Copper dross

Dressing. The impure lead bulhon, produced from any of the smelting processes, is cooled to remove dissolved copper prior to the refining operation. The operation is referred to as copper drossing, and is performed in one or two 250 t cast-iron ketdes. The process consists of skimming off the dross, stirring the lead, and reskimming. 

Soda. Process. Use of a soda smelting process for treating copper drosses in the reverberatory furnace increases the copper to lead ratios in the matte and speiss, and aUows lower operating temperatures. A flow sheet describing this process is shown in Figure 11. 

Table 4. Composition of Products from Copper Dross Treatment...

The continuous softening process used by The Broken Hill Associated Smelters Pty., Ltd. is particularly suitable for lead buUion of fairly uniform impurity content. The copper-drossed blast furnace buUion continuously flows in the feed end of a reverberatory furnace at 420°C, and the softened lead leaves the opposite end at 750°C. Oxidation and agitation is provided by compressed air blown through pipes extending down through the arch of the furnace into the bath. 

Precipitation can also occur upon chemical reaction between the impurity and a precipitating agent to form a compound insoluble in the molten metal. The refining of cmde lead is an example of this process. Most copper is removed as a copper dross upon cooling of the molten metal, but the removal of the residual copper is achieved by adding sulfur to precipitate copper sulfide. The precious metals are separated by adding zinc to Hquid lead to form soHd intermetaHic compounds of zinc with gold and silver (Parkes process). The precious metals can then be recovered by further treatment (see Lead). 

Continuous cellulosic fibers, 20 557 Continuous compression filters, 77 379-381 Continuous conveyors, 9 119 Continuous cooling, in austenite transformation, 23 282-283 Continuous-cooling transformation (CCT) diagrams, 77 16 23 280 Continuous copper-drossing process, 74 745-747... 

Copper dichromate, molecular formula, properties, and uses, 6 56It Copper(II) diphosphate hydrate, molecular formula and uses, 7 778t Copper drossing, 14 145—141 Copper electrodes, 3 430 Copper(II) fluoborate, molecular formula and uses, 7 1111... 

The different concentrates, battery paste, recycled products such as dusts, refinery intermediates and copper dross are transported using closed-belt conveyers, the so-called pipe conveyers, thus drastically reducing emissions. 

Trial work took place during 1996 on treating ISF bullion cast directly fix>m the furnace. This work resulted in an extension to the kettle floor such that it is now capable of treating 55,000 TPA of direct cast ISF bullion fioih BZL and 36,000 TPA of similar material from MHD. Around 11,000 TPA of copper dross is generated from the revised operation and is sold. It is treated through a purpose-designed plant so that it can be hygienically transported by sea. 

No. 34 Melting/Copper Drossing 250 tonnes (with beach)... 

Time Cycle Copper Dross Make Fuel Consumption Final Copper Level Pump Out Temperature... 

The various by-products are stockpiled to accumulate sufficient material to fill a silo. By far the lai est amount of material requiring treatment is the BRM floor copper dross. The material is allowed to cool for several days to less than 30°C. The molasses will degrade at... 

The first observation of CuS as a (transient) constituent of copper dross was made in 1956 by McClincy, a PhD student in Golden, Colorado, and Professor Schlechten, his department head at the Colorado School of Mines, gave colloquia in Australia on this topic. McClincy and Larson (24) showed that reaction (3) is very fast, so that CuS is always formed initially. Clark (9), Womer (25) and Pollard (26) all confirmed the early formation of CuS, but as it is rapidly consumed by reaction (4) it is never a major constituent of the final dross, which consists of CuzS, PbS, entrained Pb, and some PbO. Although several investigators have paid a great deal of attention to the transient existence of CuS, there seems to be no reason why the process should not proceed equally well if there were no formation of CuS. 

The feed is prepared by mixing, grinding and drying of the following materials (in weight %) a lead-copper-zinc bulk concentrate 78-80% iron concentrate or metal chips 2.5-3.0% copper drosses 2.5-3.0% limerock 8-9% quartzite ore 7-8%. The calorific value of this kind of charge (feed) is in the range from 600 to 660 kcal/kg. 

Normally copper in lead smelter feed is sufficiently low to fully dissolve in bullion and be recovered by copper drossing as part of the refining stage. However, in the case of high copper feeds (above five per cent of the lead content), a matte can be formed during smelting. This will require retention of sufficient sulfur to form the matte, which tends to be a mixture of lead, iron and zinc sulfides as well as copper sulfide. 

Any lead bullion recovered from matte treatment will be rich in copper and can form a significant circulating load through the lead bullion refining stage (see Chapter 12 - Copper Removal or Copper Drossing). 

A significant part of any refinery can be the various processes required to treat drosses and residues produced from each of the separate refining steps for the purpose of recovering by-products, recovering lead for recycle, or rendering the material suitable for disposal. Such processes include the conversion of copper dross into a marketable form for copper recovery, the production of silver and gold, the recovery of zinc for recycle, the recovery of antimony to produce antimonial lead alloy and the conversion of arsenic into a stable material suitable for disposal. 

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