In the depths of the huge plant, heat waves distort the air, and blazing rays of light reflect the resolute
faces of the workers. Here, the copper smelting furnace is the furnace of copper metal rebirth. It is like
the heart of the steel beast, devouring the ore at a thousand degrees of heat, and turning the stubborn
stone into flowing copper liquid. From the ancient blast furnace to the modern flash smelting tower, every
evolution of the copper smelting furnace is engraved with the wisdom and power of mankind to seize
the industrial bloodline from the depths of the earth. It is not only the core of the production process,
but also the ultimate battleground for efficiency, environmental protection and metal quality.
The Furnace: The Mission and Classification of the Melting Furnace
The core objective of copper smelting is to efficiently separate high-grade copper matte (ice copper) or crude
copper from ores (concentrates or lumps) containing only a few to several tens of percent copper, while
maximizing the recovery of valuable elements (gold, silver, platinum group, etc.) and controlling pollution.
According to the position and core function in the process, copper smelting furnaces are divided into two
main categories:
Smelting Furnaces: Process copper concentrates or lump ores to produce copper matte (Cu2S-FeS) and slag.
This is the first fire of the fire method of copper smelting.
Refining furnace: processing smelting furnace output of crude copper (or copper matte after blowing crude copper),
through redox refining, removal of impurities (iron, sulfur, oxygen, arsenic, antimony, lead, etc.), the output can be
powered by the solution of the refined anode copper. This is the key furnace for purification.
Smelting furnace: from ore to copper matte flame transformation
Modern mainstream melting furnace technology, the pursuit of high intensity, low energy consumption, high oxygen
concentration and high SO2 recovery:
Flash Furnace:
Principle of operation: Dried, finely ground copper concentrate with oxygen-enriched air (up to 70-85% O2) or industrial
oxygen is injected at high speed into a hot reactor tower through a concentrate nozzle.
Core Reaction: Inside the column, the concentrate particles are instantaneously (milliseconds) suspended, heated, oxidized
and melted. The sulfide minerals (CuFeS2, etc.) react vigorously: 2CuFeS2 + 5/2O2 -> Cu2S-FeS + FeO + 2SO2 + heat. The
resulting copper matte (liquid) and slag (liquid) are separated in a settling tank at the bottom due to their different densities.
Advantages: very high intensity (huge capacity of a single furnace), low energy consumption (full use of reaction heat),
small flue gas volume and very high SO2 concentration (>30%), facilitating efficient acid production, significant
environmental advantages.
Key structures: reactor, settling tank, concentrate nozzle, rising flue, waste heat boiler (recovering heat from high temperature
flue gas). Refractory materials are subjected to intense chemical attack and high temperatures (up to 1300-1400°C in the
reactor tower), which are key to the life of the furnace.
Melting Bath Melting Furnaces:
Representative furnaces: Noranda Reactor, Teniente Converter, Ausmelt/Isasmelt Furnace, Vanyukov Furnace.
Principle of operation: Oxygen-enriched air (or oxygen-enriched air + fuel)** is drummed directly into the bath (copper
matte or slag layer)**. Concentrate or lump ore is added from the top of the furnace, and the oxidation and smelting
reaction is completed in the violently stirring molten pool.
Core feature: Strong turbulent mixing in the bath, which greatly enhances the mass and heat transfer process.
Advantages: Good adaptability to materials (can handle lumps, miscellaneous materials), relatively flexible operation,
relatively simple furnace structure (especially top/bottom blowing).
Challenges: Relative to flash smelting, higher flue gas volume, slightly lower SO2 concentration; furnace lining (especially
in the area of the air inlet/lance) is subject to serious melt scouring and chemical erosion, high maintenance requirements.
Refining furnace: final furnace for crude copper purification
The copper matte from the melting furnace is blown into crude copper (~98.5% Cu) in a converter (P-S converter). The
crude copper still needs to be further refined to remove impurities, which is the battlefield of the anode furnace (fire
refining furnace):
Rotary Anode Furnace:
Charging and melting: Load crude copper ingot or liquid crude copper, heat and melt.
Oxidizing period: Compressed or oxygen-enriched air is blown into the molten copper. Iron, lead, zinc, tin, arsenic, antimony,
sulfur and other impurities preferential oxidation: 2Fe + O2 -> 2FeO (into the slag); S + O2 -> SO2 (escape). The generated
cuprous oxide (Cu2O) contributes to the oxidation of impurities. The impurity oxides are skimmed off after slagging (by
adding a melting agent such as quartz sand).
Reduction period: At the end of the oxidation, natural gas, liquefied petroleum gas (LPG) or ammonia is introduced, or the
traditional wood insertion reduction (hydrocarbon-rich wood, such as pine, is inserted into the copper solution) is used.
The aim is to reduce Cu2O: Cu2O + H2 (or CO) -> 2Cu + H2O (or CO2), to prevent porosity in ingot casting and to
deoxidize deeply.
Mainstream furnace type: The most widely used refining furnace at present.
Structure: Large tiltable cylindrical furnace, lined with magnesium-chromium or aluminum-chromium refractory bricks. Burners
(oil/gas) and oxidation/reduction ducts (or wood inserts) are provided in the furnace head.
Refining Process:
Casting: After refining, high purity copper liquid (>99.3% Cu) is dumped into the furnace body, cast into anode plates
and sent to electrolytic refining.
Advantages: large capacity, mature and reliable operation, good refining effect.
Reflector type refining furnace:
Traditional furnace type with fixed furnace body. Through the furnace door for charging, oxidation (insert air duct), slagging,
reduction (insert wood or spray fuel gas), copper and other operations.
Disadvantages: high labor intensity, poor environment (fugitive smoke), low thermal efficiency, gradually replaced by
rotary anode furnace.
Furnace lining: guarding the furnace's “diamond armor”.
Whether it is a melting furnace or a refining furnace, the refractory lining is the core element that determines the life,
safety and operating costs of the furnace. They are subjected to extreme tests:
High temperatures: typically 1300-1500°C in the melting zone and 1100-1200°C in the refining zone.
Chemical attack: Acidic slag (SiO2-based), alkaline slag (FeO/CaO-based), copper matte, sulfur, oxidizing/reducing atmosphere.
Mechanical scouring: Violent scouring caused by melt flow, charging, gas injection.
Thermal shock: Cracking and spalling caused by opening and closing the furnace, temperature fluctuations.
Commonly used refractory materials:
Magnesium-chromium brick (MgO-Cr2O3): the traditional main force, high temperature resistance, good resistance to
alkaline slag erosion. But there is hexavalent chromium environmental issues, the use of limited.
Direct bonded magnesium-chromium bricks / re-bonded magnesium-chromium bricks: improved, better high
temperature performance.
Chromium-magnesium bricks (Cr2O3-MgO): high chromium content, excellent erosion resistance, especially suitable for
harsh environments (e.g., flash furnace settling tank slag line, converter vent area).
Aluminum-chromium bricks (Al2O3-Cr2O3): good resistance to acid slag and copper matte erosion.
Chromium-free environmentally friendly bricks: such as spinel bricks (MgO-Al2O3), magnesium-aluminum bricks (MgO-Al2O3),
magnesium-calcium bricks (MgO-CaO), etc., is an important direction of development, the performance needs to be
continuously optimized.
The heel of environmental protection: flue gas, slag and heat of the contest
Copper smelting furnace is the focus of energy consumption and pollution control:
Flue gas control (top priority):
High-efficiency sealing and trapping: Strict sealing at the connection between the furnace body and the fume hood prevents
flue gas from escaping.
Waste heat boiler: Recover the sensible heat of high temperature flue gas (>1000°C) to generate steam for power generation
or utilization.
High-efficiency dust removal: Electrostatic precipitator (ESP) or bag filter (BF) removes soot (containing heavy metals such as
copper, lead, arsenic and rare precious metals).
High concentration SO2 acid production: High SO2 flue gas (>6%) from flash furnaces, melting pot smelting furnaces and
converters is used to produce concentrated sulfuric acid (H2SO4) by double-contact method, with a conversion rate of >99.5%.
This is the core of resource utilization.
Low-concentration SO2 treatment: Low-concentration SO2 flue gas, such as anode furnace, is desulfurized by limestone/lime-gypsum
method, sodium-alkali method and organic amine absorption method.
Slag treatment and resourceization:
Depletion treatment: Smelting slag usually contains 0.5-2% copper, which needs to be recovered in the electric furnace or slag
depletion furnace by adding coke/pyrite reduction and sedimentation or beneficiation.
Water quenching and utilization: The water quenching of the depleted rejected slag into granulated slag (water slag), the main
composition of iron olivine (2FeO-SiO2), etc.. The goal is to utilize it as a building material such as cement mix, road base material,
and aggregate. Achieving high value-added utilization is a continuing challenge.
Energy saving and consumption reduction:
Oxygen-enriched/oxygen-enhanced melting: Dramatically increase the reaction strength and reduce the amount of flue gas and
the heat loss carried away by nitrogen.
Waste heat recovery: In addition to waste heat boilers, explore furnace cooling water and casting waste heat recovery.
Intelligent combustion control: Optimize the ratio of fuel and air.
High-quality refractory materials: Reduce heat loss and prolong furnace age.
The fire of innovation: more efficient, cleaner, smarter
Copper smelting furnace technology never stops:
Ultra-intensive smelting: flash furnaces move towards higher oxygen enrichment and larger scale.
Short process: Explore “one-step copper smelting” (direct output of crude copper) or continuous melting and blowing
(e.g. Mitsubishi method, flash blowing).
Intelligent Furnace Control: Based on big data and AI model, real-time optimization of wind/coal ratio, oxygen/feed ratio,
temperature field, and charging speed to achieve precise control, improve efficiency, quality and stability, and reduce energy
consumption and emission.
Long-life furnace lining technology: new chrome-free environmentally friendly refractory materials, furnace lining monitoring
and early warning system, intelligent spray maintenance.
Low-carbon/zero-carbon smelting: application of green power (hydropower, wind power, photovoltaic); substitution of clean
fuels such as hydrogen; exploration of carbon capture, utilization and storage (CCUS) technology.
Conclusion
The copper smelting furnace, a fiery furnace standing in the heart of industry, is the embodiment of power and precision.
It gulps down thousands of tons of ore and completes the most precise separation - copper and slag, sulfur and metal,
impurities and essence - in the most fiery way. From the violent microsecond reaction in the flash furnace reaction tower,
to the delicate redox “dance” in the anode furnace, to the never-ending struggle between the refractory lining and the
high-temperature melt, the birth of each furnace is a challenge to the limits of efficiency, environmental protection and
metal quality. Furnace fire never stops, innovation is more than that. With the advancement of intelligence and green
wave, the copper smelting furnace will continue to be more efficient, cleaner and tougher, melting and casting the
indispensable metal bloodline of the modern industry, and quenching the light of the future of sustainable
development in the flames.