Isasmelt concept

Document Sample
Isasmelt concept Powered By Docstoc
					SMELTER START UP OF NEW ISA FURNACE
      AND PROGRESS TO DATE




  Mopani Copper Mines
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 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)
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.
          OldElectric Furnace failed during Isasmelt
           commissioning
      Exporting concentrates difficult due to transport
       constraints
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.
 PROJECT DESCRIPTION
                                                                                                                    Equipment Legend
                                                                                                                                              -
                                                                                                                                Smelter Upgrade Phase1

                     MCM                             Sulphuric Acid Plant      Tail gas to
                  Concentrators                          (1150tpd)            Atmosphere                                                      -
                                                                                                                                Smelter Upgrade Phase2
                                                                                                      Offgas to
                                                                                                     Atmosphere



                   Concentrate                             Offgas
                                            Diesel                                           Coke

                                                                                                                               Discard slag
                                                                                                                                   to
                                                                                                                                  Dump
                                   Cons   ,
  Purchased
 concentrate,
                  Concentrate     reverts   ,         Isasmelt furnace      Matte,            Matte Settling
                   storage          flux,               (850
                                                           ,000tpa)         Slag             Electric Furnace
coal and fluxes
                                    coal




                                                          Oxygen                             Matte     Slag

                                                                                                                    Offgas
                                                                                                                      to
                                                                                                                  Atmosphere
                                                       Oxygen Plant                                                                Fire Refining and
                                                        (650tpd)                            PS Converters                              Casting
                                                                                                                     Blister
                                                                                                    )4
                                                                                         (upgrade fromto 5                              2          ,
                                                                                                                                 (install x 400t AFs
                                                                                                                                                   )
                                                                                                                                 80 tph casting wheel
                                    Reverts



                                                                                                                                      Anode Copper
                                                                                                                                          to
                                                                                                                                        Refinery
Post-combustion air (N2, O2)
                                      Oxygen (O2)                  ISASMELT
Offgas                                Air (N2,O2)                  CONCEPT
(CO2,SO2,H2O,N2)                      Diesel / Fuel Oil       Concentrates
                               Slag box                       (CuFeS2,Cu2S,CuCO3.(OH)X,
                                                              FeS2,SiO2, and others . . .)
                                                              Flux (SiO2,CaCO3)
                                                              Coal (C,CH4)

   Slag                                                       Water (H2O)
   Coating                                        Smelting reactions
                                                  CuFeS2 + O2  Cu-Fe-S + FeO + SO2

    ISASMELT                                      (FeS + 3Fe3O4  10FeO + SO2)
    Lance                                         FeS2 + 5/2O2     FeO + 2SO2
                                                  2FeO + SiO2  2FeO.SiO2
                                     Matte +
                                     Slag
     ISASMELT                                                                 Slag
     Furnace

                   Matte-Settling
                   Electric                                                  Granulation
                   Furnace                Matte                              water
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
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)

          mix
     Don’t Hopper up feed materials!
                        CV121   CV123   CV124

  Front End                                     CV134 (Shuttle)
    Loader

                                        Cons    Flux
                                                       Coal   Reverts
                                        (x4)    (x2)
         Stockpiles

                                                 To Furnace
PLANT DESCRIPTION - FEED PREPARATION
                          Feed bin building
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.Con Con Reverts Coal Flux Flux
   Con   Con                                      ESP
  BN108 BN109 BN115 BN116 BN113 BN112 BN111 BN110 Dust
  Reverts, Coal and Flux bins have 2
   conveyors to measure accurately at low
     CV125   CV126   CV135   CV136   CV140           CV139           CV138           CV137


   rates.                                    CV130           CV129           CV128           CV127



                                     CV131
                                                                              To furnace
PLANT DESCRIPTION - FEED PREPARATION
Cons feeders              Flux, Reverts and
(x4)                      Coal feeders
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
                                                                 Coal reduction
                   For unsuitable feed materials                      bin

                                                             CV701
       CV131           Paddle mixer      CV133
     (mixed feed)                                           Retractable &
                                                             Reversible

                                                               Isasmelt
                                                   Bypass
                                                                furnace
                            CV132                  bunker
PLANT DESCRIPTION – ISASMELT FURNACE

   Furnace refractory:
       13.3 m tall
       4.4 m internal diameter
                                           13.3 m
       450 mm Cr-Mg (in most areas)
       100 mm insulation brick
   Roof
       Boiler tubes (part of WHB)
       Openings:
           Feed chute
           Lance
           Holding burner
           Offgas                            4.4 m
   Copper blocks
       Splash block
       Tapping blocks (inner and outer)
PLANT DESCRIPTION – ISASMELT FURNACE
  Feed chute                Lance port


                                Holding
                                burner port




   WHB




   Splash block
PLANT DESCRIPTION – ISASMELT FURNACE
  Feed chute                  Slag box
                              (Lance port)




                             Holding
                             burner port
PLANT DESCRIPTION – ISASMELT FURNACE
  Feed chute                Lance port


                                Holding
                                burner port




      Isasmelt
      furnace
PLANT DESCRIPTION – ISASMELT LANCE
   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 TAPPING
 Tapping machine
 rails




                      Bend      Head
                      section   section
                                              Shaft 1    Shaft 2


PLANT DESCRIPTION – OFFGAS

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




                                                Gas
                 Furnace roof                   cooler
                                                sprays
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.
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
MATTE SETTLING ELECTRIC FURNACE
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
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)
CONCENTRATE TREATMENT FROM START UP
REVERTS TREATMENT FROM STARTUP
                                                                                                                                                                                    Oct-08
                                                                                                                                                                                    Sep-08
                                                                                                                                                        Rebrick                     Aug-08
                                                                                                                                                                                    Jul-08
                                                                                                                                                                                    Jun-08
                                                                                                                                            O2 plant compressor                     May-08
                                                                                                                                                                                    Apr-08
                                                                                                                                            Circ pumps, grab, electrodes            Mar-08
                                                                                                                                                                                    Feb-08
                     Isasmelt Operating Time




                                                                                                                                                     Power failure, SAP Pumps       Jan-08
                                                                                                                                                     Isasmelt roof leak             Dec-07
                                                                                                                                                                                    Nov-07
                                                                                                             No venting




                                                                                                                                                                                    Oct-07
                                                 Operating time - without aisle and power constraints
PLANT AVAILABILITY




                                                                                                                                                                                    Sep-07
                                                                                                                                                                                    Aug-07
                                                                                                                                                                                    Jul-07
                                                                                                                                                                                    Jun-07
                                                                                                                                                                                    May-07
                                                                                                                                                                                    Apr-07
                                                 Overall operating time

                                                                                                                                                                                    Mar-07
                                                                                                                                                                                    Feb-07
                                                                                                                                                                                    Jan-07
                                                                                                                                                                                    Dec-06
                                                                                                                                                                                    Nov-06




                                               100


                                                                                                        90


                                                                                                                   80


                                                                                                                          70


                                                                                                                                60


                                                                                                                                       50


                                                                                                                                                40


                                                                                                                                                          30


                                                                                                                                                                  20


                                                                                                                                                                           10


                                                                                                                                                                                0
                                                                                                                               % of total time
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
ISASMELT REBRICK – WEAR PROFILE
ISASMELT REBRICK
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
SPLASH BLOCK PERFORMANCE
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)
MSEF REBRICK – WEAR PROFILE
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
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)
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
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
PROBLEMS – ESP DAMAGE
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)
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)
PROBLEMS – POST COMBUSTION
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
PROBLEMS – WHB LEAK (MAY 07)
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)
PROBLEMS – WHB ROOF LEAK (DEC 07)
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)
PROBLEMS –ROOF DAMAGE (MAY 08)
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
PROBLEMS – WHB CAPACITY
                                                                            Blow off to
                                                                           atmosphere
                            Air Cooled Condenser



                                                                               Blow off valve


               Condensate                          Steam




                                   Steam Drum




Makeup water



                                                           Heat surfaces
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.
SMELTER PROJECTS
   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.
THANK YOU

				
DOCUMENT INFO
Shared By:
Categories:
Stats:
views:406
posted:5/3/2011
language:English
pages:53