Industrial Experiment Study Of Aluminum Reduction Cells Potline With A New Type Of Cathode Design

Recent years, energy conservation is the core objectives to the fabrication of industrial enterprises in China. Aluminum electrolysis is known as more energy consumption and more pollution. Currently, the DC power of aluminum electrolysis is about13000-13500kWh/t-A1and the energy efficiency is less than50%. A significant reduction in power consumption of aluminum electrolysis comes true because of the invention of aluminum reduction cell with a new type of cathode design.The technology of aluminum reduction cells with a new type of cathode design is applied on ninty four200kA cells in Huadong Aluminum Industry Co., Ltd. Gas-Aluminum preheating method(GAP) is applied on the cells. Energy consumption of GAP method is less than the method of liquid metal and the coke preheating method.6month later, the average cell voltage of the cells with new type of cathode design is3.72V, while the cell voltage of the traditional cells is4.04V. The coefficient of AE is2.75times per cell in10days and the cell voltage when AE happens is12.12V. The average CE of the cells with a new type of cathode design is93.11%while the CE of the traditional cells is93.00%. Energy consumption of the cells with a new type of cathode design is1024.4kWh/t-Al lower than that of the traditional cells.The vertical magnetic field of liquid metal in cells with a new type of cathode design is weaker than that in traditional cells. On the condition of certain allocation of busbar, the new type of cathode can weaken the vertical magnetic field and make the interface of liquid metal become stable. The results of measurement on velocity of liquid metal show that the bumps on top of the cathodes can reduce the velocity of liquid metal.The surface stability of liquid metal in aluminum reduction cell with a new cathode design is studied with real-time monitoring system of liquid metal based on anode conductor isometric voltage drop which is designed independently and the factors which affect the stability of surface of liquid metal are researched. The results show that the amplitude of oscillation of anode conductor isometric voltage drop of aluminum reduction cell with new cathode design is less than that of traditional cathode aluminum reduction cell. The maximum amplitude of surface oscillation of liquid metal in aluminum reduction cell with new cathode design is0.45cm and the maxium amplitude of surface oscillation of liquid metal in traditional cathode cell is0.88cm. This proves that the new cathode design can block the surface oscillation of liquid metal. When cell voltage of traditional cell is decreased from4.10V to3.95V, anode conductor isometric voltage drop of comparison cell is increased from240μV to541μV rapidly and the curve of anode conductor voltage drop shows divergent patterns. The comparison cell is under the condition of unstable running. The traditional cathode cell can not work normally below cell voltage of3.95V. The anode current distribution of aluminum reduction cell with new type cathode design is554.88A. It is269.21A less than that of traditional cathode aluminum reduction cell. Thus the anode current distribution in the new type cathode aluminum reduction cell is more uniform than that in traditional cell. The period of liquid metal wave in new type cathode aluminum reduction cell is50s. And the period of liquid metal wave in traditional cathode aluminum reduction cell is the same.According to the results of voltage balance, heat balance, magnetic field, flow field in liquid metal and surface stability of liquid metal, the principle of surface oscillation weakened of cells with new type of cathode design is researched with numerical simulation. The results show that a lot of small circulation which revolves the bump of cathode formed by the horizontal current and vertical magnetic field can block the flow of liquid metal and reduce the wave of liquid metal. The horizontal current and vertical magnetic field in liquid metal in cells with new type of cathode design is less than that in traditional cells. The results of numerical simulation show that horizontal velocity and vertical velocity of liquid metal in the interface between electrolyte and liquid metal is slower than that in the traditional cathode cell. It proves that surface of liquid metal in cells with new type of cathode design is more stable than that in traditional cathode cell.A kind of equipment is designed independently which can measure electrolyte temperature, liquidus temperature and superheat degree. There are advantages of delicacy, low cost and convenience. The probe with new design can absorb the heat which is released from the phase changing of electrolyte. Thus the reproducibility and accuracy of the probe is good for the liquidus temperature of the electrolyte with complex composition and low Cryolite Ratio. It is tested in laboratory and industry factory.The results show that the accuracy and stability of the equipment is good.The effect of Cryolite Ratio and content of LiF, KF, CaF2on liquidus temperature is researched in laboratory. The results show that liquidus temperature is increased with increasing of Cryolite Ratio and liquidus temperature is decreased with increasing of the content of LiF, KF, CaF2. Liquidus temperature of system of Na3AlF6-Al2O3-LiF- KF-CaF2is simulated with the method of response surface.The regression equation of liquidus temperature is:Tl=621.822+262.139·CR-5.226·ω(LiF)-6.518·ω(KF)-0.976·ω(CaF2)-1.111.CR·ω(LiF)+2.5.CR·ω(KF)-0.139·CR·ω(CaF2)+0.125·ω(LiF)·ω(KF)-0.292·ω(LiF)·ω(CaF2)+0.028·ω(KF)·ω(CaF2)-47.870·CR+0.264·ω2(LiF)-0.354·ω2(KF)From the figure of response surface,it is shown that the ability of effect on liquidus temperature is:LiF>CR>KF>CaF2.