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!
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