Corrosion Potential -

Refinery Overhead Systems

Amit Patel

Bartlesville, Oklahoma

OLI Simulation Conference

November 16-18, 2010

Whippany, NJ

• Corrosivity – Amine Hydrochlorides – Impact of overhead corrosion

• Overhead Corrosion – Crude Unit Operation

– Controlling Overhead Corrosion

– Electrolyte Modeling

• Case Study - Use of OLI Stream Analyzer – Vacuum Tower

– Coker Fractionator

• Summary

Agenda

Outlet line on

crude vs. ovhd

exchanger

Note heavy build

up of salts and

corrosion products

Salts and corrosion products flowed out of exchanger where

corrosion was occurring

Corrosivity - Amine Hydrochlorides

- Leaks in equipment develop leading to Health and

Safety issues

- Unscheduled shutdown of equipment results in Lost

Production

Amine hydrochlorides are corrosive

salts formed from neutralizer

application and tramp amines

NH3, R-NH2

Salts (MgCl2,

CaCl2, NaCl)

Organic acids

NH3, H2S

R-NH2

(Salt hydrolysis)

** Similar crude

contaminants in slop oil

HCl

Organic acids

NH3, H2S

R-NH2

R-NH2

Neutralizer

Filming

inhibitor Water wash

Overhead corrosion control

High

Overhead

Temperature

Salt Hydrolysis

MgCl2 + 2H2O --> Mg(OH)2 + 2HCl (g)

CaCl2 + 2H2O --> Ca(OH)2 + 2HCl (g)

NaCl + 2H2O --> NaOH + HCl (g)

Salt Formation

NH3(g) + HCl(g) <=> NH4Cl(s)

R-NH2(g) + HCl(g) <=> R-NH2 HCl(s)

Corrosion

NH4Cl(s) <=> NH4+(aq) + Cl

- (aq)

NH4+(aq) + Cl

-(aq) <=> NH3(aq) + HCl(aq)

R-NH2 HCl(s) <=> R-NH3+(aq) + Cl

- (aq)

R-NH3+(aq) + Cl

-(aq) <=> R-NH2(aq) + HCl(aq)

Fe + 2HCl(aq) --> FeCl2 + H2

Overhead Corrosion

Naphtha Line Corrosion – High

Corrosion Rate of in 6 O’clock position

Liquid Amine Salts Corroding the Bottom

Side of the 18-inch Carbon Steel Pipe

Leaving the Top Pump-around Draw off of

the Crude Tower

Equilibrium Salt Formation

No salt

will form

Salt will

form

Controlling Overhead Corrosion

– Reduce contaminant levels

• Improve desalting performance, desalter wash

water quality, re-route slop streams

– Increase tower overhead temperature

– Water washing overheads

– Inject neutralizer

• Change overhead chemistry

Benefits of different corrosion control options can be evaluated

using a good overhead system model

Refining Overheads – Electrolyte Modeling

Input

• Flows

• Temperature

• Pressure

• Water Analysis

• Properties of hydrocarbons

• Neutralizer

Output

• Water dew point

• Salt Point (ammonia, amine)

• Aqueous pH

• Phase behavior

OLI Equilibrium Thermodynamic Model

– Proper selection of amines for overhead system • Different amines form salts at different temperatures

• Neutralizer amines exhibit differences in ability to control pH at

water dew point

• Model can help analyze effect of various neutralizer amines

– Troubleshoot events • Did changes in unit operation create a corrosive environment ?

• Identify significant shifts in unit operation

– NH4Cl/Amine-HCl salt point

– Water dew point

How can overhead modeling help ?

Overhead modeling can improve overall unit performance and reliability

Case Study – Vacuum Tower

Concern: Is there ammonium chloride salt formation potential in the

main overhead line of the vacuum tower ?

X-3

Slop OilSour H20

X-1

Motive Steam

X-2

Vacuum Tower

Hotwell

Vent Gas to Ejector/Liquid Ring Pump

Lab Analysis - Condensate

0

1

2

3

4

5

6

7

2/2/

2009

2/16

/200

9

2/27

/200

9

4/15

/200

9

4/24

/200

9

5/4/

2009

5/13

/200

9

5/26

/200

9

6/5/

2009

6/15

/200

9

7/3/

2009

7/20

/200

9

8/5/

2009

8/18

/200

9

8/31

/200

9

9/17

/200

9

10/2

/200

9

10/1

4/200

9

11/2

/200

9

11/1

8/200

9

12/9

/200

9

12/2

1/200

9

1/4/

2010

1/13

/201

0

1/22

/201

0

2/1/

2010

pH

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Iro

n, p

pm

Date pH Cl Fe Ammonia H2S

ppm ppm ppm ppm

1/18/2010 6.19 2.4 0.12 4 6

1/20/2010 6.27 2.4 0.1 6 10

1/22/2010 6.32 2.4 0.08 6 10

1/25/2010 6.36 2.4 0.07 6 10

1/27/2010 6.28 2.4 0.1 5 8

1/29/2010 6.28 2.4 0.09 6 8

Inputs

Pressure: 5 mmHg

Off-gas: 6.5 mscfh

Distillate oil: 10 gpm

Steam: 11600 lb/hr

Contaminants:

HCl 3 ppm

NH3 6 ppm

H2S 10 ppm

Salt point

50

70

90

110

130

150

170

Feb-0

9

Mar

-09

Apr-0

9

May

-09

Jun-

09

Jul-0

9

Aug-0

9

Sep-0

9

Oct-0

9

Nov

-09

Dec

-09

Jan-

10

Feb-1

0

Ov

erh

ea

d T

em

pe

ratu

re,

de

g F

Salt Point

Fouling

Potential

Results

- calculated salt formation temperature was 129 deg F (close to the temperature where

the tower overhead operates)

Modeling shows high risk for NH4Cl salt formation

in the main overhead line

Pressure ~ 5 mmHg

What is causing the plugging across the fin fan tubes ?

From Coke Drums

To Product storage

Sour water

E-205A/B/CE-205A/B/C

D206 Bubble Tower Overview

48

psig

284 DegF E-206

37%

62%F-203

Wild Naphtha to Light Ends4.2

MBPD

FIC794LIC202

37%

PIC202

34

psig

151 DegF 101 DegF

96%

1

5

G-102

FIC783

9.0 MBPD

63%

2%

G50116.3MMSCFD

32psig 16.7

MMSCFD

E-501

1.7 MMSCFD

E-511FIC1547

3531 BPD

53%

57%

6

9 45%

D-206

D-207

D-208

LIC747

48%

10

G-216

FIC1780

2461BPD

39%

FIC1780

12.3

MBPD39%

E-214 E-207

553 DegF

G-222

46%

8.3

MBPD

LIC792

38%

E-208

E-209

70%

1802 lb/hr

FIC788

LCGO to Production

60%

1197 lb/hr

FIC789

16

BT Diesel to SCT

LIC750

62%

46%

711 DegF

17

19

20

532

DegF679

DegF

DegF420

DegF420

FIC782

1151

BPD3 %

337

BPD

79 psig

71

psig

FIC781

23.7MBPD

29%

606 DegF

8 %

E-211

E212

G-217

G-227

54%

LIC755 21%

TIC307

0 %H-5

HCGO to tankage

3088 BPD

0 MBPD

(Start-up)

213DegF

LCGO Lab Data

95%

10%

FBP

465 DegF

783 DegF

861 DegF

95% TARGET

HCGO Lab Data

95%

10%

FBP

646 DegF

979 DegF

1158DegF

95% TARGET

BT Diesel Lab Data

95%

10%

FBP

321

612

713

DegF

DegF

DegF

Mixed Resid TK201

E-213A/B

Decant Oil

FIC777

71%

0 %

FIC776

0 BPD

2469BPD

FIC922

3 %

199 BPD

PFB from U240

VT Bottoms Resid

Coke Drums

20.5 MBPD

0 BPD

Cond. Pot

796 DegF

759DegF

1448 BPD(low)

2.6 MBPD(high)

191 DegF

U267 Resid

To U200 VT 5.3

To Tank

MBPD

0.0MBPD

10% 844 DegF

U267 Resid Lab

Mixed Resid 2469 BPD800

1000

Stab. Botts Lab Data

90%

10%

FBP

82 DegF

326 DegF

432 DegF

90% TARGET340

52%

MBPD

5.7H-204

G-218 G-213

Coil Charge to B-202

12%(start-up LIC to tray 20)

702 DegF

228 DegF

0.00psi

0.43psi

0.29psi

0.02psi756DegF

640DegF

PIC691

HCGO to U246

1127BPD

71 %

HVGO

NO DATAMBPD

57409TK201 VOL

782

LCGO Predict

DegF

COKER CHARGE

A1 Coil

A2 Coil

B1 Coil

B2 Coil

31.4 MBPD

7.9 MBPD

7.8 MBPD

7.8

7.8

MBPD

MBPD

RECYCLE RATIO:NO DATA

0 BPD

33

LCGO Adv Cont.HCGO Adv Cont.

Andvanced Control ON/OFF

01

Reflux

Contaminants:

Cl- 1 ppm

NH3 6100 ppm

H2S 8800 ppm

Pressure: 50 psig

Off-gas: 12 mmscfd

Product: 4000 bpd

Reflux: 8000 bpd

Water: 6 gpm

Case Study – Coker Fractionator Concern: Increased pressure drop observed across the overhead fin fan exchanger of the

coker fractionator would lead to equipment shutdown

Very low scaling tendency for

ammonium bisulfide (NH4HS) in

the coker fractionator overhead

• NH4HS salt formation unlikely in

this temperature region

• water dew point 192 deg F

Condensing water

Performed survey

calculation (vary chloride

composition)

NH4Cl salt can form when

HCl concentration gets

near 213 ppm in the

system

- salt formation temperature

199 deg F

- water dew point 192 deg F

Distillate wash caused

spike in overhead

chlorides

From

overhead

To accumulator 285 F

141 C

185 F

85 C

100 F

Fin Fan

Salt point

Condensing water

Summary

Corrosion never takes vacation

– Health and Safety issues and LPO

Ammonia/amine salts are major contributors to refining unit overhead

corrosion

Modeling the crude unit overhead system can improve overall unit

performance and reliability

– Troubleshooting tool

– Unit monitoring

OLI Stream Analyzer has enabled us to model potential for salt

formation in refining overhead systems

Understanding when liquid amine salts form via ionic models is

important to reliable unit operation

– Need better understanding of properties that best describe formation of amine salts

Acknowledgments

– Eric Vetters, ConocoPhillips

– Emily Amizich, ConocoPhillips

– Matt Keating, ConocoPhillips

– AJ Gerbino, OLI Systems

– Jim Berthold, OLI Systems

– Pat McKenzie, OLI Systems