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Smelter start up of new ISA furnace and progress to date

Mopani Copper Mines. Smelter start up of new ISA furnace and progress to date. Smelting at Mufulira - Developments. 1937 2 x Reverbs, 4 x PS Converters 1956 3 x Reverbs, 5 PS Converters, 4 Anode Furnaces, 2 Casting Wheels 1972

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Smelter start up of new ISA furnace and progress to date

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  1. Mopani Copper Mines Smelter start up of new ISA furnace and progress to date

  2. Smelting at Mufulira - Developments • 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 Converters4 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)

  3. Project Motivation (Phase 1) • 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

  4. Project Description (Phase 1) • 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.

  5. Equipment Legend Smelter Upgrade - Phase 1 MCM Sulphuric Acid Plant Tail gas to Concentrators ( 1150 tpd ) Atmosphere Smelter Upgrade - Phase 2 Offgas to Atmosphere Concentrate Offgas Diesel Coke Discard slag to Dump Cons , Purchased Concentrate Isasmelt furnace Matte Settling reverts , Matte , concentrate , storage flux , ( 850 , 000 tpa ) Slag Electric Furnace coal and fluxes coal Oxygen Matte Slag Offgas to Atmosphere Oxygen Plant Fire Refining and ( 650 tpd ) PS Converters Casting Blister ) ( upgrade from 4 to 5 ( install 2 x 400 t AFs , 80 tph casting wheel ) Reverts Anode Copper to Refinery Project Description

  6. ISASMELT CONCEPT Post-combustion air (N2, O2) Oxygen (O2) Air (N2,O2) Diesel / Fuel Oil Offgas (CO2,SO2,H2O,N2) Concentrates (CuFeS2,Cu2S,CuCO3.(OH)X, FeS2,SiO2, and others . . .) Flux (SiO2,CaCO3) Coal (C,CH4) Water (H2O) Slag box Slag Coating Smelting reactions CuFeS2 + O2 Cu-Fe-S + FeO + SO2 (FeS + 3Fe3O4 10FeO + SO2) FeS2 + 5/2O2  FeO + 2SO2 2FeO + SiO2  2FeO.SiO2 ISASMELT Lance Matte + Slag ISASMELT Furnace Slag Matte-Settling Electric Furnace Granulation water Matte

  7. 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 Plant Description - Feed Preparation

  8. 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! Plant Description - Feed Preparation

  9. Plant Description - Feed Preparation Feed bin building CV124 (to bins) CV133 (to furnace)

  10. 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. Plant Description - Feed Preparation

  11. Plant Description - Feed Preparation Flux, Reverts and Coal feeders Cons feeders (x4)

  12. 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 materials Plant Description - Feed Preparation

  13. 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) Plant Description – Isasmelt Furnace 13.3 m 4.4 m

  14. Plant Description – Isasmelt Furnace Feed chute Lance port Holding burner port WHB Splash block

  15. Plant Description – Isasmelt Furnace Slag box (Lance port) Feed chute Holding burner port

  16. Plant Description – Isasmelt Furnace Feed chute Lance port Holding burner port Isasmelt furnace

  17. 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) Plant Description – Isasmelt Lance

  18. Plant Description – Isasmelt Tapping Tapping machine rails Bend section Head section

  19. Shaft 1 Shaft 2 • 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) Plant Description – Offgas Transition piece To ESP Cooling screen Gas cooler sprays Furnace roof

  20. 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. Plant Description – Offgas

  21. Plant Description – MSEF • 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 • 2Return Slag Launders (PS Converter slag) • 1 Isasmelt Launder • 8 charge bins (coke and reverts) • Offgas • Naturally ventilated • Cooled by dilution air • Discharged without treatment

  22. Matte Settling Electric Furnace

  23. Operating Conditions • 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

  24. Operating Conditions • 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)

  25. Concentrate treatment from start up

  26. Reverts treatment from startup

  27. Plant Availability No venting Circ pumps, grab, electrodes O2 plant compressor Isasmelt roof leak Power failure, SAP Pumps Rebrick

  28. Isasmelt Rebrick • 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

  29. Isasmelt Rebrick – Wear profile

  30. Isasmelt Rebrick

  31. Splash Block performance • 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

  32. Splash Block performance

  33. MSEF Rebrick • 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)

  34. MSEF Rebrick – Wear profile

  35. MSEF Performance • 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

  36. MSEF Performance • 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)

  37. MSEF Performance • 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

  38. Problems – ESP Damage • < 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

  39. Problems – ESP Damage

  40. Problems – Post Combustion • 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)

  41. Problems – Post Combustion • 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)

  42. Problems – Post Combustion

  43. Problems – WHB Leak (May 07) • 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

  44. Problems – WHB Leak (May 07)

  45. Problems – WHB Roof Leak (Dec 07) • 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)

  46. Problems – WHB Roof Leak (Dec 07)

  47. Problems –Roof Damage (May 08) • 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)

  48. Problems –Roof Damage (May 08)

  49. Problems – WHB Capacity • 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

  50. Problems – WHB Capacity

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