Taking Some of the Challenge out of Challenge Crudes S.A. Lordo Nalco Company Richard Mathers Nalco 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
% Water Separated PED Results Water Separation - Whole Crude No Demulsifier 60 50 40 Forties 30 20 10 Grane Harding 0 0 5 10 15 20 25 30 35 40 45 Time (Mins) % Water Separated Whole Crude - With Demulsifier 80 70 60 Forties 50 Harding 40 30 20 Grane 10 0 0 10 20 30 Time (Mins) 40 50 60
Crude Conductivity Conductivity increases with temperature and can reduce desalting electric field strength Blending is not predictable CONDUCTIVITY PICOSIMENS/METER 1400000 1200000 1000000 800000 600000 400000 200000 0 0 10 20 30 40 50 60 70 80 90 100 TEMPERATURE o C 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 12 impacts 11 Absorbance 17 16 15 14 13 Crude A Crude B has higher stability than Crude Crude B 0 10 20 30 40 Volume of Titrant
Asphaltene Dispersancy Test Determines the relative effectiveness of dispersing asphaltenes in nonsolvent medium Field test Aids in dispersant selection Discerns dispersant performance Blank Good Dispersion Poor Dispersion
Thermal Destabilization Asphaltene destabilization can be triggered by temperature Temperature decreases the resinasphaltene interaction
Hot Liquid Process Simulator Results Used to determine fouling potential of crudes and resids Used to select antifoulants and determine their effectiveness 450 400 350 Rod Temp. Outlet Temp. (no Antifoulant) Outlet Temp. (with Antifoulant) Temperature (oc) 300 250 200 150 T = -25 o C (130 min) Begin Antifoulant T = -2 o C (112 min) 100 50 0 0 50 100 150 200 250 300 Time (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 mg KOH / g 4.0 3.5 3.0 2.5 2.0 1.5 Grana Crude - TAN / NAT Analysis TAN NAT 1.0 0.5 0.0 Whole Crude C5-165 165-250 250-320 320-350 350-375 375+ 375-420 420-525 525-565 565+ Temperature Range (oc)
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 18 16 14 Untreated Treated Corrosion Rate, MPY 12 10 8 6 4 2 0 CS 5Cr 9Cr 410SS Test Sample
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