Desalter Arreglos en Torre Atmosferica

8/4/2019 Desalter Arreglos en Torre Atmosferica

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Crude DistillationCrude DistillationChapter 4Chapter 4

Light Naphtha

CrudeOil

Desalter

AtmosphericDistillation

VacuumDistillation

GasSeparation &

Stabilizer

SolventDeasphalting

Coking

Visbreaking

FluidizedCatallytic

Cracking

Hydro-cracking

NaphthaReforming

Isom-erization

Sat GasPlant

Polymer-ization

Alkylation

NaphthaHydro-treating

Treating & Blending

Coke

Fuel Gas

LPG

AviationGasoline

AutomotiveGasoline

Solvents

Jet Fuels

Kerosene

Solvents

Heating Oils

Diesel

ResidualFuel Oils

Lubricant

Greases

Waxes

Asphalts

HeavyNaphtha

Kerosene

Distillate AGO

LVGO

HVGO

Vacuum Residuum

CatDistillates

Gas OilHydro-

treating

DAO

Isomerate

Gas

AlkylFeed

Alkylate

PolymerizationNaphtha

Gasses

Butanes

LPG

Reformate

Naphtha

Fuel OilBottoms

Distillates

DistillateHydro-treating

CatNaptha

Cycle Oils

SDA Bottoms

CokerNaphtha

CokerGas Oil

SulfurPlant

Sulfur

Naphtha

Fuel Oil

SolventDewaxing

Lube Oil

Waxes



Typical Crude Tower ProductsTypical Crude Tower Products

950 to 1100Vacuum Resid

950 to 1100800HVGO

(Heavy Vac Gas Oil)

800650LVGO

(Light Vac Gas Oil)

650420 to 520AGO

(Atm Gas Oil)

420 to 520330 to 380Distillate

(Kerosene)

330 to 380180 to 220Heavy Naphtha

180 to 22080 to 90Light Naphtha(LSR Gasoline)

TBP EP (°F)TBP IBP (°F)Cut

OverviewOverview

• Crude Stills

» Historically the oldest refining process

» Only the first step in crude oil processing

• Purpose

» To recover light materials

» Fractionate into sharp light fractions

• Configuration — May be as many as three columns inseries

» Crude Stabilizer/Preflash Column

Reduce traffic in the Atmospheric Column

» Atmospheric Column

» Vacuum Column

Reduced pressure to keep temperatures below650°F



OverviewOverview

• Crude Stills» Historically the oldest refining process


• Purpose







» Vacuum Column


Typical ConfigurationTypical ConfigurationAtmospheric Column w/oAtmospheric Column w/o PreflashPreflash

Modification of drawing in:Refining Overview – Petroleum Processes & Products,by Freeman Self, Ed Ekholm, & Keith Bowers, AIChE CD-ROM, 2000




Column Configuration

• Condenser …• Partial condenser if no

Stabilizer Column.• Total condenser if Stabilizer

Column to remove lightends.

• … but no reboiler.


Feed Preheat Exchanger Train

• All of the heat to drive thecolumn comes from the hotfeed.

• As much as 50% of theincoming crude may beflashed.







• Stripping steam to reducepartial pressure hydrocarbons.

• Condensed & removed as asecond liquid phase.

• Conditions set so it doesn’tcondense within the column.

• Can lead to foaming.• Must be treated as sour

water.



• Final heating in a direct firedheater.

• Inlet typically 550°F.• Heated no higher than 750°F

• Minimize thermal cracking.





• Actual heat exchange is withstreams from within the tower.

• Recovery of heat important todistillation economics.

• Final cooling done with aircoolers or cooling water.



• Recovery of heat important todistillation economics!




• Recovery of heat important todistillation economics.

• Final cooling done with aircoolers or cooling water.


• First absorb part of theoverhead condensation load

• Exchange with one or more of the liquid sides streams,beginning with the top(coldest ) side stream.




Desalter

• Point must be carefully selected— care taken not to let thewater vaporize

• Lighter crudes (> 40°API) @250°F

• Heavier crudes (< 30°API)@ 300°F

• Balance temperature & pressure


Desalter

• All crudes contain salts• May be sodium chloride,

magnesium chloride, etc.• Salt present in the

emulsified water• Treated in the field with

heat & chemicals tobreak oil wateremulsions.




Desalter

• Salt can cause damage toequipment

• Scale in heat exchangers• Drastically reduce heat

transfer• Hydrogen chloride formation

can lead to corrosion• Metals that can poison

refinery catalysts

Crude Electrostatic DesaltingCrude Electrostatic Desalting

Drawings from:Refining Overview – Petroleum Processes & Products,by Freeman Self, Ed Ekholm, & Keith Bowers, AIChE CD-ROM, 2000




Desalter

• Remove salts & dissolvedmetals & dirt

• Oil mixed with fresh washwater & demulsifiers.

• Mixed & heated followed bysettling

• Separated in an electrostaticsettling drum


Desalter

• Added wash water as much as10% of crude oil charge

• About 90% of the water canbe recovered

• Effluent water must be treatedfor benzene recovery




Wash Zone

• Couple trays between flash zone& gas oil draw.

• Reflux to wash resins & otherheavy materials that maycontaminate the products.


Condenser

• Typically 0.5 to 20 psig.• Balancing act

• Low pressures reducecompression on overheadsystem

• High pressures decreasevaporization but increaseflash zone temperatures & furnace duty; affects yields




Pumparounds

• Reduces overhead condenserload & achieves more uniformtower loadings

• Provides liquid reflux belowliquid draws


Side Draws & Strippers

• “Cut point” related to finalboiling point of draw stream

• Side strippers remove lightcomponent “tail” & return tomain column

• Steam strippers traditional• Reboiled strippers reduce

steam usage & associated sour water




Trays & Pressure Profile

• Typically 32 trays in tower• 0.1 to 0.2 psi per tray

• Condenser & accumulator• 3 to 10 psi across condenser• Liquid static head in

accumulator• Typically 6 to 16 psi across

entire column.

OverviewOverview

• Crude Stills

» Historically the oldest refining process


• Purpose







» Vacuum Column




Vacuum DistillationVacuum Distillation

Drawings from:Refining Overview – Petroleum Processes & Products,by Freeman Self, Ed Ekholm, & Keith Bowers, AIChE CD-ROM, 2000



• Vacuum conditions to keep operatingtemperatures low

• Large diameter column• Very low density gasses

• Condenser for water vapor• Liquid reflux from pumparounds

• No reboiler• Stripping steam may be used

• Needed for deep cuts (1100°F)




Feed

• Atmospheric residuum• All of the vapor comes from the heated

feed stream• Under vacuum (0.4 psi)

• Separate higher boiling materialsat lower temperatures

• Minimize thermal cracking

Vacuum DistillationVacuum DistillationProducts

• May have multiple gas oils• Separate products to increase the

heat recovery in the column• Products recombined downstream

• Usually FCCU via hydrotreating• Vacuum resid

• Blended — asphalt, heavy fuel oil• Further processing — thermal,

solvent• Choice depends on products &

types of crude




Dry System

• 1050°F+ cut temperature & nostripping steam

• Smaller tower diameters• Reduced sour water production

• Pressure profile• Flash zone: 20-25 mm Hg abs &

750 to 770°F.• Top of tower: 10 mm Hg abs


Deep Cut System

• 1100°F+ cut temperature & strippingsteam

• Steam reduces hydrocarbon partialpressures

• Pressure profile• Flash zone: 30 mm Hg abs

• Hydrocarbon partial pressure10-15 mm Hg abs

• Top of tower: 15 mmHg abs




Steam Ejectors & Vacuum Pumps

• Vacuum maintained on tower overhead• Steam systems considered more

reliable• Waste steam is sour & must be

treated• Combinations systems — Last steam

stage replaced with a vacuum pump

SummarySummary

• What are the important take-away messages?

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Desalter Arreglos en Torre Atmosferica

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