| In the hydrometallurgical process of nonferrous metals such as Zn, Cu, Ni, Co, Mn, the high-concentration H2SO4solution is always used and Pb-based alloys are generally used as anodes. It can meet the basic requirements, but still has problems such as high oxygen evolution over-potential, unsatisfactory corrosion resistance, heavy and easy creep, which may result in high energy consumption and lead contamination of the cathode products. In order to save these problems, research has been done, mainly focused on electrocatalytic coated anodes(DSA), Pb-based multi-component alloy anodes and porous anodes. There are certain progress but still cannot meet the industrial requirements,In order to develop low cost and high performance new composite porous anode(CPA), by adopting the latest research results in related field, the electrochemical behavior of porous anode in H2SO4electrolyte, the influence of "anti-sandwich structure" on anodic potential, anodic corrosion rate, electric conductivity and mechanical properties, and the influence of RE elements on the structure and performance of Pb-based alloys are studied. After that, the counter-gravity infiltration equipment and technologies of industrial-sized composite porous anode are developed, and then the industrial test at zinc electro winning industrial site is carried out. The main research results are as follows:(1) The electrochemical behavior of CPA in H2SO4electrolyte is studied, and the forming process, structure and component of the oxidation film, the charateristic of mass transfer and charge transfer, and the oxygen evolution mechanism of it are revealed. Inside the porous anode, mass transfer and charge transfer are parallel processes, and the electrochemical reaction strength decreases from outside to inside, the "characteristic depth" is about3mm when the pore diameter is1.43-1.60mm. The electrochemical surface area and apparent activation energy are caculated, and the electrochemical nature of energy-saving performance is indicated. The apparent activation energy of CPA is about5kJ/mol more than traditional flat plate anode, but its electrochemical surface area is about10times of the later, which can enlarge the apparent exchange current, and enhance the oxygen evolution capability.(2) The "anti-sandwich structure" composite porous anode, with the core of dense metal and two pieces of porous layers metallurgical bonding together, is designed and prepared. The core board of the composite porous anode mainly takes the role of conducting current and taking load, and the electrochemical performance depends on the lateral porous layer. When the core board is2mm thick, the ultimate tensile strength and conductivity of CPA with pore diameter of1.25-1.43mm are3times and1.3times respectively than that of pure porous anode for the same pore diameter. Compared with traditional flat anodes and pure porous anodes, its anodic potential is114mV and16mV lower, and its corrosion rate is48.7%and6.3less, respectively.(3) The influences of Gd、Pr、Nd、Sm on the metallographic structure, oxidation film and mechanism of the oxygen evolution process are revealed, and a new kind of Pb-Ag (0.6wt.%)-Nd (0.5wt.%) ternary alloy suits for the electro winning process is obtained. The ultimate tensile strength, stable anodic potential and corrosion rate are20.985MPa、1.798V and2.347g/(m2h), which is respectively113.9%,99.7%and59.9%of the traditional Pb-Ag(0.8wt.%) anode.(4) The industrial application technologies of composite porous anode in zinc electrolytic process and copper powder electrolytic process are studied and developed, and the24-day industrial test using975mm×620mm×6mm CPAs is carried out in the zinc electrolyzing plant. The anodic potential, cell voltage and energy consumption are91mV,116mV and85kWh/t-Zn lower than traditional flat plate anode, and corrosion rate, formation of anode slime and Pb in zinc product are respectively82.5%,77%and34.4%less. |
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