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1. Introduction
Pyrometallurgical copper smelting remains the dominant route for primary refined copper production, accounting for over 80% of global capacity. The process converts copper sulfide concentrates (primarily chalcopyrite, CuFeS₂) into high-purity cathode copper (≥99.99% Cu) through a series of high-temperature metallurgical operations. This article details the mainstream integrated flowsheet consisting of flash smelting, converting, anode refining, and electrolytic refining.
2. Concentrate Preparation and Blending
Copper concentrates (25-35% Cu) arrive by bulk vessel and are stored in covered stockpiles. Moisture content is typically 8-12% and must be reduced to ≤0.3% using rotary kilns or fluidized-bed dryers to prevent explosions and excessive energy consumption in downstream smelting.
Dried concentrate is blended with fluxes (quartz, limestone), reverts, and converter slag in precisely controlled proportions. Modern plants employ automated disc feeders and load-cell systems achieving blending accuracy within ±0.5%.
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3. Flash Smelting
Flash smelting is the most advanced technology for treating copper sulfide concentrates, represented globally by Outotec (now Metso) flash furnaces and Chinese-developed oxygen bottom-blown furnaces.
3.1 Process Principle
Dry concentrate is injected into a hot, oxygen-enriched airstream (oxygen concentration 75-90%) at 850-950°C. Reactions (drying, oxidation, slag and matte formation) complete in 3-5 seconds, with reaction heat sustaining autothermal operation. Key reactions include: 4CuFeS₂ + 9O₂ → 4CuS + 2Fe₂O₃ + 8SO₂ 2FeS + 3O₂ + 2SiO₂ → 2FeO·SiO₂ + 2SO₂
3.2 Key Equipment
- Reaction shaft: 11-14 m height, 7-9 m diameter, lined with high-grade magnesite-chrome brick and copper water jackets.
- Settler and uptake shaft: gravity separation of matte (65-75% Cu) and slag.
- Waste heat boiler: recovers sensible heat from ~550°C off-gas for steam generation.
- Oxygen-to-concentrate ratio: 1.15-1.25 Nm³ O₂/t dry concentrate
- Reaction shaft temperature: 1250-1300°C
- Matte temperature: 1180-1220°C
- Slag Fe/SiO₂ ratio: 1.1-1.4, copper in slag ≤0.6%
3.3 Critical Control Parameters
Single flash furnace capacity reaches 4000-5500 t/d concentrate with thermal efficiency >98% and near-100% SO₂ capture.
4. Converting
Matte is transferred via electrically heated launders or ladles to Peirce-Smith converters or continuous converting furnaces.
4.1 Slag-Forming Stage
Oxygen-enriched air (25-35% O₂) is blown to oxidize iron sulfide. Slag containing 2-8% Cu is skimmed and returned to flash smelting.
4.2 Copper-Making Stage
Continued blowing oxidizes Cu₂S to blister copper (98.5-99.3% Cu) at 1180-1230°C.
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1.Master Coil Loading & Auto-Centering → 15-ton hydraulic coil car + photoelectric servo EPC, centerline alignment error < 0.1 mm
2.Uncoiling & Tension Establishment → Magnetic powder brake + closed-loop servo control, 50–1500 N precisely adjustable
3.Precision Slitting → Imported tungsten carbide or PM HSS discs, spindle runout ≤ 0.002 mm, spacers ground to ±0.001 mm, real-time wear compensation
4.Edge Trim Handling → Independent dual-head scrap winders; trim returned as coils or crushed on-site
5.Rewinding & Tension Isolation → Individual dancing-roll isolation per strand, pneumatic mandrels + auto corner protection, face alignment ≤ ±0.3 mm
6.Automatic Cut-Off & Packaging → Decelerate → cut → paper wrap → label → discharge in 45 seconds
Complete Automatic Copper Coil Slitting Process
5. Anode Furnace Fire Refining
Blister copper is charged into 50-500 t stationary or tilting anode furnaces for oxidation-reduction refining.
5.1 Oxidation Stage
Air or oxygen lances remove residual Fe, Ni, As, Sb, and Bi as floating slag.
5.2 Reduction Stage
Oxygen is reduced using natural gas, diesel, or wooden poles to 150-300 ppm. The refined copper is cast into 300-450 kg anodes (Cu ≥99.0%).
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6.1 Operating Conditions
- Current density: 220-320 A/m²
- Cell voltage: 0.22-0.32 V
- Electrolyte temperature: 60-65°C
- Cu²⁺: 40-55 g/L, free H₂SO₄: 150-220 g/L
6.2 Electrochemical Reactions
Anode dissolution: Cu → Cu²⁺ + 2e⁻ More noble elements (Au, Ag, Se, Te) report to anode slime; less noble elements enter solution. Cathode deposition yields ≥99.993% Cu meeting LME Grade A specifications.
7. Off-Gas Treatment and Environmental Control
SO₂-rich gases from flash furnace, converters, and anode furnaces are cooled, dedusted, and processed in double-contact acid plants achieving >99.8% sulfur recovery. Tail gas SO₂ is well below 100 mg/Nm³. Arsenic, mercury, and other heavy metals are removed via specialized processes.
8. Conclusion
Contemporary copper pyrometallurgy has achieved high continuity, automation, and environmental performance. Integrated flash smelting-continuous converting-anode refining-electrorefining flowsheets deliver overall copper recovery >98.5% and specific energy consumption of 280-320 kgce/t cathode, representing world-class benchmarks. Ongoing developments in oxygen enrichment, continuous copper-making technologies, and digital process control will further advance efficiency and sustainability.
Post time: Dec-24-2025