Taking Some of the Challenge out of Challenge Crudes

S.A. LordoNalco Company

Richard MathersNalco Company, Ltd.

Topics

• What is a Challenge Crude?• Assessment Methods

– Desalting– Fouling – Corrosion

• Summary

What is a Challenge Crude?

• Challenge or Opportunity crudes are any crude that is traded at a discount– New crudes to market– Crudes that are known to have processing

problems– Distressed cargoes– Any crude that a refiner has not processed

before

Assessment Methods

• Early assessment can reduce the risk in processing these crudes

• Several key aspects that are not on the assay– How will it affect desalter operation?– Will it cause fouling in exchangers and

furnaces?– Will it cause corrosion?

Will it Affect Desalter Operation?

• Several factors can impact desalting operation– Viscosity– Gravity– Solids Content– Asphaltene content / stability– Conductivity– Operational limitations (i.e., Temp, wash water, etc.)

• The key characteristic is the crude’s emulsification tendency

Emulsification Characteristics

• Portable Electric Desalter (PED) can be used to bench test crudes– Relative

comparison between crudes and crude slates

PED ResultsWater Separation - Whole Crude No Demulsifier

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40 45Time (Mins)

% W

ater

Sep

arat

ed

Forties

HardingGrane

Whole Crude - With Demulsifier

01020304050607080

0 10 20 30 40 50 60Time (Mins)

% W

ater

Sep

arat

ed

FortiesHarding

Grane

Crude Conductivity

• Conductivity increases with temperature and can reduce desalting electric field strength

• Blending is not predictable

0

200000

400000

600000

800000

1000000

1200000

1400000

0 10 20 30 40 50 60 70 80 90 100

TEMPERATURE oC

CO

ND

UC

TIVI

TY P

ICO

SIM

ENS/

MET

ER

10% DOBA IN ARAB HVY

DOBA

ARAB HVY

0

200000

400000

600000

800000

1000000

1200000

1400000

0 10 20 30 40 50 60 70 80 90 100

TEMPERATURE oC

CO

ND

UC

TIVI

TY P

ICO

SIM

ENS/

MET

ER

10% DOBA IN ARAB HVY

DOBA

ARAB HVY

Will it Cause Fouling in Exchangers and Furnaces?

• Primary fouling mechanism is asphaltene destabilization and precipitation– Crude Compatibility– Thermal Destabilization

• Some crudes exhibit other mechanisms – Traditional organic polymerization

Crude Compatibility

• Mixing of crudes can result in asphaltene precipitation

• Nalco Fouling Potential Analyzer (FPA)– Measures stability of

crude oils and blends– Differs from the

blending indices– Indicates desalter

impacts

11

12

13

14

15

16

17

0 10 20 30 40

Volume of Titrant

Abso

rban

ce

Crude A Crude B

Crude B has higher stability than Crude

Asphaltene Dispersancy Test

• Determines the relative effectiveness of dispersing asphaltenes in non-solvent medium– Field test– Aids in dispersant

selection– Discerns dispersant

performance

Poor Dispersion

Good DispersionBlank

Poor Dispersion

Good DispersionBlank

Thermal Destabilization

• Asphaltene destabilization can be triggered by temperature– Temperature decreases the resin-

asphaltene interaction

Hot Liquid Process Simulator Results

• Used to determine fouling potential of crudes and resids

• Used to select antifoulants and determine their effectiveness

0

50

100

150

200

250

300

350

400

450

0 50 100 150 200 250 300Time (min)

Tem

pera

ture

(oC

)

Rod Temp.Outlet Temp. (no Antifoulant)Outlet Temp. (with Antifoulant)

Begin Antifoulant

T = -25oC (130 min) T = -2oC (112 min)

0

50

100

150

200

250

300

350

400

450

0 50 100 150 200 250 300Time (min)

Tem

pera

ture

(oC

)

Rod Temp.Outlet Temp. (no Antifoulant)Outlet Temp. (with Antifoulant)

Begin Antifoulant

T = -25oC (130 min) T = -2oC (112 min)

Will it Cause Corrosion?

• Majority of the challenge crudes on the market are high acid crudes – Total acidity– Naphthenic acid content– Distribution of acids

• Other species are organic chlorides / undesaltable chlorides / phantom chlorides

High Temperature Naphthenic Acid Corrosion

• Not all TAN is a problem• Measure of naphthenic acid content

better gauge of corrosivity

Grana Crude - TAN / NAT Analysis

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

WholeCrude

C5 - 165 165-250 250-320 320-350 350-375 375+ 375-420 420-525 525-565 565+

Temperature Range (oC)

mg

KO

H /

g

TANNAT

Distribution of Acid

• Distribution can be used to determine likely areas of concern– Some newer assays have this TAN data– Nalco has a library of high acid crude nap acid

distributions• Relative comparison with respect to field experience

Corrosivity testing

• Laboratory rig used to simulate temperature and shear stress

• Test metallurgy of the unit• Test inhibitor effectiveness

0

2

4

6

8

10

12

14

16

18

Cor

rosi

on R

ate,

MPY

CS 5Cr 9Cr 410SS

Test Sample

Untreated

Treated

Experience

• Crudes that this process has been used successfully– DOBA– Grane– CPC

Summary

• Processing opportunity crudes can significantly improve refinery profitability

• Testing can be done before the crude arrives to identify potential risks in desalting, fouling and corrosion

• Communication between buyers, refiners and crude process aid suppliers is key to successful introduction

• Planning ahead can allow the refiner to reduce unknown risks associated with running Challenge/Opportunity Crudes