NiFe2O4-10NiO-based cermet inert anodes for aluminium electrolysis were prepared and their properties were investigated in a lab-scale electrolysis cell. The results show that the inert anodes exhibit good performance...NiFe2O4-10NiO-based cermet inert anodes for aluminium electrolysis were prepared and their properties were investigated in a lab-scale electrolysis cell. The results show that the inert anodes exhibit good performance during electrolysis in molten salt cryolite at 960 °C, but according to the analyses of phase compositions and microstructures through XRD, SEM/EDX and metallographic analysis, the metal in the anodes is preferentially corroded and many pores are produced on the anode surface after electrolysis. The preferential dissolution of Fe in the NiFe2O4 phase may lead to the non-uniform corrosion of NiFe2O4 grains. Moreover, a dense protective layer of NiFe2O4-NiAl2O4-FeAl2O4 is formed on the anode surface, which originates from the reaction of Al2O3 dissolved in the electrolyte with NiO or FeO, the annexation of NiFe2O4-NiAl2O4-FeAl2O4 to NiO and volume expansion. Thus, the dense NiFe2O4-NiAl2O4-FeAl2O4 layer inhibits the metal loss and ceramic-phase corrosion on the surface of the cermet inert anodes.展开更多
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 labo...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.展开更多
The properties and blending recipe of petroleum cokes used to make high quality carbon anodes for aluminium electrolysis were studied. Three kinds of green cokes were selected for bench scale study to illustrate the e...The properties and blending recipe of petroleum cokes used to make high quality carbon anodes for aluminium electrolysis were studied. Three kinds of green cokes were selected for bench scale study to illustrate the effects of cokes properties and its blending recipe on anode performances. The results show that impurities derived mainly fi＇om cokes remarkably affect the CO2 reactivity and air reactivity of carbon anodes. Ca, Na and V can increase CO2 reactivity of calcined cokes but S has the contrary effect, and the cokes of high V level generally present high air reactivity. The anodes with good quality can be made by properly selecting and scientifically blending of cokes, some poor quality cokes can also be used to produce high quality anodes with a reasonable blending recipe. Na contaminated anodes have high CO2 reactivity and air reactivity, so the recycled anode butts should be well cleaned to reduce Na content before being introduced into anode production, which is especially important to the low S cokes.展开更多
With the SCF-ab initio and EHMO method used in quantum chemistry, the total energy and charge distribution are calculated for O ions which are adsorbed on the different positions of various C lattices. Furthermore, th...With the SCF-ab initio and EHMO method used in quantum chemistry, the total energy and charge distribution are calculated for O ions which are adsorbed on the different positions of various C lattices. Furthermore, the microstructure is dis- cussed for O ions discharging on the graphite anode.展开更多
This study deals with SnO2-based ceramic anodes doped with Sb203 and CuO, aiming at contributing new data regarding their electrochemical behavior in cryolite melts. The performances of the anodes were evaluated by an...This study deals with SnO2-based ceramic anodes doped with Sb203 and CuO, aiming at contributing new data regarding their electrochemical behavior in cryolite melts. The performances of the anodes were evaluated by anodic polarization, cyclic voltammetry, and current efficiency and corrosion measurements. The investigation proves that the anodic process of SnO2-based inert anodes occurs at a low overvoltage and the oxygen discharge takes place in one step with an exchange of two electrons. The current efficiency and corrosion were proved to be dependent on the electrolysis parameters and composition of electrolysis bath. For a long term electrolysis, the dissolution of the anode in the cryolite-alumina melt produced small aluminium contamination（ca. 0.2%, mass fraction）.展开更多
A mathematical theory and the software application based on the full MHD model of the electrolysis cell is used to predict the electric current distribution over the anodes from the measurement of magnetic fields at s...A mathematical theory and the software application based on the full MHD model of the electrolysis cell is used to predict the electric current distribution over the anodes from the measurement of magnetic fields at specifically defined node points assumed to be available from the wireless sensors.The full 3d busbar configuration of two different commercial ceils are used for the model simulations.It is demonstrated that a unique solution for the electric current can be obtained when two sensors per each anode are used to detect the single component of magnetic field.The mathematical software is tested for the sensitivity to the busbar configuration complexity.The ability to monitor continuously the electric current distribution to high accuracy helps to control disturbances and deviations from a normal production process.展开更多
A two-step alkaline-acidic leaching process was conducted to separate the cryolite from spent pot lining and to purify the carbon. The influencing factors of temperature, time, and the ratio of liquid to solid in alka...A two-step alkaline-acidic leaching process was conducted to separate the cryolite from spent pot lining and to purify the carbon. The influencing factors of temperature, time, and the ratio of liquid to solid in alkaline and acidic leaching were investigated. The results show that the recovery of soluble compounds of Na3AlF6 and Al2O3 dissolving into the solution during the NaOH leaching is 65.0%,and the purity of carbon reaches 72.7%. During the next step of HCl leaching, the recovery of soluble compounds of CaF2 and NaAl11O17 dissolving into the HCl solution is 96.2%, and the carbon purity increases to 96.4%. By mixing the acidic leaching solution and the alkaline leaching solution, the cryolite precipitates under a suitable conditions of pH value 9 at 70 °C for 2 h. The cryolite precipitating rate is 95.6%, and the purity of Na3AlF6 obtained is 96.4%.展开更多
According to the problems of short life and low strength of TiB2 coating cathode for current technology in aluminium electrolysis industry,this work synthesized TiB2-TiB/Ti gradient composite with TiB2 coating and TiB...According to the problems of short life and low strength of TiB2 coating cathode for current technology in aluminium electrolysis industry,this work synthesized TiB2-TiB/Ti gradient composite with TiB2 coating and TiB whiskers in metallic Ti matrix by a electrolytic boronizing method based on similar density and thermal expansivity of the three materials.The phase composition and morphology of the cross-section were determined by X-ray diffraction(XRD),scanning electronic microscope(SEM)and X-ray energy dispersive spectrum(EDS).The results show that uniform TiB2 layer with a thickness of 8-10μm is continuously coated on the surface while the TiB whisker connected with TiB2 layer was embedded dispersedly into the matrix.The TiB crystal whisker has a maximum length of about 220μm.The growth rate of TiB2 and TiB is enhanced by the strong reduction of B4C.The novel gradient design of the composite helps to extend life and improve strength of the TiB2 cathode in aluminium electrolysis.展开更多
The anodic behaviour of pre-oxidised and non-oxidised Cu-Al-based anodes(Cu-10Al and Cu-9.8Al-2Mn)in KF-AlF_(3)-Al_(2)O_(3)melts was studied through galvanostatic and potentiodynamic polarization techniques.The alloy ...The anodic behaviour of pre-oxidised and non-oxidised Cu-Al-based anodes(Cu-10Al and Cu-9.8Al-2Mn)in KF-AlF_(3)-Al_(2)O_(3)melts was studied through galvanostatic and potentiodynamic polarization techniques.The alloy compositions were oxidised for a short-term(8 h)at 700℃,followed by galvanostatic polarization for 1 h at 800℃with an applied current density of 0.4 A/cm^(2).The potentiodynamic curves were recorded with a sweep rate of 0.01 V/s.XRD analysis was conducted on frozen melt samples collected on the surface of the anode,and SEM observation was performed on the anode after the experiment to study the phases of the scales formed on the alloys.All the anode materials had a steady potential between 2.30 and 2.50 V(vs Al/AlF_(3)).The corrosion rates of the anodes were calculated from the data acquired through potentiodynamic polarization.It was seen that pre-oxidised anodes possess a low corrosion rate compared to those without pre-oxidation treatment.展开更多
基金Project (2012FJ6123) supported by the Project of Science and Technology of Hunan Province,ChinaProject supported by Post-Doctoral Foundation of Central South University,China+1 种基金Project (CL12100) supported the Undergraduate Innovative Training of Central South University,ChinaProject (2282013bkso13) supported by Free Exploration Plan of Central South University,China
文摘NiFe2O4-10NiO-based cermet inert anodes for aluminium electrolysis were prepared and their properties were investigated in a lab-scale electrolysis cell. The results show that the inert anodes exhibit good performance during electrolysis in molten salt cryolite at 960 °C, but according to the analyses of phase compositions and microstructures through XRD, SEM/EDX and metallographic analysis, the metal in the anodes is preferentially corroded and many pores are produced on the anode surface after electrolysis. The preferential dissolution of Fe in the NiFe2O4 phase may lead to the non-uniform corrosion of NiFe2O4 grains. Moreover, a dense protective layer of NiFe2O4-NiAl2O4-FeAl2O4 is formed on the anode surface, which originates from the reaction of Al2O3 dissolved in the electrolyte with NiO or FeO, the annexation of NiFe2O4-NiAl2O4-FeAl2O4 to NiO and volume expansion. Thus, the dense NiFe2O4-NiAl2O4-FeAl2O4 layer inhibits the metal loss and ceramic-phase corrosion on the surface of the cermet inert anodes.
文摘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.
文摘The properties and blending recipe of petroleum cokes used to make high quality carbon anodes for aluminium electrolysis were studied. Three kinds of green cokes were selected for bench scale study to illustrate the effects of cokes properties and its blending recipe on anode performances. The results show that impurities derived mainly fi＇om cokes remarkably affect the CO2 reactivity and air reactivity of carbon anodes. Ca, Na and V can increase CO2 reactivity of calcined cokes but S has the contrary effect, and the cokes of high V level generally present high air reactivity. The anodes with good quality can be made by properly selecting and scientifically blending of cokes, some poor quality cokes can also be used to produce high quality anodes with a reasonable blending recipe. Na contaminated anodes have high CO2 reactivity and air reactivity, so the recycled anode butts should be well cleaned to reduce Na content before being introduced into anode production, which is especially important to the low S cokes.
文摘With the SCF-ab initio and EHMO method used in quantum chemistry, the total energy and charge distribution are calculated for O ions which are adsorbed on the different positions of various C lattices. Furthermore, the microstructure is dis- cussed for O ions discharging on the graphite anode.
文摘This study deals with SnO2-based ceramic anodes doped with Sb203 and CuO, aiming at contributing new data regarding their electrochemical behavior in cryolite melts. The performances of the anodes were evaluated by anodic polarization, cyclic voltammetry, and current efficiency and corrosion measurements. The investigation proves that the anodic process of SnO2-based inert anodes occurs at a low overvoltage and the oxygen discharge takes place in one step with an exchange of two electrons. The current efficiency and corrosion were proved to be dependent on the electrolysis parameters and composition of electrolysis bath. For a long term electrolysis, the dissolution of the anode in the cryolite-alumina melt produced small aluminium contamination（ca. 0.2%, mass fraction）.
文摘A mathematical theory and the software application based on the full MHD model of the electrolysis cell is used to predict the electric current distribution over the anodes from the measurement of magnetic fields at specifically defined node points assumed to be available from the wireless sensors.The full 3d busbar configuration of two different commercial ceils are used for the model simulations.It is demonstrated that a unique solution for the electric current can be obtained when two sensors per each anode are used to detect the single component of magnetic field.The mathematical software is tested for the sensitivity to the busbar configuration complexity.The ability to monitor continuously the electric current distribution to high accuracy helps to control disturbances and deviations from a normal production process.
基金Project (50804010) supported by the National Natural Science Foundation of China
文摘A two-step alkaline-acidic leaching process was conducted to separate the cryolite from spent pot lining and to purify the carbon. The influencing factors of temperature, time, and the ratio of liquid to solid in alkaline and acidic leaching were investigated. The results show that the recovery of soluble compounds of Na3AlF6 and Al2O3 dissolving into the solution during the NaOH leaching is 65.0%,and the purity of carbon reaches 72.7%. During the next step of HCl leaching, the recovery of soluble compounds of CaF2 and NaAl11O17 dissolving into the HCl solution is 96.2%, and the carbon purity increases to 96.4%. By mixing the acidic leaching solution and the alkaline leaching solution, the cryolite precipitates under a suitable conditions of pH value 9 at 70 °C for 2 h. The cryolite precipitating rate is 95.6%, and the purity of Na3AlF6 obtained is 96.4%.
基金Project(21473042) supported by the National Natural Science Foundation of ChinaProject(GUIKE-AD18126001) supported by the Guangxi Science and Technology Special Project on Bases and Talents,China
文摘According to the problems of short life and low strength of TiB2 coating cathode for current technology in aluminium electrolysis industry,this work synthesized TiB2-TiB/Ti gradient composite with TiB2 coating and TiB whiskers in metallic Ti matrix by a electrolytic boronizing method based on similar density and thermal expansivity of the three materials.The phase composition and morphology of the cross-section were determined by X-ray diffraction(XRD),scanning electronic microscope(SEM)and X-ray energy dispersive spectrum(EDS).The results show that uniform TiB2 layer with a thickness of 8-10μm is continuously coated on the surface while the TiB whisker connected with TiB2 layer was embedded dispersedly into the matrix.The TiB crystal whisker has a maximum length of about 220μm.The growth rate of TiB2 and TiB is enhanced by the strong reduction of B4C.The novel gradient design of the composite helps to extend life and improve strength of the TiB2 cathode in aluminium electrolysis.
文摘The anodic behaviour of pre-oxidised and non-oxidised Cu-Al-based anodes(Cu-10Al and Cu-9.8Al-2Mn)in KF-AlF_(3)-Al_(2)O_(3)melts was studied through galvanostatic and potentiodynamic polarization techniques.The alloy compositions were oxidised for a short-term(8 h)at 700℃,followed by galvanostatic polarization for 1 h at 800℃with an applied current density of 0.4 A/cm^(2).The potentiodynamic curves were recorded with a sweep rate of 0.01 V/s.XRD analysis was conducted on frozen melt samples collected on the surface of the anode,and SEM observation was performed on the anode after the experiment to study the phases of the scales formed on the alloys.All the anode materials had a steady potential between 2.30 and 2.50 V(vs Al/AlF_(3)).The corrosion rates of the anodes were calculated from the data acquired through potentiodynamic polarization.It was seen that pre-oxidised anodes possess a low corrosion rate compared to those without pre-oxidation treatment.
