Comprehensive Analysis of Wet Leaching Technology for Lead Zinc Ore

Comprehensive Analysis of Wet Leaching Technology for Lead Zinc Ore

1、 Basic principles and process flow of wet leaching

Wet leaching is the core process of wet metallurgy, which refers to the process of selectively dissolving valuable metals such as lead and zinc into the liquid phase by contacting them with aqueous solutions or other liquids.

 This technology mainly includes the following key steps:

 

Leaching process: Acid or alkaline solution is used to react with the ore to dissolve the metal.

 Common leaching agents include:

 

Ferric chloride solution: When treating lead sulfide concentrate, the lead leaching rate can reach 99%, and sulfur enters the slag in elemental form

Dilute sulfuric acid: mainly used for leaching zinc to form zinc sulfate solution

Sodium hydroxide solution: suitable for processing lead-zinc oxide ores

Liquid-solid separation: The leached slurry is separated into solid and liquid through filtration, sedimentation, and other methods to obtain metal containing leachate and leaching residue.

 

Solution purification: Remove impurity ions from the leachate through methods such as chemical precipitation and solvent extraction.

 

Metal extraction:

 

Lead: After the leaching solution is cooled and crystallized to obtain lead chloride, a chloride salt system is used for molten salt electrolysis (temperature 723-773K, current density 4000-10000A/m ²)

Zinc: Zinc sulfate solution is used to produce metallic zinc through electrolytic deposition

Wastewater treatment: Neutralization, sedimentation and other treatments are carried out on process wastewater to achieve standard discharge or recycling.

 

Typical process flows include ferric chloride leaching electrolysis method, fluoroborate iron leaching method, and slurry electrolysis method.

 The United States Bureau of Mines and several research institutions in China (such as Shenyang Institute of Mining and Metallurgy) have conducted large-scale experiments to verify the feasibility of the technology

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2、 Common methods and their technical characteristics

The wet leaching of lead-zinc ore mainly adopts the following methods:

 

Method type, technical characteristics, applicable scenarios

The ferric chloride leaching method uses FeCl ∝+HCl or FeCl ∝+NaCl mixed solution, with a high lead leaching rate (99%), and sulfur is recovered as elemental sulfur to treat lead sulfide concentrate

Direct treatment of unburned concentrate using oxygen pressure leaching method at 140-150 ℃ and 700kPa oxygen partial pressure, with a zinc leaching rate of over 98% for sulfide zinc concentrate treatment

Slurry electrolysis leaching and electrolysis are carried out synchronously, simplifying the process, but requiring complex minerals with high specific composition for equipment

The alkaline leaching method uses NaOH solution, which has a good effect on the treatment of oxidized ores, but the reagent cost is high for the treatment of lead-zinc oxide ores

Wet leaching has significant characteristics compared to traditional pyrometallurgical lead smelting:

 

Environmental advantages: No production of SO ₂ gas, minimal emission of lead containing smoke and volatile substances

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Low energy consumption: The reaction temperature is usually below 100 ℃, and the energy consumption is about 60-70% of the pyrometallurgical process

Strong resource adaptability: particularly suitable for processing low-grade ores (lead zinc grade<5%) and complex associated ores

Technical challenges: Long process flow (3-5 more steps than pyrometallurgy), high reagent consumption, and prominent equipment corrosion issues

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3、 Application Status and Development Trends

The application of hydrometallurgy in the development of lead-zinc mines has made significant progress:

 

Industrial application:

 

China Zhongjin Lingnan Danxia Smelter completed its first 100000 tons/year oxygen pressure leaching plant in 2009

Western Mining's 2015 project overcomes high-altitude production challenges

Some enterprises have reduced the zinc content in lead mud to below 8% and significantly improved the zinc recovery rate through technological upgrades, such as improving the pressure filtration system

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Technological innovation:

 

Optimization of leaching system management: shorten operation time and improve leaching efficiency

Equipment upgrade: such as changing the filter press tube shaped liquid box to a square shape to reduce liquid leakage

Pipeline renovation: adopting a serpentine layout to reduce resistance and minimize metal loss

Industry development trend:

 

Transforming towards intelligence and greenness, utilizing AI and big data to optimize processes

Pay attention to wastewater treatment and resource recycling to reduce environmental pollution

Develop more efficient leaching agents and corrosion-resistant materials

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At present, wet lead smelting has not yet achieved large-scale industrialization, mainly limited by:

 

Lead is a low value-added metal, and the cost advantage of wet processing is not significant (the cost of pyrometallurgical processing is about 900 yuan/ton, while wet processing is higher)

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The process is complex, and the comprehensive recovery technology for associated metals is not mature

Large equipment investment and high maintenance costs

4、 Comprehensive analysis of advantages and disadvantages

Advantage:

Environmentally friendly: No SO ₂ emissions, reducing exhaust emissions by over 80%

High resource utilization rate: can handle low-grade ores that are difficult to utilize by traditional pyrometallurgical methods (lead and zinc grades can be as low as 3-5%)

High metal recovery rate: lead and zinc recovery rates can reach 95-99%, and there is great potential for comprehensive recovery of associated metals

Low energy consumption: The energy consumption per ton of metal is reduced by 30-40% compared to pyrometallurgical methods

Limitations:

Complex process: 3-5 more steps than pyrometallurgy, with greater difficulty in operation and control

Corrosion issue: Strong acid/alkali environments require high equipment and material requirements, resulting in an increase of 20-30% in maintenance costs

Reagent consumption: 0.5-1.2 tons of chemical reagents are consumed per ton of metal, which increases production costs

Difficult slag treatment: The composition of leaching slag is complex, and the comprehensive utilization technology is not yet fully mature

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5、 Summary and Prospect

The wet leaching technology of lead-zinc ore, as an important direction of green metallurgy, has shown unique advantages in the context of increasingly strict environmental requirements.

 The current technology can achieve a lead leaching rate of 99% and a zinc leaching rate of 98%, which is particularly suitable for processing complex and difficult to select ores.

 However, high cost and technological complexity remain the main bottlenecks restricting its large-scale application.

 

Future development directions may include:

 

Develop a new efficient and low-cost leaching system

Improve equipment corrosion resistance and reduce maintenance costs

Optimize the process flow and shorten the production cycle

Strengthen the research and development of comprehensive recovery technology for associated metals

Promote intelligent control and improve process stability

With the tightening of environmental regulations and the decline in resource quality, the application proportion of wet leaching technology in the field of lead zinc metallurgy is expected to gradually increase, but it will still form a complementary pattern with pyrometallurgical processes in the short term.