Advances in the Manufacturing of Lead Based Anodes for Electrowinning

Transcription

1 Advances in the Manufacturing of Lead Based Anodes for Electrowinning Dr. Abbas Mirza, Senior Process Engineer, RSR Technologies, Dallas, TX Mr. Jerry Gagnon, Sales Manager, Quemetco Metals, Casa Grande, AZ Mr. Patricio Ugarte, RSR Chile, Peru, Argentina

2 RSR Anodes Group US Quemetco Metals Ltd. LePlomb Francais France Castle Lead Works South Africa Mr. Patricio Ugarte RSR: Chile, Peru, Argentina Castle Lead Works Zambia MESCO Japan BROCHOT Asia

3 Manganese Problem Copper EW solutions often contain some manganese. Manganese can react with the stable PbO2 corrosion layer on the anode surface making it unstable, less dense, less adherent, and susceptible to shedding Cobalt has been added to the electrolyte in amounts of ppm based on the manganese content and current density

4 Manganese Problem The manganese attacks the PbO2 layer and causes MnO2 to build up in the layer. MnSO 4 + PbO 2 -> PbSO 4 +MnO 2 The PbSO4 is converted back to PbO2, but it is now deposited in loose layers. These layers are easily spalled off causing contamination of the copper cathode. Must remove MnO 2 periodically!!!

5 Manganese Problem In Zinc Electrowinning with high Mn content, we need to modify anode surface so MnO 2 can stick to the anode and build up instead of spalling off Sandblasting traditionally used to increase surface roughness. Environmental issues with worker exposure and leadcontaminated silica. RSR Scarification process greatly minimizes environmental issues associated with sandblasting Establish cleaning frequency!!!

6 Zinc Electrowinning: Laboratory Case Study Cell muds at PbAg and PbCaAg anodes Pb-Ag - SB Pb-Ag - A Pb-Ag - B Pb-Ag - C Pb-Ag - AR PbCaAg - SB PbCaAg - A PbCaAg - B PbCaAg - C PbCaAg - AR

7 RSR Surface Treatment 35 Pb-Ca-Ag for Zinc Electrowinning Surface profile makes MnO 2 stick better to the anode

8 RSR Cast-Around Anode Design Covered Copper Electrowinning Cells Copper tankhouses covered to minimize acid exposure Additional corrosion protection for copper hanger bars

9 RSR Advanced Welding Technique Copper Liberator Cells Cast around portion welded to rolled alloy sheet Conventional welding: Lead exposure and possibility of defective welds RSR is in the process of developing an advanced, automated solid state welding technique Eliminate variance between operators Consistently high quality of welds through anode thickness

10 Lead Anodes for Copper Electrowinning Management of Elements of Electrochemical Significance

11 Hydrogen and Oxygen Float Currents Elements Upper Level Rate of Change (ma Ah-1 per ppm) Level (ppm) I float I hydrogen I oxygen I float I H 2 I O 2 Ni Sb Co Cr Fe Mn Cu Ag Se Te As Sn Bi ? 500? 500? Ge Zn ? 500? 500? Cd ALABC N3.1 (R.D. Prengaman, Improvements to active material for VRLA batteries, J. Power Sources 144 (2) (2005) )

12 SYNERGISTIC EFFECTS Beneficial Detrimental Hydrogen evolution: Ag, Bi, Cd, Ge, Zn Ni, Se, Te Ag, Bi, Zn Oxygen evolution: Bi (Neutral) Ag (Beneficial) Ni, Se, Te

13 Environmental Management in Lead Production Maximum Available Control Technology (MACT)

14 NOx and SOx Scrubbers

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16 Regenerative Thermal Oxidizer Thermal Beds Exhaust Duct Inlet Blower

17 Emissions Pre and Post Installation (Pounds/Year)

18 Conclusions RSR anodes group has developed a surface treatment for Zinc EW that is comparable to SB, and that greatly minimizes the environmental and exposure problems. RSR is developing an advanced, automated welding technique to weld cast around copper bars to rolled sheet. Management of elements of electrochemical significance extremely important Maximum Available Control Technology (MACT) to operate lead smelters with the highest environmental standards

19 THANK YOU VERY MUCH FOR YOUR ATTENTION