Smelting & Refining

Production Routes

Three Metal Streams,
One Integrated Plant

Each metal stream follows a purpose-engineered refining route — from concentrate feed through to finished high-purity metal — with shared infrastructure, common utilities, and integrated by-product recovery linking all three circuits.

51

Sb

Antimony

Metal Stream 01

Antimony Refining

Target purity: 98.5 – 99.5% Sb

Antimony is extracted from stibnite concentrate (Sb₂S₃) using a three-stage pyrometallurgical route: volatilisation roasting drives off sulfur as SO₂, reverberatory furnace smelting reduces antimony oxide to crude metal, and chlorination refining in a graphite-lined reactor removes residual impurities to achieve high-purity ingot grade. The resulting metal is cast into ingots essential for flame retardants, alloys, and electronics.

01

Stage One

Volatilisation Roasting

Stibnite concentrate is roasted at controlled temperatures, converting Sb₂S₃ to antimony trioxide (Sb₂O₃) and driving off sulfur as SO₂ gas. The volatilised Sb₂O₃ is captured in bag filters — a cleaner capture pathway than wet scrubbing. SO₂ off-gas is directed to a sulfuric acid plant as a recoverable by-product rather than an atmospheric emission.

Sb₂S₃ → Sb₂O₃ + SO₂ · Bag filter capture

02

Stage Two

Reverberatory Furnace Smelting

Antimony trioxide is reduced to crude metallic antimony in a reverberatory furnace using carbon reductants. The furnace design concentrates radiant heat from the roof onto the charge, achieving the temperatures required for complete reduction while maintaining energy efficiency. Molten crude antimony is tapped and transferred directly to the chlorination refining stage.

Sb₂O₃ + C → Sb⁰ + CO₂ · ~650°C

03

Stage Three

Chlorination Refining

Crude antimony is refined in a graphite-lined chlorination reactor, where chlorine gas selectively reacts with trace impurities — arsenic, lead, iron, sulfur — forming volatile or immiscible chloride compounds that separate cleanly from the purified antimony melt. The result is high-purity antimony metal at 98.5–99.5% Sb, cast into standardised ingots meeting international specifications.

Graphite-lined reactor · 98.5–99.5% Sb output

29

Cu

Copper

Metal Stream 02

Copper Refining

Target purity: 99.99% Cu — Cu-CATH-1

Copper is refined via the Solvent Extraction and Electrowinning (SX/EW) process — a hydrometallurgical route that bypasses smelting entirely for oxide ore feeds, producing Grade A cathodes at 99.99% Cu directly from leach solution. For sulfide concentrate feeds, conventional smelting to blister copper followed by electrorefining achieves equivalent purity. Precious metal by-products (gold and silver) are recovered from the anode slime generated during electrorefining.

01

Stage One

Leaching / Smelting

For oxide ore feeds, dilute sulfuric acid irrigates heap-leached ore, dissolving copper into a Pregnant Leach Solution (PLS) — no high-temperature step required. For sulfide concentrate feeds, flash smelting or reverberatory smelting converts chalcopyrite to blister copper at ~1200°C, which is then cast into anode slabs for the electrorefinery. Both pathways converge at the electrochemical refining step.

H₂SO₄ leach (oxide) · Flash smelt (sulfide)

02

Stage Two

Solvent Extraction

PLS from the heap is contacted with an organic extractant in mixer-settler vessels, selectively stripping copper ions from impurities including iron, arsenic, and manganese. The loaded organic is then stripped with strong sulfuric acid to produce a pure, concentrated copper electrolyte — ready for the electrowinning tankhouse. The raffinate is recycled to the leach pad, closing the water loop.

Cu²⁺ (aq) → Cu²⁺ (org) → Cu²⁺ (EW feed)

03

Stage Three

Electrowinning / Electrorefining

Direct electrical current plates copper ions from the purified electrolyte onto stainless steel cathode blanks — producing dense, smooth, LME-deliverable copper cathodes at 99.99% Cu. In electrorefining circuits, blister copper anodes dissolve and replate as pure copper; precious metals concentrate in the insoluble anode slime and are recovered as gold and silver by-products of significant commercial value.

Cu²⁺ + 2e⁻ → Cu⁰ · 99.99% · Au/Ag slime recovery

50

Sn

Tin

Metal Stream 03

Tin Refining

Target purity: 99.9% Sn

Tin is extracted from cassiterite concentrate (SnO₂) using a three-stage pyrometallurgical route closely parallel to the antimony circuit: roasting removes sulfur impurities from mixed concentrates, reverberatory furnace smelting reduces tin oxide to crude metal, and chlorination refining achieves high-purity tin suitable for solders, alloys, and electronics applications. The shared reverb furnace and chlorination infrastructure with the antimony circuit creates significant capital and operating cost efficiencies.

01

Stage One

Roasting

Cassiterite concentrate is roasted to remove sulfur and arsenic impurities present in mixed sulfide-oxide concentrates, converting the feed to a cleaner oxide calcine suitable for smelting. Roasting also eliminates carbonaceous material that would interfere with downstream reduction. The calcine is blended with reductant and flux before charging to the reverberatory furnace. Roasting off-gas is captured for sulfuric acid recovery.

SnO₂ calcination · Sulfur removal · H₂SO₄ recovery

02

Stage Two

Reverberatory Furnace Smelting

Tin oxide calcine is smelted in a reverberatory furnace with carbon reductant (coal or coke), producing crude tin metal at approximately 99% Sn purity — alongside a slag phase containing residual tin and gangue minerals. The slag is re-treated in a secondary furnace to maximise tin recovery. Crude tin is tapped in molten form and transferred directly to chlorination refining. The shared furnace design with the antimony circuit enables flexible campaign scheduling.

SnO₂ + 2C → Sn⁰ + 2CO · ~1000°C

03

Stage Three

Chlorination Refining

Crude tin is refined in the graphite-lined chlorination reactor — shared with the antimony circuit — where chlorine selectively reacts with impurity metals (lead, bismuth, iron, copper) to form chloride compounds that float to the surface and are skimmed off. The process achieves 99.9% Sn purity, with the refined metal cast into standardised ingots meeting specifications for soldering, plating, alloy manufacture, and electronics applications globally.

Graphite-lined reactor · 99.9% Sn output · Shared Sb circuit

Refined Products

Three High-Purity
Metal Outputs

Each product from our refining operations undergoes rigorous quality control and certification — meeting international standards for purity, physical format, and traceability before leaving our facilities.

99.5%

Purity Sb

51

Sb

Antimony

Refined Metal

Antimony Ingots

Antimony Ingots are the primary output of our volatilisation-reverb-chlorination refining circuit. The silvery-grey, brittle metal is cast into standardised ingots and certified for purity, consistency, and traceability. Critical designation as a US/EU strategic mineral drives sustained premium pricing and long-term offtake demand from flame-retardant, battery, and defence sectors.

Purity98.5 – 99.5% Sb

Process RouteRoasting → Reverb → Cl₂

FeedStibnite (Sb₂S₃)

StandardGB/T 1599 · ASTM B899

FormStandard ingots · Trioxide

Applications

Flame Retardants

Lead-Acid Batteries

Alloys

Electronics

Defence

Sb

99.99%

Purity Cu

29

Cu

Copper

Refined Metal

Copper Cathodes

With unmatched 99.99% purity achieved through the electrowinning process, our copper cathodes support applications in construction, electrical systems, EV motors, grid infrastructure, and precision manufacturing. Produced to the Cu-CATH-1 / LME Grade A standard, cathodes are directly deliverable to wire rod mills and copper fabricators without further processing.

Purity99.99% Cu — Cu-CATH-1

Process RouteSX/EW · Electrorefining

FeedOxide ore · Chalcopyrite conc.

StandardBS EN 1978 · ASTM B115 · GB/T 467

By-ProductAu · Ag from anode slime

Applications

Wire & Cable

EV Motors

Grid Infrastructure

Construction

Electronics

Cu

99.9%

Purity Sn

50

Sn

Tin

Refined Metal

Tin Ingots

Tin is extracted from cassiterite ore (SnO₂) using roasting, reverberatory furnace smelting, and chlorination refining to achieve high-purity ingot metal. Our Tin Ingots are essential for solders, alloys, and electronics — delivering exceptional performance and reliability. The shared chlorination infrastructure with the antimony circuit enables competitive production economics for both metals simultaneously.

Purity99.9% Sn

Process RouteRoasting → Reverb → Cl₂

FeedCassiterite (SnO₂)

StandardISO 3715 · ASTM B339

FormStandard ingots · Slabs

Applications

Solders

Tin Plate

Alloys

Electronics

Coatings

Sn

Plant & Equipment

Refinery
Infrastructure

Three core equipment types underpin our smelting and refining operations — each chosen for its process efficiency, product quality, and operational flexibility across multiple metal campaigns.

650–1200°C

Equipment 01

Reverberatory Furnace

The reverberatory furnace is the primary smelting vessel for both antimony and tin circuits. Its horizontal design concentrates radiant heat from a flat, reflective roof onto the charge bed — achieving the temperatures required for oxide reduction without direct contact between fuel and charge. This architecture enables precise temperature control and clean separation of molten metal from slag.

Shared across Sb and Sn campaigns, the furnace is refractory-lined for long campaign life, with tapping facilities for both metal and slag streams. Slag is re-treated in a secondary electric arc furnace to recover residual metal value before disposal.

Metals Processed

Antimony (Sb)

Tin (Sn)

Cl₂ Refining

Equipment 02

Graphite-Lined Chlorination Reactor

The graphite-lined chlorination reactor is the final purification stage for both antimony and tin. Chlorine gas is bubbled through molten crude metal: impurity elements (As, Pb, Fe, Bi, Cu) react preferentially with Cl₂ to form volatile or immiscible metal chlorides that segregate from the purified melt and are skimmed or distilled off.

Graphite lining provides chemical inertness against both molten metal and chlorine gas — avoiding contamination from the reactor walls. The system includes chlorine scrubbing and tail gas treatment to prevent atmospheric release, with chloride by-products directed to downstream processing where commercially viable.

Metals Processed

Antimony (Sb)

Tin (Sn)

~3–4 kWh/kg

Equipment 03

Electrowinning Tankhouse

The electrowinning (EW) tankhouse is the heart of copper cathode production. Rows of electrolytic cells contain purified copper electrolyte through which direct current is passed — plating copper ions onto stainless steel cathode blanks at 99.99% purity. Cathode blanks are stripped on a 5–7 day cycle, producing 125 kg copper sheets in the LME standard format.

In electrorefining mode, cast blister copper anodes dissolve and replate as pure copper cathodes. The anode slime — an insoluble residue collecting at the base of the cells — contains gold, silver, and platinum-group metals from the original ore, which are separately processed through a precious metals refinery to recover full value.

Metals Processed

Copper (Cu)

Au/Ag recovery

Waste to Wealth

Sustainability Through
By-Product Recovery

Sustainability drives everything we do at United Metals. Our smelting and refining operations are designed to minimise waste and maximise resource efficiency — turning process by-products that other operations discard into commercial assets.

The Circular Refinery

Every Stream
Has Value

Our integrated refinery is designed so that no significant process stream leaves the site as waste. Sulfur from antimony and tin roasting becomes sulfuric acid. Gold and silver from copper electrolysis become saleable precious metals. Even chloride by-products from the chlorination reactor are managed for recovery where economically viable.

This approach doesn't just reduce our environmental footprint — it generates meaningful incremental revenue from materials that a conventional operation would treat as liabilities.

By-Product Revenue Streams

Gold & Silver — from copper anode slime

Sulfuric Acid (H₂SO₄) — from SO₂ roasting off-gas

Metal Chlorides — selective by-product recovery

By-Product Recovery 01

Precious Metal Recovery

During copper electrolysis, gold and silver from the original ore concentrate in the insoluble anode slime that accumulates at the base of electrorefining cells. Rather than treating this slime as waste, United Metals processes it through a dedicated precious metals recovery circuit — dissolving, purifying, and precipitating gold and silver as high-purity products.

This turns what is typically a disposal cost into a significant revenue stream — with precious metal recovery often representing a disproportionate share of the economic value in complex polymetallic ores where gold and silver are present at sub-economic concentrations in the primary concentrate.

♦ Au · Ag recovered from every copper electrorefining campaign

By-Product Recovery 02

Sulfuric Acid Production

Roasting of antimony and tin concentrates generates SO₂-rich off-gas streams that, in a conventional operation, would require expensive scrubbing to prevent atmospheric release. At United Metals, these gas streams are directed to a contact-process sulfuric acid plant — converting the SO₂ to H₂SO₄ and generating industrial-grade sulfuric acid as a saleable product.

The acid is repurposed for industrial applications in the region — reducing the demand for virgin acid synthesis from elemental sulfur and providing a local supply of acid to industries (including our own heap leach operations) that would otherwise source it from distant suppliers.

♦ H₂SO₄ from SO₂ off-gas · Eliminates atmospheric emission

Three Metal Streams,One Integrated Plant

Three High-PurityMetal Outputs

RefineryInfrastructure

Sustainability ThroughBy-Product Recovery

World-Class Smelting & Refining Services

Smelting &
Refining

Three Metal Streams,
One Integrated Plant

Three High-Purity
Metal Outputs

Refinery
Infrastructure

Sustainability Through
By-Product Recovery

World-Class Smelting
& Refining Services