Hot metal flow scheduling
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Transcript of Hot metal flow scheduling
Hot-metal flow SchedulingSébastien MouthuyMay, 2015
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Summary
•Steel-making process•Hot-metal flow•Hybrid solution to the HMF•Challenges•Future
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Steel-making process
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Steel-making process
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Hot-metal flow
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Hot-metal flow
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Steel-making process: Blast furnaces> Alternated Mix of coke and Iron
Ore> Coke provides heat to melt Iron
Ore
> BF produces hot-metal with> A given temperature> A given chemical content:
> S, Si, Mn and P
> A lot of inertia
> Hot-metal is poured into torpedo cars
> Alternating through tapping holes
> 2 lanes per tapping hole
> Torpedoes have to be on time under BF!!!
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Steel-making process: O2 converters> Mix Hot-metal and scraps
> Pressurize O2 in order to remove C content from Hot metal
> Schedule set by another process> Quantity of Hot-metal> Maximum sulfur content> Time of rendez-vous
> 204t with Smax= 9‰ at 11:23am> 215t with Smax= 3‰ at 11:45am> 224t with Smax= 5‰ at 12:05am> …
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Steel-making process: Desulfurization
CaD
> Adding a desulfurizing agent in the torpedo
> Precipitation of sulfur by adding calcium sulfice
> Desulfurization equation linking> Quantity of HM in torpedo> CaD flow into torpedo> Initial sulfur (from BF)> Target sulfur
> Highly non-linear desulfurization equation
> 2 desulfurization stations available
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Steel-making process
•Cleaning of the TC▫Remove sulfur that would remain at the top of the
torpedo car▫At least once in every N rotations▫At most once in every M rotations
•Emergency pit▫Used when Steel Making shop does not consume as
much HM as BF are producing▫Only way to free a torpedo to get back under the BF▫Only one torpedo at the EP at a time
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Steel-making process: Pouring> 2 pits at the Steel making shop> 2x2 lanes
> 1 torpedo pouring at a time
> Torpedo cars and ladles have different capacity: 3/2 ratio
> A torpedo car can pour into max 3 ladles
> A ladle can be filled by at most 2 torpedo cars
> Mix !!!
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Hot-metal flow
> 3 BF, 8 tapping holes> >15 torpedoes> 2 desulf stations> 2 pits> 4 ladles> 3 converters> 3 locomotives
> …and many more business constraints
GOAL: MITIGATE RISK AND INCREASE PRODUCTIVITY
Our solution aims to mitigate risk and increase productivity of equipment, thanks to industry expertise and advanced mathematical modeling techniques
RISKMITIGATION+INCREASED PRODUCTIVITY
INTEGRATED
MODELING OF HOT METAL FLOWS
FROM A 2-HOUR TO A 8-
HOUR HORIZON
> Emergency pit use minimization: reduce waste by knowing evolution in time
> Less over-desulfuration
> Planning maintenance of tools correctly
> Improved communication
> Better use of resources: increasing use of cleaning stations (torpedos, ladles), desulfuration stations
> Flux minimization by optimal blending from torpedo to ladle
> Minimization of thermal losses
HYBRID SOLUTIONOur HMF optimizer is used as a real-time operational tool, taking all operational constraints into account to determine optimal HMF planning for the next 8 hours
Steel production planning Blast furnace prediction Localization of torpedos and ladles Quantity and quality of HM in each torpedo
and ladle Status of torpedos: cleaniness Status of ladles: cleanliness Unavailabilities of the tools
Planning of the all the tools for next 8 hours
Quantity of HM in torpedos for next 8 hours
Target sulfur for all torpedos, to minimize flux usage
Availability of torpedos over time
INPUTS
Moves of torpedos and ladles+ Complex moves of torpedos (2 torpedos per locomotive at desulfuration)
Desulfuration equation (non-linear) Cleaning of torpedos (e.g. 1 cleaning
out of 5 cycles) Variable numbers of locos over time …
OUTPUTS
Varia
bles
Ope
ratio
nal
cons
trai
nts
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Demo
•Main result of the solution
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Hybrid solution in OscaR• Constraint programming model▫Priority is given to finding a solution▫Easily state combinatorial operational constraints▫High scheduling components▫Sometimes data is invalid need for proving or explaining
infeasibility
• Search heuristics▫Highly based on business knowledge we got through interviews▫Based on LP, clustering algos
•Optimization▫Using LNS: easy when you have model and search
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CP Model
•Designing jobs with consecutive or collated activities and posting redundant constraints was key
Complex model1. All activities of a torpedo have to be collated2. Some activities are optional, other are mandatory
if the job is performed
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Search heuristics
•Constraint programming model•Search heuristics:
many different kind of decisions:▫Mix▫Emergency pit▫Desulfurization setup▫Assignment of the torpedoes▫Start times of the activities
• Learn how to find a good solution through interviews with operators
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Search heuristics
•When to take non-scheduling – and important – decisions ?▫At first ? Then there is a risk of infeasible schedule▫At the same time we are doing the schedule ?
Reinforce pruning
Take the good decision
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Infeasibilities
•Pay attention of validation of ▫Real-time data▫Requirements from the customer
•Strong need for highlighting these inconsistencies
Garbage In Garbage Out
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Infeasibilities
•Most time-intensive task: proving inconsistencies▫ If the model fails with no search
Post model several times with constraints shuffled randomly▫Else
we had a set of relaxations We applied them all We minimized the set until finding the smallest for which
we found a solution
Garbage In Garbage Out
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Questions ?