taking some of the challenge out of challenge crudes · taking some of the challenge out of...
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Taking Some of the Challenge out of Challenge Crudes
S.A. LordoNalco Company
Richard MathersNalco Company, Ltd.
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
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
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