Oxidized copper ores, as an important reserve of copper resources,
account for about 20% of the global mineable copper resources.
The copper element in these ores exists in the form of carbonates,
oxides, hydroxysilicates and other compounds, which are difficult
to be processed directly by traditional pyrometallurgy. With the
development of hydrometallurgical technology, the leaching-
extraction-electrowinning (LX-EW) process system has become
the mainstream solution for copper extraction from oxidized
copper ores, which is also applicable to the treatment of some
secondary sulfide ores, and shows significant advantages in
resource utilization and environmental performance.
Leaching process innovation for copper
oxide ores
Ore pretreatment directly affects the leaching efficiency. For
different types of oxidized ores, the crushing size should be
controlled in the range of 1-5mm, over-crushing will increase
acid consumption, and coarse particles will reduce the leaching
rate. The heap leach field adopts layered fabric technology, through
the 0.5-1.0m layer stacking, with the bottom ventilation system, so
that the leaching liquid uniform penetration. For high mud quality
oxidized ores, adding 3%-5% lignosulfonate can effectively
improve the permeability.
The leaching system is adjusted according to the difference of ore
characteristics: the acidic system (pH1.5-2.5) is suitable for malachite,
blue chalcopyrite and other carbonate minerals, and the sulfuric acid
concentration is controlled at 5-15g/L; the ammoniacal system
(pH9.5-10.5) is used to treat silicate minerals such as silica malachite,
and the ammonia concentration is maintained at 5-8%. Bioleaching
technology has obvious advantages in treating low-grade ores
containing 0.3%-0.8% copper, and Thiobacillus ferrooxidans can
shorten the leaching cycle to 20-30 days.
The quality control standard of leaching solution is strict: the
concentration of copper ions should be stabilized at 2-5g/L, the
concentration of iron ions should be no more than 1g/L, and the
fluctuation range of pH value should be ±0.2. The online monitoring
system adjusts the flow rate of leaching agent in real time, and
the parameter is controlled at 400-450mV through the oxidation
reduction potential (ORP) sensor, which ensures that the copper
leaching rate reaches 85%-92%.
Technological breakthrough in solvent extraction
The extractant system has gone through three generations of development:
the selectivity of LIX series chelating extractant has been significantly
improved, and the extraction rate of copper ions can reach 98% under the
condition of pH1.8-2.3. New hybrid extractants (e.g. LIX984N) reduce the
phase separation time from 5 minutes to 90 seconds through synergistic
effects and increase the processing capacity by 30%. The extraction ratio
(O/A) is optimized to 1:3 and copper loading of 4-6 g/L is achieved.
Multi-stage countercurrent extraction design for precise separation.
Three-stage extraction - two-stage counter-extraction modular device
to enrich copper concentration from 5g/L to 45g/L. Intelligent control
system dynamically adjusts the mixing intensity to control the entrainment
loss below 0.005%. After the extraction residue is neutralized by lime,
the copper residue is ≤0.01g/L, which can be directly returned to the
leaching system.
Anti-pollution technology guarantees stable operation of the system.
The front oil removal device can remove 95% of organic phase
impurities, and the depth filtration system (1μm precision) intercepts
solid suspended matter. When the concentration of Fe³+ exceeds the
critical value, the reduction process is automatically started and SO₂
is added to convert trivalent iron to divalent, maintaining the
extraction efficiency above 95%.
Energy Efficiency Optimization of
Electrowinning Process
The structural design of the electrolyzer is continuously improved.
The 3m³ large-scale electrolyzer made of polymer concrete, together
with double-layer PP cathode/anode plates, increases the current
density to 220-260A/m². The same pole distance is reduced to 90mm,
the tank voltage is reduced to 1.9-2.1V, and the DC power
consumption of tons of copper is controlled at 1800-2000kWh.
The electrolyte circulation system realizes fine management. The titani
heat exchanger is used to stabilize the temperature at 45±2℃, and the
flow control system maintains a flow rate gradient of 2-3m/s. The on-line
copper ion analyzer automatically replenishes the electrolyte. The online
copper ion analyzer automatically replenishes the liquid to maintain the
concentration of the main metal at 40±2g/L and the acidity at 160-180g/L.
The intelligent filling system of additives (thiourea+colloid) improves the
crystalline density of copper cathode surface by 15%.
The quality control of copper cathode reaches a new height.316L stainless
steel master plate with automatic stripping system, the output copper foil
thickness tolerance ≤ 0.5mm.The product is purified by four levels, the
copper purity reaches 99.99%, the surface is bright and no nodule. The
electrolysis waste liquid is recycled 98% of sulfuric acid by membrane
treatment technology, and the comprehensive metal recovery rate is
increased to 99.2%.
Environmental protection and comprehensive
utilization of resources
After the leaching tailings are recovered residual copper by flotation, they
are treated by solidification and stabilization, and the toxicity of heavy metal
leaching is lower than the national standard. Wastewater treatment system
integrates biodegradation + reverse osmosis technology, with water reuse
rate exceeding 95%. Sulfur dioxide recovery device converts the sulfur
element in the waste gas into industrial-grade sulfuric acid, with an annual
emission reduction of up to 10,000 tons.
Development of associated resources creates new value. Cobalt, nickel and
other strategic metals are extracted from process intermediate products,
and the recovery rate of rare earth elements exceeds 85%. Waste heat
generated from the leaching process is used to generate electricity, meeting
20% of the plant's energy demand. The ecological restoration of the mining
area adopts in-situ substrate improvement technology, and the cycle of
vegetation restoration has been shortened to 3 years.
Intelligent transformation has brought about a leap in quality and efficiency.
The digital twin system simulates the leaching dynamics in real time, and
the big data algorithm predicts the equipment failure rate up to 95%. 5G
Internet of Things realizes remote control and reduces manual intervention
by 70%. The energy efficiency management platform reduces the
comprehensive energy consumption by 18% and achieves the
first-class standard of clean production.
Advances in wet copper extraction technology from oxidized copper
ores have resulted in a 35% real increase in recoverable reserves of
global copper resources. The transformation process from low-grade
ore to high-purity copper cathode demonstrates the successful
practice of the circular economy concept in the metallurgical industry.
As the demand for copper in the new energy industry continues to
grow, this green metallurgical technology will play a greater role in
the efficient utilization of resources and promote the sustainable
development of the mining industry into a new stage.