New - 11 Process Units

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Process Units

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Outcomes

Correlate units and locations within units to typical corrosion, fouling, and alloy degradation problems

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Operating Guidelines

Only operating guidelines to prevent corrosion, fouling, and alloy degradation are included hereSome may be contrary to making most/best product

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Desalter

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Typical Corrosion and Fouling Problems

Corrosion of water outlet lines (brine)Fouling of inlet heat exchangers

(generally oxygen and excessive temperature)

Remaining problems with desalters arent problems in the desalter

Affect efficiency and downstream corrosion

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Two Stage Desalter

May be Monel

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Keep inlet heat exchangers below 300oF (150oC) Reduces corrosion rates in exchangers Reduces fouling in exchangers Allows Monel exchanger tubes when necessary

Caustic embrittlement possible if adding caustic before desalter

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Water quality is important Low oxygen most important

Minimizes fouling

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Crude Unit

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HCl corrosion in overhead system ammonium chloride ammonium bisulfide

High temperature sulfur corrosionNaphthenic acid corrosionAsphaltene/wax/polymer foulingPolythionic acid SCC (300 series SS)

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Nitrogen contamination of downstream units from corrosion inhibitorSodium contamination of downstream units from caustic injection

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Typical Alloy Degradation Problems

Creep in heaters

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Crude Unit

- 500 F Zone

Steam

NH3 UNICOR

ChargeHeater

Fresh Water

Crude

Make-up Water

To Flare

Crude Column

SidecutStrippers

Overhead Receiver

RecontactDrum

Stabilizer

Splitter

Reduced Crude

Light Gas Oil

Kerosene

LPG

LightNaphtha

HeavyNaphtha5 Cr -

1/2 Mo

Heavy Gas OilSteam

Monel Lined

Base MaterialKCS

Lined withTP405 orTP410S

Tube Side -90 - 10 Cu - Ni

90 - 10 Cu - Ni

Usually9 Cr - 1 Mo

CS Lined withTP405 orTP410S

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Crude Unit

5 Chrome, 9 Chrome, 405, 410 Sulfur resistance

405, 410 good lining materials 5 and 9 chrome are not good for linings

Monel HCl resistance in overhead

90-10 Cu Ni / Monel Chloride resistance in desalter brine

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Crude Unit

If naphthenic acids are an issue All 5 and 9 Chrome, 405, and 410 change to

317 or 316 with 2.5% (min) Mo Carbon steel in light gas oil cut may also

change to 317 or 316 with 2.5% (min) Mo2.5% moly requiredMust guard against polythionic acid SCC

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Desalt well

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Operate top of column above dew pointUse corrosion inhibitors if necessary

Oil soluble inhibitors travel with productBlend crudes for TAN and sulfur based on unit metallurgyOperate heaters to:

Avoid flame impingement Stay within design tube metal temperatures

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Overhead, Well Operated

Sour Water

Water Wash

pH ControlDew Point

Inhibitor

Gases

Product

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Overhead, Poor Control

Sour Water

Water Wash

pH ControlNatural Dew Point

Inhibitor

Gases

Product

Monel

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FCC

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Typical Corrosion Problems

High temperature combustion corrosion Regenerator O2, CO2, CO, NOx, SOx

High temperature sulfur corrosion Reactor Bottom of main column

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Fouling by heavy PNAs Bottom of main column and exchangers

Ammonium Chloride corrosion and fouling Main column overhead Nitrogen in feed plus generated hydrogen

form ammonia Cl- from NaCl in feed Form NH4Cl - sublimates in overhead system

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Fouling by polymerization Gas concentration section Oxygen (from upstream wash water), olefins,

proper temperatureCoking

(Condensation of heavies) Transfer lines Main column bottoms

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HCN Forms at high temp in reactor Increases corrosion in all wet areas

downstream Disrupts protective sulfide scale Increases hydrogen penetration into steel

Metals contamination in feed Regenerator Low melting point oxides and sulfides

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Creep (all high temperature components)Creep embrittlement (1 Cr)885 embrittlement (Cr stainless internals)Thermal fatigue (high/low temp mix points)Sigma phase embrittlement (internals)

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FCC Reactor / RegeneratorReactor Effluent

11/4 Cr - 1/2 Mo

Fuel Gas

11/4 Cr - 1/2 Mo

AirTP304 H

Steam

11/4 Cr - 1/2 Mo

Reactor Effluent

11/4 Cr - 1/2 Mo

1 Cr - 1/2 Mo or 11/4 Cr - 1/2 MoLined with TP405 or TP410S1 Cr - 1/2 Mo or 11/4 Cr - 1/2 MoLined with TP405 or TP410S

Fuel Gas

TP 304 H

11/4 - 1/2 Mo Lined KCSTP304 H Internals

AirTP304 H

Steam

11/4 Cr - 1/2 Mo

Feed

CrRefractory

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FCC Reactor / Regenerator

1 and 1 1/4 Chrome High temperature strength

304 H High temperature strength, oxidation

resistance Consider Polythionic Acid SCC

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FCC Main Column Overhead

Sour Water

Gasoline

FlareWetGas

Compressor

Water Wash

NH4ClDeposits

NH4Cl Deposits

KilledCarbonSteel

1/8" CA

Killed Carbon SteelTubes & Headers

3/16" CA on Headers

Killed Carbon SteelPWHT

1/4" CA on Boot

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FCC Main Column Overhead

Killed carbon steel Wet H2S corrosion Hydrogen blistering

PWHT Carbonate Cracking

High corrosion allowances H2S and NH4Cl corrosion

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FCC Main Column Bottoms

Raw Oil

OtherHeat

ExchangeStreams

SteamGenerator

BFW

Steam

SlurrySettler

DiluentSlurry

CWClarifiedSlurry OilProduct

ReactorVapor

1 1/4 Cr - 1/2 MoWith or WithoutTP 405 or 410S

Lining

Carbon Steel405 or 410S

Lining

5 Cr - 1/2 Mo

1 1/4 Cr - 1/2 Mo

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FCC Main Column Bottoms

1 1/4 Cr inlet piping High temperature strength

All vapor - sulfur not as much of an issue here

1 1/4 Cr vessels w/wo lining Strength Sulfur

5 Cr piping Sulfur

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Sulfur Check corrosion vs. sulfur and temperature

before making operational changesH2S

Some H2S in wet sections of unit is good Sulfide scale resists corrosion

CN- Keep below 20ppm (lower is better)

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Bottoms exchangers (PNA fouling) Tube velocities 4-7 ft/sec Antifoulants may be effective

Check for CO32- (originates as CO2 in regenerator) May require PWHT to prevent cracking

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Ammonium chloride / ammonium bisulfide Water wash

Continuous Counter current

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FCC Water Wash System

To Sour WaterStripper WGC

1st StageCondensate

InterstageDrum

WGC2nd Stage

Main ColumnReceiver

MainColumn

High PressureReceiver

HydrocarbonWater

Water must not be injected here

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Hydrotreaters

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Rust from tankage Oxygen in tank/transport Plugs reactor bed

Ammonium chloride in hydrogen recycle gasAmmonium bisulfide

REACs

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Oxygen from tankage/oxygenates from FCC, cokers, purchased feed

Polymerization fouling Enhanced by olefins in feed

High temperature sulfur corrosionHigh temperature H2/H2S

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High temperature hydrogen attack (all high temperature components)Temper embrittlement where 2 Cr is used for hydrogen resistanceHydrogen embrittlement (due to rapid cooling of hydrogen charged material)

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Hydrotreater

Gas

LightNaphtha

HeavyNaphtha

LGO

HGO

SourWater

Gas

Feed

Hydrogen

Quench

LeanAmine

RichAmine

WaterR

eactor

Absorber Fractionater

AusteniticStainless Steel825

Austenitic Lined2 1/4 Cr

or CS

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Hydrotreater

Reactor feed and effluent piping Austenitic stainless steel

Often 347 or 321 High temperature hydrogen High temperature hydrogen sulfide

Reactor Austenitic lined low alloy steel

Hydrogen/hydrogen sulfide

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Hydrotreater

Reactor effluent air cooler and piping Carbon steel or 825

Other alloys becoming more common Ammonium bisulfide

Fractionator Carbon steel May be alloy depending on temperature and H2S

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Oxygen in feed (rust in tanks and polymerization fouling)

Gas blanket tankage Nitrogen best Natural gas may have air in it Fuel gas good - no oxygen

Avoid tankage all together

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Ammonium chloride Remove by water wash Location of water wash depends on concentration

- may be same water wash as for ammonium bisulfide - may be intermittent wash upstream of ammonium bisulfide water wash

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Ammonium bisulfide Continuous water wash upstream of REAC Balanced exchanger 20% of injected water not vaporized

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Balanced REAC

Water

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For older 2 Cr reactors know and adhere to minimum pressurization temperatureCool at no more than 50 to 100oF / hr (28-55oC) to prevent hydrogen embrittlementOperate heater to avoid tube metal temperatures higher than design

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Reformer

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HCl corrosion Wet feed Stripper overheads Water removes chlorides from the catalyst

Nitrogen Problems Nitrogen in the feed Corrosion inhibitors, antifoulants Converts to ammonia in reactor

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Ammonium chloride reaction of HCl and ammonia Ammonium chloride sublimes (gas/solid) in

overhead of stripper and hydrogen gas recycle

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High temperature hydrogen attack (reactors)Temper embrittlement or creep embrittlement depending on which low Cr alloy is employed to resist high temperature hydrogen

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Continuous Platforming

Feed

CFE

1 1/4 Cr1/2 Mo

9 Cr Tubes

Reactors

1 1/4 Cr - 1/2 Mo321 or 347Internals

1 1/4 Cr - 1/2 Mo

Catalyst

Regeneration

Platformate

NetHydrogen

LightEnds

Stabilizer

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CCR Platformer

Reactors Design for high temperature hydrogen

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Stabilizer

If too wet, stabilizer may need to look much like crude unit overheadMay need some or all of:

Monel trays and linings Water wash Inhibitor injection

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Stabilizer

Sour Water

Water Wash

pH ControlNatural Dew Point

Inhibitor

Gases

Product

Monel

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Operating Guidelines CCR

Control water in feed Minimize chloride stripping

Control nitrogen in feed Use ammonia as neutralizer in crude column Neutralizing amines may go through

hydrotreater unaffected and break down in reformer

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Operating Guidelines CCR

Regenerator Burn at prescribed rate

Too fast, too much waterStrips chloridesAcid corrosion

Keep caustic fresh in scrubber

Documents

New - 11 Process Units