This new anode concept patented and developed by John Turner and Thomas Meyer provides a rolled anode without a welded joint or soldered slotted

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2 Homogeneous one piece Rolled Lead Alloy Anode This new anode concept patented and developed by John Turner and Thomas Meyer provides a rolled anode without a welded joint or soldered slotted joint. The method of manufacture ensures that the header, straight or cranked, rolled and/or cross-rolled, is of the same material throughout. In cases where the anode corrodes quicker at the solution level, the method allows the anode to be rolled thicker from the header to +30mm below the solution level and then the balance of the blade is rolled to the clients required thickness. The solution can also be raised to under the lead encased copper bar, increasing the surface area. The method is suitable for any alloy, gives maximum electrical conductivity and the ultimate mechanical strength of a rolled anode.

3 This graphic shows the various methods of anode manufacture. Note that there are no welded joints and the lead alloy is the same material on the header bar as well as the blade. Fig. 1. A fully cast anode Fig. 2. A cast-rolled anode Fig. 3. A cast-rolled anode with thicker section at the electrolyte level Fig. 4. A welded rolled anode indicating position of weld in relation to solution level

4 Lead anode plant

5 Completed anode

6 Fig. 1 Micrograph showing the transverse view of the as-cast plate Fig 2. Micrograph showing the transverse view of the 6mm rolled-1 plate

7 Fig. 3 Micrograph showing the longitudinal view of the 6mm Rolled-1 plate Fig 4. Micrograph showing the plan view of the 6mm Rolled-1 plate

8 Fig.7 Micrograph showing the longitudinal view of the 6mm Rolled-14 plate Fig.8 Micrograph showing the plan view of the 6mm Rolled-14 plate

9 Cathode Design Alternatives Type Description Qty in Service Outotec Cobra EPCM SP Xstrata ISA Xstrata Kidd Welding SS sheet to a SS hanger bar with a Cu Core Welding SS sheet to a Cu Hanger Bar Welding SS sheet to a Cu Hanger Bar * Stainless Steel Sheath. Ends Sealed Welding SS sheet to SS header bar, electroplated with Cu Welding SS sheet to a Cu Hanger Bar * Stainless Steel Sheath. Sheath filled with Epoxy 60, ,000 65,000 1,400, ,000

10 Electrical Resistance For the purpose of this paper, the resistance is calculated by adding the theoretical resistance in the hanger bar and the calculated resistance in the stainless steel sheet. Data All Cathodes Electrical Resistivity of copper: micro ohm x m Electrical Resistivity of 316L SS: 0.74 micro ohm x m End of Hanger Bar to Center of Cathode 665 mm SS length from Hanger Bar to bottom of window: 57 mm SS length from bottom of window to Electrolyte level: 29 mm SS width below window: 1018 mm SS thickness: 3.25 mm Nominal Current through Cathode: 600 amps Operating Hours per year : 8240 hours Power Costs: US $0.055 per kwh

11 Electrical Resistance Con t

12 Chloride Pitting Chloride Pitting occurs generally near the solution line Pitting is caused by high chloride levels in the electrolyte All Cathodes being considered would be similarly affected by chloride pitting as all use 316L stainless steel New materials are being substituted for the 316L SS and this will be discussed further in the next slide.

13 New Materials Type %Cr %Ni %Mo PRE Surface Finish 316L B LDX E AL B Super Ferritic Grades B

14 Dissolution of Copper Hanger Bars Cause: Due to the solubility of copper in sulphuric acid. The presence of acid mist in the air above the cells. Cell ventilation systems can have an adverse affect. Generally more aggressive in SX-EW tankhouses Will increase the cathodes electrical resistance over time Cathode Blank will require a major repair.

15 Galvanic Corrosion Cause: Where Dissimilar metals are in contact in the hanger bar or the hanger bar/sheet connection Prevalent in SX-EW Primarily Aggravated by Acid Mist Acid Mist Ventilation systems can have an affect on the rate of Galvanic Corrosion

16 Cathode Corrosion Summary Type Outotec Advantage/Disadvantag e Advantage Comments Cobra Cathode Disadvantage Subject to Galvanic Corrosion EPCM SP Cathode Advantage Xstrata ISA Disadvantage Subject to Copper Dissolution Xstrata Kidd Advantage

17 Maintainability/Durability Maintainability Considerations Minor Repairs Edgestrip Replacement Surface scratches Straighten minor bends in sheet Surface Cleaning Major Repairs Recuperation of Damage Sheet Replace Hanger Bar Replace damage sheet Replace stainless steel header bar Recommended edgestrip: Schiebler Edgewise. Operational savings over pinned edgestrips and extrusion welded edgestrips can be as high as $7.40 per cathode per year. Recuperation of Damaged Sheets: The ability to remove the header bar can allow damaged sheets to be salvaged. Replace damaged sheets with new sheets Ability to replate header bars locally

18 Advances in Cathode Maintenance Advances Pictures Recuperation Re-use previously discarded cathodes Extend the cathode operational life Sheet Cleaning Reduce hand buffing Consistent Surface finish Non-destructive

19 Thank you