Sleeping lead ore deep in the earth's crust has been tempered by fire and wisdom, and eventually
transformed into a flowing silver-gray metal. This is not a simple melting, but a sophisticated
symphony of ancient experience and modern technology - lead smelting. In the vein of industrial
civilization, lead, a seemingly low-profile metal, with its unique density, ductility and corrosion
resistance, quietly support the key areas from energy reserves to security protection. However,
the path from ore to refined lead is full of fiery challenges and green innovations.
Core Furnace: The Heritage and Evolution of Pyrometallurgy
Despite technological advances, pyrometallurgy is still the mainstay of primary lead production globally,
and its core lies in separation and purification at high temperatures:
Sintering - Blast Furnace Lead Smelting: The Classic “Two-Step Dance”
Step 1: Sinter Roasting - Prelude to Preheating: Finely crushed lead concentrate (mainly galena PbS) is mixed
with a flux (limestone, quartz sand, etc.) and reclaimed material and ignited in the sinter. A forced air flow
penetrates the material layer and the sulfides are oxidized to oxides (PbO), while releasing a high concentration
of SO₂ fumes (which need to be forcibly recovered for acid production). The sintering process also removes
some of the volatile impurities such as arsenic and antimony, and produces a hard, porous sintered block.
Step 2: Blast Furnace Smelting - The Fiery Core: Sintered blocks, coke and flux are added from the top of the
furnace, and preheated air (“blast air”) is forcefully blown into the furnace from the lower air opening. The
burning of the coke produces high temperatures (>1200°C) and a reducing atmosphere (CO). In the melting
zone, lead oxide (PbO) is reduced to liquid crude lead (Pb) by CO, and slag is formed from pulsite and flux.
Liquid crude lead sinks to the bottom of the furnace cylinder due to its high density, and the slag floats on
it and is released from different outlets. Zinc vapor (from the raw material in the zinc) in the upper part of
the furnace condensation for zinc slag (containing zinc, lead). High lead fumes are produced as a by-product
of this process and need to be recycled.
Direct lead refining: an “evolution” in efficiency and environmental protection
A one-step innovation: In order to overcome the shortcomings of long sinter-blast furnace processes, high
energy consumption and decentralized treatment of flue gases, direct smelting technologies such as Kivcet,
QSL and ISA/Ausmelt have emerged. The core is to spray the concentrate (or lump ore) into the reactor
(flash smelter, top/bottom blowing furnace), and realize the oxidation and exothermic reaction of sulfide,
smelting and partial reduction reaction in a single step under the oxygen-rich environment, and directly
produce crude lead and slag. Significant advantages: short process, low energy consumption, high sulfur
recovery (>95%), more centralized and efficient environmental control.
Wet smelting: a “gentle” solution for complex raw materials
For low-grade, complex polymetallic ores or specific secondary resources, wet smelting provides an alternative path:
Leaching-electrolysis: Lead-containing materials (e.g., oxidized ores, certain slags) are dissolved in an acid
(sulfuric acid, hydrochloric acid) or alkali (ammonia, carbonates) solution, and the lead enters the solution.
Subsequently, the solution is purified to remove impurities (e.g., precipitation to remove iron and copper),
and then electrolytic deposition (similar to copper and zinc electrolysis) is carried out to obtain electrowinning
lead at the cathode. This method is suitable for processing materials that are difficult to be treated by traditional
thermal methods and is environmentally friendly, but the cost is usually high and the scope of application is
relatively narrow compared to thermal methods.
Crude lead refining: a journey towards 99.99% purity
Whether obtained by thermal or wet process, crude lead (purity of about 95-98%) contains impurities such as
copper, arsenic, antimony, tin, silver, bismuth, etc., which must be refined to meet industrial applications:
Fire refining (mainstream)
In addition to copper (molten precipitation & sulfur): Crude lead slow cooling (molten precipitation) so that
the high melting point of copper and its compounds crystallization precipitation (copper slag); or add sulfur,
generate copper sulfide slag skimming.
In addition to arsenic, antimony, tin (alkaline refining): add caustic soda (NaOH) and nitrate (NaNO₃) or air to
molten lead. Impurities are oxidized, arsenic, antimony and tin form sodium salts into the slag (alkali slag).
Removal of Silver and Precious Metals (Zinc Shell Method - Parkes Process): Utilizes the strong affinity of zinc
for silver. To the molten lead add zinc (1-2%), stirring vigorously after cooling, silver, gold and other precious
metals and zinc to form a high melting point alloy (zinc shell) floating on the surface of the lead, it will be
fished out. This zinc shell is an important raw material for the recovery of precious metals.
Zinc removal (vacuum dezincification or alkaline refining): The residual zinc is removed by vacuum distillation
or alkaline refining again.
Bismuth Removal (Electrolytic Refining or Calcium and Magnesium Addition): For lead requiring very high purity
(e.g. 99.99%+), electrolytic refining is often used (with crude lead as the anode, pure lead sheet as the cathode,
and lead silicate fluoride solution as the electrolyte), or bismuth is removed by adding calcium and magnesium
to form a bismuth compound with a high melting point (Kroll-Betterton method).
Electrolytic refining (high purity safeguard): After the initial fire refining of lead cast into an anode plate, in the
lead silicate fluoride electrolyte, direct current, pure lead precipitation in the cathode, impurities remain in the
anode mud or solution. This is the most reliable method to obtain the highest purity of refined lead (over 99.99%).
The invisible battlefield: environmental protection and resource utilization
The core competitiveness of modern lead smelting lies not only in yield and purity, but also in green and recycling:
Sulfur “roundup”: Sintering flue gas, smelting furnace flue gas with high concentration of SO₂ (>3.5%) is forced to adopt
double-rotation and double-absorption acid production process, which is converted into commercial sulfuric acid to
realize sulfur resource utilization. Low-concentration flue gas is subject to high-efficiency desulfurization (e.g.,
limestone-gypsum method).
Dust “Zero Fugitive”: Each dust generation point (charging, lead release, slag release, transfer) is equipped with efficient
dust collection equipment (bag filter, electric dust collector), and the dust is returned to the process to recover lead
and zinc.
Solid waste “gold spotting”: After the slag is depleted, those with low lead content can be used as building materials or
safely landfilled; zinc-rich soot and slag are important raw materials for zinc extraction; anode sludge and zinc shells are
the treasures for the recovery of gold, silver, bismuth, antimony, copper and other valuable elements.
Wastewater “closed-loop”: production wastewater (especially wet plant) is neutralized, precipitated, treated in depth
and recycled to minimize external discharge.
Energy saving and carbon reduction: Adopting measures such as oxygen-rich combustion, waste heat generation
(using high-temperature flue gas), and optimization of the thermal system to reduce energy consumption and
carbon emissions.
Lead's heavy weapon: an indispensable application map
Refined lead is irreplaceable in a number of key areas thanks to its unique properties:
Lead-acid batteries: undisputedly the largest field of application (about 80%+ of global usage), the core of automotive
starting, electric vehicle power, uninterruptible power supply (UPS), and energy storage systems.
Radiation protection: high density makes it an ideal material for shielding X-rays, γ-rays, used in medical, nuclear
industry, scientific research.
Chemical corrosion-resistant materials: manufacture of sulfuric acid industry pipes, reaction tank lining (lead lining).
Cable sheath: traditional but reliable communication and power cable protection layer (especially in direct burial or underwater).
Alloying elements: tin added to make solder; antimony added to increase hardness and strength (used in bearings,
bullets, counterweights); lead alloys (still used, though in decline).
Stabilizers: heat stabilizers in PVC plastics (environmental requirements, lead-free is the trend but still exists).
The Way of the Future: Deep Integration of Green, Intelligent and Circulation
The lead smelting industry is undergoing a profound transformation:
Green upgrading of primary smelting: Continuously optimize the direct lead smelting process to improve the sulfur
capture rate and energy efficiency; research and develop cleaner wet process technologies; explore low-carbon
paths such as hydrogen reduction.
The “Rise” of Recycled Lead: Recycling lead from waste lead storage batteries (recycled lead) consumes only 1/3
of the energy of virgin lead, and pollution is greatly reduced. The establishment of an efficient, standardized,
environmentally friendly recycling system for recycled lead is the key to the sustainable development of the industry.
Mining of “urban mines”: Strengthen the recycling network and technology research and development of e-waste
and industrial waste containing lead, and improve the recycling rate of lead resources.
Intelligent smelting: Apply IoT, big data and AI to optimize production control, predictive maintenance, energy
management and pollution monitoring, and build “smart factories”.
Material innovation: Develop lead-based alloys or alternative materials with better performance and
environmental protection (especially in the field of stabilizers).
Conclusion: Moving forward in fire and responsibility
Lead smelting, an ancient craft that runs the gamut between fiery furnaces and sophisticated chemistry, has always
been a source of challenge and innovation. It is not only an essential process for obtaining important industrial
metals, but has also become a benchmark for measuring how modern industry balances resource utilization and
environmental protection. From the efficient recovery of every gram of sulfur to the closed-loop treatment of
every drop of wastewater, from the green smelting of primary ores to the standardized regeneration of used
batteries, the lead smelting industry is striving to wash away the dust and haze of the past and provide
indispensable basic support for the energy storage, security and industrial development of the modern society
in the form of a cleaner, smarter, and more recycling attitude. This is a journey of refining in fire and transforming
in responsibility, with the end pointing to a green future of sustainable resources and ecological harmony. Every
refinement is a commitment to be more responsible to the earth.