natco 48674699 electrostatics separation technology[1]

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

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

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

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?

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 testAmperage against test temperature

0 10 20 30 40 50 60 70 80 90

Temperature (°C)

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)

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

Outlet

FLOW DISTRIBUTION

PerforatedDistributorBaffles

UP-FLOW

LONGITUDINAL-FLOW

COALESCING SURFACES CAN SPEED UP SEPARATION

HeatChemistryFlow RegimeCoalescing SurfacesElectrostatic Fields

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

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

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

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

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

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

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

Kvaerner (HRI) Electrical treaters

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

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

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

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

+ - + -

PLASTIC PLATECONDUCTIVESTRIP

CONDUCTIVE STRIP

TAPERED VOLTAGE FIELD

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

RANSFORMER

HI VOLTAGE TO PROCESS

POWER SUPPLY

LOAD RESPONSIVE CONTROLLER

Another way to control power … time-based voltage

chopping

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

ltag e

Effect of Base Frequency on Voltage DecayIncreases Coalescence Performance

sin z( )

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

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

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

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)

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

50,000 mg/l200,

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.

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

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

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

Grid 1 Grid 3Grid 2

Grid 3 Grid 2

Power Unit 3

Grid 1

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

Power Unit 2

Grid 1

Grid 2Grid 3

Power Unit 1STAR

Power Unit 3

Phase A

Phase B

Phase C

Power Unit 1

Power Unit 2

TRIGRID AC ELECTROSTATIC COALESCER

Earth GridGrid 2

Grid 1

Grid 1 Grid 2

Phase A

Phase B

Grid 2

Grid 1

Power Unit

Phase A

Phase B

Power Unit

Power Unit 1

Power Unit 2

Power Unit 3

Grid 1 Grid 2 Grid 3

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

Grid 1

Power Unit 2

Grid 2Grid 3

Power Unit 1STAR

Power Unit 3

Phase A

Phase B

Phase C

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

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

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

Recycle Pump

Mix Valve

InternalRecycle

INTERNAL RECYCLE

First Stage Second Stage

Crude Oil Inlet

Wash Water Inlet

Brine 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

. . . . . .OIL COLLECTOR

SPREADER

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

OUTLET

WATER OUTLET

WASH WATERHEADER

WASHWATERINLET

ELECTRO-DYNAMIC DESALTER -LOAD RESPONSIVE CONTROLLER

ELECTRO-DYNAMIC DESALTER - PC BASED LOAD RESPONSIVE CONTROLLER

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

CRUDE OIL INLET

FIRST WASH WATER INLET

COUNTERFLOW WASH WATER

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

• 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.

Characteristics:

A PC-based process controller defines the voltage production.

• 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.

0 500 1000 1500 2000

Frequency, Hz

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 20000 40000 60000 80000 100000 120000

Dual Polarity

Composit

Dual Frequency

Capacity (BOPD)

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.

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

natco 48674699 electrostatics separation technology[1]

rapid sedimentation

shrouded pipe

electrical

improved technology

power unit

crude oil

wash water

dehydration

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