a new toolbox for optimising converter aisle operation … · a new toolbox for optimising...
TRANSCRIPT
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A New Toolbox for Optimising Converter Aisle Operation
Pascal Coursol and Phillip Mackey Consultants-Extractive Metallurgy
Xstrata Process Support
Presented at the Copper 2010 ConferenceJune 8th, Hamburg, Germany
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Presentation Outline
• How were Peirce Smith converters operated/controlled in period 1920-1990
• Development of new tools in the last 20 years
– Process Modelling Tools
– Process control Tools
• How far can we go with Peirce Smith converters ??
– Further improvements possible
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How were Peirce Smith converters operated/controlled in period 1920-1990
• Visual end point detection (flame) from earliest times
• Systematic air flow and temperature measurements 1950s onwards
• Gaspé puncher 1960s, higher matte grades, concentrate injection
• Some control on flux addition-still variable, poor slag control
• Introduction of primary and secondary hooding (SO2 recovery)
• Mass and energy balance modeling
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Modern Modeling Tools
• Slag Chemistry Modelling (Factsage)
– Slag Liquidus, optimal %Fe/SiO2 ratio and temperature...
• Flowsheet Analysis (METSIM)
– Heat and mass balance
– Minor element deportment
– Blow by Blow Modelling (METSIM)
Minimise metal losses in slag
Optimise heat balance
Process more reverts
• Logistics/scheduling (ARENA)
– Consider maintenance and equipment availability, personnel as regards plant capacity calculations
• Finite element modelling
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Slag Chemistry Modeling
• Find optimal operating conditions (%Fe/SiO2, T, %O2)
• Impact of minor components in converting flux (CaO, Al2O3, MgO...)
Modelling tools are useful to perform slag chemistry
calculations and better understand the converters slag
chemistry
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Factsage SoftwareSlag Chemistry ModelingImpact of %Fe/SiO2
1150
1175
1200
1225
1250
1275
1300
1325
1350
0.7 0.9 1.1 1.3 1.5 1.7 1.9
%Fe/SiO2 in Slag
Tem
pera
ture
(0C
)
Liquid
Slag
Liquid +
Spinel
Liquid
+Silica
Impact of the %Fe/SiO2 in Slag on Slag Liquidus ([Cu]matte=68%, [Fe]matte=6.8%,
[ZnO]slag=4.0%, [CaO]slag=3.3%, [Al2O3]slag=2.0%, [MgO]slag=0.8%, P(SO2)=0.25;
the open star indicates present operating conditions)
Similar graphs can
be prepared for
each blow and
considering minor
slag components.
Optimal operating
conditions can be
deduced.
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Slag Chemistry ModelingImpact of %CaO in Slag (Factsage)
Impact of %CaO on the Copper blow slag liquidus. (5% Al2O3, 3.5% ZnO, 1%MgO, 7.5%PbO,
and p(SO2)=0.25 atm). The star indicates approximate present operating conditions at site.
CaO “robs” the SiO2
and raises the
magnetite liquidus
CaO + 2SiO2 =
Ca2SiO4
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Flowsheet Modeling-METSIM
• Impact of changing operating conditions in converters and smelting furnace
– Matte grade
– Furnace %Fe/SiO2
– Oxygen enrichment
– Dust Recycling
– Reverts recirculation
– ...
• Techno-economical evaluations can be performed directly in METSIM or on an EXCEL sheet where the METSIM data are exported
• Other similar softwares are available (HSC, Aspen,..)
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Flowsheet Illustration for Isasmelt + PS Converting + Slag Cleaning
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Converter Blow by Blow Analysis-METSIM
Parameters to optimize in a blow sequence
• Amount of matte in each blow (tonnes)
• Amount of reverts or recyclable per blow (tonnes)
• Coke rate (tonnes) and oxygen enrichment (%)
• Specific blowing rate for each blow (Nm3/tonne)
• Silica flux added at each blow (target %Fe/SiO2)
• Magnetite level in slag
• ...
From a simple mass balance model and from basic plant
data, it is reasonably easy to optimise the blowing sequence
for converters.
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Converter Blow by Blow Analysis METSIM Steady State (3 blows, heat losses distributed between blows)
Air+
O2
Air+
O2
Air+
O2
Blow 1
Blow 2
Blow 3
Matte 1st blow
+ slag left
Matte 2nd blow
+ slag left
Matte from smelting unit
Flux, coke, reverts
Flux, coke, reverts
Flux, coke. reverts
Blister Copper
to Anode
Furnaces
Recyclable Materials
Slag 3rd blow
Slag to slag
cleaning
process
Slag 3rd blow
Slag 3rd blow
Sla
g 2
nd
blo
w
Slag 2nd blow
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Scheduling Aspects of a Converter Aisle
• Some factors influencing converter aisle and smelter capacities
• Scheduled/unscheduled maintenance
• Cranes, acid plant, oxygen plant…
• Matte availability (smelting unit reliability)
• Shift change (operators)
• Blowing rates, oxygen enrichment
• Casting wheel preparation time
• Vessel availability (relining),…
The plant processing steps need to be coordinated in order to
reach the maximal capacity.
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Sudbury Smelter Capacity Project (ARENA scheduling model)
Capacity study to go from 66ktpy Nickel to 85
ktpy. Debottlenecking study with the ARENA
software to confirm a viable solutionThe solution to reach
85ktpy was found to
be a combination of
the following
parameters:
•Increased slag
cleaner capacity
•Increased converter
blowing rate
•Increased matte
granulation capacity
Screen Shot of the Sudbury Smelter ARENA Model
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Horne Smelter Capacity Project (ARENA Model)
Screen Shot of the Horne Smelter ARENA Model
Study to increase copper capacity from 180ktpy
to over 200ktpy. Debottlenecking study with the
ARENA software to confirm a viable solution.
The solution to reach
200+ktpy was found to
be a combination of the
following parameters:
•Reduced preparation
time casting wheel
•Variable casting rate to
“piggy back” a new
anode charge on the one
casting
•Number and
availability of operating
vessels identified
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Finite Element Modelling (Converters, slag cleaner, Anode furnace, casting,...)
• Modeling of PSCs and Anode furnaces
• Burner selection/optimization
• Feed entrainment in freeboard
• Tap hole design to minimize entrainment of matte in slag during tapping (diameter, slag/matte levels,…)
• Selection of correct lining materials (thermal profile, heat flux calculations)
• Mechanical stress and impact of thermal expansion during start-up (refractory spacers)
• Environmental Aspects
• Stack dispersion and in-plant hygiene
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Finite Element Modelling-Velocity fields in a smelting/converting vessel
Variable velocity
fields inside a
smelting/converting
vessels can lead to
solid entrainment
and localized hot
spots .
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Process Control ToolsSome suggestions….
The following are considered important in maximizing the performance of converters
1. Matte grade control in smelting furnace
2. Fe/SiO2 control in converter slag
3. %Fe in matte at the end of each blow
4. Level of magnetite in slag
5. Slag or matte temperature
Optimal conditions can be identified with the models, but an adequate control strategy is required in order to reach these conditions.
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Matte Grade Control in Smelting furnaces
• Feed blending to reduce variability at the smelting furnace
• Good matte sampling and frequent analysis of the %Fe in matte
• Correction of matte and slag assays for entrainment (e.g. correction to remove the %Fe in matte related to entrained slag)
• Adjust O2 enrichment and/or coke addition to correct the smelting furnace temperature rather than changing the %Fe in matte
Constant matte grade to the converter aisle will facilitate optimization of the converters
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%Fe/SiO2 Control in Converters
• Optimal slag conditions depend strongly on the accuracy of the flux addition in the converters.
• Batch addition vs continuous addition
• Accuracy, reproducibility
• Proper Flux Selection
• Minor gangue components (MgO, Na2O, CaO, Al2O3,…) tend to increase the flux requirements, but may enhance smeltability.
• Size distribution impacts smeltability and carryover
• In cases where the heat balance need to be satisfied, lowering the flux to improve the heat balance may not be the best solution
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%Fe in Matte at the End of Each Blow
• Many factors affect slag quality and metal losses in a converter cycle. It is better to control all the inputs to reach a better performance.
• Matte grade from the smelting unit
• Accuracy on added materials (flux, slag, reverts,..)
• Slag left in the vessel after each blow
• Air leakage at the tuyeres.
• There are control tools to maintain performance even when the feed is variable.
• Example: SEMTECH instrumentation-tracking of trace components (PbS, PbO and CuOH) in the converter off-gas and temperature.
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PbS increases immediately upon start of cycle: Rapid fayalite formation, minimized magnetite formation.
Very high PbO and CuOH, PbS decreases to zero: Spinel formation, increased foaming risk.
Addition of fresh matte: Slag recovers, cycle terminated properly.
Converter Cycle (SEMTECH)
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Smelter Year Number and Type of FurnaceDegerfors Jernverk 1990 1 Alloy steel converter
Boliden Mineral 1994 3 PS Copper converter
Norddeutsche Affinerie 1994 2 PS Copper-Lead converter
(Phelps Dodge Hidalgo 1996 3 PS Copper converter; Smelter shut down)
Norddeutsche Affinerie 1997 3 PS Copper converter
Chuquicamata 1998 4 PS Copper cvonverter
Norddeutsche Affinerie 2000 2 Anode furnace
(Hüttenwerke Kayser 2000 2 PS Scrap recycling converter; Furnaces shut down)
Mount Isa 2002 4 PS Copper converter; OPC not in use)
Boliden Harjavalta 2004 4 PS Copper converter
Atlantic Copper 2004 4 PS Copper converter
Onahama Smelting 2006 5 PS Copper converter
(Thai Copper 2006 3 Hoboken copper converter; Smelter shut down)
La Caridad 2007 3 PS Copper converter
Southern Peru Copper 2007 4 PS Copper converter
Cumerio 2007 3 PS Copper converter
Tamano 2007 3 PS Copper converter
Doe Run 2008 2 PS Copper converter
Lonmin 2009 3 PS Copper-Nickel-PGM converter
Kazzinc 2010 2 PS Copper converter
Toyo 2010 4 PS Copper converter
Xstrata Falconbridge 2010 2 PS Copper-Nickel converter
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Process Control Tools-Modern Tools
• Magnetite analyzer (Satmagan) to obtain magnetite level in slag after each blow
• Portable X-Ray analyzer for rapid determination of the %Fe in Matte and %Fe/SiO2 in slag
• Slag/matte temperatures
• Tuyere pyrometer available for matte temperature
• Optical pyrometer can be installed in Converter Hoods
• Oxygen enrichment and coke/fuel addition used to obtain the proper end-point temperature
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How far can we go with the Peirce-Smith Converters ?
• Further improvements are possible in PSC operation
• Slag chemistry and impact of minor components on magnetite formation and Cu losses
• Optimal cycle to maximize slag cleaning and reverts processing during PSC cycles
• Good process control (Flux, %Fe matte, SEMTECH(end point),%Fe3O4 slag (Satmagan),..)
• Limitation compared to continuous converting
• PSCs require matte and slag transfer by ladles and emissions are harder to control
• Continuous converters can allow a better energy efficiency (heat losses per ton of anode Cu)