Lead-Copper Anode Slime Converter

— Lead-Copper Anode Slime Converter: TBRC Smelting to Doré

A lead-copper anode slime converter (also built as a Top Blown Rotary Converter, or TBRC) is a tilting, rotating, top-blown pyrometallurgical reactor for the by-products of copper and lead electrolytic refining. Anode slimes carry gold, silver and platinum-group metals alongside lead, copper, selenium and tellurium, and the lead among them is not an impurity but the collector metal that gathers the gold and silver into the metal phase — which is why the vessel is a lead-copper converter rather than a general slime smelter. itcombines smelting, converting and impurity slagging in one vessel where a traditional route needs a leach circuit, a roaster and a large reverberatory doré furnace: de-copperised, roasted slime charged with a soda-based slag and silica, driving unwanted elements into a slag phase; oxygen-enriched air blown through a top lance, oxidising lead, iron and residual copper into lead and silica slags; and selenium driven off into gas collection with the base metals fluxed out, What remains is a purified silver-gold bullion ready for casting and final parting.

Product Overview

A lead-copper anode slime converter is a pyrometallurgical reactor defined by three features: it rotates about an inclined axis, it tilts to pour, and it blows oxygen-enriched gas onto the bath through a water-cooled lance. Rotation stirs the bath continuously, so reactions are limited by chemistry rather than by diffusion through a static melt, localised overheating is avoided and the lining wears evenly instead of in one hot band; tilting lets the vessel be emptied and skimmed without cutting a stream; and top blowing means no submerged tuyere and no lance in the melt, so shell life is not set by a tuyere and thermal control is the lance’s. One shell therefore replaces a slime circuit that otherwise needs four units, with no transfer, skull or refractory inventory between stages. Its inputs are copper and lead tankhouse slimes — fine, wet and chemically awkward, generated at roughly 5–10 kg per tonne of copper cathode, with assays spanning copper 0.4–53%, selenium 0.2–46%, silver 1.5–33% and lead 0.05–32% — and both arrive at roughly 35–40% moisture as a mud, which is why the front end — de-copperising status, drying, binder dosing and pelletising — is part of the machine.

The chemistry is a ladder rather than a reaction. The slime is first roasted at the 650 °C level, where selenium oxidises to selenium dioxide and leaves with the off-gas and part of the sulfur leaves as sulfur dioxide; volatilising it here is what makes the sequence work, because selenium left in the bath reports to a soda slag published at concentrations around 30% and to the matte, and both must then be treated before the metal can be sold. Reduction and smelting follow at and above roughly 950 °C, where a soda-based slag with silica and a carbonaceous reductant reduces the lead oxides to lead metal. That lead is the collector: it dissolves the gold, silver and platinum-group metals and carries them into the bullion phase, while the gangue oxides go into the slag and the sulfur partly fixes in the matte. A converting blow up to roughly 1,185 °C then oxidises the remaining base metals out of the bullion and produces the silver selenide matte, and a refining blow with a borax-based flux cuts residual copper to about 0.2% against about 0.7% on soda, leaving bullion at 99.2–99.6% combined gold plus silver.

The decisive design decision is why lead and copper sit on opposite sides of the boundary. Copper is a problem here: it oxidises into the slag as copper oxide, increasing slag volume and viscosity, and it partitions into the matte as a copper-silver selenide, lowering the matte’s silver grade and increasing the mass shipped — so every tonne of copper charged is a tonne of slag and matte to handle for no precious-metal gain. Lead is the opposite: it dissolves gold and silver and settles with them, it is why a slime of modest precious-metal content can still be concentrated into a small, rich bullion, and it is recovered afterwards by vacuum distillation or cupellation and returned to the lead circuit as metal. The consequence is a feed rule: de-copperise before charging, and where the slime is lead-poor, add lead deliberately as a flux so the collector phase exists in sufficient mass.

Temperature and the refractory decide the economics, and both are counter-intuitive. The roast band governs how much selenium leaves as gas, and running hotter does not recover more selenium: it volatilises lead with it into a gas train that must then capture, weigh and recycle that lead. The converting band around 1,150–1,250 °C is set by the oxidation kinetics of the base metals, and exceeding it volatilises lead and bismuth where neither can be recovered economically. The most counter-intuitive figure is the skim temperature: a stationary hearth needs its slag above roughly 1,300 °C to be fluid enough to pour, a temperature at which lead is already leaving as fume, whereas the rotating vessel rakes and skims below about 1,200 °C. On the refractory, a deep stationary hearth holds a large pool of precious-metal-bearing melt against a large area of brick and leaves absorbed gold and silver behind until the vessel is demolished, while a rotating vessel carries a shallower pool with far less wetted brick per tonne and wears it uniformly — the published comparison at equal capacity putting the precious metal locked up per square metre roughly thirty times higher in the stationary arrangement.

The off-gas train is built around the gas this duty makes, which is not the gas a board or e-waste smelter makes. Anode-slime smelting carries selenium dioxide, sulfur dioxide, lead fume, arsenic and a fine, easily dispersed precious-metal-bearing dust, and no halogenated organic load — so it is a sealed enclosure at negative pressure with induced draught, a cooling stage, coarse dust removal with its particulate collected sealed, weighed and assayed as value rather than waste, wet gas cleaning with selenium recovery, arsenic capture with its own sludge handling, and final caustic scrubbing ahead of the stack, with local exhaust at the lance and the tap, supplied-air stations, sealed dust and sludge handling and HEPA vacuum housekeeping around all of it. What the customer receives is bounded and documented: function-tested modules, a site interface schedule, supervised installation and commissioning, the first campaign run on the customer’s own slime, and a performance trial confirming the assays and the closed balance. The limits are stated in the same document: the station does not de-copperise, does not part doré, does not accept wet, unassayable or high-copper slime as charged, and does not offer a first-pass recovery percentage it cannot support from published data.

Application Scenarios

Copper refineries treating their own tankhouse slime. Slime from anode bags and cell bottoms, de-copperised, dried and charged on site rather than shipped out as a wet, low-grade residue with a treatment charge attached; the converter becomes the plant’s precious-metal concentrator and the entry point to its own silver and gold refining, or to selling doré bullion and selenium metal rather than finished gold.
Lead refineries processing lead anode slime. Lead electrolysis produces a slime higher in antimony and arsenic than copper slime and rich in silver, treated through the same vessel with the lead in the feed doing part of the collector work rather than acting as an impurity to reject.
Integrated copper-lead refineries blending both slimes in one campaign sequence. Sites producing copper slime, lead slime and slime treatment residues that can campaign them through one vessel — which is why the vessel is bought as a lead-copper converter rather than as a single-feed unit.
Nickel and cobalt electrorefining slime processors. Fine, wet, precious-metal-bearing slime from nickel and cobalt tankhouses, treated on the same sequence where the contract allows the nickel to be managed in the matte and the leach liquor.
Precious-metal refineries buying slime and residues as toll feed. Refineries whose business is to buy other plants’ slime, filter cake, anode bag contents and treatment residues and concentrate them to doré, where the vessel’s tolerance of a variable feed and its campaign balance are the commercial basis of the operation.
Smelters whose stationary hearth doré furnace has become the constraint. Operations whose hearth cycle has stretched into days and weeks and whose refractory lock-up has become a visible line in the metal account; and sites where open charging, manual skimming and fugitive fume are the permitting problem — answered by a rotating vessel whose sealed enclosure, lance blowing and enclosed tapping turn the emission question from an argument into an instrument reading.
Operations replacing a multi-furnace slime line with one vessel. Published retrofits have replaced two roasting units, a short rotary smelting furnace and a separate converting and refining furnace with a single converter, reporting emission reductions of 80–99.5% alongside the simplification.
Slime circuits that also carry the plant’s own electrolysis residues. Anode residues, spent electrolyte sludges and bag slimes from the plant’s silver and gold electrorefining, returned to the converter rather than accumulated — with the electrolysis duty on our high-current density silver electrolytic cell and high-current density copper electrolytic cell pages.
Selenium and tellurium producers working backwards from the metal. Plants whose product is selenium or tellurium and whose feedstock is slime, using the roast stage for the selenium off-take and the matte tap for the tellurium, with the finishing duty on a dedicated circuit such as our tellurium electrolytic cell line.
Bismuth-bearing and platinum-group-metal-bearing slime processors. Feeds where bismuth, palladium or platinum justify their own recovery, concentrated into the bullion and the lead-rich stream and separated afterwards — with the PGM separation duty on our platinum, palladium and rhodium purification system equipment page.
Board-processing plants feeding a concentrate into a slime circuit. Operations whose e-waste line produces a precious-metal-bearing concentrate alongside a copper product, blended into the campaign at a controlled rate after its halogen content is established — with the front-end duty on our waste circuit board recycling equipment page.
Pilot plants, laboratories and teaching facilities. Bench-scale converter work used to establish how a particular slime behaves — how much selenium volatilises at which temperature, what flux produces a skimable slag, what the matte assays — before a production vessel is committed, and to train operators on the charging, skimming, converting and sealing discipline.

Applicable Raw Materials

The vessel is fed a solid, dried, pelletised slime, and what decides whether a lot is admitted is its chemistry, its de-copperising status, its moisture and its identifiable origin rather than its commercial description. Material already de-copperised, dried, correctly sized and inside the selenium, copper and moisture window is pelletised and charged; material that is wet, fine, copper-loaded, chloride-bearing or unassayable is dried, leached, blended, screened or refused first. Output is stated for each feed, and it is what the next step receives rather than what the marketing claim says.

De-copperised copper anode slime. Tankhouse slime after an acid or oxidising leach has taken the copper down to the design window, filtered and dried. Output: selenium off-take to wet gas cleaning, silver selenide matte, precious-metal-bearing slag, doré bullion.
Lead anode slime. From lead electrorefining, higher in antimony and arsenic than copper slime and higher in silver relative to gold, de-leaded and de-copperised as far as the contract requires. Output: doré bullion with antimony and arsenic in the slag and matte, and a lead-rich stream to the lead circuit.
Nickel and cobalt electrorefining slime. Fine, wet, precious-metal-bearing, treated where the contract allows the nickel to be managed into the matte and the leach liquor. Output: doré bullion and a nickel-bearing matte or slag stream with its own destination.
Leach residue, decopperising filter cake, cementate and anode bag contents. The solids left after the upstream copper leach, the cementates from displacing metals out of a slime liquor, and the heavier fraction from bag changes and cell cleaning, screened of cell hardware and blended. Output: the precious metals, selenium and lead the leach did not take into solution, recovered into the matte and bullion rather than leaving as a sold residue.
Spent silver and gold electrolyte sludge, anode and parting-cell residues. Sludges and bag residues from silver and gold refining circuits, including chloride-bearing parting-cell residues. Output: silver and gold recollected into the matte and bullion, with the chloride managed in the gas train and the slag.
Selenium- and tellurium-bearing fractions and deselenising residues. Soda slags, scrubber sludges, matte screenings and cell residues from a selenium or tellurium recovery step that still carry precious metals and lead. Output: recovered precious metals and lead, with the residual selenium volatilised to the gas cleaning stage and the tellurium reporting to the matte for the tellurium circuit.
Off-gas dust, baghouse catch and wet-gas cleaning sludge. Particulate from the plant’s own slime drying, roasting or furnace off-gas train and the sludge from the selenium and caustic scrubbing stages, collected sealed, weighed and assayed. Output: the precious-metal content returned to the vessel by pelletising, and a sludge with a documented destination instead of an undocumented one.
Bismuth- and platinum-group-metal-bearing slime and refinery residue. Feeds in which bismuth, palladium or platinum justify their own recovery. Output: bismuth concentrated into the bullion and lead-rich stream for removal as its own product in the lead circuit, and platinum-group metals carried with the gold and silver to the parting circuit.
Returned materials: converter slag, hearth doré slag and noble-lead bullion. The vessel’s own slag returned until its measured precious-metal, lead and selenium content falls to the discard band; slag from an existing stationary hearth campaign, published as carrying 10–30% of a slime campaign’s precious-metal value; and lead bullion or lead-rich material in which lead has already collected gold and silver. Output: precious metals recovered into the next campaign’s bullion, and a lead stream returned to the lead circuit as metal.
Board-processing concentrate, hydrometallurgical residues, spent catalyst and refinery sweeps. The precious-metal concentrate from an e-waste or board line, blended at a controlled rate after its halogen content is established; the solids left by the plant’s own wet route; catalyst residues that still carry platinum-group metals; and vacuum-collected tankhouse, refining-area and converter-bay sweeps, screened, milled and blended. Output: the precious-metal content concentrated into doré, with the halogen load managed in the gas train.
Feeds admitted only after preparation. Wet slime dried to the moisture window; binder-dosed and pelletised fines; oversized lumps milled and re-pelletised; screen undersize returned to the pelletiser; high-copper slime returned to the leach; high-chloride material leached, blended down or refused; screen and grate hardware removed by magnet and by hand. Output: a charge the vessel can accept without throwing metal into the duct, without a steam event and without loading the matte with copper.
Feeds routed to a different step before conversion. Material whose value sits in a leach solution; material whose selenium and tellurium content justifies a wet circuit of its own; material still above the copper window; material whose platinum-group-metal content warrants a dedicated separation flowsheet. Output: a converter feed inside specification, and by-products recovered on the route built for them.
Not admitted — unassayable, wet, dripping or acid-bearing, or copper above the window. Drums, bags and containers that cannot be opened, inspected, sampled and identified before charging, including tankhouse slime received without an assay; slime above the moisture window, free-draining slime, ice-bearing material and material carrying free acid; and slime whose copper has not been leached down to the design figure. Water entering the bath flashes to steam at a volume ratio that turns the vessel into a mortar, free acid attacks the lining and loads the gas train with sulfate, and copper charged above the window becomes slag and matte mass with no precious-metal gain. Output: not admitted; opened, sampled and assayed first, dewatered and neutralised first, or returned to the leach first.
Not admitted — halide-rich or organic-bearing. Chlorinated and brominated plastics, halogenated solvents, board laminate, PVC-bearing cable scrap and any feed whose halogen content exceeds the window the lining and the gas train were designed for: halogens attack the refractory, carry into the bullion and, with an organic matrix, create the dioxin and furan problem this gas train was not built to solve. Output: not admitted in bulk; organics separated upstream and the remainder leached or blended down.
Not admitted — mercury, cadmium, thallium or cyanide bearing, reactive, oxidiser-bearing or radioactive. Mercury-contaminated slime, amalgam, mercury-cell residues, cadmium-bearing fractions, thallium-bearing residues and cyanide-bearing material, which either volatilise into a gas train not sized or permitted for them or react with the bath instead of dissolving; sealed containers, gas-cylinder fragments, live primers and ammunition fractions, nitrate, chlorate and peroxide-bearing residues and any material that reacts violently with a molten bath; and scale, filter cake and dust carrying naturally occurring radioactive material above the clearance level, or any lot found to carry a radioactive source. Output: not admitted; made safe under a competent authority’s procedure or routed to a dedicated treatment step with its own abatement and monitoring, and decided at the radiation screening gate before the material is accepted for storage, let alone for charge.

Finished Products

The station is configured around the products the plant sells or feeds forward, from a matte for the silver and tellurium circuits through to the doré bullion, the selenium off-take, and the slag and dust that each have their own market or return route. Where the plant already runs silver and gold electrorefining, a gas cleaning plant and a slag storage area, the converter is delivered as the vessel, drive, lance and gas train, the drying and pelletising front end, the enclosure and the off-gas train; where it does not, those interfaces are inside the scope.

Silver selenide matte. The primary intermediate: the sulfidic and selenidic phase formed during the converting blow and tapped separately, published at silver 50–60%, selenium 7–25%, lead 3–15%, copper 0.8–4% and tellurium 0.7–1.5%. Output: a weighed and assayed matte consigned to the silver circuit and, on its tellurium content, to the tellurium circuit.
Doré bullion. Gold and silver concentrated into a metal phase by the lead collector and fluxed to drive residual base metals out. Output: doré bullion at published campaign assays of 97.3–99.6% combined gold plus silver depending on the flux route, released against assay for the parting refinery.
Lead-rich bullion or lead stream. The lead that carried the gold and silver, recovered as metal rather than as a residue — separated from the bullion by vacuum distillation or cupellation where the plant runs a lead circuit, and returned to it. Output: recovered lead metal for the lead refinery or for sale, with the precious metals stripped into the parting feed.
Selenium off-take to wet gas cleaning. Selenium volatilised as selenium dioxide in the roast and captured in the scrubber circuit as a selenium-bearing solution or sludge. Output: a selenium-bearing stream to the plant’s selenium recovery step, and the reason a separate deselenising roaster is not required ahead of the vessel.
Tellurium-bearing matte or slag fraction. Tellurium reporting to the matte in the converting blow, and to the slag where the flux route puts it there. Output: a tellurium feedstock for the plant’s tellurium circuit, recovered as a metal product rather than lost in a discard slag.
Bismuth concentrate. Bismuth reporting to the bullion and the lead-rich stream, concentrated rather than dispersed because the process works on a small mass of metal. Output: a bismuth-bearing intermediate recovered in the lead circuit as its own product.
Precious-metal-bearing slag and lead-bearing discard slag. Slag from the reduction and smelting stage, published as able to carry 10–30% of a campaign’s precious-metal value, granulated, crushed, sampled and assayed; and the same slag once reduced to the plant’s measured discard band, quenched into granules or cast into blocks. Output: a slag whose precious-metal content is measured and either returned to the next campaign, bled to a lead circuit or declared spent on its assay, and a granulated discard slag within the plant’s own band, assayed before the spent declaration and disposed of or sold under the applicable requirement.
Precious-metal-bearing filter dust and wet-gas cleaning sludge. The fine particulate captured by the off-gas train, collected sealed under the enclosure regime, and the sludge from the selenium and caustic scrubbing stages. Output: a weighed and assayed dust returned to the charge by pelletising, and a sludge with a documented destination — the selenium circuit where its assay justifies it, the vessel where the permit allows it.
Pelletised recycle feed. Filter dust, screen undersize, granulated slag returns and clean-up residues consolidated with binder into a chargeable pellet. Output: a recycle feed that re-enters the vessel without being entrained into the duct.
Campaign record and closed precious-metal balance. Slime weight and assay in; flux, reductant, lead addition, binder and oxygen; roast, smelt and converting temperatures with their hold times; matte, slag, bullion, dust and sludge out with their weights and assays; and the difference closed as the measured loss. Output: a campaign whose gold, silver, selenium and lead balance can be reconstructed and defended, and a slag figure comparable with the design target.
Doré bullion released against assay and ready for parting. Bullion weighed, sampled, granulated or cast, and released with its campaign number and assay in a form the electrorefining lines can charge directly. Output: a documented handover to the parting stage, on the terms set out on our silver refining process and gold refining process pages.

Lead-Copper Anode Slime Converter Process Flow

The nine stages below are one full conversion campaign, from the slime survey that decides whether a lot is admitted through to a vessel reset with the gas train cleaned and the lining inspected. Stage 4 and Stage 5 decide the campaign: the roast is the only point at which the selenium locked in the slime can be taken off as a gas rather than left to report to a slag and a matte, and the reductive blow is the only point at which the gold and silver can be moved into the lead collector phase. The vessel itself neither de-copperises the slime nor parts the doré: the first is an upstream leach, the second belongs to electrorefining.

Steps 1 — Slime Survey and De-Copperising Handover. Nothing is charged before the lot has been surveyed, because the selenium the roast must volatilise, the lead the collector phase needs, the soda, silica and carbon the slag and oxides need and the matte mass the converting blow will produce all come from that survey. The lot is weighed wet and dry, its moisture established, and its gold, silver, selenium, tellurium, copper, lead, antimony, arsenic, bismuth, sulfur and chloride content established by sampling, XRF and reference analysis. The de-copperising handover is the control gate: copper above the design figure oxidises into the slag and partitions into the matte as a copper-silver selenide, lowering the matte’s silver grade and increasing the mass shipped. Reagent and utility input: wet and dry weighing and sample preparation, moisture determination, XRF and reference analysis, campaign plan and route sheet. Output: a surveyed slime lot with its flux, lead-addition and reductant basis established and its campaign number allocated, or a documented diversion with the reason stated.

Steps 2 — Drying and Pelletising to the Moisture Window. Slime arrives from the tankhouse at roughly 35–40% moisture and is a mud, not a charge. Drying runs at a controlled temperature rather than at whatever the dryer will deliver, because the object is to remove water without volatilising selenium or entraining precious-metal-bearing fines into a dust system that must then be cleaned and returned. The dried slime is dosed with a binder — published practice for converter pellets being a bentonite addition in the region of 8% by weight — mixed, pelletised and screened, and the finished pellet is held below about 3% residual moisture, because water meeting a bath of molten slime and molten lead flashes to steam at a volume ratio that turns the vessel into a mortar. Reagent and utility input: controlled-temperature dryer with vent dust capture and return, binder dosing and mixing, pelletiser with screen and undersize return, pellet moisture measurement and covered storage. Output: a binder-dosed pellet at or below the design moisture figure, sized and screened, with its dry-weight assay attached and no free fines reaching the charge.

Steps 3 — Vessel Preheat at the Working Angle. The vessel is brought to the roast band before the first charge, because a cold lining takes a wet or seleniferous charge to the wrong reaction and thermal-shocks the brick as it goes in. The drive turns the shell about its inclined axis at the working angle while the burner and the lining come up together on a controlled curve, since a lining heated faster than its own conductivity allows will spall at the hot face; and the enclosure, induced draught and gas train run before the vessel is opened. The published geometry places the longitudinal axis about 25–30° above the horizontal, and the drive is set so the internal surface’s tangential velocity sits inside the published 5–25 cm per second band, which governs mixing, heat transfer to the lining and the throw of the charge up the shell wall. Reagent and utility input: burner start-up and controlled heat-up curve, rotation drive at the working angle, enclosure and induced draught verified, gas train differential pressures logged, lance, cooling circuits and seals checked. Output: a preheated vessel at the roast band, rotation set to the working tangential velocity, its enclosure and gas train verified and a lining brought up on a documented heating curve.

Steps 4 — Oxidative Roasting and Selenium Off-Take. The slime is roasted at the 650 °C level with air or oxygen-enriched air blown through the top lance, and this stage exists for one reason: to move selenium out of the charge as a gas. Selenium oxidises to selenium dioxide and leaves with the off-gas, as does part of the sulfur as sulfur dioxide, and both are captured downstream in wet gas cleaning — where the selenium becomes a saleable product instead of a soda slag carrying it at concentrations published around 30% and then needing its own treatment. The band is held rather than pushed, because running hotter does not volatilise more selenium: it volatilises lead with it, which reports to the gas train as a dust that must then be captured, weighed, assayed and returned. Reagent and utility input: top lance with air or oxygen-enriched gas, burner for thermal compensation, roast temperature control at the 650 °C level, off-gas temperature, draught and gas sampling logged. Output: a deselenised charge with a defined residual selenium figure, and a selenium-bearing off-gas transferred to wet gas cleaning as a recoverable stream.

Steps 5 — Reductive Blowing to Bullion and Fluid Slag. This is the reduction, and it is also the stage at which the lead earns its place in the feed. A soda-based slag with silica and a carbonaceous reductant reduces the lead oxides to lead metal, and the lead released becomes the collector phase into which the gold, silver and platinum-group metals dissolve; where the slime is lead-poor, lead is added deliberately as a lead-bearing flux so that phase exists in sufficient mass, and where it is lead-rich the flux schedule is adjusted down. The bath is mixed by rotation rather than by diffusion, and the temperature is held inside the reduction band rather than pushed, because overheating buys nothing in reduction and costs refractory, oxygen and the lead that volatilises into the gas train. Reagent and utility input: top lance at the reduction blow rate, soda ash as slag former and sulfur binder, silica or sand as slag conditioner, carbonaceous reductant, lead-bearing flux where the assay requires collector make-up. Output: a reduced bath with the precious metals collected into a lead-bearing bullion and the gangue and part of the sulfur in a fluid slag, ready to be skimmed and tapped.

Steps 6 — Slag Skimming and Skull Return. The slag is skimmed rather than poured, and the temperature at which it is skimmed is a designed figure rather than whatever the bath happens to be. A stationary hearth furnace needs its slag above roughly 1,300 °C before it will run out of the vessel, and at that temperature lead is already volatilising into the bag filter; the rotating vessel can be raked and skimmed below about 1,200 °C, so lead stays in the vessel as metal and matte instead of leaving as fume that must be captured and recycled. The skull adhering to the shell wall and accumulating around the mouth is taken back into the next reduction rather than allowed to build a ring that restricts the mouth, and this is where the campaign’s slag sample is taken, because the slag carries 10–30% of a slime campaign’s precious-metal value in published figures. Reagent and utility input: tilt to the skimming angle, raking tools and slag rakes, slag pot or granulation launder, skull removal and return to the charge, slag sampling and weighing. Output: a skimmed bath and a weighed, sampled slag whose precious-metal, lead and selenium content will decide whether it is returned or declared spent.

Steps 7 — Converting Blow to Silver Selenide Matte. The converting blow oxidises the remaining base metals out of the bath and concentrates what is left into a silver selenide matte that is tapped separately. The blow is held in the published band around 1,150–1,250 °C — hot enough to drive the oxidation of the residual lead, copper and base metals, cool enough to keep lead and bismuth out of the off-gas. The matte is a product rather than an intermediate to be discarded: published analyses put it at silver 50–60%, lead 3–15%, selenium 7–25%, copper 0.8–4% and tellurium 0.7–1.5%, which makes it the plant’s silver-bearing stream, the carrier of the tellurium that would otherwise be lost, and a payment stream in its own right. Reagent and utility input: top lance at the converting blow rate with the designed oxygen enrichment, band held at roughly 1,150–1,250 °C, matte tap through the mouth or tap port, matte weight and sample, bath temperature and off-gas logged. Output: a tapped, weighed and assayed silver selenide matte for the silver and tellurium circuits, and a bullion from which the base metals have been driven.

Steps 8 — Refining Blow to a Refined Doré Bullion. The refining blow is the last oxidative stage and the one at which the flux choice decides how clean the bullion gets. Published figures show a borax-based refining flux — a borax-and-silica mixture in the region of three parts borax to one part silica — driving residual copper down to about 0.2% against about 0.7% for a soda flux, with the bullion reaching 99.2–99.6% combined gold and silver. Selenium in the refined bullion sits below 0.005%, or below 50 ppm, and is achieved by the vessel itself because the roast at Stage 4 has already taken it off; the blow ends on the bullion assay the parting refinery requires, with the flux added in stages so the reaction is not quenched by one large addition. Reagent and utility input: top lance at the refining blow rate, borax and silica refining flux added in stages, refining band temperature control, bullion sampling and assay, off-gas logged. Output: a refined doré bullion at the assay the parting refinery specified, with its selenium, copper and lead figures established by sample.

Steps 9 — Bullion Granulation, Assay and Refinery Handover. The bullion is tapped, granulated or cast, weighed and released against assay, and this is where the converter’s responsibility ends and the parting refinery’s begins. Granulation is used where the downstream electrolysis prefers a granular anode feed and casting where a plate is required, and the lead that carried the gold and silver is separated from the bullion by vacuum distillation, which leaves the precious metals as a high-grade residue, or by cupellation, with the recovered lead returning to the lead circuit as metal — the point at which the lead-copper coupling this vessel is built around is finally unwound. The station reports what the metal contains and hands it to the stage built to separate those metals, the electrorefining circuit covered by our silver refining process and gold refining process pages. Reagent and utility input: bullion tap and granulation or casting, vacuum distillation or cupellation for lead separation, recovered lead return to the lead circuit, calibrated balance with sample preparation and assay. Output: a bullion lot released against assay with its campaign record attached, a recovered lead stream returned to the lead circuit, and a documented handover to the parting refinery.

Product Structure (Main Equipment)

Vessel body, inclined-axis drive and lining

The vessel shell. A welded steel shell with a flanged mouth, a charging and pouring opening, a tap port and the stiffening the tilting loads require, sized to the campaign weight and charge bulk density rather than selected from a model list. Output: a shell whose working volume, bath depth at the working angle and mouth opening are each a designed dimension.
The inclined axis, tilting frame and drive. A frame that rotates the vessel continuously about an inclined longitudinal axis and tilts it to the charging, firing, skimming and tapping angles — the published geometry placing the axis about 25–30° above the horizontal, with load, firing and tapping angles in the region of 0°, 65° and 130° — driven by a variable-speed geared or hydraulic unit sized to turn a loaded shell and hold it against an unbalanced bath, on a separate tilting circuit with a load-holding brake. Output: a vessel that mixes the bath in every position, with a drive specified against the tangential velocity of the internal surface rather than a quoted rotational speed.
The refractories and the wear record. A basic or chrome-magnesite working lining at the slag line, the lance zone and the mouth with high-alumina behind it, selected for the soda slag system and the halide load the feed was accepted at; thermocouples or a periodic thermal scan trended against a warning threshold. Output: a lining whose grade, thickness and campaign target are stated, with a wear curve that lets a reline be scheduled instead of triggered by a failure.
Mouth, seal and skull management. A cooled or refractory-protected mouth, a sealing arrangement for the charging and off-gas connection, and the raking and skull-removal provisions that keep the mouth from ringing closed across a long campaign. Output: a mouth that stays open for the campaign and a skull that returns to the charge.

Lance, oxygen and combustion train

The water-cooled top lance. A multi-pass lance inserted through the mouth and lowered to a controlled working distance above the bath, carrying oxygen or oxygen-enriched gas and, where required, fuel for in-bath thermal compensation; the published range for the oxidising gas on this duty spans about 20–100% oxygen, with no submerged tuyere and no lance component in contact with the melt, so shell life is not set by the life of a tuyere. Output: a lance whose position, gas rate and cooling are controlled through the roast, smelt and converting sequence, with wear parts outside the melt.
Oxygen supply, control and metering. The oxygen source, flow control and metering that make oxygen consumption a measured cost per campaign rather than a plant overhead — which matters here, because published oxygen utilisation for a top-blown rotary vessel is around 60%, so the gas that does not react is a direct line item. Output: a metered oxygen balance per campaign.
Burner, cooling circuit and lance change-out. A burner for preheat, lining heat-up and the heat the reactions do not supply with flame-failure protection in hardware; a closed cooling circuit with flow, pressure and temperature instrumentation and interlocks that pull the lance before the tip is damaged; and a parking station, spares and a change-out procedure that keeps a campaign running through a lance failure without cooling the vessel. Output: a vessel that can be preheated safely, a lance protected by instrumentation and a campaign that survives a lance change without a shutdown.

Slime drying, pelletising and enclosed charging

The slime dryer. A controlled-temperature dryer sized on your slime tonnage and as-received moisture, with its own vent capture and dust return so the fines removed with the water are recovered rather than emitted. Output: dried slime at the moisture the pelletiser needs, with the dryer dust accounted for.
Binder dosing, mixing, pelletising, screening and covered storage. A metered binder system and a mixer that puts the binder through the slime rather than on top of it — published practice sitting in the region of 8% bentonite by weight — feeding a disc or drum pelletiser with a screen that returns undersize to the pelletiser; and covered drained storage and conveying that neither re-wets the pellet nor generates dust on the way to the vessel. Output: a homogeneous mix, pellets inside the size band with the undersize recycled, delivered at the moisture they were made at.
The sealed charging arrangement. A charging chute or feeder opening into the enclosure and delivering into the vessel under induced draught at a controlled rate, so the bath is not thermally shocked and the gas volume leaving the vessel stays inside the duty the train was built for. Output: a charge positioned to melt and react without throwing the pellet bed up the shell wall.
The enclosure and its pressure control. An enclosure over the vessel mouth, the charging point, the skimming position, the tapping positions and the pellet handling route, held at negative pressure at all times with the pressure measured and trended. Output: a station where the fugitive fraction is captured by design rather than by housekeeping.

Slag skimming, matte tapping and bullion tapping

The tilting skimming position, slag tooling and granulation. A working angle for raking, rakes and skimming tools sized to the campaign, and the tilting control that holds the vessel steady while a slag-heavy bath is worked; a granulation launder or slag pot arrangement with the granulation water circuit closed and recycled, so entrained metal droplets in a viscous slag can settle and be reclaimed rather than cast into a block where they cannot. Output: a slag skimmed to a sample-able thickness rather than poured over into the bullion, then granulated or blocked for crushing, sampling and assay.
The matte tap and the bullion tap. A separate tap or mouth-pour for the silver selenide matte on the same tilting drive, so the matte is a stream with its own weight and sample rather than something cut out of the bullion; and a low tap or mouth-pour for the bullion with granulation, moulds or a shotting arrangement selected against what the parting refinery’s electrolysis prefers to charge, plus a forehearth where the plant runs one, separating the last of the entrained slag at the spout. Output: a matte stream kept apart for the silver and tellurium circuits, and bullion in a form the downstream refinery can charge directly.
Weighing and sampling at each stream. A calibrated balance and a sample station at the slag, the matte and the bullion, because the campaign balance is only as good as the samples taken at the tap. Output: three streams, each weighed and sampled where it was produced rather than after it has cooled on the floor.

Off-gas cooling, wet gas cleaning and selenium recovery

The sealed off-gas path, induced draught, cooling and coarse dust removal. Ducting from the vessel mouth and the enclosure to a fan sized on the calculated gas volume from the lance, the reactions, the burner and the infiltrated air, with the enclosure pressure held by the fan; a quench or surface cooler bringing the gas into the band the cleaning stages will accept; and a coarse dust collector capturing the precious-metal-bearing particulate as a collected, weighable stream. Output: a gas path sized on a calculation rather than on the vessel’s tonnage, a cooled gas and a precious-metal-bearing dust returned to the charge.
Wet gas cleaning with selenium recovery, and arsenic capture. A scrubbing stage taking the selenium dioxide and sulfur dioxide into solution, which is where the roast’s selenium becomes a product rather than an emission; and a stage designed for the arsenic load that lead anode slime in particular brings, with its own sludge handling. Output: a selenium-bearing solution or sludge consigned to the selenium recovery step, and an arsenic-bearing stream with a documented destination.
Final caustic scrubbing, the stack and the scrubber bleed. A caustic scrubbing stage and a monitored stack or vent with the permit’s monitoring points built into the duct, plus the bleed from the closed scrubbing circuits, its neutralisation, solids handling and disposal or recovery route. Output: a gas train that can be demonstrated rather than argued about, and an effluent route scoped with the machine instead of discovered with it.

Instrumentation, control, recycle return and the campaign record

The control system, campaign recipe and interlock schedule. A control system holding the roast, reduction, converting and refining profiles as staged recipes with a defined end point for each, a manual mode for skimming, tapping and sampling, and the alarm and interlock schedule that goes with them: lance cooling failure, oxygen pressure low, off-gas temperature high, enclosure pressure loss, induced-draught failure, rotation or tilt drive fault, bath temperature deviation, burner flame failure and emergency stop, each with a defined trip action. Output: profiles that repeat campaign after campaign, and a defined response instead of a reaction.
The return circuits, sampling and the campaign record. Screen undersize to the pelletiser, skull to the charge, granulated slag to its return or spent decision, filter dust to the pelletiser and scrubber sludge to its destination, each a controlled circuit rather than a pile; sample preparation at the vessel, the slag notch and the matte and bullion taps; and the record closing slime in, additions, oxygen, temperatures and hold times, matte, slag, bullion, dust and sludge out, with the difference reported as the measured loss. Output: every recycle stream with a specified destination and a measured rate, and a campaign balance that rests on samples rather than estimates.
Workplace provisions. Enclosure and local exhaust at the drying, charging, skimming and tapping positions, supplied-air stations at the tap, sealed dust and sludge handling, HEPA vacuum housekeeping, and the change, wash and eating arrangements the applicable occupational standard requires for lead, arsenic and selenium exposures. Output: a station where the exposure controls are part of the delivery rather than a later retrofit.

Product Features

Four furnace duties in one rotating shell. Roasting, reduction smelting, converting and refining run in the same vessel by changing the gas, the flux and the temperature band rather than by moving the charge between four units.
A feed gate built on mechanisms rather than warnings. Lead is admitted as the collector and copper is leached out first; and the refused classes — unassayable, wet or acid-bearing, copper above the window, halide or organic bearing, mercury, cadmium, thallium or cyanide bearing, reactive or oxidiser bearing, and radioactive — are each stated with the physical reason they are excluded, so a receiving clerk can apply the rule without a metallurgist present.
An oxidative roast that recovers selenium instead of deferring it. Selenium volatilised as selenium dioxide at the 650 °C level and captured in wet gas cleaning, so the vessel reaches a bullion with selenium below 50 ppm without a separate deselenising roaster, and the selenium leaves the plant as a product rather than as a soda slag carrying it at concentrations published around 30%.
A skim temperature chosen to keep lead in the vessel. Raked and skimmed below about 1,200 °C against roughly 1,300 °C for a stationary hearth, so lead reports to bullion and matte where it can be recovered rather than to the bag filter where it must be captured and recycled.
A mixing specification expressed as a velocity. The drive set so the tangential velocity of the internal surface sits inside the published 5–25 cm per second band at an axis inclination of 25–30°, because a revolutions-per-minute figure without a diameter says nothing about whether the bath is being mixed or thrown.
A lining monitored rather than trusted. Basic or chrome-magnesite brick at the slag line, lance zone and mouth with high-alumina behind it, and shell thermocouples or a periodic thermal scan trended against a warning threshold, so the campaign has a visible wear curve and the reline is scheduled against production.
Oxygen metered, with its utilisation figure published as it is. Around 60% against up to about 100% for a bottom-blown shell, so oxygen purity, lance distance, bath depth and blow rate are managed as a cost set and reported per campaign instead of presented as a saving.
A measured destination for the matte, the slag and the dust. The silver selenide matte — published at silver 50–60%, selenium 7–25%, lead 3–15%, copper 0.8–4% and tellurium 0.7–1.5% — is tapped, weighed and assayed separately for the silver and tellurium circuits; the slag, published as able to carry 10–30% of a campaign’s precious-metal value, is sampled and formally declared as return feed, bleed to a lead circuit, or spent; and the off-gas dust is captured sealed, weighed and assayed per campaign and returned through the pelletiser.
A refining flux specified because it changes the bullion. Published figures show a borax-and-silica refining flux driving residual copper to about 0.2% against about 0.7% for a soda flux, with the resulting bullion at 99.2–99.6% combined gold plus silver.
No first-pass recovery percentage, and a better substitute for it. Published bands run 70–92.5% for a stationary hearth and 95–97.5% for the bottom-blown family, with the top-blown rotary figure unpublished; rather than invent one, this station commits to a measured slag assay, a measured matte assay and a documented return decision every campaign.
A dryer, binder system, pelletiser, screen and undersize return inside the supply scope. Slime arrives at 35–40% moisture and the vessel needs it below about 3% in a pellet that survives charging, with a binder addition published in the region of 8% bentonite by weight.
A gas train built for the gas this duty makes, and workplace controls named for arsenic and selenium. Selenium dioxide, sulfur dioxide, lead fume and arsenic are the load and are removed by cooling, coarse dust removal, wet gas cleaning with selenium recovery, arsenic capture and final caustic scrubbing; no halogenated organic load is present, so no dioxin and furan provisions are fitted. Enclosure at negative pressure, local exhaust at the lance and the tap, supplied-air stations, sealed dust and sludge handling and HEPA vacuum housekeeping are delivered with the vessel because on this duty they cannot be retrofitted.
A campaign record that closes the metal balance. Slime in, additions, oxygen, temperatures and hold times, matte, slag, bullion, dust and sludge out, each with a weight and an assay, and the difference reported as the measured loss — one document that answers a toll customer, a lender and a regulator.

Technical Parameters And Specifications

The Table is the standard design basis, confirmed or adjusted in process design once the slime survey is complete. Campaign capacity, vessel working volume and shell thickness, drive and lance rating, oxygen flow, off-gas volume, gas cleaning duty, refractory quantity, lining campaign, floor loading and station footprint are engineered to your slime assay, tonnage, shift pattern and building services rather than taken from a catalogue of fixed models. Figures marked published come from operating practice and are given as ranges, because a number copied from another plant’s lining campaign or slag assay is not a specification.

Lead-copper anode slime converter — technical parameters and specifications.

Parameter	Specification
Station type	Inclined-axis top-blown rotary vessel with drive and lining; water-cooled lance with oxygen, fuel and cooling train; slime drying and pelletising front end; sealed enclosure with induced draught, off-gas cooling and wet gas cleaning with selenium recovery; dust and sludge return; slag, matte and bullion handling; campaign record
Vessel family	Top-blown rotary converter standard; bottom-blown oxygen vessel quoted where the plant’s published priority is oxygen utilisation rather than single-vessel roasting, smelting, converting and refining
Applicable feed state	Solid, de-copperised, dried, pelletised anode slime and slime-derived residues: lead, copper, nickel and cobalt electrorefining slimes; leach residues; decopperising filter cake; cementates; spent silver and gold electrolysis residues; slime flue dust; precious-metal concentrates and sweeps
Slime basis and assay window	Published: 5–10 kg copper anode slime per tonne of copper cathode. Assays — Cu 0.4–53%, Se 0.2–46%, Ag 1.5–33%, Pb 0.05–32%, Te 0.14–22%, Bi 0.01–15%, Sb 0.01–33%, As 0.01–9%, Au 200 ppm to >11% (survey average ≈0.5%). Lead anode slime runs higher in Sb and As at equivalent Ag
Feed copper window	Set in process design from the matte mass and matte silver grade the plant intends to ship; above the figure the lot returns to the leach rather than being blended down
Feed conditioning	As received 35–40% moisture; as charged dried and pelletised to <3%, binder addition published at ≈8% bentonite by weight. Pellet size band, strength and screen undersize return per the charging arrangement; no loose fines charged
Capacity, duty, footprint, crew	Engineered per campaign and per year; campaign weight, working volume and campaigns per period stated in the process design package. Published comparison: converter class >2,000 t anode slime per year vs few-tonne-per-batch small-scale class. Footprint engineered to vessel size, tilting clearance, drying and pelletising line, gas cleaning train, bay, headroom and duct run; crew to your shift structure
Campaign cycle	Published: ≈30 h converter slime campaign vs ≈18 h bottom-blown oxygen vessel vs 7–20 days stationary hearth. Full cycle — drying, pelletising, charging, skimming, two blows, tapping, reset — engineered to your slime and shift pattern
Vessel geometry and tilting	Inclined-axis cylindrical shell, flanged mouth, tap port, tilting frame; internal diameter, shell length, working volume and bath depth at the working angle set by campaign weight and pellet bulk density. Published geometry: axis 25–30° above horizontal; load / firing / tapping angles ≈0° / 65° / 130°
Mixing basis and drive	Rotation specified as internal-surface tangential velocity, published 5–25 cm/s. Published rotational speeds span 1–15 rpm because a design maximum, a pilot range and a production band are three different bases; a speed without a diameter is not a specification. Variable-speed geared or hydraulic drive sized for the loaded shell and for holding position against an unbalanced bath, separate tilting circuit with load-holding brake
Lance, oxidising gas and fuel	Water-cooled multi-pass top lance, controlled working distance above the bath, no submerged tuyere and no lance component in the melt; published oxidising-gas range 20–100% O₂, design enrichment fixed against reaction rate, permitted gas volume and the plant’s oxygen supply. Air-fuel or oxy-fuel burner on natural gas, LPG or diesel (dual-fuel available) for preheat, lining heat-up and in-bath thermal compensation; charge exothermics reduce fuel once the bath is hot
Oxygen utilisation and consumption	Published: ≈60% O₂ utilisation, against ≈100% for a bottom-blown oxygen vessel; oxygen is the dominant consumable and is metered and reported per campaign. Consumption engineered from the roast, reduction and two blows at the design enrichment
Temperature ladder and control	Roast 650 °C level (held, not pushed); reduction and smelting from ≈950 °C upward, published plant reference ≈950 °C; converting blow published 1,150–1,250 °C, plant reference ≈1,185 °C; skimming <≈1,200 °C against >≈1,300 °C for a stationary hearth. Control by lance, bath immersion or shell measurement driving gas rate, burner and blow programme, plus shell scan trended against a warning threshold
Refractory lining, wear and metal lock-up	Basic or chrome-magnesite brick at slag line, lance zone and mouth; high-alumina upper shell; castables where geometry requires. Grade selected for the soda slag system and the accepted halide load; thickness set for a defined campaign. Rotation wears the brick uniformly; published comparison at equal capacity puts precious metal locked per m² of refractory ≈30× lower than a deep stationary hearth. Reline interval established from the shell temperature record
Slag system and precious-metal return	Soda-based slag on sodium carbonate with silica and a carbonaceous reductant; boron-based refining flux reserved for the final blow. Composition, basicity window and silica-to-soda ratio calculated from the slime assay and recorded per campaign. Published: 10–30% of a campaign’s precious-metal value can report to the slag, which is granulated, crushed, sampled and assayed every campaign and declared as return feed, bleed to a lead circuit, or spent
Flux, reductant and refining flux	Soda ash as slag former and sulfur binder; silica or sand as slag conditioner; carbonaceous reductant for oxide reduction; lead-bearing flux where the slime’s own lead cannot form the collector phase — each weighed per campaign on a calibrated scale. Published: borax and silica refining flux (≈3 parts borax to 1 part silica) drives residual copper to ≈0.2% vs ≈0.7% for soda
Selenium off-take and sulfur handling	Selenium volatilised as SeO₂ in the roast and captured in wet gas cleaning as a selenium-bearing solution or sludge — the stage that lets the bullion reach <50 ppm Se without a separate deselenising roaster. Sulfur: part to SO₂ captured in wet gas cleaning, part fixed in matte and slag, partition calculated from the slime sulfur assay and confirmed per campaign
Matte and bullion composition	Matte published: Ag 50–60%, Se 7–25%, Pb 3–15%, Cu 0.8–4%, Te 0.7–1.5%. Bullion published: Au+Ag 97.3–99.6% by flux route, Se <0.005%, Cu ≈0.2% (boron-based refining flux) or ≈0.7% (soda), residual Pb and Te in the low-hundredths to low-thousandths of a percent
Downstream streams and parting interface	Lead separated from the bullion by vacuum distillation or cupellation and returned to the lead circuit as metal, precious metals left as a high-grade residue; separation duty specified with the vessel. Tellurium to the matte, recovered on a dedicated circuit; bismuth concentrated into the bullion and lead-rich stream and removed as its own product. Bullion weighed, sampled, granulated or cast and released on campaign number and assay for direct charging to silver and gold electrorefining. Published terminal grades: 99.99% Ag and Au, smaller-scale plants 99.95% Ag and 99.99–99.999% Au
Off-gas train and sizing basis	Sealed path from vessel mouth and enclosure to induced draught; quench or surface cooler; coarse dust collection with sealed weighed return; wet gas cleaning with selenium recovery; arsenic capture with its own sludge handling; final caustic scrubbing to a monitored stack or vent. Off-gas volume, cooling, scrubbing and fan duty calculated from lance gas flow, water evaporated from the charge, roast and blow reaction gases, burner products and infiltrated air — stated as figures, not matched to tonnage
Emission, exposure and compliance basis	Gas train designed to the Se, SO₂, As and Pb limits of the permitting jurisdiction, monitoring points built into the duct, and to the site’s waste classification requirements for discard slag, scrubber sludge and spent refractory. Workplace provisions designed to the applicable national occupational standard for lead, arsenic and selenium compounds; clause numbers issued in the permit-support package. No numeric limit is quoted that cannot be attached to your permit, and no emission-free claim is made
Total enclosure, dust and sludge return	Vessel mouth, charging point, drying and pelletising route, skimming position, matte and bullion tapping positions, slag handling and dust and sludge handling each enclosed and held at negative pressure, enclosure pressure measured and trended. Off-gas dust collected sealed, weighed and assayed per campaign and returned through the pelletiser; wet gas cleaning sludge to the selenium circuit or back to the vessel per assay and permit
Instrumentation, recipes and interlocks	PLC with staged campaign recipes (preheat, roast, reduction, converting, refining), manual mode for skimming, tapping and sampling, trended bath, shell, draught, scrubber and enclosure records, interface to the plant’s assay and campaign balance records. Interlocks: lance cooling failure, O₂ pressure low, off-gas temperature high, scrubber or duct ΔP high, induced-draught failure, enclosure pressure loss, rotation or tilt drive fault, bath temperature deviation, burner flame failure, lance position out of window, emergency stop — each with a defined trip action
Site services	Oxygen supply and purity; fuel pressure and flow; electrical supply and rating; cooling-water flow and inlet temperature; compressed air; floor loading and headroom for vessel, frame and charging arrangement; containment and drainage under tap and slag area; reagent storage; off-gas route to atmosphere with sampling provisions — issued as a schedule with a value against each line
Materials of construction	Boiler-quality steel plate shell; basic, chrome-magnesite and high-alumina refractories; heat-resistant alloy lance and mouth components; stainless hot-end ducting; corrosion-resistant scrubbing and ducting materials selected for SeO₂, SO₂ and chloride-bearing gas; sealed enclosures, hoods and containers throughout material handling
Workplace provisions	Enclosure and local exhaust at drying, charging, skimming and tapping positions; supplied-air stations at the tap; sealed dust and sludge handling; HEPA vacuum housekeeping rather than dry sweeping or compressed air; change, wash, eating and medical surveillance arrangements per the applicable occupational standard
Campaign balance	Slime weight and assay in; flux, reductant, lead, binder and oxygen; temperatures and hold times; matte, slag, bullion, dust and sludge out with weights and assays; difference reported as the measured loss, closed separately for Au, Ag, Se and Pb
Economic floor	Stated, not implied: below the slime tonnage that lets the vessel carry its lining, lance, draught, gas cleaning, reagents and crew, the honest answers are a smaller shell, a toll arrangement or the wet route; the tonnage figure is issued in the process design package

Technical Advantages

Four duties in one shell is a metal-account advantage before it is a capital advantage. Removing three inter-furnace transfers, three skull inventories and three additional refractory linings removes three places where gold and silver were recoverable only at a reline rather than at a tap.
The lead-copper split is the design, not an incidental property of the feed. Copper is leached out because every tonne charged becomes slag and matte mass with no precious-metal gain; lead is kept, and added where it is short, because it dissolves the gold and silver and carries them into a bullion small enough to ship. That distinction separates a slime plant that concentrates value from one that circulates it.
The roast is placed where it recovers rather than where it defers. Volatilising selenium at the 650 °C level turns a future soda-slag problem into a present selenium product and removes a separate deselenising roaster — its equipment, its refractory inventory and its hold-up — from the circuit.
The skim temperature is a chosen number with a named consequence. Skimming below about 1,200 °C instead of above roughly 1,300 °C keeps lead in the vessel as recoverable bullion and matte rather than sending it to the bag filter as dust that must be captured, weighed, assayed and re-pelletised.
Refractory lock-up is addressed by geometry rather than by a better brick. A shallower pool against a smaller wetted area, worn uniformly by rotation, is the mechanism; the published comparison puts precious metal locked per square metre roughly thirty times lower than in a deep stationary hearth. That is a recoverable-metal figure rather than an equipment claim, and it is the strongest single reason a converter replaces a hearth furnace.
Rotation is specified as tangential velocity, so the mixing argument survives a change of vessel size. Because the design quantity is the internal surface velocity at the inclined axis — published at 5–25 cm per second at 25–30° — the same argument holds whether the shell is small or large.
The gas train is matched to this duty instead of inherited from another. Paying for a board or e-waste train’s thermal oxidiser and dioxin provisions on a slime duty is a permanent operating cost against no emissions benefit, because anode slime brings no halogenated organic matrix to destroy.
Skull is managed as a campaign variable, not as a shutdown cause. Returning the shell-wall and mouth skull to the next reduction keeps the mouth open, stops a ring growing inside the vessel and puts the metal in the skull back into the balance instead of into a chipping operation.
Drying and pelletising are delivered as a controlled system, which is what protects the rest of the plant. A pellet at or below about 3% moisture with dispersed binder and screened undersize protects the vessel from a steam event, protects the gas train from a dust load it was not sized for, and protects the campaign balance from metal that left as fines before the bath saw it.
The matte and the slag are managed against measured numbers rather than recovery claims. Tapping the silver selenide matte as its own stream makes the tellurium a product and the residual silver a payable instead of two values diluted into a discard slag; and with published figures allowing 10–30% of a campaign’s precious-metal value to report to the slag, that slag is assayed every campaign and formally returned, bled or declared spent. A plant that measures its slag can improve; a plant that trusts a supplier’s percentage cannot.
Oxygen is treated as a cost line, and publishing no first-pass figure is itself an advantage. The published utilisation figure, around 60% against up to about 100% for a bottom-blown shell, is stated on the page, and purity, lance distance, bath depth and blow rate are actively managed with consumption reported per campaign; while substituting a measured slag and matte assay for an unpublished headline percentage gives the buyer a number they can audit against their own assay bench instead of one they must take on trust.
The refining flux is specified, the oxidation is split into two documented blows, and the compliance position rests on instruments. A boron-based refining flux driving residual copper to about 0.2% against about 0.7% on soda is a difference that shows up at the parting refinery’s assay; giving the converting and refining blows their own end points, products and samples turns a furnace operation into a campaign with a balance; and enclosure pressure, duct and scrubber differential pressures, gas temperatures and the campaign’s dust and sludge weights are all recorded, so a permit application, a stack test and an exposure monitoring programme rest on the station’s own instruments rather than on a supplier’s letter.
The economic floor and the wrong-feed boundary are stated, which is the cheapest thing a supplier can do for a buyer. Where the tonnage is too low, where the value sits in a leach solution, where selenium and tellurium justify a wet circuit of their own, or where the material is a low-grade residue rather than a tankhouse slime, this page names the route that fits — including our precious metal hydrometallurgical refining system and precious metal extraction equipment ranges.

Service Process

Step 1 — Slime data and duty review. You provide the slime types and their proportions, an assay covering gold, silver, selenium, tellurium, copper, lead, antimony, arsenic, bismuth, sulfur, chloride and moisture, the form the slime arrives in and its as-received moisture, whether it has been de-copperised and to what figure, the tonnage per campaign and per year, the doré specification or parting route you intend to sell into, and the site constraints on oxygen, fuel, power, draught, floor loading and headroom. We state whether each lot is chargeable as surveyed or needs drying, pelletising, blending, re-leaching or refusal, and whether the plant’s real answer is the wet route instead. Output: a preliminary route statement, the boundary conditions and a clear scope of supply.
Step 2 — Flux, reductant and lead-addition schedule, and vessel configuration. The slag composition with its basicity and silica-to-soda window, the reductant quantity, the refining flux route, the lead addition required to form the collector phase, the campaign weight, working volume and shell dimensions, the axis inclination, the drive and lance ratings, the temperature profiles, and the off-gas, gas cleaning and draught duties are calculated from your slime survey, with the slag precious-metal target and expected bullion assay written down beside them. Output: a configuration proposal with the design basis stated, plus a draft site interface schedule.
Step 3 — Laboratory conversion test on your material. A representative sample is roasted, reduced and blown at bench scale to establish how much selenium volatilises at which temperature and hold time, what flux and reductant quantities release the most precious metal into the collector phase, what slag forms and what it carries, what the matte assays, what bullion grade the feed reaches, and how the gold, silver, selenium, tellurium and lead partition between the four streams. Output: a test report with bullion, matte and slag samples returned for your own assay.
Step 4 — Module fabrication and factory function test. Vessel shell, frame, inclined-axis drive, lining, mouth and seal, water-cooled lance with its oxygen, fuel and cooling train, the drying and pelletising front end, the enclosure, the off-gas cooling and wet gas cleaning train, the scrubber circuit, the recycle returns, the slag and matte handling and the control system are fabricated, assembled and function-tested before shipment, with material certificates issued. Output: a factory function test record and the shipping documentation set.
Step 5 — Site interface schedule and building preparation. Site services are confirmed against your building together with the foundation and vessel support structure, the floor loading for the loaded vessel and the tilting clearance, containment and drainage under the tap, the slag and matte handling areas and reagent storage, the oxygen supply route and its safety provisions, the off-gas route with its sampling provisions, and the dust and sludge storage areas. Output: a signed interface schedule, equipment layout and utility connection drawings your builder can work from.
Step 6 — Installation, lining dry-out, enclosure verification and gas train commissioning. Our engineers supervise setting the vessel and aligning the drive, drying out and bringing up the lining on a controlled heating curve, checking out the lance and the oxygen and cooling circuits, verifying the enclosure’s negative pressure with every door, the mouth and the feeders open, balancing the ducting, commissioning the wet gas cleaning and scrubber circuits, and proving the induced-draught duty against the calculated volume. Output: a mechanically complete station with a measured enclosure pressure, a verified gas train duty and a lining dry-out record.
Step 7 — First campaign on your own slime. The first campaign runs on your slime with the drying and pelletising settings, the flux, reductant and lead-addition schedule, the roast temperature and hold time, the reduction and converting bands and the refining flux written against that slime’s assay, and the bullion, matte and slag assays and the closed precious-metal balance measured against the design basis. Output: a commissioned station with its setpoints recorded and a measured slag and matte assay for your material.
Step 8 — Operator training and production qualification. Training covers the slime survey and the de-copperising gate, drying and pelletising control, charge make-up and weighing discipline, vessel preheat, the roast band and the selenium off-take, the reduction blow and its hold time, skimming and skull return, the converting and refining blows and their end points, tapping and stream separation, gas cleaning and scrubber operation, enclosure discipline and the campaign record — taught on the actual vessel. The production trial confirms the bullion, matte and slag assays and the precious-metal balance, and the operators sign off the standard operating procedures. Output: trained operators, a signed SOP set and a performance certificate.
Step 9 — Consumables, spares and continuing process support. Refractory and patching stock, lance components and tips, binder supply arrangements, scrubbing reagents, filter and scrubber media, raking and tapping tooling and their replacement intervals are handed over with the station, spare parts are supplied afterwards, and our engineers stay available for troubleshooting and for re-specifying the flux schedule, the lead addition and the temperature profiles as your slime assay or contract specification changes. Output: continuing production support with a stocked consumables position and revised procedures as the feed changes.

Warranty And After-Sales Service

Warranty period and performance commitment. Twelve months from successful commissioning or eighteen months from shipment, whichever falls earlier, covering design, manufacture and assembly defects; consumables are excluded — refractory brick and patching material, lance tips and nozzles, binder, scrubbing reagents and media, grinding and screening wear parts and raking and tapping tooling — as is damage from misuse or from a feed outside the agreed specification. Where the slime matches the tested sample we stand behind the bullion, matte and slag assays and the closed precious-metal balance established in the process design package; where the slime changes, the commitment is re-established on a new bench test. Output: a documented warranty and performance acceptance on the station’s file.
Spare parts, refractory and consumables supply. Refractory brick, castables and patching material, lance bodies, tips and cooling components, burner parts and quarls, thermocouples, drive and tilting-frame parts, mouth and seal components, pelletiser and screen wear parts, scrubber pump parts, filter and media consumables and control hardware are quoted at the time of order and held available afterwards, with a recommended on-site stock list issued at handover. Output: an on-site consumables position agreed before the station enters production.
Remote and on-site support. Telephone, email and messaging support on operating questions, alarm interpretation, roast and blow end-point decisions, slag behaviour and its assay, matte grade problems, lance and oxygen problems, enclosure pressure and scrubber differential-pressure diagnosis, and the flux schedule, whenever the station is running; plus engineer attendance for warranty faults, process problems and periodical check-ups, with response and attendance times agreed in the contract. Output: same-day response on operating issues and on-site intervention with a service report.
Lining and refractory assessment visits. Periodical measurement or thermal-scan assessment of the lining against its wear curve and campaign target, with a written view on how much of the remaining campaign is consumed by the feed’s halide load, the bath temperature and the slag basicity — so reline planning rests on measurement and the precious metal inventory held in the brick is known before the vessel is taken out of service. Output: a reline plan and a metal-in-lining estimate built from your own records.
Campaign and metal-balance review. A periodical review of the matte, slag, bullion, dust and sludge assays, reagent and oxygen consumption and the closed precious-metal balance against the design targets, with the levers actually moving the slag figure identified and a revised flux schedule issued where the slime has changed. Output: a revised flux and reductant schedule and an updated expectation of the plant’s metal recovery.
Retraining, refresher visits and slime-source change support. Additional training, refresher sessions and process optimisation visits as the slime assay, tankhouse practice, doré specification or permit condition changes; and where a customer adds a slime or residue, we assess it against the acceptance screen, establish the de-copperising requirement and the flux and lead additions it needs and the matte it will produce, run a bench conversion where the answer is not obvious, and update the route sheet and the campaign recipe. Output: updated training and procedures, and a documented admission decision with a revised recipe for each new feed.
Documentation set. Operation and maintenance manuals, the process design package with the slime survey basis, the flux and reductant schedule and the metal-balance method, the site interface schedule, equipment layout, electrical, oxygen, fuel, water and ducting drawings, the alarm and interlock schedule, the campaign record and metal-balance templates, the spare parts catalogue, the safety and hazard assessment for the reagents, the oxygen system and the molten metal, the exposure control and housekeeping procedure, and the emergency response plan. Output: complete documentation handover at commissioning.
Compliance support and lifetime technical support. Assistance with the emission and enclosure parameter declarations, the stack and ambient monitoring arrangements, the gas cleaning and scrubber performance verification, the waste classification of the discard slag, the scrubber sludge and the spent refractory, and the exposure monitoring programme for lead, arsenic and selenium — the technical data for your permit applications and periodic compliance reporting; and our engineering team remains available for modification and expansion advice for the operating life of the station. Output: long-term engineering continuity.

Frequently Asked Questions

What is a lead-copper anode slime converter?

A lead-copper anode slime converter is a tilting, rotating, top-blown pyrometallurgical vessel that treats the anode slime produced by copper and lead electrorefining and concentrates its gold, silver and platinum-group metals into a doré bullion while taking selenium off as a gas and the base metals into a matte and a slag. “Lead-copper” describes the feed, because the vessel is built around slimes from both tankhouse types; “converter” describes the duty, because the same rotating shell roasts the slime, reduces it, converts the base metals out of the bullion and refines what is left. The published plant reference for this arrangement is a single top-blown rotary converter replacing four separate units, and the family is reported as effective for slime from copper, lead and nickel electrorefining.

Why is the lead in the slime an advantage rather than an impurity?

Because gold and silver do not report to a slag by gravity; they report to a metal phase that dissolves them, and in this feed the lead is that phase. Lead dissolves the gold, silver and platinum-group metals and settles with them into a dense bullion, which is why a slime with a modest precious-metal content can still be concentrated into a small, rich bullion rather than spread through a large slag. A plant that refuses lead-bearing slime in the belief that lead is a contaminant removes the only metal in the charge capable of collecting the gold, and then pays to recover the gold from a slag instead. Where the slime is lead-poor, the correct response is to add lead as a flux so the collector phase exists, not to refuse the feed.

Why must the slime be de-copperised before it is charged?

Because copper in this vessel does not leave with the gas; it oxidises into the slag and partitions into the matte as a copper-silver selenide. That has three consequences, all of them costs. It lowers the matte’s silver grade, so the matte is worth less per tonne. It increases the matte mass, so more material has to be shipped and treated downstream. And it increases slag volume and viscosity, which makes skimming harder and raises the metal the slag can carry. Copper is taken down by an acid or oxidising leach upstream, and the converter is designed against the figure that leach achieves. A lot above that figure goes back to the leach, and is not blended down and hoped for.

Which furnace should be used for anode slime, a converter or a stationary doré furnace?

It depends on the scale, the feed and whether the plant wants one vessel or four. A stationary hearth is simple and is the classical route, but its published cycle runs from about seven to twenty days per campaign, its precious-metal lock-up in the brickwork is far higher per square metre of refractory, and it needs its slag above roughly 1,300 degrees Celsius to run out — which is a temperature at which lead is already volatilising into the bag filter. A top-blown rotary converter roasts, smelts, converts and refines in one shell, skims below about 1,200 degrees, and wears its lining uniformly. Published first-pass recovery figures run 70 to 92.5 percent for the stationary hearth and 95 to 97.5 percent for the bottom-blown vessel family, with the top-blown rotary figure left unpublished in the review literature. We publish the comparison and then quote the vessel your tonnage and your slime actually call for.

How is selenium recovered, and why is the roast done inside the converter?

The slime is roasted in the vessel at the 650 degrees Celsius level, which oxidises selenium to selenium dioxide and drives it off with the off-gas. It is then captured in wet gas cleaning as a selenium-bearing solution or sludge and sent to the plant’s selenium recovery step. The roast is done in the converter rather than in a separate roaster because the vessel can be run oxidising at one stage and reducing at the next without moving the charge, which removes a whole piece of equipment, its refractory inventory and its hold-up from the circuit. The practical payoff is the bullion: published converter campaigns reach selenium below 0.005 percent, which is under 50 parts per million, without a separate deselenising roaster in front of the vessel.

What temperature does an anode slime converter run at?

Three bands, not one. The roast runs at the 650 degrees Celsius level, because that is where selenium volatilises as selenium dioxide without taking lead with it. The smelting and reduction stage runs from about 950 degrees upward at the published plant reference for this duty, hot enough to keep the soda-based slag mobile so it releases the metal droplets it has taken up. The converting blow runs in the published band of roughly 1,150 to 1,250 degrees Celsius, with the plant reference at about 1,185 degrees, hot enough to oxidise the residual base metals and cool enough to keep lead and bismuth out of the gas train. Skimming is done below about 1,200 degrees, which is the temperature at which the rotating vessel can still rake a slag that a stationary hearth would have to run at over 1,300 degrees to pour.

How fast does the vessel rotate, and does the rotation speed matter?

Rotation speed on its own is not a specification, and that is the honest answer. Published rotation speeds for this vessel family span roughly 1 to 15 revolutions per minute, and the spread comes from three different bases being quoted as if they were the same thing: a design maximum, a pilot vessel’s range, and a production working band. The quantity that actually governs mixing, heat transfer to the lining and the throw of the charge is the tangential velocity of the vessel’s internal surface, published in the range of 5 to 25 centimetres per second with the longitudinal axis inclined about 25 to 30 degrees above the horizontal. We design the drive against that velocity, so the mixing argument still holds when the shell gets larger.

What are the products, and what grades does the converter actually deliver?

Four main streams. The silver selenide matte, published at silver 50 to 60 percent, selenium 7 to 25 percent, lead 3 to 15 percent, copper 0.8 to 4 percent and tellurium 0.7 to 1.5 percent, tapped and assayed separately for the silver and tellurium circuits. The doré bullion, at published campaign assays of 97.3 to 99.6 percent combined gold plus silver depending on the refining flux, with selenium below 0.005 percent and residual copper driven down to about 0.2 percent with a boron-based refining flux against about 0.7 percent with soda. The slag and the off-gas dust, both of which carry value and both of which are assayed and returned or declared. And a lead-rich stream, recovered from the bullion by vacuum distillation or cupellation and returned to the lead circuit as metal.

How much precious metal is lost to the slag, and how is that controlled?

Published figures allow 10 to 30 percent of a slime campaign’s precious-metal value to report to the slag, which is why the slag is treated as a carrier rather than a residue. Four things drive the figure. The slag composition and its silica-to-soda window, because a slag that is not mobile at the working temperature traps droplets instead of releasing them. The lead addition, because a collector phase that is too small cannot gather the metal before the slag is skimmed. The temperature and hold time of the reduction, because they decide how far the collection is taken before the skim. And the skimming practice itself, since a slag pulled over with metal in it is a slag loss no chemistry explains. Our design target for the slag is stated for your feed in process design, the slag is assayed every campaign, and a deviation triggers a diagnosis of flux, lead addition, temperature, hold time or skimming practice rather than a repeat.

Which anode slime and residues are refused, and why?

Seven classes, each refused for a physical reason. Unassayable or unidentifiable slime and residues, because the vessel is the last place on a site to discover what a material contains and the discovery is paid for in the matte assay, the bullion assay and the gas cleaning load. Wet, dripping or acid-bearing material, because water entering the bath flashes to steam at a volume ratio that turns the vessel into a mortar and free acid attacks the lining. Slime whose copper is still above the design window, because that copper becomes slag and matte mass with no precious-metal gain. Halide-rich or organic-bearing material, because halogens attack the refractory, carry into the bullion and, with an organic matrix, create the dioxin and furan problem this gas train was not built to solve. Mercury, cadmium, thallium and cyanide-bearing material, which either volatilise into a gas train that was not sized or permitted for them or react with the bath rather than dissolving. Reactive, explosive and oxidiser-bearing material, which reacts violently rather than dissolving. And radioactive or naturally occurring radioactive material, which is screened at the gate before the material is accepted for storage, let alone for charge.

How is the off-gas treated, and what emission limits apply?

The gas is captured at the vessel mouth and inside the enclosure and held under induced draught, cooled to the band the cleaning stages will accept, stripped of its precious-metal-bearing dust in a coarse collector that returns it to the charge, washed in a wet gas cleaning stage that takes the selenium dioxide and the sulfur dioxide into solution for selenium recovery, treated for arsenic with its own sludge handling, and finally scrubbed in caustic before the stack or vent. What it is not is a bag filter on its own, or a dioxin and furan system copied from a board or e-waste furnace, because anode slime does not bring the halogenated organic matrix that would require one. On limits, the gas train is designed to the selenium, sulfur dioxide, arsenic and lead limits of the jurisdiction the plant is permitted in and its monitoring points are built into the duct; this page does not quote a numeric limit it cannot attach to your permit, and it does not make a zero-emission claim.

What does the converter scope include, and what does the warranty cover?

The station is delivered as function-tested modules with material certificates: the inclined-axis vessel with its frame, drive, lining and shell instrumentation; the water-cooled lance with its oxygen, fuel and cooling train; the slime drying, binder-dosing, pelletising and screening front end; the sealed enclosure; the off-gas cooling, dust collection, wet gas cleaning, arsenic capture and caustic scrubbing train; the recycle returns; the slag, matte and bullion handling; and the control system with its campaign recipes and alarm schedule. Installation, lining dry-out on a controlled heating curve, enclosure pressure verification, ducting balance, lance commissioning and gas train performance verification are supervised by our engineers, and the first campaign is run on your own slime with the flux, reductant and lead-addition schedule and the roast and blow profiles written against that slime’s assay. The production trial confirms the bullion assay, the matte and slag assays and the closed precious-metal balance, and the operators are trained on the actual vessel and signed off against the standard operating procedures. The warranty runs twelve months from successful commissioning or eighteen months from shipment, whichever falls earlier, covering design, manufacture and assembly defects, with refractory and other consumables excluded. Spare parts, refractory and scrubbing media are quoted at the time of order and held available afterwards, and our engineers remain available for slime changes, flux revisions and reline planning for the operating life of the station.