14 Exploiting the Use of Compact Heat Exchangers on Preheating Trains

8/13/2019 14 Exploiting the Use of Compact Heat Exchangers on Preheating Trains

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Exploiting the Use of Compact HeatExchangers on Preheating Trains

(AIChE 2008 Spring Meeting 165d)

PETROBRAS R&D Center CENPES

Antonio V. S. de Castro*, M.Sc.

Alan T. Vilas BoasClaudio L. M. Kuboski

Diomedes C. da Silva, M.Sc.

Roberto A. Oliveira, M.Sc.Washington de O. Geraldelli, Ph.D.


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Introduction

Higher prices of energy and oilCrude oil distillation unit is one of thehighest energy consumers in a refinery.

Opportunities for heat integration:

In revamps to process advantageous

crudes Special Metallurgy higher heat recovery

Threats:

Special Metallurgy due to naphtenic acids- higher investments at preheating train

increase on plot area due to increase onheat recovery - might be a constraint


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Introduction

Compact Welded Plate Heat Exchanger: Special Metallurgy (Titanium, SMO, etc.)

leads to attractive costs compared to a S&T

Compact (less plot area)

Lower temperature approaches than S&T

Innovative solution Refinery designers don't have enough

information regarding the performance:

Fouling Mechanical resistance

Operational cautions, such as start-up and

shut-down


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PETROBRAS Experience

End of 2001, PETROBRAS Engineersvisited a Refinery, in Europe, where aCompabloc CP75 was installed

Overhead Condenser with Crude

Special Metallurgy required due toChloride

4 years without maintenance

August, 2002. Service with two heavy

fluids 13 exchangers at refinery since 1994

Maintenance during winter shut-down

Focus on Process Issues

Visit to refinery with two parallel units(one stand-by) Sep,2005

HVGO vs. Crude Oil (high temperature)

Problems during the start-up (blocked

pipe) Operating since November,2004

Ref.: ALFA LAVAL


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June,2002 ALFA LAVAL trained PETROBRAS

Engineers how to design Compabloc using CAS200(ALFA LAVAL software)

September,2006 Two-phase fluid ALFA LAVAL

course, concerning crude oil vaporization Lack of data for temperature x shear stress x fouling rate

May,2006 Visit to ALFA LAVAL factory in France:

- Maintenance/Inspection/Cleaning Requirements

- Manufacturing Process

PETROBRAS Experience


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P-68322A/B

Feed pre-heater

P-68323A/B

Ovhd Condenser

P-68324A/B

Ovhd Gas

Heater

P-68325A/B

Reboiler

PETROBRAS Cases

Sour WaterStripping Unit:

Feed preheater Overhead

Condenser

Ovhd Gas Heater

Reboiler

Plot areaconstraints

Fouling at Feedpre-heater

Leakage at OvhdGas Heater

CASE 1


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Fouling at Feed preheater

Inadequate H2S Stripping TowerOperation corrosion

Actual Flow Rate (90m3/h) Design (160m3/h)

Actual Shear Stress (22Pa) Design (60Pa)Mitigation:

Increase passes number ( Shear Stress)

Control Review (by-pass)

Self-cleaning Strainers

Leakage at Ovhd Gas Heater

Material replacement:From Titanium to SMO

PETROBRAS Cases

CASE 1, cont.


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Basic EngineeringDesign - Crude

Distillation UnitRevamp:

Increase FeedRate

Heat Integration

Plot AreaConstraints

3 Services: MVGO(2) and VR

220,000 bbl/d

Start-up: 2011

PETROBRAS Cases

CASE 2


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Conceptual Design

(Revamp)140,000 bbl/d

- MetallurgicalAdaptation(TAN=2.1)

- OperationalDebottlenecking

- Heat Integration

Study PinchAnalysis

- Plot Area and

Shutdown timeconstraints

- Full Compablocnew preheat trainsuggested.

PETROBRAS Cases

CASE 3


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Compabloc Test at Refinery

During conceptual design,necessity of a performancetest.

A Compabloc CP30 unit hasbeen installed, in order toevaluate the performance ofthis equipment under unit

conditions

Vacuum Residue preheatingCrude before the Desalter

Low Crude Temperature:~100 to 115C

Operational and

Maintenance experience


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Vacuum Residue

E-106D

E-150

Crude Oil

103

113

172

160


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Similar to phase 1.3 months100%6

b) Cleaning with hidroblasting.

a) Open the equipment to check deposits;Cleaning5

b) Equipment shut-down for 10 days and restart it.

a) Check pressure drop;Fouling2 months25%4

b) Auto cleaning capabity.

a) Check pressure drop;Thermal performance

and fouling

2 months100%3

if not, go to phase4.

b) if fouling, go to phase 1;

a) Check pressure dropFouling2 months50%2

b) Compare design X operational data using CAS200.

a) Check pressure drop;Thermal performance6 months100%1

(design basis)

ProcedureObjectivePeriodFlow rateStep


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1st Phase Results: Crude side measured pressure drop was

from 29 to 47% of calculated values byCAS200;

VR side measured pressure drop was from123 a 167% of calculated values by CAS200;

Difference in global heat transfer coefficients(HTC) was much lower. Measured valueswere from de 88 a 111% of calculated valuesby CAS200;

Problems with Instrumentation could be thecause of such difference in pressure drop


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Crude Inlet Vacuum Residue Inlet

Compabloc Opening after 1st step (8 months)

Deflected Baffle (mechanical resistance) it wasnot designed for that purpose

C


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Pressure drop results - phases 2, 3 and 4


0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

2.00

1-Sep 2-Oct 2-Nov 3-Dec 3-Jan 3-Feb 6-Mar 6-Apr 7-May 7-Jun 8-Jul 8-Aug 8-Sep 9-Oct

Period from 2006 up to 2007

pressuredrop,

kgf/cm

CRUDE

VACUUM RESIDUE

50% flow rate 25% flow rate 100% flow rate

C bl T R fi


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Flow Rate Vacuum Residue vs CrudeAd-Hoc Trend

01/08/05 00:00:00 20/09/07 00:00:002.14 Year(s)

1210-FI-299

M3/D

1210-FI-298

M3/D

500

1000

1500

2000

2500

0

3000160.63

28.689

1210-FI-299

M3/D

1210-FI-298

M3/D

C bl T t t R fi


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Positive Aspects:- Equipment kept its thermalperformance;

- Design, Operational and

Maintenance experience

- No fouling observed

Negative Aspects:

- Mechanical Resistance(Leakage and Baffle);

- Aspects not related to

exchanger (instrumentation,flow fluctuation, )

C bl T t t R fi


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Crude Side

Period: Jul/16/07 up toSep/20/07

Zero Flow Rate forabout 3 weeks.

No abnormal pressurevariation.

Pressure

Flow Rate



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Vacuum Residue Side Period: 16/Jul/07 up to

20/Sep/07

Zero Flow Rate for 10 days. Significative pressure and

flow rate variation.

Pressure

Flow Rate

PressureSep/01 to 17



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Inlet Pressure VR vs Crude (Accordeon Effect)



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Problem Root Cause Consequense

Leakage Joint Failure Vacuum Residue Leakage

Baffle Deflection Overpressure or fatigue Thermal performance loss

ALFA LAVAL: Development of new gasket;

Adoption of reinforced baffles (for high viscous fluids);

PETROBRAS: Avoid surge pressure (hydraulic hammer):

Startup and shutdown procedures; Slow valve action;

Drain the equipment, in case of several days of shutdown.

Panels bolting hot retightening after startup Deposits prevention:

Strainers;

PETROBRAS Cases


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Basic Engineering Design (Oct/07)

Preheat Train before

Desalter Carbon Steel

Equivalent Cost

Preheat Train betweenDesalter and PreFlashTower

Crude Vaporization

Special Metallurgy

Parallel Arrangement

PETROBRAS Cases

CASE 3

PETROBRAS Cases


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Basic Engineering Design (Oct/07)After PreFlash Tower Preheat Train

(High Temperature Special Metallurgy)

SERVICE Shear (Pa) WALL TEMPERATURE (C)

E-166 A/B (x HVGO) 112 264

E-167 A/B (x HD) 113 289

E-169 C/D (x BPA) 113 295

PETROBRAS Cases

CASE 3

Petrobras Current Case


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CS

CS CS

CS AE

V

V

HT

HT

HT HT

HT

CB CB

Petrobras Current Case

CB CompablocCS Carbon Steel

HT High TemperatureAE accordion Effect

V Crude Vaporization

CASE 4 Basic Engineering Design CDU Grass root Refinery

PETROBRAS Current Case


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COMPARISON OF EQUIPMENT COSTS

SERVICE Compabloc (US$) Shell and Tube (US$)

P-10 x ~ 5.6 x

P-11 y ~ 3.8 y

* Installation costs not included;

* Equipment designed with the same allowablepressure drop;

* Compabloc design and budget by Alfa Laval;

* Shell and Tube budget by Aspen Icarus (Brazil

Base)

PETROBRAS Current Case

CASE 4 Basic Engineering Design CDU

Grass root Refinery

Compabloc Design


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Compabloc Design

Design Parameters:

Minimum Shear Stress

Higher Pressure drop

Countercurrent Pinch Analysis

Strainers / Maintenance facilities Parallel Arrangement (flexibility)

Accordeon Effect Crude Vaporization

High temperature

Next Compabloc Tests


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Next Compabloc Tests

Next Step at the same refinery:Operational practice and fouling at

high temperatures;

Service: Not defined yet;Wall temperature above 270C (target

300C)

Test at Case 2 refinery :

Operational practice and fouling withcrude vaporization;

Service: Not defined yet (desaltedcrude vs heavy diesel)

Crude Temperature from 150C to220C


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Thank you very much!

Antonio V. S. de Castro, [email protected]

Alan T. Vilas Boas

Claudio L. M. Kuboski

Diomedes C. da Silva

Roberto A. OliveiraWashington de O. Geraldelli

14 Exploiting the Use of Compact Heat Exchangers on Preheating Trains

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