11 B Petrus Online control of spray cooling using Cononlineccc.illinois.edu/s/2010_Presentations/11_B... · ANNUAL REPORT 2010 UIUC, August 12, 2010 Online control of spray cooling

ANNUAL REPORT 2010UIUC, August 12, 2010

Online control of spray cooling using Cononline

University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Lance C. Hibbeler • 1

Bryan Petrus(MSME/Ph.D. Student)

Department of Mechanical Science and Engineering

University of Illinois at Urbana-Champaign

using Cononline

Outline

• Brief overview of Cononline project• Challenges in dynamic control of spray

cooling– Saturation and anti-windup– Saturation and anti-windup– Setpoint choice– Sticker slowdowns

• Offline simulator• Simulation example: sticker slowdown

University of Illinois at Urbana-Champaign • Mechanical Science & Engineering • Metals Processing Simulation Lab • Bryan Petrus • 2

Overview


Overview: Consensor

• Con1d– Fundamentally-based heat transfer

and solidification model of continuously cast strand

– Assumes heat transfer in axial direction is dominated by flow of material at casting speed (true at typical casting speedstypical casting speeds

– Simulates a 1-D “slice” through the centerline of the strand, moving down the caster at casting speed

• Goal:– Apply Con1d as the basis of a real-

time model of the strand– Then, use model for “feedback”

control of water cooling sprays instead of relying on pyrometers

CONSENSOR

output domain

Distance below meniscus, z

Tim

e, t


Overview: Consensor

• Consensor: “Software sensor”– Manages 200 Con1d slices– Each second, gets updated casting

conditions from Level 2, simulates each slice for 1 second of travel at casting speed

– Uses “delay interpolation” for points – Uses “delay interpolation” for points in between slices

5 5.2 5.4 5.6 5.8 6960

980

1000

1020

1040

1060

1080

1100

1120

Distance from meniscus (m)

She

ll su

rfac

e te

mpe

ratu

re (o C

)

Actual temperature profileExact slice estimatesSpatial interpolation of slice estimates

CONSENSOR

output domain

Distance below meniscus, z

Tim

e, t

01t

02t

CON1D slices

CONSENSOR updates

Delay interpolation

Exact estimate

Surface temperature output locations


Nucor Decatur cooling sprays

Zone 1

Zone 2

Zone 3

4 x 1 + 3 x 2 = 10 separate spray zones, along centerline

Zone 6

(Inner/Outer)

Zone 4

Zone 7

(Inner/Outer)

Zone 5

(Inner/Outer)


Overview: Concontroller

• Each spray zone is controlled by a separate PI controller

• Every second, for each zone, j1.Calculate the average tracking error:

2.Calculate the spray-water flow rate command for the next time interval,

Pjk ΣΣΣΣ

Saturation

predictedsetpointjjj TTT −=∆

command for the next time interval, via the classic PI control law:

• Additional term on integral is anti-windup correction to prevent delays after saturation

3.Send spray rates to all other programs

jk

Ijk

0

tdt∫

ΣΣΣΣ

ΣΣΣΣ ΣΣΣΣ +-awjk

( ) ( ) ( )tuttuttu Ij

Pjj ∆+∆+=∆+

( ) ( )tTkttu jIP

j ∆=∆+

( ) ( ) ( ) ( ) ( )[ ]tutukttTktuttu jmeasuredj

awjj

Ij

Ij

Ij −−∆∆+=∆+


Overview: Programs

• Programs run on separate computers for stability and speed– Consensor runs on

CentOS Linux– Concontroller runs on

Slackware Linux CommServer CONCONTROLLER

Caster AutomationCommClient

Current control logic

Slackware Linux– Communicate with each

other and Level 2 via TCP/IP programs written by Rob Oldroyd (Nucor Decatur)

– Also send information to Windows PCs via monitor programs


Controller Computer

(Slackware Linux)

shared memory

CommServer

ActiveXServer

Model Computer

(CentOS Linux)shared memory CommClient

CONSENSOR

Windows Computers

CononlineMonitorTCP/IP connection

Shared memory connection

Overview: Monitor


Anti-windup: benefits

• In normal casting conditions, some valves may be fully open or closed

• After the valve can’t move any further, the integral controller continues to integrate (windup) and takes a while to return to normal

• Anti-windup subtracts the difference between controller and actuator to reduce this delay

Anti-windup test simulation

Spr

ay fl

ow r

ate

(L/s

)

Cas

ting

spee

d (m

/min

)

3

3.5

4

4.5

10

15PI, no saturation

PI, no anti-windup

PI, standard anti-windup

spray table

casting speed

reduce this delay

Valve fully open, not hitting setpoint

Spr

ay fl

ow r

ate

(L/s

)S

urfa

ce te

mpe

ratu

re (

deg

C)

Cas

ting

spee

d (m

/min

)

Time (sec)


1000

1020

1040

1060

0 100 200 300 400 500

PI, no saturation

PI, no anti-windup

PI, standard anti-windup

spray table

2.55

Anti-windup: problems

• However, too aggressive anti-windup was found to over-react to chattering in the spray valves

• We responded to this by Cononline turned on

August 2009 Trial – Flow rates

( ) ( ) ( )( ) ( )[ ]tutuk

ttTktuttu

jmeasuredj

awj

jIj

Ij

Ij

−−

∆∆+=∆+

1060

1062

1064

1066

1068

1070

12:04 12:07 12:10 12:12Inn

er

rad

ius

surf

ace

tem

pe

ratu

re (d

eg

C)

Segment 4/5 setpoint Segment 4/5 predicted

• We responded to this by averaging the error signal before anti-windup

( ) ( ) ( )

( ) ( )[ ]∑−

=

∆−−∆−−

∆∆+=∆+1

0

1 N

nj

measuredj

awj

jIj

Ij

Ij

tntutntuN

k

ttTktuttu

Cononline turned on

July 2010 Trial – Flow rate and surface temperature

Flow rate legend— Measured flow rate— Concontroller suggest flow rate


200

250

300

350

400

1000

1200

1400

1600

1800

Sp

ray

flo

w r

ate

(l/m

in/r

ow

)

Inn

er

rad

ius

surf

ace

te

mp

era

ture

(de

g C

)

controlled setpoint spray table controlled

Setpoints

• Cononline setpoints are based on spray table, estimate mold heat removal based on mold flux properties

• Formerly, interpolated setpoints in

( )*027.0

107.0exp152.011063.4

2047.019.109.06

−−−×= −− pcvTq cmµ

0

50

100

150

200

0

200

400

600

800

0 2000 4000 6000 8000

Sp

ray

flo

w r

ate

(l/m

in/r

ow

)

Inn

er

rad

ius

surf

ace

te

mp

era

ture

(de

g C

)

Distance below meniscus (mm)

• Formerly, interpolated setpoints in top 4 zones with respect to actual mold conditions

• Nucor Decatur wants to use Cononline to fix the temperature in the bender (zones 2 and 3)

• PI control reacts to differences in mold heat removal by changing the sprays drastically in upper zones

C. Cicutti, M. Valdez, T. Perez, G.D. Gresia, W. Balante and J. Petroni: "Mould thermal evaluation in a slab continuous casting machine," Proc. 85th Steelmaking Conference, (Nashville, TN, USA), 2002, vol. 85, pp. 97-107, 282.

(*)

55 % increase


Setpoints

• Regenerated setpoints– instead of equation (*),

used average recorded mold heat removal at Nucor Decatur over last year

15.7 31.5 47.2 78.7 98.4 118.1 137.8 157.5 196.8 speed (ipm)

Pattern 0.40 0.80 1.20 2.00 2.50 3.00 3.50 4.00 5.00 speed (m/min)

1 1.346 1.454 1.498 1.711 2.343 2.548

2

3 0.0106 1.656 1.462 1.367 1.734 2.363 2.526

4 1.967 1.666 1.642 1.83 2.442 2.569

5 2.69

6 1.385 1.653 1.777 2.143 2.374

7 6.0735 1.346 1.408 1.605 1.837 2.226 2.393

8 1.624 1.371 1.531 1.794 2.146 2.352

Average mold heat removal (MW/m 2)

0

50

100

150

200

250

300

350

400

0

200

400

600

800

1000

1200

1400

1600

1800

0 2000 4000 6000 8000

Sp

ray

flo

w r

ate

(l/m

in/

row

)

Inn

er

rad

ius

surf

ace

te

mp

era

ture

(de

g C

)

Distance below meniscus (mm)

controlled, new setpoint new setpoint

spray table controlled, new setpoint

year

• Results are much better, but there may be other differences to account for– Grade?– Mold flux?

26 % increase


• Dynamic controller also may have problems dealing with unusual casting conditions, e.g. sticker slowdowns

• Sticker detection:– Shell surface touches mold hot

face, leading to thin spot in shell– Nucor Decatur breakout detection

alarm is triggered when mold

Sticker slowdowns

alarm is triggered when mold thermocouples drop suddenly in temperature

– Typically have more false positives than actual detections

• Caster response:– Immediately slowed to 20 ipm to

prevent breakout– Sprays are taken from spray table

at 80 ipm (higher spray rates than 20 ipm) to prevent bleeders

(Ed Szekeres)


Sticker slowdowns

• Cononline response– Cononline is only given

average heat removal rate in mold, so it does not predict the localized thin spot in the shell

– Because of sudden drop in temperature due to the slowdown, the PI controller reaction is turn all sprays down

Light blue boxes: spray table at 80 ipmDark blue outlines: spray table at 20 ipm

reaction is turn all sprays down• Added some extra logic to

Concontroller to handle this:– In first three zones (through

the bender) the controller uses the 80 ipm flow rates instead of applying temperature control


Original heat transfer coefficients

New heat transfer coefficients

Tuning Con1d to Nucor Decatur caster: pyrometers

1400

1600

1800

She

ll Te

mpe

ratu

re (

C)

Ts RHS Ts LHS Slab temperature Test pyrometer

1400

1600

1800

She

ll Te

mpe

ratu

re (

C)

Ts RHS Ts LHS Slab temperature Test pyrometer


(Xiaoxu Zhou)

0

200

400

600

800

1000

1200

0 5000 10000 15000 20000

She

ll Te

mpe

ratu

re (

C)

Distance from meniscus (mm)

0

200

400

600

800

1000

1200

0 5000 10000 15000 20000

She

ll Te

mpe

ratu

re (

C)


40.0

45.0

50.0

LiqLoc RHS SolLoc RHS Shell RHS

40.0

45.0

50.0

LiqLoc RHS SolLoc RHS Shell RHS

Original heat transfer coefficients

New heat transfer coefficients

Tuning Con1d to Nucor Decatur caster: shell

End of containment End of containment

0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

0 5000 10000 15000 20000

She

ll Th

ickn

ess

(mm

)


0.0

5.0

10.0

15.0

20.0

25.0

30.0

35.0

0 5000 10000 15000 20000

She

ll Th

ickn

ess

(mm

)Distance from meniscus (mm)

University of Illinois at Urbana-Champaign • Metals Processing Simulation Lab • Bryan Petrus • 19

(Xiaoxu Zhou)

Whale predicted

Offline simulator

• Implementing Cononline as an offline simulator1. “Offline” monitor allows direct

user input of casting conditions2. Database querier in Excel pulls

conditions by caster, sequence, heat, slab, and/or time and date, sends to

Nucor Decatur database querier

time and date, sends to “replay” program that feeds data to Consensor

• Potential uses:– Testing out new casting

practices prior to implementation

– Defect or event investigation– Operator training


Offline simulator


Simulation – Sticker slowdown


Thank you

• NSF grants– GOALI DMI 05-00453 (Online)– GOALI CMMI-0900138

• CCC students– Xiaoxu Zhou, Huan Li (former student), Sami Vapalahti, Hemanth

Jasti• Nucor Decatur• Nucor Decatur

– Level 2 programmers: Rob Oldroyd, Teri Morris, Kris Sledge, James– Metallurgists: Ron O’Malley, Bob Williams– Electrical: Steve Dunnavant, George, Bill James, Jeff White– Caster supervisors and operators: Scott Ridgeway, Caster Green,

Rodney Thrasher, Bryan Thornton, Josh– Everyone else

• Continuous Casting Consortium members (ABB, Arcelor-Mittal, Baosteel, Corus, LWB Refractories, Nucor Steel, Nippon Steel, Postech, Posco, ANSYS-Fluent)


Documents

11 B Petrus Online control of spray cooling using Cononlineccc.illinois.edu/s/2010_Presentations/11_B... · ANNUAL REPORT 2010 UIUC, August 12, 2010 Online control of spray cooling