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Using Control for Adding ValueUsing Control for Adding Valueto Energy Efficiency of Mineralto Energy Efficiency of Mineral
Processing PlantsProcessing PlantsAndrAndr DesbiensDesbiens 11, Eduardo Nez, Eduardo Nez 11, Rene del Villar, Rene del Villar 22,,
DanielDaniel HodouinHodouin 22,, ricric PoulinPoulin 33
LOOP (Laboratoire dobservation et doptimisation des procds)LOOP (Laboratoire dobservation et doptimisation des procds)11 Department of Electrical and Computer EngineeringDepartment of Electrical and Computer Engineering
22 Department of Mining, Metallurgical and Materials EngineeringDepartment of Mining, Metallurgical and Materials Engineering
Universit Laval,Universit Laval, QuebecQuebec City,City, QuebecQuebec, Canada, Canada
33 Breton Banville etBreton Banville et assass..
MontMont--SaintSaint--HilaireHilaire, Quebec, Canada, Quebec, Canada
IntroductionIntroduction EnergyEnergyefficiencyefficiencyandand thethe mineralmineral processingprocessingplantsplants
ExampleExample ofofpressure forpressure for energyenergyeffciencyeffciency
TwoTwo approachesapproaches toto increaseincrease energyenergyefficiencyefficiency
OnOn--line dataline data processingprocessing
ProcessProcess observationobservation ProcessProcess controlcontrol
ProcessProcess optimizationoptimization
CaseCase studiesstudies ObservationObservation andand controlcontrol ofofaa grindinggrindingcircuitcircuit
ControlControl ofofaa grindinggrindingcircuitcircuit
Observation, control and optimization of electric arc furnacesObservation, control and optimization of electric arc furnaces
Optimization of anOptimization of an indurationinduration furnacefurnace
ConclusionConclusion
OUTLINEOUTLINE
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INTRODUCTIONINTRODUCTION -- EnergyEnergy efficiencyefficiency andandthethe mineralmineralprocessingprocessingplantsplants
Globalization
Environmentaland social
pressure forenergy efficiency
Energy costs
Internationalcompetition
Energy efficiency challengebecomes unavoidable.
Intensive
energyconsumers
Objectives:Reducing production costsIncreasing throughputIncreasing product quality
HydroHydro--Qubec:Qubec:
QuebecQuebec hydroelectricalhydroelectrical producer andproducer and
distributor.distributor.
Most extensive transmission systemMost extensive transmission systemin North America (32539 km).in North America (32539 km).
Pool up to 165Pool up to 165TWhTWh/year (93%/year (93%
hydroelectric).hydroelectric).
Offers financial assistance to largeOffers financial assistance to large--
power customers to reduce specificpower customers to reduce specific
energy consumption.energy consumption.
INTRODUCTIONINTRODUCTIONExampleExample ofofpressure forpressure for energyenergy effciencyeffciency
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INTRODUCTIONINTRODUCTIONExampleExample ofofpressure forpressure for energyenergy effciencyeffciency
First program:First program: Objective: to save 100Objective: to save 100 GWhGWh from 2003 to 2006.from 2003 to 2006.
Financial assistance budget: 8.5 M$.Financial assistance budget: 8.5 M$.
Customers must present their proposals.Customers must present their proposals.
They must agree to take measurements before andThey must agree to take measurements before andafter to show savings.after to show savings.
Payback period: 1 year.Payback period: 1 year.
Project completion: 18 months.Project completion: 18 months.
Customers must pay 25% of the total costs.Customers must pay 25% of the total costs.
INTRODUCTIONINTRODUCTIONExampleExample ofofpressure forpressure for energyenergy effciencyeffciency
Second program:Second program:
Financial assistance forFinancial assistance for
an energy consumption analysis at the industrialan energy consumption analysis at the industrial
site, orsite, or the demonstration that the firstthe demonstration that the first--timetime
implementation in Quebec of a new technologyimplementation in Quebec of a new technology
would result in energy savings.would result in energy savings.
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INTRODUCTIONINTRODUCTION -- TwoTwo approachesapproaches totoincreaseincrease energyenergy efficiencyefficiency
ApproachApproach 2:2:
OnOn--line dataline data processingprocessing:: judiciousjudicious onon--line useline use ofofprocessprocess sensorssensors andand largelarge operationoperation databasesdatabases..
ApproachApproach 1:1: ReplacingReplacingexistingexistingequipmentequipmentwithwith more efficientmore efficient
onesones..
InstallingInstallingnewnewequipmentequipment aimingaimingatat reducingreducing
specificspecific energyenergyconsumptionconsumption ofofexistingexistingprocessesprocesses..
ONON--LINE DATA PROCESSINGLINE DATA PROCESSING
Process
Actuators
Sensors
ObservationMeasurements
Quality
information
Control
Manipulatedvariables
Optimization
Setpoints
Knowledge aboutthe process
Knowledge aboutthe process
Measurements + knowledge = Possibility to automatically, continouslyand adequately manipulate actuators to achieve a specific objective.
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ONON--LINE DATA PROCESSINGLINE DATA PROCESSINGProcessProcess observationobservation
Process
Actuators
Sensors
ObservationMeasurements
Qualityinformation
Control
Manipulatedvariables
Optimization
Setpoints
ObservationMeasurements
Quality
information
ToTo seesee thethe processprocess states, tostates, to obtainobtain aa betterbetter picturepicture
ofofthethe processprocess.. ToTo detectdetect operationoperation problemsproblems,, abnormalabnormal
performances, etc.performances, etc.
ONON--LINE DATA PROCESSINGLINE DATA PROCESSINGProcessProcess observationobservation
FaultFault detectiondetection andand isolation:isolation:
RapidlyRapidlydetectdetect andand physicallyphysicallylocalizelocalize problemsproblems
suchsuch asas sensorsensor biaises,biaises, leaksleaks, etc., etc.
AllowAllowrapidrapid correctionscorrections reducingreducingbadbad
consequencesconsequences onon thethe production.production.
DataData reconciliationreconciliation::
ImprovesImproves thethe qualityqualityofofnoisynoisymeasurementsmeasurements..
MakesMakes themthem consistentconsistentwithwith processprocess knowledgeknowledge
suchsuch asas massmass andand energyenergyconservationconservation lawslaws..
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ONON--LINE DATA PROCESSINGLINE DATA PROCESSINGProcessProcess observationobservation
ObserversObservers::
SoftSoft sensorsensor algorithmsalgorithms..
TheyTheyinferinfer signalssignals thatthat cannotcannot bebe measuredmeasured..
TheThe availabilityavailabilityofofthesethese signalssignals cancan improveimprove thethe
plantplant operationoperation..
ProcessProcess observation:observation:
EvenEven ififnono automaticautomatic actions areactions are takentaken, a, a betterbettervisionvision allowsallows engineersengineers toto modifymodifyequipmentequipment oror
changechange operationoperationwhenwhen requiredrequired..
ONON--LINE DATA PROCESSINGLINE DATA PROCESSINGProcessProcess controlcontrol
Process
Actuators
Sensors
ObservationMeasurements
Qualityinformation
Control
Manipulatedvariables
Optimization
Setpoints
Manipulated
variables
Qualityinformation
Set
points
Control
ToTo maintainmaintain thethe measuredmeasuredvariablesvariables atat selectedselected setsetpoints bypoints byautomaticallyautomaticallyandand constinuouslyconstinuouslymanipulatingmanipulatingthethe actuatorsactuators..
MakesMakes useuse ofoffeedbackfeedbackandand feedforwardfeedforward..
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DisturbancesDisturbances ((suchsuch as changes inas changes in thethe oreorepropertiesproperties) must) must bebe quicklyquicklyrejectedrejected..
ProvidesProvides stabilizationstabilization aroundaround thethe set pointsset points andand aadecreasedecrease ofofthethe processprocessvariabilityvariability..
ONON--LINE DATA PROCESSINGLINE DATA PROCESSINGProcessProcess controlcontrol
Fineness
Duration
F
A
B
C
spAspB
spC
SmootherSmoother operationoperation..
LessLess costlycostlyoperationoperation ((eveneven ififset points areset points are notnot
changedchanged).).
ONON--LINE DATA PROCESSINGLINE DATA PROCESSINGProcessProcess optimizationoptimization
Process
Actuators
Sensors
ObservationMeasurements
Qualityinformation
Control
Manipulatedvariables
Optimization
SetpointsSet
points
Optimization
ToTo automaticallyautomaticallyselectselect thethe set points byset points byoptimizingoptimizingaa costcost functionfunction:: minimizationminimization ofofenergyenergyconsumptionconsumption,,
maximizingmaximizingprofits,profits,
etc.etc.
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ONON--LINE DATA PROCESSINGLINE DATA PROCESSINGProcessProcess optimizationoptimization
VeryVeryflexibleflexible tooltool:: SelectionSelection ofofthethe costcost functionfunction..
AdditionAddition ofofconstraintsconstraints suchsuch asas takingtakingintointo accountaccount
energyenergyconsumptionconsumption regulationsregulations..
ONON--LINE DATA PROCESSINGLINE DATA PROCESSING
AddedAddedvalues forvalues for energyenergysavingssavings..
ForFor severalseveral plants,plants, nono oror littlelittle newnewequipmentequipment
neededneeded..
SeveralSeveral additionaladditional benefitsbenefits::
BetterBetter knowledgeknowledge ofofthethe plant.plant.
ProductProduct qualityqualityrespectingrespectingmoremore oftenoften thethe specificationsspecifications..
ThroughputThroughput increaseincrease..
EasierEasier--toto--operateoperate plantplant thusthus more effective usemore effective use ofof
personnel.personnel.
DecreaseDecrease inin thethe maintenancemaintenance costscosts..
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ONON--LINE DATA PROCESSINGLINE DATA PROCESSING
EnergyEnergysavingssavings areare oftenoften underestimatedunderestimated becausebecausethethe plantplant unitsunits areare consideredconsidered separatelyseparately..
ExampleExample:: thethe optimizationoptimization ofofaa flotationflotation plantplant
DoesDoes notnot procureprocure anyanyrealreal energyenergysavingssavings..
May have importantMay have important energeticenergetic impacts onimpacts on subsequentsubsequent
processingprocessing((mealmeal extractionextraction andand smeltingsmelting).).
PlantPlantwisewise evaluationevaluation shouldshould bebe performedperformed
((howeverhowever, a, a difficultdifficult tasktask).).
Water
Pumpbox
Ball mill
Feed
Rod mill
Water
CASE STUDIESCASE STUDIES -- ObservationObservation andandcontrolcontrol ofofaa grindinggrinding circuitcircuit
Kidd CreekKidd Creekgrindinggrinding circuit control:circuit control:
Objectives (noneObjectives (none relatedrelated toto energyenergy):):
IncreaseIncrease plantplant throughputthroughput ((notnot an issue 2an issue 2 yearsyears laterlater).).
PreventPrevent pumppump boxbox levellevel andand cyclonecyclone overflowoverflowdensitydensityupsetsupsets..
StabilizeStabilize
productproduct qualityquality..
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CASE STUDIESCASE STUDIES -- ObservationObservation andandcontrolcontrol ofofaa grindinggrinding circuitcircuit
DesignDesign basedbased on aon a phenomenologicalphenomenological simulatorsimulator((DynafragDynafrag).).
DynafragDynafragrequiredrequired toto bebe calibratedcalibrated: 3: 3 samplingsamplingcampainscampains..
Data reconciliation revealed some abnormalData reconciliation revealed some abnormaloperating conditions such as extremely high milloperating conditions such as extremely high millcirculating load ratios (CLR) (around 1800%).circulating load ratios (CLR) (around 1800%).
1800% CLR: 36501800% CLR: 3650 t/ht/h of pulp at the cyclone feedof pulp at the cyclone feed(250 HP for pumping)(250 HP for pumping)
500% CLR: 1154500% CLR: 1154 t/ht/h of pulp at the cyclone feedof pulp at the cyclone feed(55 HP for pumping)(55 HP for pumping)
1800% CLR: a pulp residence time within the mill1800% CLR: a pulp residence time within the mill
of about 0.5 minute.of about 0.5 minute.
500% CLR: 2 min residence time.500% CLR: 2 min residence time.
In other words: a lot more energy was spent inIn other words: a lot more energy was spent in
pumping a huge circulating load to achieve verypumping a huge circulating load to achieve very
little grinding.little grinding.
CASE STUDIESCASE STUDIES -- ObservationObservation andandcontrolcontrol ofofaa grindinggrinding circuitcircuit
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FTWater
FC
LT
LC
Pump box
Ball mill
SP
SP
DC
SP
Feed
Water
SC
WT
M
RFC
FT
SPSP
Rod mill
DT
DT
DC
SP
Because of equipment and objectives changes, difficult toBecause of equipment and objectives changes, difficult to
quantify the energetic and metallurgical improvements.quantify the energetic and metallurgical improvements.
Total costs: around 0.2 M$.Total costs: around 0.2 M$.
Revenue improvements: conservativelyRevenue improvements: conservatively
estimated to 1 M$/annum.estimated to 1 M$/annum.
CASE STUDIESCASE STUDIES -- ObservationObservation andandcontrolcontrol ofofaa grindinggrinding circuitcircuit
CASE STUDIESCASE STUDIESControlControl ofofaa grindinggrinding circuitcircuit
ToquepalaToquepala grindinggrinding circuit control:circuit control:
The rodThe rod--mill discharge is distributed to 3 parallel ballmill discharge is distributed to 3 parallel ball--
mills using a threemills using a three--way splitter.way splitter.
The operator decides the splitter palettes position.The operator decides the splitter palettes position.
Level of 3 sump boxesLevel of 3 sump boxes
controlled withcontrolled with
variable speed pumps.variable speed pumps.
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CASE STUDIESCASE STUDIESControlControl ofofaa grindinggrinding circuitcircuit
Results:Results:
Better stability of the circuit operation, particularly of theBetter stability of the circuit operation, particularly of thethree ball mills.three ball mills.
Tonnage increase from 245.7Tonnage increase from 245.7 t/ht/h to 253.6to 253.6 t/ht/h (2 % to 4%).(2 % to 4%).
Slightly finer product.Slightly finer product.
Reduction inReduction in monthly energy consumption from 1607750 kWh to 1528797 kWh.monthly energy consumption from 1607750 kWh to 1528797 kWh.
specific energy from 9.20 kWh/t to 8.42 kW/t (8% to 10%specific energy from 9.20 kWh/t to 8.42 kW/t (8% to 10%decrease).decrease).
A greater availability of operators.A greater availability of operators.
Total gains/year : 4.9 M$Total gains/year : 4.9 M$ If applied to the 8 lines of the concentrator: savings wouldIf applied to the 8 lines of the concentrator: savings would
be 8 x 900000 kWh/year.be 8 x 900000 kWh/year.
CASE STUDIESCASE STUDIES -- Observation, control andObservation, control andoptimization of electric arc furnacesoptimization of electric arc furnaces
Electric arc furnaces:Electric arc furnaces:
Consume a large amount of energy in ferroalloy and steelConsume a large amount of energy in ferroalloy and steel
industries.industries.
No direct measurement of how the energy is used inside theNo direct measurement of how the energy is used inside the
furnace is made.furnace is made. OnOn--line information about the internalline information about the internal behaviorbehavior of the furnace:of the furnace:
the arc signature (voltagethe arc signature (voltage--current characteristic at the tip of thecurrent characteristic at the tip of the
electrode).electrode).
Observation of the arc signature gives the possibility to inferObservation of the arc signature gives the possibility to infer
strategic variables such as length, stability, symmetry, dynamicstrategic variables such as length, stability, symmetry, dynamic
resistance and power dissipation of the arc.resistance and power dissipation of the arc.
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CASE STUDIESCASE STUDIES -- Observation, control andObservation, control andoptimization of electric arc furnacesoptimization of electric arc furnaces
Objectives:Objectives: Optimization of the energy usage.Optimization of the energy usage.
Reduction of the production costs.Reduction of the production costs.
Arc signature system combined to control have been testedArc signature system combined to control have been testedand installed on submerged arc furnaces and long arc furnacesand installed on submerged arc furnaces and long arc furnaceswith foamy slag.with foamy slag.
Typical results for submerged arc furnaces:Typical results for submerged arc furnaces: 5 % reduction of the specific consumption (5 % reduction of the specific consumption (MWh/tMWh/t).).
Increase of operating power and thus 25% increase of the productIncrease of operating power and thus 25% increase of the productionionrate.rate.
30% reduction in the amount of corrective loads to stabilize the30% reduction in the amount of corrective loads to stabilize thefurnace.furnace.
The signature is used to support operation, anticipate and preveThe signature is used to support operation, anticipate and preventntproblematic situations.problematic situations.
CASE STUDIESCASE STUDIESOptimization of anOptimization of an indurationinduration furnacefurnace
IndurationInduration furnace:furnace:
PC
V3
V2
V1
P6
P
P4
P2 P1
P0
T8 T7 T6
T4T5 T2 T1
T
Fm,PC Fm ,C2Fm,C1
Fp
T10
T3
T9
V4
P5
P
V5
P7 P3
P T
T11
T12
ogT
opT
UD DD Cooking 1 Cooling 2Cooling 1Cooking 2PC
V3
V2
V1
P6
Pi
P4
P2 P1
P0
T8 T7 T6
T4T5 T2 T1
Ti
Fm,PC FmFm
F
T10
T3
T9
V4
P5
Pi
V5
P7 P3
Z
Pi T i
T11
T12
gT
T
igFgF
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CASE STUDIESCASE STUDIESOptimization of anOptimization of an indurationinduration furnacefurnace
Optimization criterion must reflect precisely the producer objeOptimization criterion must reflect precisely the producer objectives:ctives:
to maximize the net revenue, i.e. the product value minus theto maximize the net revenue, i.e. the product value minus theproduction costs; may lead to a minimization of the total consumproduction costs; may lead to a minimization of the total consumededenergy, but not necessarily.energy, but not necessarily.
to maximize the production rate at constant energy consumption;to maximize the production rate at constant energy consumption;leads to the minimum energy consumption per ton of pellet producleads to the minimum energy consumption per ton of pellet produced,ed,but not to the minimal total energy consumption.but not to the minimal total energy consumption.
to maximize the product quality (to increase the product value)to maximize the product quality (to increase the product value) atatconstant production rate; will not be optimal for energy consumpconstant production rate; will not be optimal for energy consumption,tion,except if the total energy consumption is constrained at a predeexcept if the total energy consumption is constrained at a predefinedfinedvalue.value.
to find, at constant production rate and product quality, theto find, at constant production rate and product quality, thedistribution of consumed energy between the coke addition, the tdistribution of consumed energy between the coke addition, the threehreeburner zones and the five fans, which minimized the energy cost.burner zones and the five fans, which minimized the energy cost.
etc.etc.
CASE STUDIESCASE STUDIESOptimization of anOptimization of an indurationinduration furnacefurnace
the total energy per ton of product does not much varythe total energy per ton of product does not much vary
the total fuel consumption can widely varythe total fuel consumption can widely vary
the maximum profit (run 7) is not necessarily a goodthe maximum profit (run 7) is not necessarily a goodcriterion to maximize energy efficiencycriterion to maximize energy efficiency
111105100101103110108Normalized profits ($)
100.9101.3100.7100.6100101.0100.5Energy index per ton
0.8180.6740.8200.8200.8580.8200.820Total fuel (kg/s)
110103100101104109107Production rate index0, 5, 950, 6, 940, 5, 954, 10, 860,13, 870, 5, 954, 10, 86Fuel (%) at PC, C1, C2
ConstrConstrMaxMaxMaxConstrConstrPellet quality
OptOptOptNomOptOptNomFuel distribution
OptMinNomNomOptNomNomFuel consumption
OptNomOptOptNomMaxMaxProduction rate
7654321Simulation run
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CONCLUSIONCONCLUSION
ProcessProcess observation, controlobservation, control andand optimizationoptimization:: increaseincrease thethe energyenergyefficiencyefficiency,,
provideprovide severalseveral additionaladditional benefitsbenefits,,
oftenoften requirerequire nono oror littlelittle newnewequipmentequipment..
ThroughThrough thethe implementationimplementation,, thethe plant personnelplant personnelwillwill
mostmost likelylikelydiscoverdiscover problemsproblemswithwith equipmentequipment oror
operationoperation..
Thank you!
11th IFAC Symposium on
Automation in MMM Processing
2007
Qubec City, Canada