In the field of non-ferrous metal smelting, lead and gold refining is a key link in
metal purification. As the two mainstream processes, thermal refining and electric
refining have become the focus of industry attention due to the differences in their
technical characteristics and application scenarios. In this paper, we will discuss the
core principles of the two processes, technical processes and advantages and
disadvantages of the comparison, to provide practitioners with technical reference.
Technical Logic of Fire Refining Process
Fire refining to high temperature melting as the core, through physical and chemical reactions
to achieve metal separation. The process is divided into three stages: pretreatment, smelting
and redox.
Pretreatment link
After the raw material is crushed and screened, volatile impurities such as sulfur and arsenic are
removed through roasting, which reduces the energy consumption of subsequent smelting.
Melting system
In the melting pool of 1200-1300℃, lead and gold raw materials are mixed with slagging agent,
and the metal phase and slag phase are separated in layers. Coke participates in the reaction as
a reducing agent to ensure the full reduction of metal oxides.
Refining and purification
Oxidizing refining method is adopted, in which air or oxygen is pushed into the molten metal to
make the residual impurities form slag. The degree of oxidation needs to be precisely controlled
to avoid loss of precious metals.
The advantages of this process are large capacity (up to 200 tons/day in a single furnace) and
adaptability to complex raw materials. However, there are high energy consumption (energy
consumption of about 450kWh per ton of lead), exhaust gas treatment costs and other
pain points.
Technological breakthrough of electrochemical refining
Electrochemical refining realizes metal purification through electrolysis deposition, and the core
equipment is electrolysis tank system. Its technology path includes:
Electrolyte configuration
Lead silicofluoride solution as the electrolytic medium, control the concentration of lead ions at
80-120g/L, acidity maintained at 100-140g/L.
Electrode system
Titanium-based coated anode and stainless steel cathode are used, tank voltage is controlled at
0.3-0.5V, current density 200-300A/m².
Deposition control
Optimize grain structure by pulse current technology, cathode lead purity up to 99.995%. Real-time
monitoring of electrolyte composition, automatic replenishment of additives to maintain system stability.
The metal recovery rate of the electrolytic process is up to 98.5%, which is especially suitable for high
purity lead production (above 99.99%). However, the investment cost of equipment is about 30%
higher than that of thermal process, and it is more sensitive to raw material impurities.
Decision-making model for process selection
Enterprises need to be based on raw material characteristics, product positioning, environmental
requirements for technology selection:
Raw material adaptability
Fire process can handle 30% -70% of the lead content of the complex ore material, the electric
method requires raw material lead grade > 90
Comparison of energy consumption
Comprehensive energy consumption of thermal process is about 580kg of standard coal per ton
of lead, while that of electric process can be reduced to 420kg due to the adoption of green
power technology.
Environmental performance
The sulfur dioxide emission of the electric process is only 1/5 of the thermal process, but the
treatment of hazardous waste electrolyte requires professional qualification.
Economic analysis
When the amount of precious metals associated with >50g/t, the comprehensive income
of the thermal process to enhance the 15%-20
Development trend of technology integration
The industry is exploring the combined process of thermal and electric power:
The composite process of thermal roughing + electric refining, with the straight metal
recovery rate increased to 96%.
Integration of waste heat power generation system, reducing comprehensive energy
consumption by 18
Intelligent control system application, automation rate of refining process exceeds 85%.
Environmental protection technology innovation
The thermal process is equipped with bi-alkaline desulfurization + SCR denitrification, and the
emission index is 30% better than the national standard.
Electrolyte closed-loop recycling technology, water resource utilization rate of 95%.
Research and development of heavy metal trapping agent, reducing the amount of hazardous
waste generated by 40%.
Market Application Prospect
With the outbreak of new energy battery recycling industry, the two processes show
new application characteristics:
Pyrolysis maintains 75% market share in the field of waste lead-acid battery treatment.
Electrolysis dominates the technology in the preparation of electronic grade high purity lead (6N grade).
The two processes complement each other in precious metal recovery, and the comprehensive recovery rate
of gold and silver exceeds 99%.
In the next five years, the refining process will be upgraded in the direction of low-carbonization and intelligence.
New technologies such as microwave smelting and ionic liquid electrolysis are expected to realize industrial
breakthroughs and push lead and gold smelting into a new stage of clean production.
Conclusion
As the classic processes of lead and gold purification, thermal refining and electric refining continue to evolve
under the drive of technological innovation. Enterprises need to be based on their own conditions, grasp the
window of process upgrading, and achieve the dual goals of quality improvement and cost reduction and
efficiency through the optimization of technology routes. Under the background of dual-carbon strategy,
the R&D and application of green refining technology will become a new track for industry competition.