When the smartphone in your hand transmits information, the wires in your home deliver light, or the electric
car speeds down the road, an ancient metal - copper - is silently supporting all of this with its excellent electrical,
thermal and ductile properties. However, the transformation of copper from an ore buried deep in the ground to
the ‘red metal’ that drives modern civilisation has been an extraordinary journey of smelting, combining millennia
of wisdom with cutting-edge technology. At the heart of this journey is the highly efficient, clean and intelligent
modern copper smelting process.
The Source: The Mystery and Challenge of the Ore
Copper is not widely available in its pure, monolithic form. Its story begins with ores in a variety of forms:
Sulphide ores (e.g. chalcopyrite CuFeS₂, porphyry Cu₅FeS₄): This is by far the most important source of copper
(around 80%). They are usually of low grade (0.5-2% Cu) and are closely co-occurring with iron, sulphur and a
variety of impurities (arsenic, antimony, bismuth, lead, zinc, precious metals, etc.).
Oxide ores (such as malachite Cu₂CO₃(OH)₂, chalcopyrite Cu₂O): relatively rare, often processed by wet smelting.
Natural copper: extremely rare.
The common challenge for these ores is: how to efficiently, economically, and environmentally extract, enrich,
and refine trace amounts of copper from a large number of veins and complex impurities into a high-purity
metal? Modern copper smelting is a sophisticated systematic project centred around this core proposition.
Modern Pyrometallurgy: Magnificent Metamorphosis under High
Temperature (Leading Process)
Pyrometallurgical smelting is the mainstream treatment of copper sulphide concentrates, the core of which
lies in the use of high-temperature chemical reactions to gradually enrich and purify copper, mainly through
three key stages:
Smelting: the molten stage of enrichment and separation
Mission: The finely ground copper concentrate (containing 20%-30% copper) is melted at high temperatures
(1150°C-1300°C), where a complex reaction occurs, separating two main products:
Ice Copper: A liquid metal-sulphide melt dominated by cuprous sulphide (Cu₂S) and ferrous sulphide (FeS),
which is a copper enricher (upgrading the copper content to 45%-75%).
Slag: Molten silicate consisting mainly of chalcopyrite oxides (SiO₂, FeO, CaO, Al₂O₃, etc.) with a density lower
than that of ice-copper, which floats in the upper layers and is discharged as the main carrier of impurities.
Core ‘stage’ technology:
Flash smelting: Modern mainstream technology. Dry fine-grained concentrate is instantly sprayed into a
high-temperature reactor with oxygen-enriched air (or industrial oxygen). The materials are oxidised and
exothermic in suspension, and the smelting reaction is completed instantly. Advantages: High reaction intensity,
high efficiency, low energy consumption (mainly self-heating), small amount of flue gas and high concentration
of SO₂ (>25%), which is extremely conducive to the subsequent high-efficiency acid production, with
significant environmental advantages.
Melting pool smelting: Concentrate is directly added to the high temperature melting pool (liquid slag or ice
copper), and oxygen-enriched air or oxygen is injected through submerged lances (e.g., top blowing, bottom
blowing, and side blowing) to complete the smelting reaction in the strongly stirring melting pool. Representative
furnace: Noranda furnace, Mitsubishi method continuous melting furnace, Ausmalt/Esa furnace, etc. Characteristics:
Wide adaptability of raw materials (can handle part of the miscellaneous materials or lump ore), relatively flexible operation.
Blowing: the oxidising leap from ice copper to crude copper
Mission: To further oxidise the liquid ice copper (mainly containing Cu₂S and FeS) produced from smelting, to
remove iron, sulphur and other impurities, and to produce Blister Copper with a copper content of 98.5%-99.5%.
Core equipment: Converter (PS Converter).
Process: Liquid ice copper is poured into the converter, and air or oxygen-enriched air is blown into the melt by
means of an airend or lance. Two main phases occur:
Slagging: FeS is preferentially oxidised to FeO, which is discharged as a slag with the addition of quartz frit (SiO₂)
(converter slag is usually returned to the furnace for copper recovery).
Copper phase: Once the iron has been largely removed, Cu₂S begins to oxidise, producing crude copper (Cu) and
SO₂. This stage requires precise control of the end point to avoid over-oxidation of the crude copper.
Key points: Strong exothermic reaction; high concentration of SO₂ fumes (need to collect acid efficiently); high
copper content in converter slag need to be recovered; intermittent operation.
Fire Refining and Electrolytic Refining: Towards Ultimate Purity
Fire refining: Melting, oxidation and reduction of crude copper in an anode furnace (usually rotary anode or reflector furnace).
Oxidation: Air or oxygen is injected to oxidise or volatilise impurities (e.g. residual sulphur, iron, lead, tin, arsenic,
antimony, bismuth, etc.) to slag.
Reduction: Removal of dissolved oxygen from molten copper by means of a reducing agent such as natural gas or
ammonia to prevent porosity in the ingot.
Output: Pouring of anode plates with a copper content of about 99.2-99.7 per cent.
Electrolytic refining:
Core process: Anode plates (with impurities) and pure copper starter plates (or stainless steel master plates) are
used as electrodes and immersed in an electrolytic solution of sulphuric acid and copper sulphate. A direct
current is applied.
Result: The anode copper is dissolved and pure copper ions are deposited and precipitated on the cathode (initiator
sheet) to form copper cathode (electrolytic copper) with a purity of 99.99% or more (conforming to the standard
of Grade A copper). Precious metals (gold, silver, platinum group) and selenium, tellurium and other valuable
elements enriched in the anode mud recovery. Impurities (such as nickel, arsenic, antimony, bismuth) enter the
electrolyte and are recovered or removed through purification.
Core value: It is the most effective means to obtain the highest purity commercial copper and comprehensively
recover valuable elements.
Wet smelting: the rise of the mild route
Hydrometallurgy offers an important route for oxidised ores, low-grade ores, complex hard-to-select ores or
specific wastes:
Core principle: Using a chemical solvent (mainly dilute sulphuric acid) to selectively dissolve copper from the ore
into solution (leaching) at room temperature or moderate heating and pressure, and then recovering the copper
from the solution through a variety of methods (extraction-electrowinning, replacement, precipitation, etc.).
Mainstream process: Leaching-Extraction-Electrowinning (L-SX-EW)
Leaching: Spraying or stirring the ore heap/slurry with a dilute sulphuric acid solution dissolves the copper
(generating a copper sulphate solution).
Solvent Extraction (SX): Selective ‘capture’ of copper ions in the leach solution with organic extractants, separating
them from most of the impurity ions (e.g., iron, aluminium) to obtain a high-purity, high-concentration, copper-rich
solution (the loaded organic phase is regenerated by back-extraction).
Electrowinning (EW): The copper-rich solution (electrolyte) is passed into the electrolysis tank, and under the
action of direct current, the copper ions are deposited and precipitated on the cathode (stainless steel or copper
mother plate), and high purity copper cathode (purity >99.99%) is obtained.
Advantages: Relatively low investment; suitable for processing low grade/complex ores; more environmentally
friendly (no SO₂ emissions, relatively stable slag); copper cathode can be produced directly near the mine.
Challenges: Relatively low treatment efficiency for sulphide ores; costly reagent consumption; long leaching
cycle; large amount of leach slag to be processed.
Green and smart: the future engine of copper smelting
Facing the severe challenges of resources, energy and environment, modern copper smelting is accelerating
its evolution towards greening and intelligence:
Extreme environmental protection:
Zero escape of sulphur: through oxygen-enriched smelting, high-efficiency closed dust collection and
double-rotation double-suction acid production technology, >99.9% of SO₂ in smelting flue gas is converted
into commercial sulphuric acid, completely eliminating the potential danger of acid rain. The tail gas is deeply
desulphurised to meet the emission standards.
Solid Waste Resourcing: Slag is slow-cooled, beneficiated or directly processed into high value-added building
materials (microcrystalline glass, aggregates, cement additives). Anode sludge systematic recovery of gold, silver,
selenium, tellurium and other rare precious metals. Wastewater deep treatment and reuse.
Harmful element control: Develop advanced process to treat complex raw materials such as high arsenic/
antimony/bismuth to achieve targeted removal, solidification and safe disposal of harmful elements.
Energy saving and carbon reduction:
Optimisation of energy structure: Improve the utilisation rate of oxygen enrichment/oxygen purification,
strengthen waste heat recovery (power generation, steam, preheating materials), and explore the substitution
of fossil fuels by clean energy sources such as biomass fuels and green hydrogen.
Process enhancement: Continuous smelting process (e.g. Mitsubishi method, flash blowing) to reduce heat
loss and improve thermal efficiency. Intelligent control systems to optimise energy use.
Intelligent Manufacturing:
Digital Twin & AI Optimisation: Build virtual smelters to simulate, predict and optimise production processes
(dosing, oxygen ratio, temperature, end point judgement) in real time to improve recovery and reduce energy
and material consumption.
Robot automation: Apply robots to pre-furnace operations (poking wind eyes, temperature measurement
and sampling), anode plate handling, flaking and packing, etc. to improve safety and efficiency.
Big Data and Predictive Maintenance: Real-time monitoring of equipment status using a network of sensors
to predict failures and reduce unplanned downtime.
Conclusion: The ‘red bloodline’ that keeps flowing forever
Copper smelting, the journey of transformation from ore to copper, is an eternal symphony of human wisdom
and the power of nature. From the flaming flash furnace, to the precision-controlled electrolytic bath, to the
gentle and efficient leaching yard, each process is a crystallisation of engineering technology, carrying the
unremitting pursuit of maximising resource utilisation and minimising environmental impact.
As an indispensable ‘red bloodline’ of modern industry, high-purity copper cathode continues to inject
surging power into electrification, new energy, digital infrastructure and other fields. The profound changes
in the smelting process in the direction of green and intelligence not only guarantee the stable supply of
copper as a strategic resource, but also demonstrate the determination and ability of industrial civilisation
to coexist harmoniously with the ecological environment. Is your production line also exploring a cleaner
and smarter way to obtain copper metal? Understanding and embracing the cutting-edge technology of
copper smelting in depth is undoubtedly a key cornerstone in safeguarding the resilience of the supply
chain and enhancing industrial competitiveness.