cbi.desalter

7/28/2019 Cbi.desalter

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Designing a crude unit heatexchanger network

A well-designed crude andvacuum unit (CDU/VDU)heat exchanger network is

essential to meet product yield,product quality, unit reliability andcrude processing exibility objec-

tives when processing heavycrudes. Preheat trains conceivedwith the wrong ow scheme orthose with multiple parallel pathsthat are complex to operate rarelyhave the exibility needed tohandle a range of crude blends oreven the variability of many heavyCanadian crudes. Standard shelland tube exchangers designed withlow velocity are prone to rapid andheavy fouling.

It is becoming ever more impor-tant to temper crude train designthat has been developed fromcomposite curves, optimal energytargets and pinch points with crudeunit experience and know-how.Practical concerns include operabil-ity, reliability, exchanger type andminimal fouling design. Real-worldexperience using exible preheatnetworks, good exchanger designpractices and proven exchangertechnology is proving to be more

important than theory. This articlecovers practical considerationswhen designing CDU/VDU preheatnetworks for heavy crudeprocessing.

Ha c chasThe desalter is an integral part of the crude unit, and unit reliabilityis directly related to desalterperformance. Desalting is becomingincreasingly important as crudes

get heavier and contain morecontaminants that increase the dif-culty to desalt. Poorly performing

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Tony BArleTTA a STeve WHiTe Process Consulting Services

KriSHnAn CHunAngAd Lummus Technology Heat Transfer

desalters with a high desalted crudesalt content are dramaticallyincreasing unit corrosion andwreaking havoc on unit reliability.

With heavy crude processing —particularly with some heavy

Canadian crudes — it is becomingmore important to have the exibil-ity to operate the desalter at anoptimum temperature. The opti-mum desalter temperature is nolonger a single, xed design target;it is an operating variable that must

be adjusted to maintain peak

desalter performance. In heavyCanadian crude processing, theoptimum temperature can change

by 15-25°C, depending on the crudeor crude blend, to avoid massiveasphaltene precipitation. The abilityto change the desalter temperature

by 15-25°C must be part of thepreheat train’s design objectives.This requirement must be identi-ed, since a preheat train designedwith normal methods will notprovide the massive amount of swing heat that will need to beshifted to/from the cold crude

train.Many heavy Canadian crudes

have a high asphaltene and solids

content and considerably higherfouling potential compared withother crudes. Blending these crudeswith parafnic diluents or otherparafnic crudes can precipitateasphaltenes in the preheat train or

desalter. Special exchanger designconsiderations are required toreduce fouling.

Reners have noticed a variablecomposition with some heavyCanadian crudes. Some of thesecrudes, such as Western CanadianSelect (WCS), are blends of otherheavy crudes. As blend ratioschange, so does the composition.Some heavy Canadian crudes aredistillate laden, while others contain

more gas oil. It is becoming appar-ent that reners with preheat trainsexible enough to handle variableproduct yields will benet mostfrom processing these crudes.

Ct twk s pactcCDU/VDU preheat train designsare relying more and more on theo-retical constructs such as pinchanalysis without sufciently consid-ering realities such as foulingtendency and system operating

exibility required for heavy crudeprocessing. Advances in computerspeed and easy-to-use targetingprograms have made pinch analysisa prerequisite for network design.While pinch technology can be avery useful tool, a preheat network cannot be designed for a singletheoretical optimum point, nor canit ignore the practical realities of running today’s ever more chal-lenging crudes.

The preheat train is part of anintegrated system and needs tohave the exibility to process

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answer. Computer programs fornetwork design solve equationsdeveloped around a design meth-odology. The solutions to theequations must be tempered oraugmented with practical crudeunit know-how. Without this know-how, it is unlikely that an optimaland reliable design will be achieved.Four critical considerations neces-sary for preheat train design are theexchanger network design philoso-phy, process ow scheme,exchanger design guidelines andexchanger type. Attention to thesekey considerations will result in amore robust design.

Cdu/vdu phat ta sphsphCompared with other crudes, heavy

Canadian crude processing requiresmore exibility in the preheat trainto adjust the desalter temperaturein order to avoid asphaltene precip-itation. Distillation column heatremoval requirements require moreexibility because of seasonal dilu-ent ow rates and variable crudecompositions. The amount of required exibility should be quan-tied as an objective of the preheattrain design.

Multiple parallel crude trains arerarely optimal. While they mayappear to be benecial on paper,they should be avoided becausethey are difcult to operate andthey generally have little exibilityto handle the required product ratevariability and the large cold trainpreheat duty swings required forgood desalting of heavy Canadiancrude.

In the preheat train (see Figure 1),crude is heated in the cold train

from the tanks to the desalter, inthe desalted crude train from thedesalter to the preash drum orcolumn, and in the ashed crudetrain from the preash drum/towerto the heater. The cold train dutymust have enough exibility tomeet the optimum desaltertemperature.

Desalter temperature is a criticaloperating variable, especially withthe heavier, nasty crudes from

Venezuela, Canada and otherregions. Desalters remove contami-nants that play a major role in

varying crude blends while meetingseasonal or economic product yieldtargets. These days, few renershave the luxury of running one

crude or even a consistent crude blend. Increasingly, reners areprocessing larger quantities of opportunity or heavy crudes toremain protable.

To make matters worse,outmoded design approaches thatrely on exchanger experts andvendors to design around an allow-able pressure drop, withoutsufcient understanding of the inte-grated system, continue to be used.

Today, most projects use systemengineers to develop P&IDs, withhydraulic calculations for eachcircuit setting hydraulic allowancesfor exchangers, control valves,strainers and other equipment. Inmany cases, system engineers donot do the process modelling andtherefore do not have a thoroughunderstanding of the variability of all potential operating scenariosthat are required of the exchangernetwork.

This approach then uses in-housespecialists or vendors to design theexchangers, with a major focus onallowable pressure drop. While thisapproach may be efcient from anexecution standpoint, it is aprescription for poor performance.Reliable, low fouling exchangersshould be the goal of preheat traindesign, with pressure drop simplya factor that the hydraulic systemneeds to handle.

Crude unit exchanger networksmust operate reliably for four tosix years. Proprietary exchanger

technologies with helical bafedesigns, such as the HelixChangerheat exchanger, have proven essen-tial in reducing fouling when

designed at high velocity. Yet,many recent designs have not takenadvantage of the benets of thistechnology because of the perceivedadded exchanger cost. It is notsurprising, then, that many crudeheater inlet temperatures degrade

by 25-40°C within the rst fewmonths of operation.

A m ffct appachExchanger networks must have the

exibility to meet critical objectivessuch as desalter temperature inaddition to satisfying column heat

balances that may be variable as aresult of changes in crude composi-tion. Process engineers must rstidentify the need for and degree of exibility required for speciccrudes or crude blends and makethat exibility requirement part of the preheat train design. Theremust be more interaction andcommunication between process

and systems engineers to assureexibility is incorporated intodesigns.

Secondly, strict adherence to“allowable pressure drop” as themain design criterion must betempered so that low-velocity, high-fouling designs can be replacedwith high-velocity, low-foulingdesigns. Larger acceptance of the

benets of reduced fouling that aproperly designed exchanger can

bring is needed.Finally, energy-targeted method-

ology can only be part of the

Tanks

Desalter

Flash drum

Hydraulic circuit No. 1 Hydraulic circuit No. 2 Hydraulic circuit No. 3Crude

column

Crudecolumn

Desaltedcrude preheat

Hot train

Cold train Water

F 1 Simplied preheat train




CDU/VDU run length as well asdownstream unit reliability. A highdesalted crude chloride contentincreases crude unit corrosion and,in some cases, can reduce thedownstream hydrotreater and cokerrun length, as well as increasemaintenance costs. In the short run,it is possible to have poor desalterperformance and be protable;however, unscheduled outagesand/or loss of containment cancause major prot losses and possi-

bly much worse.The cold train heats the crude

from the storage tanks to thedesalter through seasonal changesin raw crude temperatures. Forexample, Canadian crude oil pipe-line temperatures vary seasonallyfrom 20-40°C, with the optimum

desalter temperature varying from120-140°C, depending on the crude

blend. The amount of cold trainduty that needs to be shifted tomeet the wide range of desaltertemperatures, while also handlingthe variable raw crude temperature,is very large. This is a major chal-lenge because of the large amountof swing heat that must be moved

before and after the desalter.Identifying services that allow

heat adjustments upstream anddownstream of the desalter is criti-cal. Typically, the crude columnkerosene pumparound, vacuum gasoil product, diesel product andsometimes vacuum bottoms whenit is being run down to storage atlow temperatures are good candi-dates. Exchanger services thatprovide swing heat should haveow-controlled bypasses so thatadjustments can be made as needed.Some Canadian crude blends have

large middle distillate productyields, whereas others produce highpercentages of VGO. Column heatremoval must be sufcient to dealwith these variations while meetingdesalter and product rundowntemperatures. Preheat system exi-

bility is essential.Low-fouling exchanger design

should be an objective, while theoutdated practice of designing forallowable pressure, which leads to

low velocity and high fouling,should be discarded. Old rules-of-thumb that require the dirtier

service on the tube side for ease of cleaning no longer apply. For exam-ple, placing vacuum residue on thetube side will result in poorexchanger design with a high pres-sure drop and high fouling. Placingvacuum residue on the high-velocity shell side of theHelixChanger heat exchanger willprovide a higher heat transfer coef-cient, less surface area, lowerfouling and less cleaning.

Cdu/vdu pcss w schmSelecting the right process owscheme for a crude unit can have alarge impact on preheat train designoptimisation and unit reliability.Unfortunately, there is no computerprogram that determines the opti-mum ow scheme. It is determined

from experience and thoughtfulevaluation of distillation columnheat and material balance require-ments dictated by crude blends andtheir variability. Other factors, suchas the mitigation of a high-risk,high-corrosion surface area andcrude tower stability, are alsoimportant.

Three areas in which the designerpositively inuences the preheattrain are: energy recovery from the

top of the crude tower, the numberof crude tower pumparounds andtheir location, and the number of vacuum column product draws.Selecting the right ow scheme, inmany cases, can signicantly reduceexchanger surface area require-ments. In other instances, selectingthe wrong ow scheme for the sakeof network optimisation can destroyunit reliability and protability.Reners processing opportunitycrudes have learned this the hard

way. Many have experienced shortrun lengths or periodically mustreduce the crude charge rate toclean rapidly fouling exchangers.Others have had extremely highcorrosion rates in the crude over-head system, causing unscheduledoutages. Clearly, the ow schemematters.

Many heavy Canadian crudescontain large portions of naphthaused as diluent. In these cases, it is

necessary to recover some low-levelheat in the crude column overhead,where raw crude is heated with

overhead vapour. However, thecrude overhead exchanger is ahigh-fouling and often severe corro-sion service. Since this is a high-risk exchanger, the design shouldmaximise heat recovery with mini-mal surface area.

When crude overhead exchangersare used, viscous crude should berouted through the shell side tominimise the surface area. This israrely done, because many design-ers still believe raw crude shouldalways be in the tubes for ease of cleaning. However, it is nearlyimpossible to get a reasonableheat transfer coefcient with thehighly viscous crude on the tubeside. In fact, the ow regime isoften laminar, resulting in largesurface area requirements with a

high pressure drop. Shell-sidedesign can be further improved byusing helical bafes to minimisedead areas and maximise theconversion of pressure drop to heattransfer. To keep the exchangerclean, it is important to targetvelocities of 1.5-2.4 m/s on the shellside of the exchanger.

When crude is put on the shellside, the exchanger must bemounted vertically so that the crude

overhead can be water washedeffectively to minimise corrosion.Crude overhead exchanger corro-sion is one of the most commoncauses of unscheduled outages dueto tube failures. Good desalting andan effective water wash system areessential for crude overhead corro-sion control.

Horizontal exchangers, withcrude routed through the tubesand crude overhead condensing onthe shell, have a proven track

record of high fouling and arevirtually assured of high corrosionrates when processing heavycrudes. It is simply not possible tothoroughly water wash the shellside of conventional exchanger

bundles, with inherent “dead”areas that are nearly impossible toreach with water wash. It isalso very difcult to effectivelywater wash the crude overheadstream when it is on the tube side

of a horizontal exchanger.However, a vertical exchanger withcrude overhead condensing on the



crude, the diesel/AGO productfractionation is poor, resulting inexcessive diesel boiling range mate-rial in the AGO product. However,this is often overlooked in favour of the high draw temperature associ-ated with AGO pumparounds.

Most vacuum towers are designedwith light (LVGO) and heavyvacuum gas oil (HVGO) products,

which sets the amount of heat avail-able at a given temperature level.Two-product vacuum towersproduce draw temperatures of approximately 145°C and 270°C forLVGO and HVGO streams, respec-tively. Most, if not all, of thelow-level LVGO pumparound heatis lost to air or cooling water becausethere are not many heat sinks for thelow draw temperature. HVGO prod-uct heat can be recovered into crude,

waste heat steam generation or toreboil light ends towers. Therequired HVGO pumparound rate


tube side has no dead areas andcan be effectively water washed.

A top pumparound can be addedto further reduce the amount of high-risk surface area in the crudeoverhead system. This is especiallyimportant with heavy Canadiancrude processing. Without a toppumparound all of the reux forthe top tray must be condensed in

the crude overhead exchangers.With a top pumparound to supplythe reux the crude overheadexchangers will only condense theproduct. To be effective, the toppumparound return temperaturemust be high enough to avoidsublimation of amine salts andwater condensation in the top of the crude tower.

Crude column pumparound andproduct streams can be drawn from

the same location or from differentlocations in the column. Forexample, some designers will draw

diesel product and diesel pumpa-round from different locations.While this provides some benets indraw temperature, it can adverselyaffect fractionation. Low liquid rateson fractionation trays can ultimatelylead to product draws that dry outat certain conditions, resulting inunstable operation. When thisoccurs, as it frequently does, the

benets of split draw are dimin-ished. Crude units designed toprocess a wide range or variablecrude blends should draw productand pumparound from the samelocation in the column.

Atmospheric gas oil (AGO)pumparounds (see Figure 2) areonly warranted when the crude

blend is light enough to generatehigh lift in the crude tower andthen provide sufcient reux

between diesel and AGO productfor good fractionation. If an AGOpumparound is used with heavy

Top PA

KerosenePA

DieselPA

AGO PA

Very lowreflux rate

Low efficiencylow strtippingsteam

High amountof 200-316ºChydrocarbon

Condensers

Keroseneproduct

Dieselproduct

AGOproduct

Crudecharge

Remove PA

Top PA

KerosenePA

DieselPA

High reflux

Very low amountof 200-316ºChydrocarbon

Condensers

Crudecharge

Higher stripping steam

Keroseneproduct

Higher dieselproduct yield

Morefractionationtrays

Improvedefficiency

Lower overflash

F 2 Crude tower pumparounds



and exchanger surface area are typi-cally very high with two productvacuum towers due to a relativelylow temperature and high duty.

Adding medium vacuum gas oil

(MVGO) product produces threetemperature levels (see Figure 3),minimises heat loss to air andwater, maximises the heat recov-ered into crude preheat, andreduces the overall surface area.MVGO and HVGO pumparoundstreams are approximately 250°Cand 320°C, respectively, dependingon the product split betweenMVGO and HVGO. The higherHVGO draw temperature reduces

the number of exchanger shells andsurface area compared to only anHVGO pumparound.

Figure 4 shows a fully optimisedvacuum tower producing diesel,LVGO, MVGO and HVGO productstreams. This maximises theproduction of high-value diesel

boiling range material from theCDU/VDU and optimises both theMVGO and HVGO pumparounddraw temperature for a givenamount of recoverable heat.Drawing LVGO product from the

bottom of the fractionation bedfurther increases the MVGO drawtemperature, reducing the capitaland operating costs to recover it.

lw-f s

Fouling is a layer that accumulateson the inside and outside of thetubes, reducing heat transfer. The

higher the fouling resistance, thelower the heat transfer. The foulingresistance can be between 50-85%of the total resistance for a heavilyfouled exchanger. To compensate

for high fouling, more area isneeded; however, adding more areacan be counterproductive because itgenerally results in lower velocityand higher fouling.

Crude preheat exchangers can besusceptible to very high fouling.Fouling factors as high as 0.01hr-m2-°C/Kcal have been back-calculated from operating data.Exchanger design and selection areimportant and can have a signi-

cant impact on fouling. Lowvelocity designs result in high foul-ing, even for light crudes. A


CW

Crude

270ºC

Reduced

crude

CW

Crude

320ºC

Crude

250ºC

Reduced

crude

F 3 Vacuum tower MVGO pumparound



properly designed exchanger withhigh tube- and shell-side velocitieswill minimise fouling. Certainheavy crude oils are incompatiblewhen mixed together, causingasphaltenes to precipitate. These

crude oils are highly unstable, so itis very important to design theexchangers for high velocity.

excha s sThe designer cannot control thecrude fouling tendency, only theexchanger design and exchangertype. For new designs, exchangerscan be designed with high velocityand reasonably low fouling factors,which results in a minimal excess

surface area. However, for revamps,it is not always possible to rectifyall low-velocity designs and

realistic fouling factors must bedetermined from actual plant dataso that future performance can bepredicted.

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Low tube velocities result in highfouling. To minimise fouling, veloc-ities are ideally kept above 2.4 m/sand sometimes higher on the tubeside and between 1.2-2.4 m/s onthe shell side. High shell-side veloc-ities are achievable with advanced

bundle designs, such as that of theHelixChanger heat exchanger,whereas a high shell-side velocity isnot practical with standard segmen-tal bafes.

For a new design, when crude isplaced on the tube side, a two-passexchanger with 1in tubes should be

used. The number of tubes neededto obtain 2.4 m/s sets the shell’sinside diameter. The length of theexchanger or number of shells isadjusted to meet surface arearequirements. Increasing the shell’sinside diameter and the number of tubes to meet the surface arearequirements reduces the tube- andshell-side velocities and increasesfouling. Designers will sometimesenlarge the shell’s inside diameterto reduce the number of shells toreduce costs. However, this designresults in lower velocity, more foul-ing and higher lifecycle costs thatare greater than the originalsavings.

For a new design, a 1in tube withtwo passes minimises the pressuredrop. A typical two-pass crude

exchanger with crude on the tubeside at 2.4 m/s will have less than0.7 kg/cm2 pressure drop per shell.One-inch tubes are preferred over0.75in tubes because the pressuredrop per metre of tube is lower atthe same velocity.

For grassroots crude units, a low-fouling design can be incorporatedinto the pump head specications.In revamps, exchanger velocitiesare often limited by existing pump

size, pipe ange ratings andexchanger design pressure. Pumpsystem hydraulics must be evalu-ated carefully for each circuit todetermine opportunities to increasevelocity and reduce fouling. A lowfouling design is not always possi-

ble in a revamp because of existingconstraints.

Shell-side velocity is limited bythe bundle’s inside diameter, and

bafe geometry and spacing. Forexample, velocities much higher

than 0.62 m/s are not practical in asegmental bafed exchanger. Toincrease shell-side velocity, bafespacing and cut must be reduced.A higher pressure drop generallyincreases ow in the leakage and

bypass areas of the bundle. Poorlymatched bafe spacing and cuts canalso lead to large eddies and “dead”zones.

Advanced bafe designs such asthat used in the Lummus

Technology HelixChanger designuse quadrant-shaped bafes at anangle to create a helical ow pattern


Crude

Ejectors

Diesel

LVGO

MVGO

HVGO

Crude

Vacuum tower bottoms

Crude Crude

Feed

Strippingsteam

F 4 Optimised four product vacuum tower



F 5 HelixChanger tube bundle in fabrication Courtesy: Lummus Technology Heat Transfer

through the bundle. This owpattern reduces dead areas andresults in a lower pressure drop forthe same velocity compared with asegmental bafed exchanger. The

benet is that the shell-side velocitycan be designed for 1.5-2.48 m/s.Crude preheat exchangers designedwith high velocity on both the shelland tube side of a HelixChangerhave demonstrated extremely lowfouling in heavy crude service.

is th pss p a w?Fouling begins as soon as anexchanger starts up and continuesuntil the terminal velocity isreached. After the terminal velocityis reached, fouling continues but ata much slower rate. Low-velocityexchangers foul rapidly, sometimes

reaching the asymptotic foulinglevel within the rst 6-12 months of operation. However, most crudeunits are being operated for four tosix years between planned turna-rounds. A fouled pressure drop issignicantly higher than a cleanpressure drop for low-velocityexchangers. It is not uncommon forthe fouled pressure drop to be twoto three times higher than the cleanpressure drop.

An exchanger designed for highvelocity results in a higher initialclean pressure drop. However, ahigh-velocity exchanger’s fouledpressure drop is less than 1.5 timesthe clean pressure drop. So, doesdesigning a low velocity reallyresult in less pressure drop?

This is especially true for crudepreheat trains with multipleexchangers in series. Designing forhigh velocity will appear to add topumping costs at rst; however,

this is not necessarily true afterfactoring in the signicantly higherfouled pressure drop of the low-velocity design. The problem is thatthere is no way to calculate fouledpressure drop. Most designers donot get feedback from their designsand they do not go to the eld tomeasure pressure drop. If they did,they would appreciate the differ-ences in fouled pressure drop

between a low-velocity and high-

velocity design.It is slowly becoming accepted

that a high-velocity (high shear


stress) design is the main variableneeded to produce a low-fouling

design; however, there is still reluc-tance to specify exchangers thisway because of a higher initial pres-sure drop and corresponding higherpumping costs. What is notnormally factored in is the fuelcosts of a low-velocity, high-foulingdesign, not to mention the highermaintenance costs associated withmore frequent cleanings.

HxCha hat xcha

aataThe inherent deciencies of conven-tional segmental bafe shell-and-tubeexchangers are widely understood.The key deciencies are:• The shell-side region is compart-mentalised. Pressure energy iswasted in expansions, contractionsand turnarounds in multiple bendsrather than in generating heat trans-fer. The pressure gradient acrossthe bafes drives a signicantamount of ow through the tube-

to-bafe and shell-to-bafeclearances that escapes heat trans-fer. The result is inefcientconversion of shell-side pressuredrop to heat transfer• The ow leakage streams distortthe temperature prole, reducingthe effective mean temperaturedifference (MTD) for heat transfer• The perpendicular bafes encour-age dead spots or recirculationzones where fouling or corrosion

could occur.The HelixChanger design removes

most of the above deciencies.

Quadrant-shaped bafe segments,arranged at an angle to the tube

axis in a sequential pattern, guidethe shell-side uid in a helical paththrough the tube bundle. Figure 5shows a tube bundle in fabrication.The bafe segments serve as guidevanes without any compartmentali-sation, and the ow traverses on

both sides of the bafes. The helicalow path through the bundleprovides the necessary characteris-tics to reduce ow dispersion andgenerate near plug-ow conditions,

resulting in high thermal effective-ness. It ensures a certain amount of cross-ow to the tubes to achievehigh heat transfer coefcients.Uniform ow velocities areachieved through the tube bundle,and the smooth helical ow elimi-nates unnecessary pressure lossesin the exchanger. There is alsonegligible dead volume in the heli-cal shell space.

rc f chaactstcs

The design offers reduced foulingcharacteristics for the followingreasons:• There are few dead spaces withinthe helical shell space• The helical ow velocitiesachieved are signicantly higher(1.5-3 times higher) than the aver-age cross-ow velocities achievedin equivalent segmental bafedesigns. Thus, the shear forcesacting on the tube wall are signi-

cantly higher in the HelixChangerdesigns• Uniform ow velocities through



the tube-bundle are achieved due tothe relatively constant helical owarea. This also translates into moreuniform tube-wall temperatures.

CcsPreheat train design for heavyCanadian crudes can be very

F 6 HelixChanger bundle after two years of operation in hot crude vs hot resid service

challenging. Different requirementssuch as the need to vary desaltertemperature dictate a differentapproach not normally requiredwith other crudes. A well-conceiveddesign, with the exibility to handlethe variable composition of diluents

being used to transport the crude in

pipelines, is also required.Designing for high velocity andusing advanced exchanger technol-ogy has proven that low-foulingdesigns are possible (see Figure 6).

HELIXCHANGER is a mark of Lummus

Technology Heat Transfer.

T Batta is a Chemical Engineer with

Process Consulting Services, Inc, in Houston,

Texas. His primary responsibilities are

conceptual process design and process design

packages for large capital revamps.

Email: [email protected]

St Wht is a Chemical Engineer with

Process Consulting Services, Inc, in Houston,

Texas. He has more than 30 years of process

design experience for renery revamps and

grassroots units. Email: [email protected]

Ks Chaa is Director of Heat Exchangers

at Lummus Technology Heat Transfer, a CB&I

company in Bloomeld, New Jersey. He has

more than 18 years of experience in the design

and development of advanced heat exchanger

equipment, as well as their specialised

application in the oil and gas, rening,

petrochemical and chemical industries.

Email: [email protected]


HELICAL BAFFLES AND hiTRAN TUBESIDE

ENHANCEMENT REDUCES CRUDE SHELL

AND TUBE COUNT FROM 9 TO 2 ON FPSO

Designing in partnership, Calgavin and Lummus Technology

deliver high performance compact shell and tube exchangers

reducing weight from 400 tonnes to just 130 tonnes.

Challenged with minimum space requirement and maximum

e ciency, the 2x 4MW exchangers operate at 8x tube-side

heat transfer co-e cient and deliver long run times through

minimal fouling.

RESEARCH. EVALUATION. INNOVATION. SOLUTION.

CONVENTIONAL

SHELL AND TUBE

COMPACT, ENHANCED

SHELL AND TUBE

talk to our engineers +44 (0) 1789 400401

Image courtesy of Total. - Gonsalez Thierry

PLAIN / SINGLE

SEGMENTAL BAFFLE

hiTRAN /

HELICAL BAFFLE

GAIN

OHTC [W/m2k] 59.9 242.7 4X

TUBE SIDE

HTC [W/m2k] 95 770 8X

DP [bar] (ALLOWED 1.50) 1.40 1.50 -

SHELL SIDE

HTC [W/m2k] 455 789 ~ 2

DP [bar] (ALLOWED 1.50) 1.50 1.25 -

GEOMETRY

TOTAL NO. OF SHELLS [-] 9 2 -7

TOTAL HT AREA [m2] 6420 1704 ~ 1/4

PLOT SPACE [m2] 104.5 26.2 ~ 1/4

WEIGHT WET [kg] 401148 130716 ~ 1/3

EXCHANGER COSTS [%] 100 35 ~ 1/3

‘HELI-TRAN’

EXCHANGERS

cbi.desalter

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