Presentation is loading. Please wait.

Presentation is loading. Please wait.

Smelter start up of new ISA furnace and progress to date

Similar presentations

Presentation on theme: "Smelter start up of new ISA furnace and progress to date"— Presentation transcript:

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

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 36 MVA Electric Furnace, 4 PS Converters 4 Anode Furnaces, 2 Casting Wheels 2006-Present Isasmelt Furnace, 12 MVA Slag cleaning furnace 5 x PS Converters, 2 x 400 tonnes Anode furnace, 1 x twin casting wheel(commissioned in March 2009) 1937 – Final production was blister

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 Project Description Equipment Legend MCM Concentrators Concentrate
storage Sulphuric Acid Plant ( 1150 tpd ) Isasmelt furnace 850 , 000 tpa Oxygen Plant 650 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 Purchased concentrate coal and fluxes Cons reverts flux coal Offgas Coke Oxygen Matte Reverts Slag Blister Tail gas to Atmosphere Anode Copper Refinery Discard slag Dump Diesel Offgas to Equipment Legend Smelter Upgrade - Phase 1

6 ISASMELT CONCEPT Slag Coating Smelting reactions ISASMELT Lance
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 Plant Description - Feed Preparation
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

8 Plant Description - Feed Preparation
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!

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

10 Plant Description - Feed Preparation
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.

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

12 Plant Description - Feed Preparation
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

13 Plant Description – Isasmelt Furnace
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

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 Plant Description – Isasmelt 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)

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

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

20 Plant Description – Offgas
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.

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 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

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 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 Cu – 32 Fe – 22 S – 29 SiO2 - 7

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 oC 56-58% Cu in matte 0.8 SiO2:Fe 8% Fe3O4 in slag MSEF Products Matte % Cu (1180 oC) Slag 0.7% Cu (1250 oC)

25 Concentrate treatment from start up

26 Reverts treatment from startup

27 Plant Availability Rebrick No venting Sept+ No venting
December – WHB roof leak January – WHB pumps, Nation wide power failures March – Circ pumps, Grab failures, Electrode Hydraulic Problems, May – O2 compressor failure August - Rebrick Circ pumps, grab, electrodes O2 plant compressor Isasmelt roof leak Power failure, SAP Pumps Rebrick

28 Isasmelt Rebrick General Wear control 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 Wear control
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 Accretions
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 Rebuild Post Rebuild
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)
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)
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 days (including reheating furnace)

46 Problems – WHB Roof Leak (Dec 07)

47 Problems –Roof Damage (May 08)
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
WHB design exit temperature 700 oC Actual exit temperature 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

51 Problems – WHB Capacity
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.

52 Smelter Projects HFO Conversion Aisle debottlenecking
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.


Download ppt "Smelter start up of new ISA furnace and progress to date"

Similar presentations

Ads by Google