Afton, new Canadian copper mine-T he unusual geology of the Afton de­

posit has resulted in a two productconcentrator and the first application inNorth America of the top blown rotaryconverter (TBRC™) for copper smelt­ing. The new Canadian mine beganstripping waste in February. 1977; theconcentrator milled the first ore in De­cember. 1977; and the smelter isscheduled to corne on line late thisspring. Design mill throughput of 7,000tons per day has already been exceeded.

The copper ore mining and proces­sing complex, located about 10 milesfrom downtown Kamloops, BritishColumbia, is the only major integratedmine through blister copper operationin Canada to come into production in re­cent years. The last major copper minein British Columbia was started by Lor­nex Mining Corporation Ltd. in 1972,45miles southwest of Kamloops. The Af­ton concentrator produces a native cop­per gravity concentrate and a flotationchalcocite concentrate. The AftonTBRCT!III smelter is the only coppersmelter in the province.

Teck Corporation has 63 percent in­terest in Afton Mines Ltd., 50 percentthrough direct ownership, and an addi­tional 13 percent through Teck's 57 per­cent owned Iso Mines Ltd., which con­trols 23 percent of Afton shares. Teckacquired its interest in Mton in 1972.

The new project was managed byTeck and Commonwealth ConstructionLtd. was the principal contractor.Wright Engineers Ltd. designed theconcentrator and related facilities,while Dravo Corporation designed thesmelter complex. Total project cost was$C85.000,OOO ($93,500,000).

AFTON PLACEFIX MAP-+N

BRITISHCOLUMBIA

Senior fmancing was via loans fromthe Bank of Montreal and the CanadianImperial Bank of Commerce. Importantlines of credit have also been obtainedfrom U.K. customers (BTCC and DeltaMetal) who will be buying the nutput.

Area HistoryThe first indication of mineralization

in the new mine area was in 1898 whenthe 330-foot Pothook shaft was sunk.Two mines in the area, the Iron Maskand the Copper King, were worked to asmall degree during the early part of thiscentury.

Axel Bergland. in 1949, staked eightclaims in the area which he called Afton.In 1964, Chester Millar became in­terested in Bergland's claims. Millarconvinced Colonial Mines Ltd. to con­duct a percussion drilling program.After II holes had been drilled, Colonialwithdrew from the project. Millarformed a private concern in 1965, stakedmore claims adjacent to the Trans­Canada Highway, and drilled 30 morepercussion drill holes.

An east-west trending zone of coppermineralization was revealed extendingto the west and below the drilling area.A consulting geological firm recom­mended .drilling nine diamond drillholes, five of which were completed.One of these intersected 170 feet of al­tered diorite, grading 0.4 percent cop­per.

After Duval Corporation refusedfirst rights on the deposit and QuintanaMinerals conducted an unsuccessful 17percussion drill hole program, Millardecided Afton Mines would continuedrilling in the area of the diamond drillhole which intersected copper. In 1971,17 vertical percussion drill holes bot­tomed in ore.

In 1972 Teck and Iso Mines acquiredtheir interest in Mton. More than 29miles of drilling was conducted between1970 and 1973. The decision to go aheadwith the project was made in October,1975.

It is interesting to note that severalcompanies missed the opportunity 10

become involved with this venture, in­cluding New Jersey Zinc Company,Colonial Mines Ltd., Noranda MinesLtd., Kennecott Copper Corporation,Duval Corporation, Quintana Minerals,and Cane x Placer Ltd. Canex hadsigned an agreement with Afton Mines,previous to Teck involvement whichprovided for a Canex interest in Afton inexchange for development work sup-

port. In an out-of-court seulement,Teck and Iso paid Canex $4.000,000 topurchase its agreement with Mton.

A difficult period for Afton was ex­perienced during the interim betweenthe decision to go ahead with the projectand the final project development.Three miles of the Trans-Canada High­way had to be moved, and of course,environmental permits had to be ob­tained. Canadian environmental groupsappealed the issuing of the smelteremission pennit. The appeals were dis­missed after careful review by the Pollu­tion Control Board. It was determinedthat the new smelter would not be det­rimental to the Kamloops area environ­ment.

Afton GeologyThe Afton copper deposit is charac­

terized by two distinct mineralizationzones. The first is a deeply penetratingsupergene zone which comprises theore body which will be mined at theDominion pit and has served as the basisfor design of the associated beneficia­tion plant and smelter. The predominantcopper mineralization in the supergenezone is native copper and chaJcocite.The second zone is the partly exploredhypogene zone, characterized by chal­copyrite and bornite mineralization.The copper grade in the supergene zoneis similar to that of the hypogene zone.

The Afton deposit is located at thenorthwest extremity of the Iron Maskbatholith, an intrusive comprising anearly diorite phase and a later fine­grained microdiorite-micromonzonitephase.

Mineralization occurs in the Sugar­loaf and Cherry Creek porphyritic intru­sives, associated with the Iron Maskbatholith, as veins, stockworks, anddisseminations. The Dominion pit ap­pears to be located at the junction of twofault systems. One system is composedof a set of echelon faults, trending eastto northeast with a dip of 60 to 7(1'southwards. This set of faults is posru­lated to be significant in ore control.The second system runs generally northto south.

The mineralization associated withthe fault systems in the supergene zoneis unique in this area. The copper con­taining minerals found in the shatteredrock of the faults in order of abundanceare native copper, chalcocite, bornite,and chalcopyrite. The following tablegives the relative abundance of the prin­cipal copper minerals in the uppennost

.n

Reprinted with permission from WORLD MINING April 1978

By Donald A. PazourAssistant Ed itor

100 meters (325 feet) of the supergenemineralization zone:

AFTON MINE P&H 1900AL shovel loads one of two Unit Rig l~ton Lectra-Haul trucks,while Bucyrus Erie 40R drills 9-inch holes in 24 by 24 foot pattern in the background.

SHOVEL LOADING haul truck with native copper-chalcocite ore. Background, left toright: primary crusher, coarse ore stockpile, concentrator. and maintenance building.

CLEAN·UP around the shovels is accomplished using Caterpillar 824 wheel-type dozer.The final 9OO-foot deep Dominion pit will cover an area 2,700 by 2,600 feet.

8510

1trace

1

Wtight PtrCtttlWl',J( EAst

6530

5t..ce

Metallic CopperChalcociteChalcopyriteCupriteITenoriteOther Minerals

SupergenelHypogene ZonesThe supergene zone is mainly above

500 meters (1.650 feet) elevation in theeast part, and 250 meters (825feet) in thewest part. The boundary of the zone isgenerally sharp and it plunges steeplywest about midway along the deposit.The deposit is tabular inside a 0.25 per­cent cut-off grade and it strikes west­northwest with an average dip of 550

south.Although the supergene zone of cop­

per mineralization at Afton comprisesthe immediate orebody and serves asthe basis for near future mining, milling,and smelting, a discussion of thehypogene zone is important for a fullunderstanding of the district geology.Furthermore, this zone presents a re­source for possible future expansionand development.

The hypogene zone is preserved onlyin the central and west parts of the pres­ent deposit and is found mainly belowthe 500 meter (1.650 foot) level. The ab­sence of metallic copper defines thezone. which does contain minor amountsof possibly supergene minerals chalco­cite and covellite in addition tohypogene sulphides bornite and chal­copyrite. Bornite abundance exceedsthat of chalcopyrite near the hangingwaU and decreases across the deposit

on stream

Metallic copper defines the zone andoccurs as fme scales. films. dendrites.and granules. but also in masses as wideas 5 millimeters (1/5 inch). Chalcocite inthe deposit is mostly of the sootysupergene variety, with some slightlygrey chalcocite (digenite) as weU. Thechalcocite is both disseminated and inveins up to 25 millimeters (I inch) wide.In a polished section. chalcocite is seenas replacing both bornite and chalcopy­rite which are relics in the zone. as issome pyrite.

Gangue materials are mostly calciteand epidote, with less commonly occur­ring gypsum, ankerite, specular hema­tite, quartz, fluorite. and zeolite.

~

t

copper gravity concentrate and achalcocite-native copper flotation con­centrate.

Ore from the mine is crushed tominus 8 inches in a 42-inch by 65-inchAllis Chalmers gyratory crusher pow­ered by a 350 horsepower motor at 900revolutions per minute. The crushed oreis conveyed to a 25,OOQ..ton live storagepile. Two reclaim conveyors, each fedby three Nico 550 H feeders, transportthe ore to the primary grinding mill feedconveyor.

The primary mill is a variable speeddrive Koppers 28 by 12 foot semi­autogenous mill. The ball charge for themill is 8 to 10 percent of the mill volumeand 4 inch and 5 inch diameter balls areused. The mill is usually run at 72 per­cent of critical speed, but during start upthe mill was run as low as 50 percent ofcritical speed on soft ore. The variablespeed drive has proven to be a usefulcontrol tool in grinding, allowing the re­duction of mill speed when soft ore is fedto that the balls do not damage the lin­ing.

Ore is ground in the primary mill toapproximately 80 percent minus 20mesh. The mill is in closed circuit withtwo 5Q..inch-diameter Krebs cycloneswith adjustable apexes. A portion of thecyclone underflow can be diverted totwo primary 24x 36inch Denver mineraljigs, with jig concentrate passing to ascrew classifier and then to the regrindmill. Jig tailing is returned with cycloneunderflow to the primary mill. Thesejigs are presently not in use.

The cyclone overflow, or the 80 per­cent minus 20 mesh material, is fed toten D20 20-inch Krebs cyclones inclosed circuit with the secondary Kop­pers 16-foot, 6-inch by 29-foot ball millwhich grinds the ore to about 70 percentminus 200 mesh. The mill is powered bya synchronous drive 4,600 horsepowermotor. Ball charge is approximately 35percent of mill volume and 2-inch ballsare used. Pulp density in the mill is 70 to72 percent solids.

From 5 to 20 percent of the second­ary cyclone underflow is diverted tofour 24 by 36-inch Denver mineral jigs.Jig concentrate flows by gravity to thescrew classifier mentioned earlier.Classifier sands are fed to the regrindmill, and tailings from the jigs are re­turned to the secondary mill with therest of the cyclone underflow. The clas­sifier overflow is used for makeup waterin the grinding circuit.

The cyclone overflow, 70 percentminus 200 mesh is feed for the rougherflotation section. Rougher flotation tail­ing is pumped directly to the tailing

9-inch holes in a 24 x 24-foot pattern.Average powder factor during this min­ing stage has been 0.26 pounds per ton.

The pit bas three P & H 1900ALshovels for loading Lectra Haul, UnitRig, tOO-ton-capacity haul trucks. Twooperating II-cubic-yard bucket shovels,with the third as standby, average12,500 tons per shovel shift. There areeleven toO-ton haul trucks in Afton'sfleet, each powered by a KTA 23OQ.CCummins engine with derated horse­power from 1,200 to 1.050. Truck pro­ductivity has been approximately 2.800tons per truck shift. Ore is hauled to theprimary crusher, an Allis Chalmers 42by 65-inch gyratory. Waste rock is piledin 5Q.foot lifts with berms spaced at 100feet for reclamation. A smaU percentageof waste rock is diverted to a $500,000crushing and screening plant located atthe tailings dam. This plant producesmaterial for the tailing dam and roadsanding.

The pit wall slope varies from 35 to45°. Benches are 30 feet high. Twobenches are combined to form ~foot

benches with 38- to 65-foot berms. Thehaul road grade is 10 percent; haulageroads outside the pit are 100 feet wide,and, right hand traffic is employed.

Ancillary equipment includes oneCaterpillar 824 wheel·type tractor, oneCaterpillar l4motor grade, three Cat D8crawler tractors, and one Cat 769 off­highway truck to be used in the winterfor sanding and as a water truck duringsummer months.

One large building serves as thewarehouse, changehouse, equipmentshop, and pit maintenance and opera­tions personnel offices.

Two-Product ConcentratorThe new Afton concentrator com­

bines gravity separation techniques inthe form of jigs and tables, and conven­tional froth flotation to produce a native

- :" , .f'}.·'"t ""'Ill f ;- , t\ :.-: I T .. ~,.{~.; .. _-:i-.'.~ ~"~.. _: 7; --~ "?/1. ,.' . _'" /~~,~,t ',\ol! • ..1 '--~-0, ~ ~~ ,.~~. .,~,~ e::::;",,__ j

"'-', ;;:--.~,.. ,- -~~ .ll. _ _. _ ~_"~,~. --- .. ~. -~ -~ ----,.". ,,'. -~ -:.~, "'-

•..•..~-~~.,.. l'"'~~'?~>~ - ..... ,~. . /....,/ "'l'i~_'~ .. ,_.. ~'.'•..... '. ~_..~'... .~-.x . /~ , - ,-., ....--~ '.' .......- . . -<:-..'sv: , >

"z.,"-.... .:~;:::tl--;;""""'r:'.' -.-;;..- . '".:::;;..-;, fr:S/'.;.<',. .~, 'b-' • .~' . ...-.; 4";t;t,' ."""Ii .' . ,,/ " . ,~. ,,"-'is"\!-./ ',~:;3~'>/, '" :, . ~

.~ ,,:::::.. ". ': :; y" "~,, .'".. ,'> - ',.' /~,---- ~ \,....- ,

Dominion PitThe Dominion pit has reached a

depth of 120 feet and presently coversan area 1,500 by 2,300 feet. The fmal900-foot-deep excavation wiD cover a2,700 by 2.80Q.foot atea. Initially,500,000 tons of glacial tiU was removedby a contractor. In late February13.000,000 tons of material had beenmoved. The initial stripping ratio (dur­ing the first five years-of operation) willbe between 6.0 and 7.0 to 1.0. Over thelife of the mining, the stripping ratio wiUaverage 4.5 to 1.0.

Two Bucyrus-Erie 40R drills average630 feet of drilling per shift consisting of

until near the foot waH wbere the ratio isreversed.

The supergene event, which trans­formed the sulphides in tbe bypogenezone, consisted of aerated groundwaterchanneling tbrough the fracturedbypogene deposit causing coincidentoxidation of magnetite to hematite andreduction of chalcopyrite and bornite tochalcocite and native copper. Themetallic copper atAftolllslikely to be ofthe supergene type because of the lackof trace elements which would be foundin native copper in a hypogene zone.Excess sulphur and soluble salts wereremoved by the departing groundwaterwhich flowed to a fault-depressed baselevel basin to the north. Essential to theformation of this supergene assemblagewould be the coexistence of high sul­phur copper minerals and magnetite.

The Afton pit wiU be 900 feet deepwith are reserves of 34,000,000 tonsgrading 1.0 percent copper, 0.58 gramsgold per ton (0.016 ounce per ton), and4.19 grams silver per ton (0. 120uoce perton) at a cut·off of O. 25 percent copper.An additional estimated IO,OOO,OOOtonsof ore grading 1.6 percent copper maybe recoverable through undergroundmining from the hypogene zone.

~

GRINDING AND FLOTATION sections of the Afton concentrator. Variable speed driveKoppers semi-autogenous mill, top left, secondary and regrind ball mills to the right,and flotation cells below.

1}

AFTON MINES LIMITED CONCENTRATOR FLOWSHEET

e\lrclAl::::::=:============@(j)

®

To tailings pond

-------:--~J

------- ~@

1. Allis Chalmers gyratory crusher, 42"x65"2. Nico TR 1100 hydrastroke feeder3. Asea metal detector4. Conveyor system, 48"5. Nico 550 H hydrastroke feeders6. Conveyor systems, 42"7. Conveyor system, 42"8. Merrick 440 OS-I weightometer9. Koppers primary semi-autogenous mill,

variable speed drive, 28'x12'10. Georgia Ironworks primary mill discharge

pumps11. Kreps 050 Cyclones, adjustable apexes12. Allis Chalmers SRL-e pumps13. Krebs 020 LB cyclones, pneumatic

inlet valves and adjustable apexes14. Koppers secondary ball mill, 16'6"x29'15. Denver primary mineral jigs, 24"x26"16. Denver secondary mill jigs, 24"x36"17. Tech-Taylor valves18. Triple pitch Wemco classifier, 30"x20'3"19. Conveyor system, two speed drive, 18"20. Merrick 440 OS-I weightometer

21. Krebs 015 cyclones22. Koppers regrind mill, 9'6"x12'23. Allis Chalmers SRL-e pumps24. Krebs 010 cyclones25. Deister 12-way distributor26. Concenco 999 triple deck

concentrating tables27. Straight Line metallic concencrate

filters28. Conveyor system, 18"29.Conveyor system, 18"30. Conveyor system, two speed, 18"31. Merrick 440 OS-I weightometer32. Dryer feed screw conveyor, 8"x14'6"33. Lockhead Haggerty rotary dryer with

fans and scrubber, 3'x24'34. Dryer discharge screw conveyor, 9"x25'9"35. Allis Chalmers SRL-e table tailing pumps36. Allis Chalmers SR L-e regrind cyclone

overflow pumps

37. Allis Chalmers SRL-e regrind millcyclone feed pumps

38. Denver 600H rougher and scavengerflotation cells

39. Allis Chalmers SRL-e scavengerconcentrate pumps

40. Allis Chalmers SRL-e flotation tailingpumps

41. Allis Chalmers SRL-e variable speedflotation tailing pumps

42. Denver 300V cleaner flotation cells43. Allis Chalmers SRL first cleaner

concentrate pumps44. Denver 30DR cleaner flotation cells45. Allis Chalmers SRL second cleaner

concentrate pumps46. Denver 30DR cleaner flotation cells47. Allis Chalmers SRL third cleaner

concentrate pumps48. Allis Chalmers SRL-C final concentrate

pumps49. Allis Chalmers SRL-C variable speed

final concentrate pumps50. Flotation concentrate thickener, 50'

diameter51. Denver automatic samplers52. Clarkson reagent feeders53. Final concentrate conditioner tank

~·i.COPPER SMELTER, first top blown rotaryconverter for copper in North America.

pond, rougher concentrate is fed to theregrind cyclone, and the middling pro­duct is recycled through the rougher flo­tation cells. Regrind cyclone underflowis fed, along with classifier sands. to theregrind mill, a Koppers !/-foot, 6-inch by12-fool ball mill driven by a 500 horse­power motor. This rom is charged with2-inch balls to approximately 28 percentof the volume, and the pulp density is 60to 65 percent solids.

Regrind cyclone underflow moves to

four Conceneo triple·deck concentrat­ing tables. Table concentrate is the fmalgravity native copper concentrate andto date has averaged from 78 percentcopper ~ssay. It is hoped to eventuallyobtain a 90 percent copper concentratefrom the table operation. This concen­trate is dewatered on a belt filter andthen dried in a Hoot-diameter by 24­foot-long Lockhead Haggerty rotarydryer. The dried concentrate is truckedto the TBRC~ smelter and stockpiled.The table tailing is recycled 10 tile re­grind cyclones.

Regrind cyclone overflow is pumpedto eighl Denver 300V cleaner flotationcells, the firsl of four stages of flotationcleaning cells. Tailing from the firstcleaner bank is returned to rougher flo­tation. The following three cleaningstages utilize a total of 24 Denver DR 30flotation cells. Final flotation concen­trate is pumped to a thickener adjacentto the smelter. filtered. dried. andstockpiled. To date, flotation concen­trate has averaged 47 to 53 percent cop·per. This is very close to the target assayof "in excess of 50 percent".

Flotation reagents are collector,potassium/sodium amyl xanthate; andfrather, cresylic acid/MIBC at a ratio ofone to four by volume. Flotation is car­ried out at a natural pH of 9.5.

The mill, designed for 7,000 tons ofare per day. in February averaged 7,800tons per day. Ore treated to date has

been primarily from the top benches ofthe open pit which contained lower (0. 91percent copper) than average grade,oxidized copper, and mud. Recovery todate has been 81%, with February re­covery achieving the feasibility rate of87%. As mining goes deeper, recoveriesshould improve. On one day early thisyear, recovery. in fact, averaged 92 per­cent.

Afton has incorporated very little au­tomatic control in this very simple mill.This was done in order that reliable ac­tual plant data may be monitored manu­ally to determine which, if any,parameters in this mill warrant automa­tic control.

Water and Tailing DisposalThe tailing impoundment area is

about 10.000 feet from the concentratorin the valley of Hughes Lake. The damwas geotechnically designed. The im­poundment area required two dams, oneon the east end and one on the west end.Ultimate crest elevation for the damswill be 2,400 feet maximum. Final riseabove the valley floor will be 300 feet,and the starter dams rise 100 feet abovethe floor.

The dams will be constructed fromwaste rock and till from the open pit. Agravel plant at the dam will crush andsize material both for use at the dam andfor use in sanding the pit roads duringthe winter. Both dams will have rockcore and an impervious blanket on theupstream side. They will be free stand­ing with benched downstream faceswith slopes of 2.0 to one. The upstreamslopes will be two to one. The im­poundment area has been designed tohold 95,000,000 cubic yards of tailingand will require 20,000,000 cubic yardsof waste rock for construction.

Because of the relatively low settleability of the slimes in the tailings, ini­tially no effort will be made to reclaimwater. Water for the mill and mine willbe supplied at a rate of 4,400 gallons perminute from Kamloops Lake. Researchis being conducted with the goal ofeven­tually flocculating the tailing in order toreclaim water.

New Smelting TechnologyAfton is the first copper smelter in

the Western Hemisphere to use the topblown rotary converter (TBRC™), ap­plying the technology recently de­veloped by the International NickelCompany for treating nickel concen­trates. The smelter was built underlicense from Inca and Dravo Corpora­tion. The single TBRCTli is 14 feet indiameter by 21 feet long and is expected

to produce 28,000 tons of blister copperannually as 1,200 pound billets. (Seebox describing TBRen! in detail, page47.)

The TBRCnl process was chosen byAfton over other alternatives for severalreasons. It was chosen over an electricfurnace because of a lower capital costand greater flexibility for processingvarying grades of concentrates. Hydro­metallurgical methods were ruled outbecause they offered no way of recover­ing the precious metal values from theconcentrates of ore.

The smelter will treat two heats aday, each producing approximately 50tons of blister copper. Once the workinglining refractory has worn to 4-6 inchesremaining, the vessel must be relined.

Dried gravity concentrate from themill is trucked to the smelter and flota­tion concentrate is pumped to a thick­ener. filtered. dried. and placed in astorage bin. The average grade of com­bined concentrate is 65 percent copper.

The flotation concentrate along withfluxing agents is fed to the furnace andmelted with an oxygen-natural gas flamefrom the lance. When the concentrate ismelted, the natural gas is shut off andoxygen, air or a combination, is injectedthrough the lance to sustain theexothermic oxidation of sulphur withthe corresponding production of cop­per. Charging of the flotation concen­trate continues and the molten bath isslagged. After the low sulphur flotationconcentrate has been charged and thebath has been slagged. the gravity con­centrate is charged to the furnace. If slagmust be removed after charging of thegravity concentrate. this is done. Anyhigh copper slag that requires cleaning isheld in refractory-lined ladles.

Blister copper is transferred via arefractory-lined ladle to the casting op­eration and cast into billets. Any slagthat requires cleaning is returned to theTBRenl for reprocessing. The cleanedslag is removed. and the metal recov­ered.

The process off-gases from thesmelter have a wide variance in compo­sition and are cooled to 65QO F.

Dust is removed by an electrostaticprecipitator and is briquetted and re­turned to the furnace for smelting. Thedust-free gas is scrubbed in a dual-alkaliscrubber to remove 502. Thegas is thencooled in packed towers, using 3,000gallons per minute of cold water, tocondense mercury which is collected ina mist eliminator and stored in plastic­lined drums for future sale~ The cooledprocess off-gas from the packed towersis reheated and discharged to the at-

..

T he top blown rotary converterTBRC"" process combines a fully

operational vessel with the new processtechnology to offer an alternative to

conventional smelting processes. R. A.Daniele and L. H. Jaquay of Dravo Cor.poration summarized the history andtechnology of the TBRC~ as follows ina paper to the 1972 AIME Meeting inSan Francisco, California, UnitedStates. The fi.rst application of the ves­sel (Kaldo Process) was in Sweden in1957 by Stora Kopparbergs for produc­ing steel from high pbosphorous ironore. Since that time, the process hasbeen successfully employed in eightsteel plants.

It was not uotil 1959 that theTBR~process was adapted for the treatmentof non-ferrous concentrates such asthose of nickel, copper, and lead. Atthat time, the first commercial facilitywas constructed by Dravo Corporationfor the International Nickel Companyfor producing nickel at Copper Cliff,Ontario, Canada. At this facility, two14-foot-diameter vessels with oneoperating full time and the other parttime, 276 tons per day of metallics fromnickel sulphide concentrate, copper­nickel metallics, anode residue, andTBRCTM system dusts can be produced.

The basic vessel used for producingsteel is also used for processing non­ferrous materials. The figure aboveshows the thrust rollers which securethe vessel longitudinally in the frameand the motor driven support rollerswhich both support the vessel within theframe via two cast steel track rings androtate it at speeds up to 40 revolutionsper minu teo This arrangement permitsthe vessel to rotate freely inside thesupport frame.

Trunions support the furnace so thatit can be tilted through 360" for fiDing,blowing, and pouring.

The mouth has an exhaust hood seal­ing ring which provides a bearing sur­face for a tight hood and minimizes in­leakage of ambient air to the exhausthood. A water-cooled oxygen lance andcharging chute are mounted on theexhaust hood. The charging chute isused when feeding concentrate. or addi­tives.

The TBRCTN process for primarysmelting of copper claims to offer sev­eral advantages over conventional

TBRe ARRANGEMENT

Charging Chute

Water CooledOxygen Lance

ExhaustHood

Vessel is sh~nin Blowing andRotating Position

"­Replaceable Cast""""'<If-_Iron Nose Ring ~

Exhaust HoodSealing Ring

Motor Driven ----!~~fJSupport Rollers

smelting processes. Proponents of theprocess also claim significant savings incapital and operating costs can be at­tained by using the TBRC™ process.

The water-cooled lance which is in­serted through the exhaust hood can beused to control the smelting atmosphereby injecting different combinations offuel, oxygen. and air to obtain neutral,reducing, or oxidizing conditions. Thelance can also be adjusted for depth andangle in the furnace. When commer­cially pure oxygen is used instead of air,converting rates can be increased. sul­phur dioxide concentrations in exhaustgases can be maintained as high as 50percent, and slag nuidity can be in­creased. The high sulphur dioxide con­centrations are obtained by eliminatingthe nitrogen dilUlion obtained when airis used.

Adjustment of the rotational speed ofthe furnace and adjustment of the lanceangle help to maintain high oxygen effi­ciency. Inco's testwork at its Port Col­borne Research Center indicated thatoxygen efficiency with the TBRen-: pro­cess could be maintained above 95 per­cent.

The total dust loading of the exhaustgas is reduced in the TBRCTM because ofthe double passing of the process gasesover the bath surface and the rotation ofthe vessel. The molten material wets therefractory surface and tends to absorbdust.

Thermal efficiency is usually

Removeable--BoUom

-===H--Thrust Rollers

superior with the TBRCDI than withconventional smelting. The option touse fuel with oxygen allows running thebath at higher temperatures. Even with­out the aid of fuel for heat input. a highertemperature is maintained because ofthe absence of nitrogen contained in airwhich normally consumes heat to reachoperating temperature, and rotation a]~

lows heat transfer from the refractorywalls to the molten metal. Thermal gra­dients are diminished because of thegood mixing imparted by the rotationalaction.

A cost comparison between theTBRCTM process and conventionalsmelting methods made by Afton indi­cated this process to have considerablecapital cost savings. The Mton smelterwill cost less than $1,000 per annual tonof copper.

The application of the TBR~ pro­cess above serves as a single vesselsmelter, performing as a reverberatorymelting furnace by injecting an oxy-fuelmixrure through the lance and as smelt­ing proceeds, lhe vessel becomes sim­ply a converter. with only oxygenandlor air being injected and heat beingsupplied by the exothermic sulphur oxi­dation reaction.

The TBRC~ process can be appliedto copper smelting in other ways than asan autogenous smelter. It may be usedto smelt scrap, cement copper, whitemetal. or matte from a separate rever­beratory furnace.

mosphere from a 300-foot stack, 1,500feet above the city of Kamloops.

Afton has established an ambient airmonitoring system with data teleme­tered back to the smelter. The maximumpermitted emissions are as follows:

CONtllm;nant

LeadZincCadmiumMercurySulphur Dioxide

P"m;tud Conct'nlrll/;on

0.003 grains per cubic foot0.003 grains per cubic foot0.003 grains per cubic foot

4.0 pounds per day90% removal

When operational, Afton's topblown rotary converter will be thecleanest smelter in North America. Ex­pected recovery for the plant is 99 per­cent and blister grade should exceed 99percent copper. END.