Precious Metal Hydrometallurgical Refining Plant
— Turnkey Precious Metal Hydrometallurgical Refining Plant
A Precious Metal Hydrometallurgical Refining Plant is a fully wet-chemistry refinery that dissolves, separates and recovers gold, silver and the platinum-group metals from anode slime, gold doré, karat scrap, spent catalysts and process residues using aqueous chemistry alone — oxidative leaching, solid–liquid separation, selective precipitation, solvent extraction, ion exchange and electrorefining — with no smelting, no flue dust and no slag. Because the entire route is aqueous, YuSai’s plant keeps process temperature far below pyrometallurgical levels, reaches direct recovery of Au, Ag, Pt and Pd of up to 99%, and sets finished fineness electrochemically at Au 99.99–99.999%, Ag 99.99%, Pt / Pd ≥ 99.95% and Rh ≥ 99.90%. Reagent and water circuits are closed — raffinate returns to leaching, acid mist is condensed and recovered, and off-gas and effluent are treated inside the same skid-mounted package.
Product Overview
The Precious Metal Hydrometallurgical Refining Plant is the wet-chemistry core of a modern precious-metals refinery. It takes material that already carries its value in metallic or high-grade form — copper and lead electrorefining anode slime, gold doré bars and bullion, atomised alloys, karat jewellery scrap, palladium-on-carbon and automotive catalyst concentrates, plating residues and refinery intermediates — and refines it to market fineness without ever passing it through a smelter.
The route is built from five chemical unit operations, which the industry usually summarises as four core processing steps — leaching, purification, reduction and electrorefining. Oxidative leaching brings the target metals into solution: gold and the PGMs are dissolved in hydrochloric acid with an added oxidant such as chlorine, or in aqua regia, nitric parting or a tailored acid leach, while silver behaves differently in chloride media and reports as low-solubility silver chloride. Solid–liquid separation clarifies the pregnant solution on filter presses and vacuum filters, isolates the silver chloride residue for its own refining route, and returns the insoluble lead sulfate / barium sulfate residue and any stream still carrying metal either to sale or back to the head of the circuit. Selective precipitation then pulls metals out of solution one at a time — gold reduced with sodium metabisulfite, sulfur dioxide, oxalic acid or hydrazine hydrate, platinum precipitated as ammonium salt, palladium and the remaining PGMs isolated by controlled reduction and cementation — and any gold left in the filtrate after the first precipitation is reduced in a second reactor and recycled to leaching rather than lost, which is what keeps precipitated gold at a consistently high grade. Solvent extraction and ion exchange split mixed PGM liquors into clean, single-metal streams using reagents such as TBP, DBC (dibutyl carbitol) and amine extractants on mixer-settler banks and resin columns. Electrorefining sets the final fineness: Wohlwill-type cells for gold at 60–70 °C, Möbius and Balbach-Thum type cells for silver, and high-current-density or rotating-cathode electrowinning for dilute streams and PGM finishing.
Two circuits run alongside the metal chain rather than behind it. The gas circuit — enclosed reactors, condensers, mist separators, a circulation tank and multi-stage acid / alkali scrubbing — captures acid mist, chlorine-containing vapours and nitrogen oxides, and in doing so recovers the metal droplets carried in the off-gas instead of losing them to atmosphere. The water circuit neutralises and polishes every bleed and wash stream, meets discharge standards, and recycles the acid-based leaching solutions and polished water back to the process, cutting both fresh-water intake and waste-water volume.
The plant is supplied as skid-mounted, factory-piped modules that are functionally tested before shipment, with the level of automation set to the client’s requirement: batch weighing, controlled reagent dosing, temperature and current logging, and a precious-metal accounting system that ties every batch to its input assay and output Certificate of Analysis.
The result is a compact, low-temperature, closed-loop refinery that a recycler, smelter or refinery can own and operate on site — recovering more metal, faster, with a fraction of the locked-up inventory and none of the flue-dust and slag handling that pyrometallurgical refining requires.
Application Scenarios
The plant is specified wherever precious metal already exists in a form that can be dissolved, and where the operator wants to own the final refining step instead of shipping value away.
- Copper and lead electrorefineries — treat anode slime in-house and shorten the recovery chain instead of selling slime as a discounted intermediate. Output: Au / Ag bullion, PGM concentrate, Se / Te by-products.
- Gold refineries and bullion houses — a purely hydrometallurgical route from doré or bullion to LBMA-style fine gold, with short process time and low gold inventory in the circuit. Output: 999.9 fine gold bars and granules.
- Precious-metal refineries and assay houses — replace or supplement conventional chlorination-plus-electrolysis lines with a lower-temperature wet route, and add capacity for PGM-bearing customer material. Output: 99.99% Au / Ag and ≥ 99.95% Pt / Pd.
- E-waste and PCB recyclers — refine the precious-metal alloy, concentrate or leachate produced by the front end of an e-waste line into certified metal. Output: Au / Ag / Pd bullion and powder.
- Spent-catalyst reclaim plants — dissolve and separate Pt, Pd and Rh from palladium-on-carbon, reforming, petrochemical and fine-chemical catalysts. Output: high-purity PGM sponge and powder.
- Automotive catalyst processors — refine the PGM concentrate recovered from three-way converter monoliths into individual metals. Output: Pt / Pd / Rh sponge.
- Jewellery, dental and mint operations — refine karat scrap, sweeps, sprues, polishing dust and floor residues, with fast turnaround that keeps production lines supplied. Output: 99.99% Au / Ag bars.
- Electroplating and surface-treatment plants — recover gold, silver and palladium from spent baths, drag-out, strip solutions and ion-exchange eluate. Output: recovered metal powder and recyclable process water.
- Solar-PV and electronics manufacturers — recover silver from contact pastes, silicon fines and process scrap. Output: silver powder and crystal.
- Precious-metal traders and financial institutions — refine old, damaged or mixed coins, bars and bullion back to investment grade with full batch traceability. Output: investment-grade bars with assay certificate.
- Mining and concentrate producers — refine gravity concentrate, loaded carbon and doré on site rather than exporting intermediate product. Output: cast doré and refined gold.
- Universities, laboratories and pilot facilities — bench- and pilot-scale lines for process validation, teaching and small-batch refining. Output: analytical-grade purified metals.
Applicable Raw Materials
Route selection follows the assay, so the same platform handles a wide spread of grades, matrices and physical forms.
- Copper and lead electrolytic anode slime — slimes, selenides and smelter intermediate residues carrying Au, Ag, Se, Te and PGMs, which are the classic feed for a hydrometallurgical precious-metals refinery. Output: gold and silver bullion plus selenium and tellurium by-products.
- Gold doré, bullion and atomised alloys — cyanidation-plant doré bars, melted and atomised to fine powder or granulated to give a large reaction surface, so residence time and reactor volume both come down. Output: 99.99% fine gold.
- Karat gold and jewellery scrap — 8 to 22 karat alloys, sweeps, sprues, filings, polishing dust and floor residue. Output: 99.99% gold bars and granules.
- Silver-rich material — crude silver, silver-zinc crust, silver alloy and Sterling scrap, handled on a dedicated chloride-conversion and electrolytic route because silver does not follow the gold route in chloride media. Output: 99.99% silver crystal and bars.
- Spent precious-metal catalysts — palladium-on-carbon, platinum reforming and rhodium process catalysts, alumina- and carbon-supported spent catalyst, fuel-cell and hydrogen-peroxide plant residues. Output: Pt / Pd / Rh powder and sponge.
- Automotive catalytic converter concentrate — the PGM-bearing concentrate produced from three-way converter monoliths. Output: individual Pt, Pd and Rh products.
- E-waste precious-metal fractions — the alloy, concentrate or pregnant leachate generated by a board-dismantling, carbonisation or smelting front end, including CPU, RAM, connector and component scrap. Output: Au / Ag / Pd bullion.
- Electroplating and process solutions — spent plating baths, drag-out, strip and aged strike solutions, ion-exchange regeneration eluate. Output: recovered Au / Ag / Pd metal and recyclable liquor.
- Refinery and industrial residues — platinum-rhodium thermocouple wire, crucibles, gauze, refractory brick and glass-cullet waste, photographic and imaging residue, hydroxide sludge and dilute metal-bearing effluent. Output: PGM metal, silver crystal, recovered metal powder.
- Gold ores, concentrates and loaded carbon — oxide and refractory concentrates, gravity concentrate and pregnant activated carbon from cyanidation circuits. Output: cast doré and refined gold.
Output Products
Every consignment is released against a Certificate of Analysis based on fire assay and ICP-OES before it leaves the plant.
- Refined gold — chemically reduced and electrolytically finished Au ≥ 99.99%, with a second electrolytic pass reaching 99.999% where the market requires it. Output: 999.9 fine gold bars, granules and shot.
- Refined silver — chloride-converted and electrolytically refined Ag ≥ 99.99%, in Möbius or Balbach-Thum type cells. Output: silver crystal, bars and powder.
- Platinum and palladium — separated by solvent extraction and precipitation, delivered as Pt / Pd ≥ 99.95%. Output: high-purity PGM sponge and powder.
- Rhodium, iridium and ruthenium — selectively separated and purified Rh ≥ 99.90%, with Ru and Ir recovered on request. Output: individual PGM powder, sponge and salts.
- Selenium and tellurium — precipitated and cemented from slime liquors as separately saleable by-products, which turn disposal cost into revenue. Output: Se / Te concentrate and refined metal.
- Copper and base-metal by-products — copper recovered by cementation or electrowinning from decoppering and bleed streams. Output: copper powder, cathode and copper telluride.
- Lead and other salts — lead removed by chloride leaching and cooling precipitation, then converted to a higher-purity saleable salt rather than a waste. Output: lead sulfate and similar by-product salts.
- Treated water and cleaned off-gas — neutralised closed-loop process water polished to below 10 ppm metal content, and scrubbed exhaust with NOₓ below 150 ppm. Output: compliant emission and recirculated process water.
Precious Metal Hydrometallurgical Refining Plant Process Flow
The plant runs as a staged, closed-loop aqueous sequence. Silver, gold and the PGM group are split onto their own finishing routes after the leaching and separation stages, while the gas and water circuits operate continuously in parallel with the metal chain.
The plant runs as a staged, closed-loop aqueous sequence. Silver, gold and the PGM group are split onto their own finishing routes after the leaching and separation stages, while the gas and water circuits operate continuously in parallel with the metal chain.
Steps 1 — Feed Preparation and Granulation. Doré bars and bullion are melted and atomised to fine powder, or granulated, so that the surface available for chemical attack is maximised and reactor residence time and volume are reduced; anode slime and residues are dried, milled and screened; scrap and catalyst feed is cleaned of oil, organics and gross base metal where the assay requires it. Output: uniform granules and atomised fines, ready for controlled dosing into leaching.
Steps 2 — Sampling and Assay. Each batch is weighed, representatively sampled and assayed — XRF screening with fire assay and ICP-OES confirmation — to establish true metal content, impurity levels and the correct process route, and to open a metal-accounting record that follows the batch to its final Certificate of Analysis. Output: assay report, batch route sheet and traceability record.
Steps 3 — Oxidative Leaching and Chloride Dissolution. Prepared feed is leached in glass-lined, titanium or PPH reactors under controlled reagent dosing and agitation. Gold and the PGMs dissolve in hydrochloric acid with an added oxidant such as chlorine, or in aqua regia or nitric parting; silver forms low-solubility silver chloride and stays in the residue. Reactors are enclosed and vented to the gas circuit throughout. Output: precious-metal pregnant liquor plus an insoluble silver chloride and gangue residue.
Steps 4 — Solid–Liquid Separation and Silver Chloride Recovery. The leach slurry is filtered on plate-and-frame presses and vacuum filters with liquid transferred by vacuum rather than pouring. The clarified pregnant liquor goes forward to gold and PGM recovery; the filter cake is washed to displace entrained values, with the wash liquor returned to the circuit. Output: clarified pregnant liquor, silver chloride residue routed to silver refining, and insoluble residue for sale or smelting.
Steps 5 — Silver Conversion and Silver Electrorefining. Silver chloride is converted to metallic silver and refined electrolytically in Möbius or Balbach-Thum type cells with controlled electrolyte circulation, cooling and automatic make-up, at cathode current densities up to about 750 A/m². Output: Ag ≥ 99.99% crystal, later melted and cast into bars.
Steps 6 — Gold Precipitation and Gold Electrorefining. Gold is selectively reduced from the pregnant liquor with sodium metabisulfite, sulfur dioxide, oxalic acid or hydrazine hydrate; the fine gold sand is filtered, washed and dried, while the filtrate goes to a second reduction reactor that recovers the remaining gold and returns it to leaching — which is how product purity is held batch after batch. Where the market requires finer product, the reduced gold is further refined in a Wohlwill-type electrolytic cell at 60–70 °C. Output: Au ≥ 99.99% powder, and 99.999% after a second electrolytic pass.
Steps 7 — PGM Separation and Purification. The gold-barren liquor is treated for platinum-group metals: solvent extraction on mixer-settler banks with reagents such as TBP, DBC and amine extractants, supported by ion-exchange resin columns; platinum is precipitated as an ammonium salt and the remaining metals are isolated by controlled precipitation, reduction and cementation. Output: separate Pt, Pd ≥ 99.95% and Rh ≥ 99.90% streams, plus residual metals polished out of the final solution.
Steps 8 — Off-Gas Scrubbing and Effluent Treatment. Off-gas from the reactors passes through condensers and mist separators, then multi-stage acid and alkali scrubbing with a circulation tank, with absorption efficiency of 99.5% or better and outlet NOₓ below 150 ppm; condensed and scrubbed droplets are returned to the circuit so metal carried in the gas stream is recovered rather than vented. Wastewater and bleed streams are segregated, neutralised and polished, with acid-based leaching solutions recycled to the process. Output: compliant off-gas, polish water below 10 ppm metal for recirculation, and dewatered residue.
Steps 9 — Melting, Casting and Certificate of Analysis. Dried gold, silver and PGM products are fluxed, melted in induction furnaces under inert gas or vacuum, and cast into bars, granules, shot or sponge. Each lot is re-assayed by fire assay and ICP-OES and released against a Certificate of Analysis. Output: certified bars, granules and sponge with assay documentation.
The main chain runs vertically through preparation → assay → leaching → separation → silver, gold and PGM refining → casting. Side branches route off-gas and condensate to the scrubber, raffinate and second-precipitation gold back to leaching, silver chloride to silver refining, leach residue to sale or smelting, and neutralised water to the wash and rinse loop.
Product Structure (Main Equipment)
- Purely hydrometallurgical — no smelter required. The complete route from feed to bullion is aqueous, so there is no flue dust, no slag and no high-temperature furnace section to permit, operate or maintain.
- Much lower process temperature. Chemical and electrolytic stages run from ambient up to about 90 °C, a fraction of the 1200–1500 °C needed by pyrometallurgical refining, which cuts thermal energy demand and heat-related wear on the plant.
- High direct recovery with low locked-up inventory. Short residence times and small solution volumes mean less metal is tied up in the circuit at any moment, so working capital and metal-at-risk are both lower.
- Closed-loop reagents and water. Raffinate and spent electrolyte return to leaching, acid-based solutions are recycled, scrubber condensate is captured, and polished water goes back to the rinse loop — reducing reagent make-up, fresh-water intake and effluent volume.
- Off-gas as a recovery stream, not just an emission. Condensers, mist separators and multi-stage scrubbing capture acid mist, chlorine-containing vapour and NOₓ, and return the metal droplets carried in the gas back to the process.
- Stable ultra-high fineness. Fineness is set electrochemically rather than by chemical precipitation alone, so product grade does not drift batch to batch; gold reaches 99.99–99.999%, silver 99.99%, Pt / Pd ≥ 99.95%, Rh ≥ 99.90%.
- Full-spectrum metal split. Gold, silver, platinum, palladium and rhodium leave as separate saleable streams instead of one mixed doré button, and selenium, tellurium, copper and lead are recovered as by-products rather than disposed of.
- Corrosion-engineered wetted parts. Glass-lined steel, titanium, borosilicate glass and PPH / PP with anti-ageing additive are selected against the actual process chemistry, with titanium and titanium-clad-copper conductors in the electrolytic section.
- Low-loss design details. Enclosed cell hoods with side extraction, electrolyte cooling to reduce evaporation and acid consumption, condenser recovery of volatilised electrolyte, vacuum liquid transfer instead of pouring, and wash-water return to the circuit.
- Batch accountability. Weighing, sampling and assay management are integrated into the control system, so every batch carries an input assay, a process record and an output Certificate of Analysis — essential where high-value material is being handled.
- Automated and data-logged. PLC and HMI control with parameter storage and interlocks reduces operator dependence and manual error, and provides the audit trail regulators and buyers ask for.
- Modular and scalable. Identical process logic from pilot plants of a few kilograms per day to industrial installations handling hundreds of kilograms per day, so capacity can be added without redesigning the route.
Product Features
- Recovery and refining in one continuous route. Mechanical liberation, thermal enrichment, hydrometallurgical separation and electrolytic refining are engineered as a single line, so metal freed at the front end is not lost before it reaches the cathode.
- Built for low-grade and awkward feed. The plant is designed around mixed, dilute and contaminated material — shredded board mix, slime, spent catalyst, sludge and dilute effluent — not just high-grade scrap.
- Closed-loop reagent and water circuit. Raffinate and spent electrolyte return to leaching, scrubber wash water is neutralised and recirculated, and polish water is held below 10 ppm metal content, cutting reagent make-up and effluent volume.
- Full-spectrum product split. Gold, silver, platinum, palladium and rhodium, plus copper, selenium and tellurium by-products, leave the plant as separate saleable streams rather than one mixed doré button.
- Stable ultra-high fineness. Electrolytic finishing locks product at Au / Ag 99.99% and Pt / Pd ≥ 99.95%, avoiding the grade drift that chemical-only precipitation routes suffer batch to batch.
- Corrosion-engineered contact parts. Dissolution, filtration and storage wetted parts are high-performance PPH with anti-ageing additive, PPH structural frames, titanium and titanium-clad-copper conductors, and glass-lined or titanium reaction vessels.
- Low-loss design details. Enclosed transparent cell hoods with side extraction, electrolyte cooling to cut evaporation and acid consumption, condenser recovery of volatilised electrolyte, and vacuum liquid transfer instead of pouring.
- Environmental compliance by design. Integrated NOₓ and acid-mist scrubbing, alkali polishing and closed-loop wastewater treatment keep emissions and effluent inside EPA and EU limits without a separate plant build.
- PLC-controlled and data-logged. Temperature, voltage, current and bus-bar monitoring with parameter storage and interlocks gives repeatable batches, low operator dependence and an audit trail for assay control.
- Skid-based and quick to commission. Pre-piped, factory-tested modules shrink site civil works and installation time compared with stick-built refineries.
- Scales from pilot to industrial. Identical process logic from bench and pilot lines to full industrial plants, so a client can expand without re-inventing the route.
Technical Parameters And Specifications
Values below describe the standard process envelope and product outcomes. Throughput, footprint, power and utility figures are engineered to each client’s feed assay, target metals and site conditions, and are confirmed at design review.
| Parameter | Specification |
|---|---|
| Product | Precious Metal Hydrometallurgical Refining Plant |
| Process route | Oxidative leaching · solid–liquid separation · selective precipitation · solvent extraction and ion exchange · electrorefining (fully aqueous, no smelting stage) |
| Overall precious-metal recovery | Up to 99% direct recovery for Au, Ag, Pt and Pd on suitable feed, with minimal metal locked inside the active circuit inventory |
| Refined gold purity | Au ≥ 99.99%; 99.999% with a second electrolytic pass (999.9 fine, LBMA-style good delivery) |
| Refined silver purity | Ag ≥ 99.99% by chloride conversion plus electrolytic refining; 999.0+ fine as the standard electrolytic grade, with Möbius and Balbach-Thum type cells |
| Platinum and palladium purity | Pt / Pd ≥ 99.95% |
| Rhodium purity | Rh ≥ 99.90% (Ru and Ir on request) |
| By-product purity | Se and Te concentrate and refined metal; copper powder / cathode; lead sulfate salt |
| Feed throughput | Modular and configurable: from compact units from 5 kg/day to multi-ton industrial facilities; 1–50 t per year of refined gold in a single plant |
| Feed forms accepted | Anode slime · doré and bullion · atomised alloy · karat scrap · spent catalyst · plating solution · refinery residue · concentrate and loaded carbon |
| Leaching chemistries | HCl + Cl₂ oxidative leach · aqua regia (HNO₃ + HCl) · nitric parting · pressure leach · tailored acid leach · cyanide-free alternatives |
| Gold reducing agents | Sodium metabisulfite (Na₂S₂O₅) · sulfur dioxide (SO₂) · oxalic acid · hydrazine hydrate |
| Separation reagents | TBP · DBC (dibutyl carbitol) · amine extractants · ion-exchange resin · activated carbon · cement (iron, copper, zinc) |
| Refining cells | Wohlwill-type gold cells · Möbius and Balbach-Thum type silver cells · high-current-density and rotating-cathode / pulsed electrowinning units |
| Gold cell current density | Up to 1000 A/m² cathode |
| Silver cell current density | Up to 750 A/m² cathode |
| Electrolyte operating temperature | 60–70 °C for gold; cooled and controlled for silver |
| Operating temperature range | Ambient to about 90 °C in the chemical section (versus 1200–1500 °C for pyrometallurgical refining) |
| Typical cycle time | Leaching 3–6 h depending on feed; gold chemical refining 8–12 h; electrolytic gold finishing 1–2 days; silver cells continuous with automatic powder discharge |
| Soluble-metal concentration handled | From a fraction of a gram per litre up to several hundred grams per litre |
| Reaction vessel materials | Glass-lined (enamel) steel · titanium and titanium-clad · borosilicate glass · PPH / PP with anti-ageing additive · Hastelloy on request |
| Vessel ratings | PPH vessels 0.05–5 m³, atmospheric to −0.1 MPa, −10 °C to 80 °C; heated titanium reactors for higher-temperature leaching |
| Off-gas inlet NOₓ concentration | Up to > 30,000 mg/m³ (> 20,000 ppm) |
| Treated NOₓ concentration | Below 150 ppm, within discharge standard |
| Scrubber absorption efficiency | ≥ 99.5% for NOₓ and acid-alkali gases |
| Gas streams handled | NOₓ · HCl · Cl₂ · SO₂ · acid mist · ammonia |
| Metal recovery from off-gas | Condensate and scrubber solution returned to the process circuit |
| Wastewater treatment | Segregated collection, neutralisation, metal precipitation and polishing; polish water < 10 ppm metal, recirculated |
| Casting | Bars, granules, shot and sponge; vacuum ingot casting with nitrogen or argon pressurisation |
| Assay and QC | XRF · fire assay · ICP-OES, with Certificate of Analysis per batch |
| Automation | PLC + touch-screen HMI; rectifier, pump, heating and dosing control; temperature, voltage, current and bus-bar monitoring; parameter logging and interlocks |
| Configuration scale | Laboratory bench · pilot · industrial turnkey, with equal process logic at every scale |
| Standards | CE; EPA and EU emission and discharge limits; market-tradeable (LBMA-style) bar specification |
Technical Advantages
- No smelting means no flue dust, no slag and no furnace campaign. Eliminating the pyrometallurgical section removes the single largest source of emissions, refractory maintenance and metal locked in slag and dust, and it allows a refinery to be built in jurisdictions where a smelter would not be permitted.
- Lower operating temperature, lower thermal cost. Running the chemical section from ambient to about 90 °C instead of 1200–1500 °C cuts thermal energy consumption and extends the service life of vessels, seals and instrumentation.
- Direct recovery up to 99%. Because the route works on high-grade metallic feed rather than dilute ore, and because the raffinate, the second-precipitation gold and the scrubber condensate all return to the circuit, direct recovery of Au, Ag, Pt and Pd reaches up to 99%, with minimal metal locked inside the active circuit inventory.
- Short cycle time and low inventory. Leaching at 3–6 h and gold chemical refining at 8–12 h keep residence times short, so far less gold is tied up in process inventory than in conventional pyrometallurgical-plus-electrolytic refineries — a direct working-capital saving on high-value metal.
- Electrochemical fineness control. Wohlwill-type gold cells at up to 1000 A/m² and Möbius / Balbach-Thum silver cells at up to 750 A/m² deliver fineness that chemical precipitation alone cannot hold, and higher current density raises output per unit of cell volume while shortening cycles.
- Silver handled properly, not as an afterthought. Silver chloride is deliberately separated, converted and routed to its own electrolytic circuit, avoiding the passivation and contamination problems that appear when silver-rich feed is forced through a gold-only chloride route.
- Selective multi-metal separation. Solvent extraction with TBP, DBC and amine extractants, supported by ion exchange, cementation and controlled precipitation, resolves a mixed PGM liquor into individually saleable metals at full value instead of a discounted mixed concentrate.
- Dilute streams still pay. Rotating-cathode and pulsed electrowinning plus resin capture work from a fraction of a gram per litre upward, converting wash water, bleed and eluate that would otherwise be neutralised as waste into saleable metal.
- By-products instead of disposal costs. Selenium, tellurium, copper telluride and lead sulfate leave the plant as saleable products, improving project economics and reducing the volume of residue that must be disposed of.
- Compliance built into the package. Multi-stage scrubbing at 99.5%+ absorption, condensate recovery and closed-loop wastewater neutralisation keep the plant inside EPA and EU limits and protect the operator’s licence to run.
- Metal accounting as standard. The batch traceability system ties input assay to output Certificate of Analysis, which is what banks, buyers and auditors expect when high-value metal is moving through the plant.
- Turnkey single-point accountability. One contractor owns assay, process design, equipment, skid assembly, commissioning and operator training — removing the integration risk of assembling a wet refinery from several vendors.
Service Process
YuSai delivers the plant as a full turnkey project, from feed characterisation and bench test work to a running, certified wet refinery.
Steps 1 — Feed Characterisation and Consultation. Send representative samples of your slime, doré, scrap, catalyst or residue; our metallurgical team runs XRF, fire assay and ICP-OES, identifies the recoverable metals and impurities, and proposes the optimal hydrometallurgical route and target products. Output: assay report and preliminary route proposal.
Steps 2 — Laboratory Test Work and Process Design. Bench and pilot campaigns confirm leach conditions, reagent consumption, separation sequence and expected recovery, and are converted into a mass balance, flowsheet, equipment list, vessel sizing, utility schedule and plant layout against your throughput, site and local discharge rules. Output: test report, process design package and firm quotation.
Steps 3 — Detailed Engineering and Manufacturing. Reactors, filtration skid, solvent-extraction and resin columns, electrolytic cells, scrubber and water plant, control cabinet and casting unit are fabricated, pre-assembled on skids and piped. Output: engineered, skid-mounted modules.
Steps 4 — Factory Assembly, Testing and Acceptance. Each module is functionally tested and the full train is trial-run, wherever possible on your own material, with the client invited to attend the factory acceptance test before shipment. Output: FAT-approved, pre-commissioned modules.
Steps 5 — Shipping, Installation and Commissioning. We supervise the civil interface, erection, piping, electrical tie-in and ductwork, then run an instrumented commissioning campaign on your feed until the contracted purity and recovery are demonstrated. Output: a producing plant at contracted performance.
Steps 6 — Operator Training and Handover. On-site training covers safe operation, acid and reagent handling, leaching and precipitation control, cell and furnace maintenance, assay QC and emergency procedures, supported by Standard Operating Procedures and a full handover dossier. Output: trained crew and complete documentation.
Steps 7 — Process Optimisation and Ongoing Support. Remote troubleshooting, reagent, resin, carbon and electrode supply, periodic performance audits and capacity or recovery upgrade paths keep the plant at target over its service life. Output: sustained performance and spare-part continuity.
Warranty & After-Sales Service
- Standard warranty. Twelve (12) months from commissioning, or eighteen (18) months from shipment, whichever comes first, covering structural, mechanical, electrical and control equipment against defects in material and workmanship.
- What the warranty covers. Replacement of defective components, repair or exchange of main-process equipment, and free remote technical guidance throughout the warranty period. Consumables, and damage caused by misuse, unauthorised modification or operation outside the agreed feed and process envelope, are excluded.
- Guaranteed performance. We warrant that, when fed material inside the agreed assay and throughput envelope and operated to the supplied SOP, the plant meets the contracted product purity and recovery figures, verified at commissioning by fire assay and ICP-OES.
- Response commitment. Guaranteed remote response within 24 hours, on-site engineer dispatch and hotline support for breakdowns affecting production, and expedited spare-parts supply.
- Spare parts and consumables. Genuine spares, electrodes, rectifier components, ion-exchange resin, activated carbon, membrane and extractant reagents are held as a stocking range to minimise downtime.
- Commissioning and start-up support. Supervised installation, commissioning on customer feed, performance verification and an operator competence sign-off before handover.
- Lifetime technical support. Free access to our engineering team for process questions after warranty expiry, plus optional retrofit, capacity-upgrade and reagent-optimisation services.
- Documentation. Full operating, maintenance and safety manuals, electrical drawings, P&ID, spare-parts catalogue, SOPs and training material accompany every plant.
- Compliance support. Assistance with local emission and effluent permitting documentation and with the assay and product-certification records that buyers and authorities require.
Frequently Asked Questions
Q1. What is a precious metal hydrometallurgical refining plant?
A precious metal hydrometallurgical refining plant is a refinery that recovers and purifies gold, silver and platinum-group metals using aqueous chemistry alone — oxidative leaching, solid–liquid separation, selective precipitation, solvent extraction, ion exchange and electrorefining — instead of smelting. Because every stage is wet chemistry, the plant operates from ambient temperature to about 90 °C, produces no flue dust and no slag, and can achieve higher direct recovery with far less metal tied up in process inventory than a pyrometallurgical route.
Q2. How is hydrometallurgical refining different from pyrometallurgical refining?
A pyrometallurgical refinery smelts and converts feed at 1200–1500 °C, generating flue dust and slag, and then usually refines the resulting metal electrolytically or by chlorination. A hydrometallurgical plant dissolves the values directly from slime, doré, alloy or residue, which removes the furnace section, the dust and slag handling, and the temperature and emissions problems that come with them. Process time, inventory and per-unit energy consumption all come down — which is why hydrometallurgical refining is the standard route for anode slime and high-grade secondary material.
Q3. What precious metal recovery rate can the plant achieve?
Designed direct recovery is up to 99% for Au, Ag, Pt and Pd on suitable feed, with minimal metal locked inside the active circuit inventory. Recovery is protected by returning raffinate, second-precipitation gold, condensate and filter wash liquors to the circuit. Recovery is confirmed for each project from the feed assay during test work and verified at commissioning by fire assay and ICP-OES.
Q4. What purity do the refined products reach?
Gold 99.99% as standard, with 99.999% available after a second electrolytic pass; silver 99.99%; platinum and palladium ≥ 99.95%; rhodium ≥ 99.90%. Purity is set electrochemically, so it stays stable batch to batch, and every consignment is released with a Certificate of Analysis.
Q5. Does the plant need a smelter or melting shop alongside it?
No smelter is needed — the refining route is entirely aqueous. A small induction melting and casting unit is included for the final step, because the refined gold, silver and PGM products are melted and cast into bars, granules or sponge before sale.
Q6. Which raw materials can the plant process?
Copper and lead anode slime; gold doré, bullion and atomised alloy; karat gold and jewellery scrap; crude silver, silver-zinc crust and Sterling scrap; spent Pd, Pt and Rh catalysts and automotive catalyst concentrate; e-waste precious-metal alloy, concentrate or leachate; spent plating baths and ion-exchange eluate; refinery residues, thermocouple wire, crucibles and glass-cullet waste; photographic and imaging residue; and gold concentrates and loaded carbon.
Q7. Can gold and silver be refined in the same hydrometallurgical plant?
Yes, but not in the same step. Silver forms low-solubility silver chloride in chloride media, so it is deliberately separated during leaching, then converted to metallic silver and refined on its own electrolytic circuit. Handling silver this way — instead of forcing it through a gold-only route — is what prevents silver chloride passivation and cross-contamination, and it is why a properly designed hydrometallurgical plant recovers both metals cleanly.
Q8. Is the precious metal refining process cyanide-free?
The standard configuration is cyanide-free. Gold is dissolved by oxidative chloride leaching, aqua regia or nitric parting and reduced with sodium metabisulfite, sulfur dioxide, oxalic acid or hydrazine hydrate — none of which involve cyanide salts. Cyanide-based alternatives are available where a client’s existing upstream process already uses them.
Q9. How long does a hydrometallurgical refining batch take?
Leaching typically runs 3–6 hours depending on feed and particle size; gold chemical refining runs about 8–12 hours; electrolytic gold finishing takes 1–2 days depending on anode grade and current density; silver electrolytic cells run continuously with automatic powder discharge. Short residence times are what keep metal inventory — and the working capital tied up in it — low.
Q10. How are hazardous fumes and wastewater treated?
Reactors are enclosed and vented to condensers, mist separators and multi-stage acid / alkali scrubbers sized for inlet NOₓ concentrations above 30,000 mg/m³ and reducing them to below 150 ppm, with 99.5%+ absorption efficiency. Wastewater is segregated, neutralised, metal-polished to below 10 ppm and recirculated, and acid-based leaching solutions are reused. The package also includes local extraction, fume hoods, secondary containment, acid-proof flooring and gas-detection interlocks for operator protection.
Q11. What capacity range is available for a hydrometallurgical refining plant?
The plant is modular. Capacity extends from compact units processing as little as 5 kg per day to multi-ton industrial facilities — equivalent to 1–50 tonnes per year of refined gold in a single plant. Because process logic is identical at every scale, capacity is added by duplicating reactor, cell and separation trains rather than redesigning the route.
Q12. What information is needed for a quotation?
A representative assay for Au, Ag, Pt, Pd and the main base metals; the material type, physical form and known contaminants; required batch size and batches per day or month; target products and purity; available floor area, headroom and utilities; and your local air-emission, wastewater and chemical-storage requirements. Photos help, but a sample and an assay are what let us confirm the route and the performance figures.
Q13. What warranty and after-sales support is provided?
A standard 12-month warranty from commissioning (or 18 months from shipment, whichever comes first) covers material and workmanship defects with defective-part replacement and free remote support, backed by a guaranteed-performance clause confirming contracted purity and recovery at commissioning. Remote response is within 24 hours, genuine spares and process consumables are stocked, and lifetime technical support continues after warranty expiry.
Q14. Do you provide installation, commissioning and operator training?
Yes. As a turnkey supplier we supervise erection, piping, ductwork and electrical tie-in, run commissioning on your own feed until the contracted purity and recovery are demonstrated, and deliver on-site operator training covering safe operation, acid and reagent handling, process control, assay QC and maintenance, with complete SOPs and a handover dossier.
Q15. How does the plant improve on shipping material to a third-party refinery?
Refining in-house captures the full margin between intermediate and finished metal, eliminates third-party refining charges and settlement delays, shortens the cash cycle, and gives the operator control of its own assay and product certification. The plant also makes previously unviable feed — dilute slime, mixed residue, contaminated scrap — worth processing, because the metal no longer has to justify a shipment.
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- +86 18339216321
- info@yusaipreciousmetals.com
- Zhengzhou.Henan.China
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