Petrocontrol 1

Coker advanced control application at Petronas Melaka

Azura Bt. Azahar Y. Zak Friedman Seung-Yun Nam

Petrocontrol 2

Why delayed coking unit is a good APC candidate?

•  Unit with operational difficulties – Drum switch disturbances – High temperature coking environment – Many constraints

•  APC can –  Improve response to drum switch

disturbances – Run the unit closer to constraints – Maximize middle distillates yield

Petrocontrol 3

Melaka coker design overview

Naphtha

FEED

COKE DRUMS

FRACTIONATOR

LCGO

COKER FURNACE

Fuel oil

STRIPPER

STABILIZER

LPG

QUENCH

HCGO RECYCLE

HHCGO

Petrocontrol 4

Coker fractionator configuration

FC

FC TC FC LC

FEED FC

LC

HHCGO

FC

FC

RECYCLE

FUELOIL LC FC

LC FC

FC

LCGO FC

QUENCH TC FC

FC TC

PC

NAPHTHA

LC FC

FC

HCGO

LC

Petrocontrol 5

Coker drums, drum A working

DRUM A

To FRACTIONATOR

Quench Quench

Blowdown Blowdown

Steam Steam

FROM FURNACE

DRUM B

Blowdown Blowdown

LI

FC

FC

FC

FC

LI

TI

TI TI

TI

TI

Petrocontrol 6

Drum B worming up

DRUM A

To FRACTIONATOR

Quench Quench

Blowdown Blowdown

Steam Steam

FROM FURNACE

DRUM B

Blowdown Blowdown

LI

FC

FC

FC

FC

LI

TI

TI TI

TI

TI FLOW AND HEAT DISTURBANCE

Petrocontrol 7

Drum B starting, drum A stripped

DRUM A

To FRACTIONATOR

Quench Quench

Blowdown Blowdown

Steam Steam

FROM FURNACE

DRUM B

Blowdown Blowdown

LI

FC

FC

FC

FC

LI

TI

TI TI

TI

TI 20% OF NORMAL FLOW, MUCH STEAM

Petrocontrol 8

Drum B heating, no drum A steam

DRUM A

To FRACTIONATOR

Quench Quench

Blowdown Blowdown

Steam Steam

FROM FURNACE

DRUM B

Blowdown Blowdown

LI

FC

FC

FC

FC

LI

TI

TI TI

TI

TI 30% OF NORMAL FLOW, NO STEAM

Petrocontrol 9

APC economics

•  Maximize coker distillate, subject to naphtha and distillate specifications

•  Control coker recycle ratio at target •  Maximize fresh feed •  Maintain property control, fractionator

inventory and heat balance control during drum switching

•  Avoid excessive fractionator coking

Petrocontrol 10

Robust inferential model

FC

LC FC

FC Pumpdown

Pumparound

Pot

TI PI

Reconstructed TBP cutpoint

Dewpoint

TBP IBP

GCC inferential model

Petrocontrol 11

Naphtha 90% point inference

120

130

140

150

160

170

180

190May/04/2012

May/14/2012

May/24/2012

Jun/03

/201

2

Jun/13

/201

2

Jun/23

/201

2

Jul/0

3/20

12

Jul/1

3/20

12

Jul/2

3/20

12

Aug/02/2012

Aug/12/2012

Aug/22/2012

Sep/01

/201

2

Sep/11

/201

2

Sep/21

/201

2

Oct/01/2012

Oct/11/2012

Oct/21/2012

Oct/31/2012

Nov/10/2012

Nov/20/2012

Cocker  nap

htha

 90%

 point,  d

eg  C

Lab Inferential

Petrocontrol 12

LCGO 90% point inference

330

340

350

360

370

380

390

400Ap

r/02

/201

2

Apr/12

/201

2

Apr/22

/201

2

May/02/2012

May/12/2012

May/22/2012

Jun/01

/201

2

Jun/11

/201

2

Jun/21

/201

2

Jul/0

1/20

12

Jul/1

1/20

12

Jul/2

1/20

12

Jul/3

1/20

12

Aug/10/2012

Aug/20/2012

Aug/30/2012

Sep/09

/201

2

Sep/19

/201

2

Sep/29

/201

2

Oct/09/2012

Oct/19/2012

Oct/29/2012

Nov/08/2012

Nov/18/2012

Cocker  LCG

O  90%

 point,  d

eg  C

Lab  90 Inferential

Petrocontrol 13

Two RMPCT controllers •  Furnace RMPCT

– Maximize feed to furnace constraints – Balance furnace passes –  Increase COT after drum switch to speed up

the return to normal operation •  Column RMPCT

– Control product specifications, heat balance, mass balance, column constraints

– Accept the given feed, relax product specs if needed

Petrocontrol 14

Main column control variables •  Product inferential calculations

– Naphtha and LCGO draw 90% points •  Column inventory constraints that

become active during drum switches – Draw pans and overhead drum levels

•  Temperature constraints in the lower section of the column

•  Coker recycle ratio •  Hydraulic constraints

– Maximum valve positions, flows or sometimes pump currents

•  Coking furnace constraints – Most active are skin temperatures

Petrocontrol 15

Main column manipulated variables

•  Column top temperature – Controls naphtha 90% point

•  Pump-down flows – Control side draw 90% points – HCGO pump-down controls coker recycle

ratio •  Other secondary MVs

Petrocontrol 16

Evidence of CIT increase

CIT

Steam generator valve

Petrocontrol 17

No throughput maximization currently CIT

Throughput

LCGO

Naphtha

After

Before

Petrocontrol 18

Evidence of naphtha shift to LCGO

Petrocontrol 19

Conclusion: delayed coking unit is a good APC candidate

•  Conditions of successful implementation – Knowledge of the process and economics – Good quality inferential models – Much attention to detail – Operator and process engineer participation

at the design stage

Petrocontrol 20

Example of throughput increase

150

155

160

165

170

175

180

185

190

195

200

1 14 27 40 53 66 79 92 105 118 131 144 157 170 183 196 209 222 235 248 261 274 287 300 313 326 339 352 365 378

Minutes

M3

/ Hr

Throughput before APC Throughput after APC

Drum switch

Petrocontrol 21

Naphtha 90% point inference

130

135

140

145

150

155

160

165

170

175

180

24-May-11 29-May-11 03-Jun-11 08-Jun-11 13-Jun-11 18-Jun-11 23-Jun-11

NAP90_M NAP90_L

Petrocontrol 22

LCGO 90% point inference

340

350

360

370

380

390

400

410

420

24-May-11 29-May-11 03-Jun-11 08-Jun-11 13-Jun-11 18-Jun-11 23-Jun-11

LCG90_M2 LCGO90_L