (residual porosity <3%) of titanium carbonitride samples of various compositions with the Ni–25% Mo melt (t = 1400–1500°C, τ = 0.1–25 h) are investigated by electron-probe microanalysis. It is established that the dissolution rate of the interstitial refractory phase (IRP) in the Ni–Mo melt lowers in a series TiC–TiC_0.7N_0.3–TiC_0.5N_0.5, while the degree of process incongruence rises. The composition of intermediate interaction products varies correspondingly. The peculiarities of formation of the most important phase component of the TiCN cermets—K-phase of the Ti_1–nMo_nC_x composition—are revealed. It is proven by the local mass spectrometry method that the K-phase has a carbide nature. It is also established that it is formed only if the initial titanium carbonitride TiC_1–xN_x is sufficiently enriched with carbon (x ≤ 0.5). It is stated that the K-phase is an actual basis of all cermets with the Ni–Mo binder. Its bulk concentration in alloys exceeds the content of the nominal alloy base by a factor of several times. The chemical substantiation of the selection of titanium carbonitride of the TiC_0.5N_0.5 composition as an optimal “precursor” of the K-phase, which is formed during liquid-phase sintering of TiCN cermets, is given originally.     

Effects of Coke and Formulation Variables on Fracture of Bench Scale Prebaked Anodes for Aluminum Smelting

Bench scale anodes were prepared using a number of calcined cokes, aggregate sizings, and pitch levels and tested for thermal shock resistance and flexural strength. Thermal shock resistance rose with increasing coke real density, while flexural strength tended to improve with increasing coke bulk density. With coarser aggregate sizings, a pitch level resulting in maximum baked apparent density maximized thermal shock resistance and flexural strength. With a finer aggregate sizing, thermal shock resistance and flexural strength peaked at a pitch level greater than that producing the highest baked apparent density, so maximum values require more pitch than probably practical for full-size anodes.     

SnO2-Based Gas (Methane) Anodes for Electrowinning of Aluminum

SnO₂-based and carbon-based gas anodes were studied in molten Na₃AlF₆-AlF₃-Al₂O₃ at 1123 K (850 °C) for aluminum electrolysis. Methane was introduced to the porous anodes to take part in a three-phase (anode/electrolyte/methane) boundary reaction. Carbon was used as the cathode. It was observed that the anode potential was reduced by 0.6 V and that the current was increased up to three times in galvanostatic and potentiostatic tests after the introduction of methane on SnO₂-based anodes. A measurable depolarization effect and lower consumption of carbon after the introduction of methane on carbon anodes were also demonstrated.     

Regularities of the contact interaction of titanium carbide with Ni and Ni–Mo melts

Regularities of the dissolution, the phase formation, and the structure formation implemented under the contact interaction conditions of titanium carbide of various compositions with Ni and Ni–(5–25%)Mo melts are investigated. It is originally established that the dissolution of carbide TiC_x in nickel-based melts is incongruent. Preferentially, carbon transfers into the melt at x ≥ 0.9 and titanium at x ≤ 0.8. The limiting stage of the dissolution is diffusion of metal atoms in the liquid phase. The formation regularities of carbide Ti_1–nMo_nC_x (K-phase)—the main product of the contact interaction in the TiC/Ni–Mo system—are revealed. It is established that the K-phase is formed under the relative excess conditions of the Ni–Mo melt preferentially according to the dissolution–isolation mechanism. The composition of autonomous isolations of the K-phase depending on the experimental conditions (1450°C, 0–25 h) varies in limits from Ti_0.4Mo_0.6C_0.7 (a = 4.27 Å) to Ti_0.7Mo_0.3C_0.6 (a = 4.29 Å). It is determined by the molybdenum concentration in the melt at the unsteady dissolution stage and by the concentration ratio between titanium and carbon in it at the steady-state dissolution stage.     

An investigation of the effect of the electrolyte composition on the consumption of fired anodes during electrolytic aluminum production

The effect of adding CaF₂, AlF₃, and KF into electrolyte on the consumption of fired anode during aluminum electrolysis is investigated. The CaF₂ content varied from 5 to 10 wt % in the electrolyte of the industrial composition. Correspondingly, the concentration of AlF₃ and KF varied from 4 to 10 and from 0 to 4.7 wt % in the modified electrolytes. Based on the procedure used, the total consumption of carbon and the amount of carbon transported into the gas phase (m _g) and foam (m _f) were determined. Electrolysis duration was 12 h, the distance between the poles was 40 mm, the temperature was 960°C, and the current density was 0.85 and 1.2 A/cm². It is established that adding CaF₂ and AlF₃ increases the consumption of anode, while adding KF decreases it. For CaF₂, ?m _f/?[CaF₂] is larger than ?m _g/?[CaF₂], 15.4 and 6.6 kg/(t_Al wt %) CaF₂, respectively. For AlF₃, ?m _f/?[AlF₃] is also larger than ?m _g/?[AlF₃] and equals 6.8 and 4.2 kg/(t_Al wt %) AlF₃. For KF, ?m _f/?[KF] is smaller than ?m _g/?[KF], being ?11.3 and ?8.1 kg/(t_Al wt %) KF.     

The mineralogical characterization of tellurium in copper anodes

A mineralogical study of a «normal» commercial copper anode and six tellurium-rich copper anodes from the CCR Refinery of the Noranda Copper Smelting and Refining Company was carried out to identify the tellurium carriers and their relative abundances. In all the anodes, the major tellurium carrier is the Cu₂Se-Cu₂Te phase which occurs as a constituent of complex inclusions at the copper grain boundaries. In tellurium-rich anodes, the molar tellurium content of the Cu₂Se-Cu₂Te phase can exceed that of selenium. Although >85 pct of the tellurium occurs as the Cu₂Se-Cu₂Te phase, minor amounts are present in Cu-Pb-As-Bi-Sb oxide, Cu-Bi-As oxide, and Cu-Te-As oxide phases which form part of the grain-boundary inclusions. About 1 pct of the tellurium content of silver-rich anodes occurs in various silver alloys, but gold tellurides were never detected. Surprising is the fact that 2 to 8 pct of the total tellurium content of the anodes occurs in solid solution in the copper-metal matrix, and presumably, this form of tellurium dissolves at the anode interface during electrorefining.     

Effect of carbon recycle materials on properties of bench scale prebaked anodes for aluminum smelting

Bench scale aluminum smelting anodes were produced from aggregates having butts contents of 0 to 40 wt pct, from 100 pct mixer scrap or 100 pct green anode scrap, and from aggregates having used potlining contents of 0 to 25 pct to determine effects on important properties. Butts additions increased baked apparent density, decreased electrical resistivity, baking shrinkage, and thermal shock cracking resistance, and had little effect on excess carbon consumption. Use of 100 pct mixer scrap was equivalent to use of freshly blended coke and pitch. Use of 100 pct green anode scrap increased baked apparent density, decreased electrical resistivity, and may have reduced carbon consumption. Additions of used potlining increased carbon consumption, had little effect on electrical resistivity, and had a variable effect on thermal shock cracking resistance.     

高硫焦对铝用预焙阳极理化指标的影响

探讨用高硫焦对制备的预焙阳极理化指标的影响。使用一定比例高硫焦的预焙阳极抗CO_2反应活性(质量残余率)高于低硫焦预焙阳极,而抗空气反应性无明显变化。高硫焦阳极的Ca、V、Ni元素含量低于低硫焦,而Na元素略有偏高,随着各微量元素的升高,阳极两性反应活性增大。高硫焦预焙阳极的电阻率、耐压强度、气孔率要优于低硫焦。     

A Mineralogical overview of the behavior of nickel during copper electrorefining

Nickel-bearing copper anodes and anode slimes were studied using a variety of mineralogical and chemical techniques. In anodes containing <;0.3 pct Ni, the nickel occurs only in solid solution in the copper matrix. This nickel dissolves simultaneously with the copper during electrorefining, but a small amount reprecipitates as copper-nickel sulfate or a complex Ni-bearing Cu-Ag-As-Se-S oxidate phase in the anode slimes. In anodes containing >0.3 pct Ni, NiO crystals also form. The presence of the Cu-Ni-Sb oxide, kupferglimmer, in the anode depends on its antimony content. Kupferglimmer is prevalent in nickel-rich anodes with high Sb contents (>200 ppm) but is not found in similar anodes with Sb contents <200 ppm. Various Cu-Ni and Ca-Cu-Ni silicate inclusions are present. Depending on the iron content of the anode, Fe-bearing NiO, NiFe₂O₄, and other Ni-bearing iron oxide phases also may be present. All of the oxidate nickel phases remain largely undissolved during electrorefining and concentrate in the anode slimes.     

The mechanism and kinetics of producing single-crystal powders of titanium carbide via a hydride-calcium method

The mechanism and kinetics of the reduction-carbidization of titanium oxide by calcium hydride and carbide (hydride-calcium method) are studied. This process provides the production of single-crystal powdered titanium carbide. Theoretical analysis and experimental methods is found that the mechanism of the formation of TiC forms is staged and includes two sequential reactions: TiO₂ + 2CaH₂ = Ti + 2CaO + 2H₂↑ and Ti + C = TiC. It is revealed that the formation of titanium carbide proceeds in a calcium melt by the dissolution of titanium and graphite in it with the subsequent crystallization of the TiC particles from the melt. It is noted that the kinetics of the process in the range t = 900?1200°C depends on the temperature and time of isothermal holding. At t > 1100 °C, its abrupt activization is observed. This is due to an increase in the amount of melt based on calcium and the enhancement of the solubility of titanium and carbon in it, which leads to the acceleration of reactions of reduction of titanium oxide to titanium and to the synthesis of titanium carbide. The optimum technological parameters of the process (temperature, time of isothermal holding, and conditions of the calculation of the charge) are determined. It is shown that titanium carbide obtained by this technology is homogeneous and has the content close to stoichiometric one, specifically, TiC_1.0.     

敞开式焙烧炉中挥发份的燃烧

对生阳极内作为粘接剂的沥青的受热分解所产生的 3种挥发份 (氢、甲烷和焦油 )的析出机理和燃烧特性进行分析 ,结合焙烧炉的运行原理得出挥发份充分燃烧的关键是火道与阳极之间保持较大温差 ,并从炉子结构和材质以及火道升温速度这 2个方面对如何获取这个温差进行了充分讨论 ,最后对挥发份的燃烧调节所采用的 2种办法进行了详细的描述与分析