Electrostatics Separation Technolgy Process Solution Group
Oct 30, 2014
Electrostatics Separation Technolgy
Process Solution Group
Description of Processes &
Fundamentals
YOU DRILLED AN “OIL” WELL…...
BUT ALSOPRODUCED…..
•GAS•MUD•SALT•SAND•WATER•SULFUR•CHEMICALS
TYPICAL PROCESS SCHEME
GASPROCESSING
BULKSEPARATION
WATERTREATING
OILTREATING
CONSISTS OF . . .
•DEHYDRATION(REMOVAL OF INSOLUBLE WATER)
•DESALTING(REMOVAL OF MINERAL CONTAMINANTS SOLUBLE IN WATER, AND OF SOLIDS)
CRUDE OIL TREATING
CRUDE OILDEHYDRATION
CRUDE OILDESALTING
WATER IN A CRUDE OIL PRODUCTION STREAM CAN TAKE SEVERAL FORMS EMULSIFIED
WATER
DISSOLVEDWATER
FREEWATER
STREAMSAMPLE
CRUDE OIL DEHYDRATION
OILRICH
WATERRICH
FREE WATER
Free water is either water existing as the continuous phase, or water existing as relatively large dispersed droplets, both of which separate quickly from the oil phase
DISSOLVED WATER
MEASURED WATER-IN-OIL SOLUBILITIES
TYPICAL WATER-IN-OIL EMULSION
Seen Through a Microscope
Droplet sizes range from sub-micron to several hundred microns.
Mechanism of Oil Dehydration
A Three Step Process… Coagulation
Counteracting the Droplet Surface Films Flocculation
Gathering the Destabilized Drops Together Sedimentation
Gravitational Separation of the Phases
Mechanical Forces for Coalescence and Sedimentation
STOKE’S EQUATIONDescribes Sedimentation Velocity
V = Sedimentation Velocityg = gravity D = Particle (or dispersed droplet) Diameterρ1= Density of Continuous Phase
ρ2= Density of Dispersed Phase
μ1 = Viscosity of Continuous Phase
18μρ )( 12
2 -=g DV1
ρ
DEHYDRATION OF CRUDE OILS
DROP GROWTH OF THE DISPERSED PHASE
SEPARATION OF THE LIQUID PHASES BY GRAVITY SETTLING
ACCOMPLISHED BY . . .
+
Diameter = 1 mmVolume = 0.5236 mm3
Surface Area = 3.1416 mm2
Diameter = 1.260mmVolume =1.0472 mm3
Surface Area=4.98 mm2
TOTAL VOLUME UNCHANGED
TOTAL SURFACE AREA ONLY 79% OF ORIGINAL
DROPLET GROWTH ACHIEVED BYCOALESCENCE
So why does an emulsion not rapidly coalesce and separate into distinct phases?
An emulsion is a dispersion that has been stabilized.
DROPLET COALESCENCE
WHAT IS AN EMULSION?EMULSIONS ARE TWO IMMISCIBLE PHASES, INTERDISPERSED BY MECHANICAL AGITATION, AND THE DROPLETS STABILIZED BY . . .
VISCOSITY
DENSITY DIFFERENCE
DROPLET SIZES
EMULSIFYING AGENTS
STATIC ELECTRICAL CHARGE
DESCRIBEDBY STOKE’S LAW
NOT DESCRIBEDBY STOKE’S LAW
EMULSIFYINGAGENTS
EMULSIFYING AGENTS
•HEAVY PARAFFINICCOMPOUNDS•HEAVY NAPHTHENIC ACIDS•PETROLEUM ACIDS•ASPHALTIC COMPOUNDS•ORGANIC SOLIDS•INORGANIC SOLIDS
WATERDROP
OIL
ELECTROSTATIC CHARGE
++++- - -
++++- - -
In a flowing process stream where water exists as a dispersed phase in an organic continuous phase, the water droplets tend to acquire a positive excess charge. This causes a repulsive force between droplets.
HOW CAN WE DE-STABILIZE THE EMULSION AND INCREASE SETTLING RATE?
Heat
Chemistry
Flow Regime
Coalescing Surfaces
Electrostatic Fields
Crude oil dehydration utilizes these principles to speed up the coalescence and separation of emulsified water from oil
BENEFITS OF HEATING
Viscosity Increased Differential Density
Increased Film Strength Weakened Chemical Reactivity
Accelerated Heat Chemistry Flow Regime Coalescing Surfaces Electrostatic Fields
BENEFITS OF HEATING
Heating can cause problem for heavy oil
DRAWBACKS OF EXCESSIVE HEATING
FUEL COST
LOSS OF VOLUME
LOSS OF GRAVITY
INCREASED MAINTENANCE
SAFETY
Heat Chemistry Flow Regime Coalescing Surfaces Electrostatic Fields
Chemical additives called demulsifiers are typically injected into the crude oil stream to weaken the stabilizing film surrounding the water droplets
CHEMICAL TREATMENT
Chemical Treatment
Requirements:
• Deactivate Natural Surfactants
• Enhance Condensation of Interface Zone
• Modify Wetting of Solids
• Produce No Insoluble By-Products
Major Components:
• Demulsifier (Primary Ingredient)
• Wetting Agent (Used if solids are a problem)
Selection Methods for Demulsifiers
Bottle Tests – Most Common Method Measure Sedimentation Rate Estimate Resultant Oil Quality Vary Chemical Type and Dosage
Electrostatic Bench Tests Measure Response of Emulsion to Electrostatic Field: Power
Requirements & Sedimentation Rate Measure Resultant Oil Quality Vary Chemical Type & Dosage and Electrostatic Field Type
cc Oil
cc Emulsion
cc Water
• Chemical Dossage
• Mixing
• Heating to process temperature
• 24 hours settling evaluation
t = 0 t = t1
Bottle Test
100 ccEmulsion
Equipment for electrical susceptibility test
Chemical analysis: Electrical susceptibility test
Graphical recorder Test cell
Chemical analysis: Electrical susceptibility test
Chemical analysis: Electrical susceptibility test
Chemical analysis: Electrical susceptibility testAmperage against test temperature
0.100
0.110
0.120
0.130
0.140
0.150
0.160
0.170
0.180
0.190
0.200
0 10 20 30 40 50 60 70 80 90
Temperature (°C)
Am
per
age
(mA
)
PetrozuataLagotrecoJusepín
Chemical analysis: Electrical susceptibility test Relative Electrical Conductivity against
temperature
0,0000100000
0,0000115000
0,0000130000
0,0000145000
0,0000160000
0,0000175000
0,0000190000
0,0000205000
0 10 20 30 40 50 60 70 80 90
Temperatura (°C)
Ele
ctr
ical
Co
nd
ucti
vit
y (
mA
/V)
PetrozuataLagotrecoJusepin
Comparative Results19.5ºAPI Brazilian Crude
Chemical Bottle Test Electrostatic Bench Test
Water in Oil % By Difference
BS&W Measured %
A 2.2 2.12
B 4.6 2.01
C 5.3 1.62
D 5.7 1.20
E 6 2.35
Red: Best Performance
DEMULSIFIERS
TREATER
CHEMICAL TANKAND PUMP
WET CRUDEINLET
DEMULSIFIER IS INJECTED UPSTREAM OF THE TREATER
HeatChemistry Flow Regime Coalescing Surfaces Electrostatic Fields
Flow distribution is critical to achieving
uniform velocity and avoiding excessive
turbulence
FLOW DISTRIBUTION
Distributed Flow
Distributor
Collector
Inlet
Outlet
FLOW DISTRIBUTION
PerforatedDistributorBaffles
UP-FLOW
LONGITUDINAL-FLOW
COALESCING SURFACES CAN SPEED UP SEPARATION
HeatChemistryFlow RegimeCoalescing SurfacesElectrostatic Fields
100
10
1
0.1
TR
EA
TE
D C
RU
DE
BS
&W
(%
)
10 20 30 40 50 70 100CRUDE OIL GRAVITY (DEG API)
FREE WATERKNOCKOUT
TREATER orDESALTER
ACHIEVABLE WATER REMOVAL
3-PHASESEPARATOR
HeatChemistry Flow Regime Coalescing Surfaces Electrostatic Fields
USING AN ELECTROSTATIC FIELDTO CAUSE COALESCENCE
+ -
+Dipoles Align With The Field
Droplet Elongates
POLARIZATION OF DISPERSED DROPLETS
ELECTROSTATIC EFFECTS
DIPOLAR ATTRACTIVE FORCEBETWEEN EQUAL SIZED DROPS
4
626drEKF ε=
F = Force of Attraction
ε = Dielectric Constant
E = Electric Field Strength
r = Drop Radius
d = Interdrop Distance
Notice the Limitations:
Very Sensitive to Drop Size
Operates Over Short Range
Critical Voltage Gradient
x
y
y/x>1.9
2/1)/( dEc γε<
• Drop is polarized by the electrostatic field
• Drop is more conductive than continuum
• Drop deforms to a prolate spheroid
• Drop splits when ratio of axes becomes too large
• Electrical charge on the drop promotes shattering
or
Maximum Voltage at which Specified Drop Size Can Exist
ELECTROSTATIC FIELDS
There are two basic types of electrostatic field:
AC FIELD
DC FIELD
. . . and several possible variations of each
OPPOSITE POLES OF POLARIZED WATER DROPLETS ATTRACT, PROMOTING COALESCENCE
+ - + -
DROPLET BEHAVIOR IN AN AC FIELD
ELECTROSTATICALLY INDUCED FILM RUPTURE
Absence of Electric Field
Surface Stabilized by Film
Coalescence Inhibited
Drop Stretched by Field
Surface Film Broken
Coalescence Enhanced
AC -TYPE ELECTRODESTRANSFORMER
OIL OUT
WATEROUT
OIL IN
AC FIELD BENEFITS
DIPOLAR ATTRACTION
FILM STRETCHING
WATER TOLERANCE
BUT THERE ARE LIMITATIONS…
MINIMAL DROP MOVEMENT
LOW CHARGE DENSITY
LIMITS ON USEFUL FIELD STRENGTH
+ -
Upwardoil flow A single small
water droplet
Electrodes
-+
+-
DROPLET BEHAVIOR IN A DC FIELD
- +
COALESCENCE IN A DC FIELD
+ -
- + - +
+ -
UPWARDOIL FLOW
Opposites Attract
COALESCING IN A DC FIELD
DC FIELD BENEFITS
MOST AC FIELD BENEFITS, PLUS . . .•DROPLET TRANSPORT•NET ELECTROSTATIC CHARGE
BUT. . .•MUST AVOID ELECTROLYTIC REACTIONS•WATER TOLERANCE IS REDUCED
ELECTROSTATIC FIELDS:DUAL POLARITY®
AC/DC (DUAL POLARITY®) COALESCER
PLATE ELECTRODE ARRAY
ELECTRODE PLATES
RAILS
INSULATORHANGERS
DUAL POLARITY®
Provides Combined AC/DC Fields
For Combined Benefits
Drop Polarization
Film Rupture
Water Tolerance
Drop Movement
Drop Charge Density
Minimizes Induced Corrosion
Heat Chemistry Flow Regime Coalescing Surfaces Electrostatic Fields
PROCESS EQUIPMENTDESIGN
TRANSLATING PROCESS INTO EQUIPMENT
We have looked at the the principles the industry utilizes to achieve crude oil dehydration.
Different equipment suppliers apply these principles in different ways. Following is an overview of NATCOGROUP equipment design, using these principles.
PROCESS EQUIPMENT DESIGN
FREE WATER KNOCKOUT
GAS
OIL
WATER
INLET
BATTERY OF VERTICAL TREATERS
DEGASSING
MIST REMOVAL
FREE WATER REMOVAL
HEATING
SECONDARY DEGASSING
EMULSION COALESCING/SETTLING
INTERNAL FUNCTIONS
VERTICAL TREATER(Cold climate options)
TYPICAL TREATER FIRETUBE AND DRAFT SYSTEM
STACK HEAD
FIRETUBE
STACK
TURBULATOR
AIR INTAKE/BURNER
CONE BOTTOMVERTICAL TREATER
OPTIONAL ITEMS:
CONE BOTTOM
SAND JET RING
HEATING BUNDLE
SLOPED BAFFLES
OUTSIDE LEVEL CONTROLS
CROSS DRAIN
VFH TREATER (Vertical Flow Horizontal Treater)
INLETEQUALIZER GAS OUTLET
OIL OUTLET
FREEWATEROUTLET
FIRETUBESHROUD
FIRETUBE
FULLBAFFLE
EMULSIFIEDWATEROUTLET
SPREADERS
PERFORMAX COALESCING PLATES
PERFORMAX MATRIX
MATERIAL
Polyvinylchloride PolypropyleneCarbon SteelStainless Steel
COALESCING SURFACES
PERFORMAX TREATER (Horizontal Model)
DUAL POLARITY ELECTROSTATIC TREATER (VFH-CWW)
DUAL POLARITYELECTROSTATIC TREATERS
SMALL OIL PRODUCTION BATTERY WITH SEPARATION AND TREATING
Dual Polarity® Electrostatic Treater with Degasser
Howe-Baker Electrostatic Dehydrators
AC Field electrostatic dehydrators
Petreco Electrostatic Dehydrators
AC Field electrostatic dehydrators
Kvaerner (HRI) Electrical treaters
AC Field electrostatic dehydrators
Comparative suppliers analysis
AC Field
Proven technology in conventional desalting process
Electrostatic dehydration/desalting under AC electric field
Traditional desalting technology Lower comparative cost High oversizing design High sensitivity to emulsion tightness (high
stability) and high water content High desalting multiple stages
requirements Good technical support High control requirements
Dual Polarity®
Proven technology in conventional desalting process
Electrostatic dehydration/desalting under Dual polarity (AC/DC) electric field and electrodynamic desalting process (exclusive technologies)
Improved desalting technologies Higher comparative cost Optimal design (low oversizing) Low sensitivity to emulsion tightness (high
stability) and high water content Low desalting multiple stages
requirements Excelent technical support High control requirements
ELECTROMAX® TREATER
ELECTROMAX® CRUDE OIL DEHYDRATOR
Combines Electrical and Mechanical Coalescence
High Flux Electrical Section
Downflow Sedimentation
Performax® Mechanical Coalescer
Dual Polarity® Electrostatic Field
Programmable Voltage Cycle
Composite Electrodes
Field Proven on Heavy and Difficult Oils
DUAL POLARITYTM DEHYDRATOR
TYPICAL ELECTRICAL ASSEMBLY
Following are some recent technology advancements that have significantly improved dehydration equipment performance.
TECHNOLOGY
Several Factors Influence Hydrodynamic Design of Separators
Inlet nozzle and momentum breaker design critical to efficient use of vessel volume
Internal baffle positions improve flow distribution and prevent high fluid velocity paths
Discharge nozzle designs affect fluid quality (vortex breakers may be inadequate)
Computational Fluid Dynamics Provides Insight to Fluid Flow in Separators
Velocity Vectors Colored by Velocity Magnitude
Computational Fluid DynamicsState-of-the-Art Method to Solve Practical Problems
Complex Fluid Flow Analysis
Flow Visualization and Distribution Analysis
Key Separator Components for Control of Fluid Flow Patterns
Inlet nozzle geometry and location Momentum dissipation devices (e.g., splash plate, vortex tubes, …) Solid (non-porous) weirs and dams Perforated plates Outlet nozzle geometry and location Vortex breakers or other directional flow devices
Box-Type Spreader with Open BottomTIMETIME 00 SECONDS00 SECONDS
TIMETIME 20 SECONDS20 SECONDS
Box-Type Spreader with Open Bottom
TIMETIME 40 SECONDS40 SECONDS
Box-Type Spreader with Open Bottom
TIMETIME 60 SECONDS60 SECONDS
Box-Type Spreader with Open Bottom
TIMETIME 80 SECONDS80 SECONDS
Box-Type Spreader with Open Bottom
TIMETIME 100 SECONDS100 SECONDS
Box-Type Spreader with Open Bottom
TIMETIME 120 SECONDS120 SECONDS
Box-Type Spreader with Open Bottom
TIMETIME 140 SECONDS140 SECONDS
Box-Type Spreader with Open Bottom
TIMETIME 160 SECONDS160 SECONDS
Box-Type Spreader with Open Bottom
TIMETIME 200 SECONDS200 SECONDS
Box-Type Spreader with Open Bottom
TIMETIME 220 SECONDS220 SECONDS
Box-Type Spreader with Open Bottom
Perforated Plates in Separators
Establish good fluid flow distribution to reduce short circuiting
Control liquid sloshing for ship-mounted systems
Perforated Plates in Separators
Design Criteria
Fraction of open area as holes Hole size Hole pattern Open area under plate for sand migration Placement and number of plates within separator
Fluid Flow Paths Upstream and Downstream of a Perforated Plate Show Turbulence and
Recirculation Patterns
Dual Perforated Plates Redistribute Flow Down Length of Separator
Separators on Floating Platforms are Subjected to Six Degrees of Motion
5
4
3
21
6
1. Surge: Y 4. Pitch: ZY
2. Sway: X 5. Roll: ZX
3. Heave: Z 6. Yaw: XY
For CFD Simulation, Vessels Placed in Actual Position on Platform to Accurately Capture
Vessel Movement Due to Wave Motion
Iso-surface Plot of Water/Oil Interface (Case #1)Iso-surface Plot of Water/Oil Interface (Case #1)
Time = 28.0 sec
Top of WeirPlate w/ Lip
Spill-over dueto Roll Motion
Vessel Tail
Water Spill-overReaches The Oil Outlet
Advanced Technology Reduces the Size of Downstream Separation Equipment
Electrostatic treaters dehydrate crude oil in ever decreasing vessel sizes CFD provides insight to vessel hydrodynamics Vessel internals designed to cope with process upsets
Water Treatment Systems become smaller, more efficient Improved designs for hydrocyclones extend turn-down
range and remove smaller droplets CFD-assisted column flotation design improves IGF
performance Can move IGF off-platform to save weight & space
SHROUDED-PIPE SPREADER
“Patented” Shrouded Pipe Distributor
Excellent momentum absorption
Near perfect flow distribution
No more than 5% flow recirculation
U.S. Patent 6,010,634
MODEL RESULTS - Water Table w/ Dye
STANDARDPIPE
DISTRIBUTOR
SHROUDEDPIPE
DISTRIBUTOR
ELAPSED TIME = 30 SECONDS
INTERFACE
OUTLET
STANDARDPIPE
DISTRIBUTOR
SHROUDEDPIPE
DISTRIBUTOR
ELAPSED TIME = 60 SECONDS
MODEL RESULTS - Water Table w/ Dye
Shrouded Inlet Spreader
TIMETIME 00 SECONDS00 SECONDS
TIMETIME 20 SECONDS20 SECONDS
Shrouded Inlet Spreader
TIMETIME 40 SECONDS40 SECONDS
Shrouded Inlet Spreader
TIMETIME 60 SECONDS60 SECONDS
Shrouded Inlet Spreader
TIMETIME 80 SECONDS80 SECONDS
Shrouded Inlet Spreader
TIMETIME 100 SECONDS100 SECONDS
Shrouded Inlet Spreader
TIMETIME 120 SECONDS120 SECONDS
Shrouded Inlet Spreader
TIMETIME 140 SECONDS140 SECONDS
Shrouded Inlet Spreader
TIMETIME 160 SECONDS160 SECONDS
Shrouded Inlet Spreader
TIMETIME 180 SECONDS180 SECONDS
Shrouded Inlet Spreader
TIMETIME 200 SECONDS200 SECONDS
Shrouded Inlet Spreader
TIMETIME 220 SECONDS220 SECONDS
Shrouded Inlet Spreader
Effects of Arcing
Arcing is a Natural Part of the Process
Arcs Momentarily Discharge a Steel Electrode Array
Significant Arcing Results in Performance Loss Due to Compromise of the Field
A Means of Arc Control is Needed.
COMPOSITE ELECTRODES
Conventional electrodes are constructed of Steel.
Composite Electrodes are made of plastic
COMPOSITE ELECTRODES
+ - + -
PLASTIC PLATECONDUCTIVESTRIP
CONDUCTIVE STRIP
TAPERED VOLTAGE FIELD
COMPOSITE ELECTRODES
COMPOSITE ELECTRODES PROVIDE ADDITIONAL TOLERANCE FOR WATER
AND CONDUCTIVITY
FIBER REINFORCED THERMOPLASTIC CONSTRUCTION
RELIANCE ON SURFACE CONDUCTIVITY
QUENCH ELECTRICAL ARCS
PROVIDE FIELD GRADIENT
INCREASE INTENSE-FIELD RETENTION TIME
PROVIDE HIGHLY STABILIZED ARRAY
POWER SUPPLY REQUIREMENTS
PROTECTIONMUST PROTECT ELECTRICAL COMPONENTS IN CONDUCTIVE ENVIRONMENTS
FLEXIBILITYABILITY TO HANDLE VARYING FEEDSTOCK
AVAILABILITYMINIMAL DOWNTIME IN CHALLENGING CONDITIONS
LOAD-RESPONSIVE CONTROLLER
LOAD-RESPONSIVE CONTROLLERConventional means of transformer protection: reactor in primary circuit
REACTOR
T
RANSFORMER
HI VOLTAGE TO PROCESS
POWER SUPPLY
LOAD RESPONSIVE CONTROLLER
Another way to control power … time-based voltage
chopping
Vo
lta
ge
Crude Oil Conductivity
Maintains Heat Dissipation RatingFunctions During Process Upset ConditionPreserves Coalescing EffectMicroprocessor design allows field modulation
Slow Modulation Voltage Cycle
Field Control by Load Responsive Controller (LRC®)
Modulated Dual Polarity® Benefits
Modulation offers the Following Improvements:
Added Coalescing PowerMore Effective on Smaller DropsBetter Drop GrowthHigher Water ToleranceIncreased Tolerance to Conductive Oils
Modulated Fields - Terminology Threshold Voltage Gradient
Voltage Gradient Necessary to Initiate Coalescence Critical Voltage Gradient
Limiting Maximum Voltage Gradient at Which a Drop of a Specified Diameter Can Exist
Modulation Frequency Affects Drop Transport Drop Relaxation Field Decay
State-of-the-Art Technology:Modulation of the Electrostatic Field
Slow Speed Modulation (as in EDD) Used to Control Drop Size Distribution
Pulse Modulation Used to Energize Drop Surfaces
Base Frequency ControlUsed to Limit Field Decay
Effects of Pulse Modulation & Base Frequency
Energizes Drops at Resonant Frequency
Deformed Drops More Readily Coalesced
Allows Adjustment for Physical Parameters Interfacial Tension (Pulse Modulation) Oil Conductivity (Base Frequency) Density Viscosity
Resonant Frequency Oscillation
• Electrophoretic movement becomes oscillatory
• Drop deforms
• Surface free energy counters interfacial tension
• Drop surface becomes highly reactive
• Coalescence enhanced by reduced energy barrier
• High frequency electrostatic field applied
• Marangoni Effect produces localized circulation in drop
Field Decay in Conductive OilsLimits Coalescence Performance
Increasing Conductivity
Vo
ltag e
+
-
Effect of Base Frequency on Voltage DecayIncreases Coalescence Performance
1
1−
sin z( )
200 z
1
1−
s i nz( )
2 00 z
Low Frequency High Frequency
Note deep RC discharge between voltage peaks.
Note shallow RC discharge between voltage peaks.
Low Frequency High Frequency
Note deep RC discharge between voltage peaks.
Note shallow RC discharge between voltage peaks.
PROBLEM:
Increased capacity was needed through existing desalting units in Africa, and shipping quality specifications had to be maintained.
SOLUTION:
AC Treaters were Retrofitted with Dual Polarity Electrode system.
RESULTS:
Capacity increased from 50,000 BPD to 100,000 BPD and shipping quality was maintained.
EXAMPLE OF IMPROVED TECHNOLOGY BENEFIT
EXAMPLE OF IMPROVED TECHNOLOGY BENEFIT
PROBLEM:
Existing North Sea DUAL POLARITY dehydrator designed for 60,000 BPD, but production had increased to 100,000 BPD
SOLUTION:
Retrofit unit with Composite electrodes
Retrofit unit with Pipe/Deflector spreader
RESULT:
Capacity increased to 100,000 BPD
CRUDE OILDEHYDRATION
CRUDE OILDESALTING
Mineral salts are often carried in solution in the water which is emulsified in the oil. In addition there are often small amounts of insoluble solids carried in the oil or water phases.
THE SALT PROBLEM
SALT INWATER
OIL
THE SALT PROBLEM
WHERE DOES THE SALT COME FROM?
IN THE FIELD, IT COMES FROM THE FORMATION
IN THE REFINERY IT IS EITHER RESIDUAL SALT REMAINING AFTER FIELD DEHYDRATION, OR IS SEA WATER WHICH HAS CONTAMINATED THE OIL
THE SALT PROBLEM
THE RESIDUAL WATER CONTAINS MINERAL SALTS. SALT IS A PROBLEM IN THE FOLLOWING WAYS . . .
1. IT PROMOTES CORROSION
2. IT FOULS HEATERS, HEAT EXCHANGERS, PUMPS AND TOWER
TRAYS
3. IT POISONS CATALYSTS IN REFINERY UPGRADING PROCESSES
TYPICAL SALT-IN-OILREQUIREMENTS
OILFIELD: 10 - 25 PTB
REFINERY: 0.5 - 3 PTB
CORROSIONSALT DEPOSIT FOULING
CORROSIONSALT DEPOSIT FOULINGCATALYST POISONING
(PTB = pounds of salt per 1000 bbls of oil)
FOR
THE SALT PROBLEM
THE SALT PROBLEM
S/O = 0.35 x S/W x W/L
1 - W/L
S/O = salt-to-oil (PTB)S/W = salt-to-water (mg/l water salinity)W/L = water-to-total liquid (volume fraction)
THE SALT PROBLEM
DEHYDRATION ALONE IS INSUFFICIENT TO MEET THE SALT REMOVAL REQUIREMENTS IN MANY CASES
0.1 0.2 0.3 0.4 0.5 0.6RESIDUAL WATER (%)
100 100.000 mg/l
200
0PT
B (
PO
UN
DS
OF
SA
LT
PE
R 1
00
0 B
BL
S O
F O
IL)
50,000 mg/l200,
000
mg/
l
THE SALT PROBLEM
TYPICAL FIELD REQUIREMENTS
TYPICAL REFINERY REQUIREMENTS
S/O = 0.35 x S/W x W/L
1 - W/L
This formula suggests that there are two parameters that determine salt-in-oil:
•Water Salinity
•Water Fraction of the Stream
DESALTING FUNDAMENTALS
S/O = 0.35 x S/W x W/L
1 - W/L
This formula suggests that there are two parameters that determine salt-in-oil:
•Water Salinity
•Water Fraction of the Stream
Water fraction can be reduced by simple dehydration, using principles already discussed.
To reduce water salinity, it must be diluted.
+ =
DESALTING FUNDAMENTALS
Basic desalting consists of two sub-processes:
1st - Dilution - of the dispersed brine with a water of lesser salinity (called ‘wash water’ or ‘dilution water’)
2nd - Dehydration - removal of the diluted
dispersed brine by oil
dehydration
DESALTING FUNDAMENTALS
DILUTION OF DISPERSED BRINE
Wash waterInjection
RoughDispersing
of wash water
Mixing by hydraulic or mechanical agitation, usually a
‘Mixing Valve’
To desalter vessel for dehydration
Wet Crude Oil Inlet
Desalting Chemicalinjection
Continued hydraulic Coalescence
THE MIXING VALVEDifferential Pressure Controller
Mixing Valve
CrudeFlow
Static Mixer (Optional) is occasionally installed either upstream or downstream of the mixing valve
To Desalter
DPC
MIXING VS. DEHYDRATION IN DESALTING
Single Stage Desalter
Crude Oil Inlet
Wash Water Inlet
Brine Discharge
Desalted Oil Discharge
Mix Valve
DESALTER BASIC FLOW SCHEME
CONSERVATION OF WASH WATER
There are several reasons why wash water must be conserved:
Supply of fresh or near-fresh water is often scarce, particularly in the producing field.
Disposal of effluent water is often costly, and needs to be minimized.
Too much total water can cause desalter electrodes to short-circuit.
SOURCES OF WASH WATER
RefineryCondensate from towersCooling waterUtility water
FieldDeep fresh-water formationsShallow groundwaterRiver waterSea water (often must be de-salinated)
DUAL POLARITY DESALTER (typical)
DOUBLE VOLT AC ELECTROSTATIC COALESCER
Earth
Grid 1 Grid 3Grid 2
Grid 3 Grid 2
Power Unit 3
Grid 1
DELTA
Power Unit 1
Power Unit 2Power Unit 3
Power Unit Power UnitPrimary Connections Grid Connections Secondary Connections
Phase A
Phase B
Power Unit 1
EarthPhase B
Phase C
Power Unit 2
EarthPhase C
Phase A
Power Unit 3
Earth
Power Unit 2
Grid 1
Grid 2Grid 3
Earth
Power Unit 1STAR
Power Unit 3
Phase A
Phase B
Phase C
DELTA
Power Unit 1
Power Unit 2
TRIGRID AC ELECTROSTATIC COALESCER
Earth GridGrid 2
Grid 1
Earth
Grid 1 Grid 2
Phase A
Phase B
Earth
Grid 2
Grid 1
Earth
Power Unit Power UnitPrimary Connections Grid Connections Secondary Connections
Power Unit
Phase A
Phase B
Power Unit
Earth
Power Unit 1
Power Unit 2
Power Unit 3
Grid 1 Grid 2 Grid 3
Power Unit Power UnitPrimary Connections Grid Connections Secondary Connections
Earth
Grid 1 Grid 3Grid 2
Phase A
Phase B
Power Unit 1
EarthPhase B
Phase C
Power Unit 2
EarthPhase C
Phase A
Power Unit 3
Earth
Grid 1
Power Unit 2
Grid 2Grid 3
Earth
Power Unit 1STAR
Power Unit 3
Phase A
Phase B
Phase C
DELTA
Power Unit 1
Power Unit 2
TRIVOLT AC ELECTROSTATIC COALESCER
HIGH VOLTAGE ASSEMBLY
Power Unit
Oil Level Glass
Disconnect Link
High Pressure Bushing
Continuous Vent
10” ANSI Class 300 lbPower Inlet nozzle
Vessel Wall
Power Connector Rod
WeightPick-up bucket
Overflow with liquid seal
Electrode Insulator Assembly
DESALTER SIZING
DESIGNFLOWAREA
FLOWAREA =
OIL FLOW (BPD)DESIGN FLUX
DESIGN FLUX OBTAINED FROM...
SIZING STANDARDS
LOCAL HISTORICAL NORMS
PILOT TESTS
PILOT TESTS
Natco’s HTU dehydration/desalting pilot unit in the Tulsa R&D facility simulates field or refinery dehydration and desalting processes;tests conventional and state-of-the-art
technologies
PILOT TESTS
To maintain reasonable wash water requirements, the inlet stream can contain only a small amount of dispersed brine. To reduce high inlet brine concentrations, a dehydrator is placed upstream.
LIMITATIONS OF SINGLE STAGE DESALTERS
DEHYDRATOR/DESALTERFLOW SCHEME
Wash Water Effluent
Water
Emulsion Inlet
Outlet Oil
Effluent Water
Mix Valve
TWO STAGE DESALTERSWITH INTER-STAGE RECYCLE
Brine Recycle
THREE STAGE DESALTERSWITH INTER-STAGE RECYCLE
Where extreme wash
water conservation
or deeper desalting is
required, three stages may be used
Single Stage Desalterwith Internal Recycle
Crude Oil Inlet
Wash Water Inlet
Brine Discharge
Desalted Oil Discharge
Recycle Pump
Mix Valve
InternalRecycle
INTERNAL RECYCLE
First Stage Second Stage
Crude Oil Inlet
Wash Water Inlet
Brine Discharge
Desalted Oil Discharge
Recycle Pump
Mix Valve
Internal Recycle
Mix Valve
Inter-Stage Recycle
Two Stage Desalterswith Internal and Inter-Stage Recycle
INTERNAL RECYCLE
Three Stage Desalterswith Internal and Inter-Stage Recycle
First Stage
Second Stage
CrudeOil Inlet
Wash Water Inlet
Brine Discharge
Oil Discharge
Third Stage
INTERNAL RECYCLE
REFINERY DESALTING
REFINERY
PRODUCER A
PRODUCER B
PRODUCER C
PRODUCER D
FIELD DESALTERS
(3) 2-Stage TrainsAt Sea Side, Egypt
FIELD DESALTERS
1st and 2nd Stages, Mid-East
REFINERY DESALTERS
2-STAGE, Mid-East
SEPARATION OF SUSPENDED SOLIDS
CHEMICAL TREATMENT
WATER WASH
REMOVAL OF SEPARATED SOLIDS
SAND JETS (MUD WASH SYSTEM)
INTERFACE SLUDGE DRAINS
DESIGN AND OPERATIONAL CONSIDERATIONS
OPERATIONAL CONSIDERATIONSAVOID CRYSTALLINE SALT
In the producing field, it is caused by low water-content wells being flash- stripped during degassing.
In the refinery it is caused by heating a low water-content crude to where the water solubility exceeds available water.
DESIGN AND
HEATERS
CHARGEPUMPS
FEEDSTOCKTANKS
DESALTERS
WASH WATERSUPPLY
SMALL AMOUNT OF WASH WATER
INJECTED UPSTREAMOF HEATERS
AVOIDING SALT CRYSTALLIZATION AND DEPOSITION IN REFINERY DESALTERS
Solids Control• Sources of Solids
• Formation Fines & Precipitated Scale
• Precipitated Asphaltenes
• Solids Partitioned Between Oil and Water Phases
• Chemical Treatment May Help
• Some Remain in the Vessel
• Interface Sludge
• Bottom Sediments
• Removal Is Essential For:
• Control of Conductivity
• Maintenance of Flow Distribution
Solids Removal
Interface Sludge Drain
Mud Wash (Sand Jet) System
Operated As Required
Scheduled Operation
ADVANCED DESALTING
TECHNOLOGIES
TECHNOLOGY
Combines 5 Essential Process Technologies:
Dual Polarity® Electrostatic DehydratorStart with a proven technology
Composite Plate ElectrodesProvide high water tolerance
Load Responsive ControllerControls field strength
Counterflow Dilution Water ProcessProvides multi-stage contact
Electrostatic Mixing ProcessFocuses mixing energy only on dispersed phase
ELECTRO-DYNAMIC® DESALTER
ELECTRO-DYNAMIC® DESALTER
ELECTRO-DYNAMIC® DESALTER
. . . . . .OIL COLLECTOR
SPREADER
. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
INLET
COMPOSITE ELECTRODES
OUTLET
WATER OUTLET
WASH WATERHEADER
WASHWATERINLET
ELECTRO-DYNAMIC DESALTER -LOAD RESPONSIVE CONTROLLER
ELECTRO-DYNAMIC DESALTER - PC BASED LOAD RESPONSIVE CONTROLLER
3
LRCProgramming/Monitoring
Software
DEDICATED ORPORTABLE
Feedback
Transformer,SCRs andFiring Board
JunctionBox
NATCO ControlBoard andDiagnostic
Display
PC With LRCProgram andMonitoringSoftware
LRCControl
SoftwareAC Power
LOCAL MAY BE LOCALOR REMOTE
Control
Diodes
ELECTRO-DYNAMIC DESALTER - COUNTERFLOW WASH WATER PROCESS
WASHWATERHEADERELECTRODE
PLATES
DOWNWARDWATER FLOWUPWARD
OIL FLOW
ELECTRO-DYNAMIC DESALTER
OIL OUTLET
TYPICAL SINGLE STAGE EDD
BRINE OUTLETMIX
VALVE
CRUDE OIL INLET
FIRST WASH WATER INLET
COUNTERFLOW WASH WATER
INLET
EDD IN FAR EAST REFINERY
EDD IN FAR EAST REFINERY
EDD IN FAR EAST REFINERY
Dual Frequency Technology
Transformer Three phase design Low reactance Increases power utilization up to 70%.
Voltage Control Voltage levels can be optimized. Pulse waveform can be selected.
Frequency Control Base Frequency Pulse Frequency
Modulation of the Electrostatic Field
Slow Speed Modulation Used to Control Drop Size Distribution
High Speed Modulation Used to Energize Drop Surfaces
Dual Frequency®Compact Electrostatic Dehydrator
High Speed Modulation of Field
Energizes Drops at Resonant Frequency
Deformed Drops More Readily Coalesced
Allows Adjustment for Physical Parameters Interfacial Tension Oil Conductivity Density Viscosity
Dual Frequency®Compact Electrostatic Dehydrator
Dual Frequency®Compact Electrostatic Dehydrator
• Incremental improvement, over existing best in class electrostatic technology.
• Allows the operator to minimize planned capital expansions: Increases processing capacity of existing vessels.
• Allows processing of difficult, highly conductive, viscous oils and/or oil blends.
• Debottleneck offshore platforms where minimization of space, weight and performance are critical.
Benefits:
The transformer consists of three primary components, packaged in a single oil-filled enclosure (three phase, 480 volts (50 / 60 Hz)).
• First, the 480 volts is conditioned to produce a variable amplitude and variable frequency voltage supply for the primary of the transformer.
• Second, the medium frequency transformer steps up the input voltage to a secondary voltage level necessary to promote effective coalescence.
• Third, the secondary voltage is rectified into positive and negative half-wave outputs. These polarized, half-wave voltages are then applied to the electrodes to create the benefits of both AC and DC fields.
Dual Frequency®Compact Electrostatic Dehydrator
Characteristics:
A PC-based process controller defines the voltage production.
Dual Frequency®Compact Electrostatic Dehydrator
• To highly conductive crude oils:• Increasing frequency to maximize the energy delivered to
the oil dehydration process.• Using a medium frequency transformer overcomes the
voltage decay associated with conventional 50/60 Hz transformers.
• Where the interfacial tension between the oil and water is low:• Adjust the waveform minimize destruction of the water
droplets normally caused by the application of 50/60 Hz power.
• Reducing the frequency of the waveform and the selection of the shape of the voltage waveform allow to achieve the best dehydration results.
Dual Frequency®Compact Electrostatic Dehydrator In wet crude oils (low effective impedance, rapid voltage
decay):
Reduces voltage decay and effectively sustains the applied voltage.
Seting the minimum and maximum voltage levels to increase the percentage of the entrained water that is swept by the electrostatic voltage. Maximize the droplet growth to promote a rapid sedimentation rate and reach the smallest water to develop a surface charge and promote coalescence.
Reducing the voltage to a minimum level will maximize the droplet growth to promote a rapid sedimentation rate.
PC-based Dual Frequency load responsive control system can control:
• The output of the transformer to produce an infinite variety of waveform configurations.
• The unique waveform generated is optimized to the specific oil’s physical properties, and enables higher treatment rates and lower BS&W levels than conventional technology.
Dual Frequency®Compact Electrostatic Dehydrator
0
20
40
60
80
100
0 500 1000 1500 2000
Frequency, Hz
Dem
uls
ific
ati
on
, %
1000 V3000 V
International Chemical Engineering, Vol. 33, no. 1, January, 1993
Data from German Researchers
Demulsification vs. Frequency
Dual Frequency® The Latest Development
• Combines Modulation Modes
• Maximum Drop Growth & Vessel Flux
• Optimized for Crude Oil Characteristics
• More Efficient Power Utilization
• Easy Retrofit
Dual Frequency® Field Test Results
0
0.1
0.2
0.3
0.4
0.5
0 20000 40000 60000 80000 100000 120000
Dual Polarity
Composit
e
Dual Frequency
Capacity (BOPD)
Out
let B
S&
W (
%)
Dual Frequency Results
Dual Frequency Applications
Retrofits to existing installations: Especially Dual Polarity (External Changes) Increased performance: BS&W and/or Capacity
Refinery market where: Highly conductive crudes cannot be desalted Space is a constraint
Offshore production facilities where: Space is limited Weight increases deck construction & expense
Dual Frequency Advantages
Reduced outlet BS&W by 30 to 95% Tested on oils between 17 & 40 API.
Allows an increase in vessel throughput from 50 to 100%.
Easy retrofit to existing Dual Polarity dehydrators or desalters Estimated 2000 vessels currently in service.
Replaces steel and vessel volume with advanced electrostatic controls Easily optimized to process conditions.
Dual Frequency®Compact Electrostatic Dehydrator
ConventionalA/C
14’ x 65’ CurrentState-of-the-Art
Technology12’ x 40’
DualFrequencyTM
10’ x 26’
CoalescingDroplets
Example:80,000 BOPD32° API Crude4 cps ViscosityInlet: 5% BS&WOutlet: 0.5% BS&W
Dual Frequency TM
Compact CoalescerTechnology