Mopani Copper Mines

1937 2 x Reverbs, 4 x PS Converters

1956 3 x Reverbs, 5 PS Converters,

4 Anode Furnaces, 2 Casting Wheels 1972

36 MVA Electric Furnace, 1 x Reverb, 6 x PS Converters,4 x Anode Furnaces, 2 x Casting Wheels, 1 x Holding Furnace

1991-2006 36 MVA Electric Furnace, 4 PS Converters

4 Anode Furnaces, 2 Casting Wheels 2006-Present

Isasmelt Furnace, 12 MVA Slag cleaning furnace5 x PS Converters,

2 x 400 tonnes Anode furnace, 1 x twin casting wheel(commissioned in March 2009)

Potential to treat > 420,000 tpa (ie toll)

New mines being developed in the region Improve environmental performance

From no SO2 capture to 50% Avoid ~6 m shutdown to rebuild old Electric Furnace

Old furnace at the end of its life. Old Electric Furnace failed during Isasmelt

commissioning Exporting concentrates difficult due to

transport constraints

Isasmelt furnace 850,000 tpa

Matte Settling Electric Furnace (MSEF) 850,000 tpa (equivalent) capacity (SMS Demag)

Acid Plant (Isasmelt offgas only) 1150 tpd (MECS)

Oxygen Plant 650 tpd (Air Products)

Fastest Isasmelt project 28 months from license agreement to feed on.

MCM Concentrators

Concentrate storage

Sulphuric Acid Plant(1150 tpd)

Isasmelt furnace(850,000 tpa)

Oxygen Plant(650 tpd)

Matte Settling Electric Furnace

PS Converters(upgrade from 4 to 5)

Fire Refining and Casting

(install 2 x 400 t AFs,80 tph casting wheel)

Concentrate

Purchasedconcentrate,

coal and fluxes

Cons,reverts,

flux,coal

OffgasCoke

Oxygen Matte

Reverts

Slag

Blister

Tail gas to Atmosphere

Anode Copperto

Refinery

Discard slagto

Dump

Diesel

Offgas to Atmosphere

Offgasto

Atmosphere

Matte,Slag

Equipment Legend

Smelter Upgrade -Phase 1

Smelter Upgrade -Phase 2

ISASMELTCONCEPT

Concentrates (CuFeS2,Cu2S,CuCO3.(OH)X, FeS2,SiO2, and others . . .)

Flux (SiO2,CaCO3)

Coal (C,CH4)

Water (H2O)

Oxygen (O2)

Air (N2,O2)

Diesel / Fuel Oil

ISASMELT Furnace

ISASMELT Lance

Offgas

(CO2,SO2,H2O,N2)

CuFeS2 + O2 Cu-Fe-S + FeO + SO2

(FeS + 3Fe3O4 10FeO + SO2)

FeS2 + 5/2O2 FeO + 2SO2

2FeO + SiO2 2FeO.SiO2

Matte

Slag

Matte-Settling Electric Furnace

SlagCoating Smelting reactions

Matte + Slag

Slag box

Post-combustion air (N2, O2)

Granulation water

Feed materials: Concentrates (Mopani and toll) Reverts (<25 mm) Silica flux (sand) Limestone flux (not normally used) Coal (5-20 mm) Isasmelt ESP dust WHB dust (mixed with reverts)

Feed materials stored in separate stockpiles

Feed materials reclaimed by front end loader

Conveyed to storage bins: Concentrate (4 x 150 t) Flux (2 x 80 t) Reverts (1 x 180 t) Coal (1 x 50 t)

Don’t mix up feed materials!Hopper

CV121

Cons(x4)

CV134 (Shuttle)

Flux (x2)

Coal Reverts

Stockpiles

CV123 CV124

To Furnace

Front End Loader

CV124 (to

bins)

Feed bin building

CV133 (to

furnace)

Feed materials are accurately measured (±2%) and controlled by the PWCS.

Feed rate is controlled by variable speed drives.

Flexible system allows quick blend changes.

Reverts, Coal and Flux bins have 2 conveyors to measure accurately at low rates.

ConBN108

ConBN109

ConBN115

ConBN116

RevertsBN113

CoalBN112

FluxBN111

FluxBN110

CV125 CV126 CV135 CV136 CV140 CV139 CV138 CV137

CV130 CV129 CV128 CV127

CV131To furnace

ESPDust

Cons feeders (x4)

Flux, Reverts and Coal feeders

Combined feed on CV131 Paddle mixer installed, but normally bypassed Furnace feed conveyor (CV701)

Retractable and reversible to prevent heat damage (fires) Conveyor always runs unless retracted.

Otherwise the belt will catch on fire from furnace radiant heat

Coal reduction bin (furnace reductions) Reversible to bypass the furnace

For weigher calibrations For unsuitable feed materialsCV131

(mixed feed)Paddle mixer

CV132

CV133

CV701

Bypassbunker

Isasmelt furnace

Retractable &Reversible

Coal reductionbin

Furnace refractory: 13.3 m tall 4.4 m internal diameter 450 mm Cr-Mg (in most areas) 100 mm insulation brick

Roof Boiler tubes (part of WHB) Openings:

Feed chute Lance Holding burner Offgas

Copper blocks Splash block Tapping blocks (inner and outer)

13.3 m

4.4 m

Feed chute Lance port

Holding burner port

Splash block

WHB

Feed chute Slag box (Lance port)

Holding burner port

Feed chute Lance port

Holding burner port

Isasmelt furnace

Lance 18.1 m long 350 mm body 300 mm tip Single swirler Internal air and tip pressure pipes Changed after ~ 7 days

Process Typical flow 5 Nm3/s (regardless of feed rate) 50 – 80% O2

Process air from dedicated blower Oxygen (95%+ O2) from oxygen plant (650 tpd)

Tapping machine rails

Head section

Bend section

Furnace offgas cooled using a Waste Heat Boiler (WHB) Furnace roof (inlet ~1,200 oC) Cooling screen and Transition piece Shaft 1 Shaft 2 (inlet ~600 oC) Gas cooler (inlet ~400 oC)Transition pieceCooling screen

Furnace roof

Shaft 1

Shaft 2

Gas cooler sprays

To ESP

ESP 3 field ESP. 3 perpendicular (to gas flow) drag link conveyors. Dust is pneumatically conveyed to feed system, and is

directly recycled.

Induced Draft (ID) Fan Single ID Fan. Precise control of furnace draft

Variable speed drive. Inlet damper.

General 12 MVA, 3 in line Electric Furnace 1092 mm Soderberg electrodes

Tapping 4 Matte tap holes (2 mud gun drills) 2 Slag tap holes (manual tapping) Large pit for granulated slag Reclaim slag with a grab crane

Feed materials 2 Return Slag Launders (PS Converter slag) 1 Isasmelt Launder 8 charge bins (coke and reverts)

Offgas Naturally ventilated Cooled by dilution air Discharged without treatment

Concentrates Mufulira (41%Cu, 12%Fe, 21%S, 12% SiO2) Nkana (32%Cu, 22%Fe, 29%S, 7% SiO2) Kansanshi (28%Cu, 27%Fe, 32%S, 5% SiO2) Blend (32%Cu, 22%Fe, 29%S, 7% SiO2)

(concentrate only)

Furnace feed 70-115 tph (Design 113 tph) 30-32%Cu in blended concentrate (excluding reverts) 7-9% Moisture (no water additions) 0-6 tph Silica 1-4.5 tph Coal (typically 2-3 tph) 0-25 tph Reverts Paddle mixer not used

Lance 50-80% O2 5 Nm3/s Total lance flow (design 7 Nm3/s) Minimum lance air ~1.2 Nm3/s 35 lph diesel (average during smelting)

Products 1170-1190 oC 56-58% Cu in matte 0.8 SiO2:Fe 8% Fe3O4 in slag

MSEF Products Matte 58-60% Cu (1180 oC) Slag 0.7% Cu (1250 oC)

Isasmelt Operating Time

0

10

20

30

40

50

60

70

80

90

100

No

v-06

De

c-06

Jan

-07

Fe

b-0

7

Ma

r-07

Ap

r-07

Ma

y-07

Jun

-07

Jul-0

7

Au

g-0

7

Se

p-0

7

Oct-0

7

No

v-07

De

c-07

Jan

-08

Fe

b-0

8

Ma

r-08

Ap

r-08

Ma

y-08

Jun

-08

Jul-0

8

Au

g-0

8

Se

p-0

8

Oct-0

8

% o

f to

tal

tim

e

Overall operating timeOperating time - without aisle and power constraints

Rebrick

Pow

er fa

ilure

, SA

P

Pu

mp

sIsa

smelt ro

of le

ak

Circ p

um

ps, g

rab

, ele

ctrod

es

O2

pla

nt co

mp

resso

r

No venting

General 22 month campaign duration 105 mm minimum brick thickness (~3 m) Air cooling of shell during 2nd year (offtake side of furnace) Low wear above the splash block Unusually symmetrical wear

Wear control Brick monitoring thermocouples (important)

and thermal imaging (not very important, just looking for hotspots) High wear during the first 7 months (high temps, poor slag

chemistry) Wear rates controlled for remainder of campaign Good match between physical measurements and calculations Post combustion control very important for refractory above the

splash block Injecting air through the holding burner damages refractory, and

probably the splash block

Design Single piece, cast in Monel tubes 4 cooling water passages (no air) Copper anchors on the bottom and front face of block 4 thermocouples (3 in block, 1 between block and refractory) Temperature (copper) control by manipulating cooling water flow

Performance 22 months without leaks or apparent damage (apart from anchors) Cooling water flow does vary (occasionally) to control copper

temperature (uncertain if it makes any difference to block’s life) Post combustion air injection via the holding burner heats the top

surface of the block (all slag melts leaving a bare block) 2nd Campaign Design

Anchors added to the top of the block

General Expected refractory life was 5-10 years After 2 years side walls required replacement (partial) Roof required replacement due to furnace explosions

Wear control Brick monitoring thermocouples were initially installed

(SMS Design) 3 separate brick monitoring locations spontaneously

leaked Remaining openings were closed with refractory and a steel

Additional thermocouples were not installed mid campaign due to cooling jacket design (steel cooling jacket behind working lining)

Charging Input launders directed towards dead corners

resulting in launder blockages Burners required to prevent launder blockages

Accretions No accretions on the side walls (no refractory

protection) Bottom accretions of up to 1 metre Accretions largest in non active areas of the

furnace Regular pig iron additions required to control

accretions

Matte tapping Initial tapping arrangement (4 tapholes, 1 ladle at

a time) was a major production constraint, matte bogie installed to minimise tapping delays

Matte taphole inserts (Cr-Mg, installed in outer tapping block) require replacement every 4 days. Therefore only 3 working tapholes

Matte tapholes can not be closed manually 2nd mud gun installed to prevent run aways Taphole design being improved

(eliminating outer tapping block inserts) Tapholes require deep repair every 1-2 months

(requires a 24 hour shutdown)

Refractory Disappointing performance

Low grade brick used by SMS Demag (400 mm RHI ESD) Unable to monitor brick wear, operating parameters not

optimised Technical focus on other areas (due to many other

problems) 2nd Campaign

Isasmelt style brick monitoring implemented for 2nd campaign

Improved process control Higher grade bricks (RHI FG) Consider jacket design change if wear rate can’t be

controlled Target refractory life is >= 2 Isasmelt campaigns

< February 07 ESP exit temp intermittently > inlet temperature

(believed to be instrumentation problems) ESP inspections (external) did not identify problem Shutdown February 2007 to inspect and repair ESP

(ESP could not maintain KVs) ESP internals found to be beyond repair Acid plant not commissioned at this stage

ESP Rebuild September – November 07 (US$1.4M) ESP bypassed for rebuild Additional dust load to gas cleaning plant required daily shutdowns to

remove dust from scrubbers Post Rebuild

No further damage ESP’s performance improved, but still struggles to hold KVs at times

Symptoms ESP Exit temperature increases Sulphur formation in gas cleaning plant

Factors Coal rate (high rates increase problems) Post combustion air Excessive dust in ESP (high dust levels in hoppers cause problems)

Consequences Potential damage to ESP (none since Nov 2007) Damage to gas cleaning pumps (very sensitive to S)

Detection SAP Gas Cooling Tower pump discharge pressure increases

(indicates weak acid coolers are blocking) ESP exit temperature increases Glass rod test (least reliable)

Prevention Implemented post combustion air flow smelting interlock Implemented ESP dT interlock (Outlet temp – Inlet temp) Installing CO, O2, NO monitor at WHB exit (in progress) Post combustion fan operates at maximum rate, so additional post

combustion air is provide by increasing furnace draft(not very efficient)

Problem Large water leak in the WHB’s 2nd shaft

Cause Gas cooler spray malfunctioned Water impingement on tubes causing thinning

Damage and repairs 6 tubes replaced Repair time 5 days (poor welding technique)

Actions Implemented logic to detect failure (using existing instruments) Modified spray design (sprays heads were dissolving) Regular thickness testing of tubes around sprays

Problem Furnace roof leak (bottom of roof)

Cause Consultant’s report indicated localised overheating,

however cause is unknown Damage and repairs

1 tube replaced Lost time - 6.5 days (including reheating furnace)

Problem Furnace roof leak (top of roof)

Cause Holding burner hoist rope failed, dropping holding burner Web ripped off tube causing small leak Leak noticed about 10 hours after hoist failure

Damage and repair Tube welded Web not reattached

(concerned about differential expansion causing leaks) Furnace partially cooled Lost time ~19 hours (including furnace recovery)

Actions Holding burner carriage stopper relocated (was too low) Minor repairs to roof during rebrick (tubes were not straightened) Hoist replaced (original rope was under designed)

Problem WHB design exit temperature 700 oC Actual exit temperature 400-500 oC

(under typical operating conditions) Design condensing capacity 35 tph Required condensing capacity ~50 tph

(for design conditions) Demin capacity 5 tph It is not possible to operate under design conditions Availability would be limited to ~33%

Cause (probable) Fouling on the hot side of the boiler tubes much less

than design, resulting in higher than design heat transfer

Very clean (Pb, Zn, As) concentrates

Air Cooled Condenser

Steam Drum

Blow off valve

SteamCondensate

Heat surfaces

Blow off toatmosphere

Makeup water

Mitigation Increased demin storage from 10 to 70 m3

Decrease lance flow from 7 to 5 Nm3/s Concentrate blend requires less coal than

design (very lucky) Additional 10 MW condenser was installed.

HFO Conversion Currently using diesel for the holding burner, lance and launder

burners Commissioning of HFO on the holding burner is in progress.

Aisle debottlenecking 3 x 55 tonne Main Aisle Cranes Mechanical punching machines are being commissioned.