ineos quantifying monitoring fouling refinery heat exchangers

8/19/2019 INEOS Quantifying Monitoring Fouling Refinery Heat Exchangers

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Quantifying and Monitoring FoulingQuantifying and Monitoring Fouling

of Refinery Heat Exchangersof Refinery Heat Exchangers Application to refinery pre Application to refinery pre--heat trainsheat trains

Robert Pes –

Pierre Séré

Peyrigain

INEOS -

Lavéra -

France AspenTech

User Conference, Berlin, April 2008


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Abstract Abstract

It is well known that refineries contain a large number ofheat exchangers designed in complex arrangements.Unfortunately, it is also known that fouling occurs in these

heat exchangers providing an obstruction to heat transferand fluid flow resulting in increased operating costs (lesscapacity, more cleanups…).

For the last three years, models based on AspenHYSYS and Aspen TASC have been developed to monitorheat exchanger fouling for various refining units. These

applications have been successfully installed and are still inuse to assist the manufacturing engineers in scheduling ofheat exchanger rinsing and cleaning. Optimizing theseoperations has been leading to significant savings.


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OutlineOutline

Background

Objectives

Fouling Monitoring

Cleaning / Rinsing Simulations Areas for Improvements

Conclusions


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Lavera SiteLavera Site


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Raffinate2

INEOS Arkema Naphtachimie/Appryl/Gexaro

Oxochimie

Ethylene Oxide

HuntsmanEthoxylates

Éthylene glycols

Glycols ethers

Ethanolamines

Polyethylene

Oxo Alcohols

Butadiene

Gexaro - Benzene

Polyisobutene

STE

AM

CR

ACKER

ButanolEthyl hexanols

Butadiene

C2

Ethylene

C3

Propylene

C4

C5+Gasoline

ELECTROL

YSIS

Iron Chloride

Vinyle Chloridemonomer

Chloromethanes

Chlorine

Brine

LDF(Naphta)

LPG

Pygas

Polypropylene

REFINER

Y

Gasoline

LubricantDiesel

Kerosene

Bunker Fuels

Bitumens

Gas

CrudeOil

LPG(C3 – C4)

BenzeneGasoline

Acetates

Raffinate 1Heating Oil

Lavera ProductionLavera Production SchemeScheme


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BackgroundBackground

In oil refining, it is well known that heat exchangers are prone to foulingand the increase in operating costs can be huge. Optimisation of rinsingand cleaning refinery heat exchangers is key.

Three years ago, it was decided to develop a tool that would allowmanufacturing people to optimise rinsing and cleaning operations. Atthat time, the situation was as follows:

–

It was difficult to calculate accurately and rigorously the fouling of

each heat exchanger of an entire heat exchanger train –

Heat exchanger rinsing operation was carried out on a time basis,not according to the real fouling

–

Rinsing and maintenance operations (cleaning) were not optimized,both in frequency and way to operate

–

There were no means to estimate the temperature increases at theoutlet of the heat exchangers train after a rinsing and / or a cleaning

operation


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ObjectivesObjectives

Develop a user friendly Excel Program, to be used bymanufacturing engineers, where all the heat exchanger

fouling calculations would be automatic

This program should be able to simulate the effect of a

complete rinsing or the rinsing / cleaning of one (or more)heat exchanger(s)

Calculate and then provide the operation engineers with asingle calculated parameter that indicates the fouling stateof the entire heat exchanger train


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Operatingconditions

Lab

analysis

Excel File

Source of value

Visual and quick identif ication

of fouled heat exchangers

General FrameworkGeneral Framework

Process Engineering

Aspen HYSYS®

V2004.1


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Fouling MonitoringFouling MonitoringCalculation Philosophy (1/2)Calculation Philosophy (1/2)

For a defined period of time, automatic import into Excel of the followingdata (one set of data per shift):

Plant data [Flowrate & Temperature] PI-datalink

Lab analysis [density, viscosity and TBP] QIMS Sample Manager

VBA routines developed to analyse / correct the imported data and sendthis checked data to Aspen HYSYS 2004.1

HX calculation carried out in Aspen HYSYS 2004.1 – HTFS TASC 5.10

Calculations carried out one heat exchanger at a time for the entiretime period (one HYSYS file per heat exchanger created with the

detailed geometry)

VBA routines developed to retrieve results from HYSYS 2004.1 into Excel,like the clean overall heat transfer coefficient, U(clean), outlet temperature

and pressure drop


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Dirty overall heat transfer coefficient, U(dirty), calculatedwithin Excel, from the current operating conditions

(Udirty=Qactual / A / LMTDactual)

Graphs U(dirty) / U(clean) built in Excel as a function of

time

U d

i r t y

/ U

c l e a n

Fouling MonitoringFouling MonitoringCalculation Philosophy (2/2)Calculation Philosophy (2/2)


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ExampleExample Aspen HYSYS Case Aspen HYSYS Case


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ExampleExample HeatHeat Exchanger ExchangerSetting PlanSetting Plan

5.9055 2 Bolts

Fixed

2.9528

8 8 .

3

2 2

5.9055 2 BoltsSliding

2.9528

8 8 .

3

2 2

356.2992 Overall

39.7638 28.7008 217.7165

65.6693 144.0157

Pulling Length

184

T1

T2 S1

S2

A

End Length at Rear Head = 34.2

End Length at Front Head = 14.6

Nozzle Data

Ref OD Wall Standard Notes

S1 6.625" 0.28" 150 A NSI Slip on

S2 6.625" 0.28" 150 A NSI Slip on

T1 4.5" 0.337" 150 A NSI Slip on

T2 3.5" 0.3" 150 A NSI Slip on

Empty

113760 lb

Flooded

194375 lb

Bundle

70972 lb

Weight Summary

Internal Volume ft³ 1013.511 437.5786

PWHT

Radiography None None

Number of Passes 1 14

Test Pressure psig

Corrosion Allow ance in 0.125 0.125

Full V acuum

Design Temperature F 644. 788.

Design Pressure psig 217.56 174.04

Design Data Units Shell Channel

Customer Specifications

Design Codes

ASME Section VIII Div. 1

TEMA R

Fabrication Number

Item Number

Project Location

Project Reference

P.O. Number

Customer

Revis ion Date

11/13/2006

Dw g. Chk. App.

Tasc+Version

Setting Plan

BEM 100 - 240

Drawing Number

6 3

6 3

T1

T2

6 3

6 3

S1

S2

6 4

Views on arrow A


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Fouling predictionFouling predictionNFIT Calculations (1/2)NFIT Calculations (1/2)

A file representing the entire heat exchanger train is created in HYSYS2004.1

“End point” option is used for the calculation of all the heat exchangers

VBA routines developed to export from Excel into HYSYS, constantoperating data and the overall dirty heat transfer coefficient (Udirty)

Heat exchanger train outlet temperature is calculated at these conditionsand imported back from HYSYS into Excel

NFIT is the Furnace Inlet Temperature calculated with standardconditions (temperature, flowrate & pressure) but with the current heatexchanger fouling


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Temperature@ the NFIT

conditions

Heat exchangerstrain cleanings

Fouling predictionFouling predictionNFIT Calculations (2/2)NFIT Calculations (2/2)


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Cleaning / Rinsing SimulationCleaning / Rinsing SimulationOutlet Temperature CalculationsOutlet Temperature Calculations

Select the exchangers that have to be cleaned / rinsed or theentire train to be cleaned / rinsed

Calculate the heat exchanger train outlet T, using the last setof operating conditions with an estimated dirty overall heattransfer coefficients (Udirty) in the HYSYS global heatexchanger train simulation (end point option)

•

For a cleaned heat exchanger :

U dirty = U clean•

For a rinsed heat exchanger :

U dirty = X% * U dirty

Source of value

Maximise the heat exchanger train outlet temperature+3°C ≥

-1% on Vacuum Residue flowrate ≥

7.5 k$/day


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Since 2005, three applications, based on the aforementionedprinciples, were developed: one for the CDU and one foreach VDU

It has been demonstrated (based on the graphs Udirty/Uclean)that increasing the rinsing frequency while decreasing therinsing length, allows us to maximise the outlet

temperature, all through the year This optimised rinsing procedure allows us to double the

length of operation between two physical heat exchanger

cleanings

Source of value

For one VDU unit, the profit has been

estimated between 1.5 and 2 M$/year

Cleaning / Rinsing SimulationCleaning / Rinsing SimulationBenefits and ProfitsBenefits and Profits


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Areas for Improvements Areas for Improvements

The main difficulties encountered during these projectswere linked to some limitations of TASC 5.10

–

When using HTFS-TASC, as calculation engine for detailed shell &tube exchanger simulation in HYSYS 2004.1, only a few data itemscan be linked with Excel via VBA routines

–

In TASC 5.10, if the number of tube side passes generates atemperature crossing, HYSYS does not converge and eventuallycrashes

As next step, it is planned to replace all TASC 5.10

calculations by Aspen Tasc+. –

Preliminary tests have shown that all the convergence failures dueto TASC 5.10 have been fixed thanks to Aspen Tasc+


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ConclusionsConclusions

The possibility to link Aspen HYSYS (and TASC) with Excel, using VBAcodes, is a very powerful method, which allows us to provide user friendlyand simple tools, based on rigorous and accurate calculations

It is then possible to develop tools that allow manufacturing people tooptimise rinsing and cleaning operations of refinery pre-heat trains

The first application, based on the aforementioned principles, wasdeveloped for a VDU in 2006 and is still in use. Since that time, two other

applications were developed and are used on a daily basis. The profitsalready identified are quite significant

In terms of improvements, the next step is to replace TASC 5.10 by Aspen Tasc+, in the applications already developed

And finally, the long term objective would be to couple the simulation ofthe heat exchanger trains with the simulation of the associated distillationtowers. It should allow us to perform a global optimisation of the crude

distillation and vacuum distillation units. Very challenging but exciting!

ineos quantifying monitoring fouling refinery heat exchangers

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