Plate Heat Exchangers

2000 Start of the T-series, FrontLine1999 Vicarb acquisition, Compabloc & V-series

1997 Base-line (Food)1995 Rolls Laval / Spiral C-serie

1994 AlfaRex1993 Nickel Brazed

1992 Clip-Line (Food)1989 Plate evaporator

1987 Graphite plate1986 M-series, module size & thinner plates, Double-wall

1985 Wide-gap1983 Copper Brazed

1980 Semi-welded concept, glue-free concepts1970 A-series with Alfa Flex concept, 0.6 mm

1962 Rosenblad herring-bone pattern1950 Industrial plates in exotic material

1944 Wash-board pattern1938 Pressed plates in 1.0 mm

1931 First Plate Heat Exchanger (1878 a German patent)

Plate Heat Exchanger - evolution

1931 2001

5-10 mm thick plate Milled pattern Liquids passed the plate

horizontally several times Stainless steel Up to 5 m2 per unit

Down to 0.4 mm plates Pressed plates Liquids passes over the whole

plate in one passage Various materials Up to 2000 m2 per unit

Plate Heat Exchanger - evolution

PHE - applications

Steel and metal works Power and energy production Chemical process industries Petroleum industries Refrigeration Engineering industries Central cooling engineering

Metal recovery industries Mineral processing industries Sugar, distillery fermentation Pulp and paper industries Dryers for compressed air Heating, ventilation and

air conditioning

PHE - main componentsCarrying bar

Pressureplate

Plate packTightening bolts

Frame plate

Current PHE range large units

Current PHE range medium units

Current PHE range small units

Plate - main components

Thin sheet design, cold formed in single step hydraulic pressing (up to 40000 tons)

Main heat transferarea

Distribution area

Suspension

Inlet / outlet Passing through

Gasket in gasket groove

Leak chamber

Cold inHot out

Hot inCold out

Plate pack - example single pass

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Only 2 plates that do not transfer heat - the endplates

Plate pack - example two pass

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Cold inHot outHot in

Cold out

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3 plates in each pass that do not transfer heat

Semiwelded Plate Heat ExchangersCasette - main components

Main heat transfer area

Distribution area

Media inlet / outletMedia to next plate channel

Gasket in gasket groove

Leak chamber

Two plates are laser welded to each other to form a cassette.Each cassette is sealed off with a gasket on one side. The cassettes make up the plate pack.Aggressive media on one side Combining the benefitsof welded and gasketed technology

Semiwelded PHE range

AlfaCond in reality

Why AlfaCond?instead of shell-and-tube

Save money Save space Easier maintenance Easy to increase capacity Counter-current flow

AlfaCond a paradigm shift

Innovative hole configuration Innovative pattern for

condensation

Asymmetric channels Semi-welded technology

Vapour Vapour

Waterout

Condensate

Waterin

AlfaCond

The AlfaVap plate evaporator The worlds largest rising film

plate evaporator

Unique patented flow distribution system to secure perfect wetting of complete plate pack

Special product made for evaporation

Based on the semi-welded concept

Uses steam as heating media

The other fluid is boiled so unwanted fluid is evaporated

The AlfaVap plate evaporatorFlow principle

SteamCondensateFeedVapour

AlfaVap Product Description ConnectionsAlfaVap Product Description Connections

Feed inlet

Steam inlet

Condensate outlet

SteamCondensateFeedVapour

Vapour

Concentrate

AlfaRex fully welded solution

Same as a gasketed PHE Parallel flow Fully counter-current flow for

heat recover duties

Co-current flow by switching inlet port of one of the fluids

400C & 40 bar as design temperature & pressure

Cyclic duties

Alfa Rex - applicationsDuties involving

Aggressive media (no gaskets) Duties cyclic in temperature

and/or pressure where other welded HEs meet their limits

High pressure and temperature Heat recovery (liquid-liquid) Evaporation of clean fluids For clean media or when

CIP is suitable

Typical industries

Pharmaceutical industry Vegetable oils production Refrigeration Pulp and paper Marine & Power HVAC

Gasketed and Semiwelded heat exchangersPerfomance limits

AlfaRex

Gasketed Plate Heat Exchangers

3002001000-50

10

20

30

40

50Designpressure(bar)

Temp. (C)

100% stainless steel 100% gasket-free Extremely compact no frames Low weight Wide temperature range High design pressure

AlfaNova fully welded solution

Plates are Fusion-bonded (AlfaFusion) Micro structure similar to welding

AlfaNova

Comparison in MicrostructureAlfaFusion

D: Original Base materialE: Original filler materialF: Homogenisation

D

AlfaNova, availability

Design temperature: -196C -550C

Design pressure: 30 barg 100% stainless steel Pressure vessel codes: PED,

ASME

Materials100% stainless steel

The 1st PHE Semi Welded

Fully Welded

AlfaFusionTM

1931 1960 1977 1980 1994 2003

Technology Platforms

Fish Bone pattern

x

Brazed

Compact Heat Exchangers fully welded units

Compabloc

Compabloc exploded view

CompablocPerformance Data

Temperature: From 1000C to 400C

Pressure: From FV to 40 barg

Diff. Pressure: Full differential pressure 40 bargMinimum 2 bar difference between two sides

Materials: Stainless steel 316L, Avesta 254 SMO, Incoloy 825, Hastelloy C-276, C22, B2, Ti, TiPd, Tantalum

Heat transfer area: Up to 320 m2 per unit

Pressure vessel codes: PED, ASME

Compabloc as a condenserCompabloc as a condenser

The Compabloc as a condenserwith two passes

The Compabloc as a condenserwith two passes

hCoolant

Vapour

Coolant

Condensate

CompablocVertical multi-pass condenser

Compabloc as a reboiler

Vapour/liquid mixture

Liquid

Steam

Condensate

H327

Compabloc used in a distillation system

Condenser

Reboiler

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Compabloc

EASY EASY ACCESS FOR ACCESS FOR

CLEANINGCLEANING

Spiral Heat Exchanger

Winding of a spiral heat exchanger

A single channel with countercurrent flow provides...A single channel with countercurrent flow provides...

Easy access to clean Self-cleaning effect with

Horizontal mounting Single channel

Spiral heat exchangerThe self-cleaning heat exchanger

Counter-current flow Used for tough process fluids

Slurry Sludge Fibres High-fouling fluids

Compact Very low pressure drop Column mounting Total accessibility on

process side Possibility to sub-cool

condensate

Spiral heat exchanger condensers

Top-mountedspiral heat exchanger condenser

Top-mountedspiral heat exchanger condenser

Vapour

Condensate

Inerts

Vapour

Inerts

Cond. Vapour

Inerts

Cond.

Spiral heat exchanger condensers

Spiral Heat ExchangerAvailability

Temperature: From 1000C to 400C

Pressure: From FV to 40 barg

Diff. Pressure: Max diff pressure 23 barg

Materials: Any material that can be cold-formed and welded such as:Carbon steel, 304L, 316L, 316Ti, 904L, Avesta 254 SMO, 2205 Duplex, HastelloyC-276, C22, Titanium

Heat transfer area: Up to 500 m2 per unit

Pressure vessel codes: PED, ASME

Easy accessEasy access for cleaning

AlfaDisc Shell & Plate concept

Alfa Laval Slide 49

The The AlfaDiscAlfaDisc PlatePlate

Provides true countercurrent flow, for full LMTD and close temperature approaches

Turbulence scours the heat transfer surface, reducing fouling

Alfa Laval Slide 50

The AlfaDiscAlfaDisc PlateThroat of Plate

* Fluid is forced through this section on the shell side

Throat of Plate

Fluid leaves through

the same area

Bypass Restrictors Bypass

Restrictors

Throat of Plate

* Fluid is forced through this section on the shell side

Alfa Laval Slide 51

Typical Unit with Typical Unit with Removable CoreRemovable Core

Alfa Laval Slide 52

AlfaDiscAlfaDiscMultiMulti--PassPassDesign Design

MultiMulti--pass designs are available for pass designs are available for close temperature approaches. close temperature approaches.

By-pass Restriction Diverters (fingers)

Turning Plate Port

Shell Divider

AlfaDisc, the advantages

Fully welded no gaskets Very high design pressure Resistant to thermal variations

due to the accordion like plate pack

Fully counter current flow Removable core for accessibility

on one side as option

Compact

AlfaDisc

The accordion like core construction, makes the plate pack less sensitive to thermal expansion

AlfaDisc, availability

Design temperature: -160C - 538C Design pressure: FV - 100 barg Heat transfer area:

Packinox heat exchanger Shell & Plate concept

Alfa LavalSlide 57

Product rangeProduct range

550C(1022

F)Temperature

Pressure

(580 psi)40 barg

(537 psi)37 barg

(435 psi) 30 barg

(363 psi)25 barg

160 C(320F)

350 C(662F)

400C(752F)

-50 C(-58F)

AlfaDisc

Spiral

Com

pablocGasketed

Semi-welded

AlfaN

ova(1450 psi)100 barg

Heat Exchanger selection

PHEs are used at.- Energy conservation, less CO2 SOX NOX* Feed/effluent duties at low MTDs. Offloading furnaces* Using BFW for cooling at low LMTDs - offloading steam generation

Overhead condensers (replacing air coolers), liquid/liquid duties.- Where corrosion is an issue* Oheads condensing at crude distillation, fractionators etc.* Alkylation, desalting, SWS, amine systems etc..* Poor cooling water

- Difficult thermal duties* Temperature cross high NTU* Viscous fluids- Where space and weight are issues* E.g. ohead condensers- Heavy fouling duties- Overhead condensing* Very low pressure drop required e.g. Vacuum column* Column mounted Strippers at SWS, amine systems etc.

The Compact Heat Exchanger

Corrugated plate design promotes:High turbulence

This results in:

* Efficient heat transfer

* Minimised fouling

Plate Heat Exchangers

T1, outT1, out = (T in - T out ) / MTD = (T in - T out ) / MTD

T1, inT1, in

T2, outT2, out

T2, inT2, in

Ideal for: Temperature-X and high -values

High efficiency in Heat Recovery for Energy Saving purposes

MTD

What is shear stress?Shear stress

A high shear stress ensures High turbulence High heat transfer High force on the wall Reduced fouling

The force of the flow on the heat exchanger wall

A measure of the turbulence in the heat exchanger

Also called the Tao-value ()

wall = wall shear stress, Paf = friction factor

= density, kg/m3 = velocity, m/sP = pressure drop, PaDh = hydraulic diameter, m

L = channel length, m

S&T:

= 2.0 m/s, f = 0.007=> wall = 14 PaCP:

= 0.5 m/s, f = 0.5=> wall = 63 Pa

wall = (f * * 2)/2 = (P * Dh)/(4 * L)wall = (f * * 2)/2 = (P * Dh)/(4 * L)

High shear stresscan minimize fouling

Shear stress () as a function of velocityShear stress

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100

1000

0.1 1 10V, m/s

w, N/m

PHE, H-thetaPHE, M-thetaPHE, L-thetaSHE, f=0.012SHE, f=0.008Tube, f=0.007

The three different channels gives different shear stress - L, M, HFor the same velocity

the PHE gives a higher shear stress than the Shell & Tube

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Shear stess ( pa )

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Shear stress versus fouling rate

Rule of thumb: Try to keep the shear stress >50 Pa

Two ways of including safety factors Fouling factor Defined for Shell & Tubes

K-value margin Defined for Plate Heat Exchangers

Design safety factors Why safety factors when designing?

Variation in flow rates and physical properties

Allows fouling (dirt) on the plate and it still does the job

Design safety factors Typical S&T in water-water duty

A normal Rf for S&T: 1,0 10-4 m2C/W A normal kClean for S&T: 2000 W/ m2C

4f

CleanService

102000

1Rk

1k

1 +=+= kService= 1667 W/ m2C

What does this correspond to in K-value margin?

%201667

16672000100100arg ===service

serviceclean

kkkinM

Normal margin for S&T Works with lower turbulence More fouling Area not so easy to access for cleaning

Design safety factors What if we apply the Rf on a PHE in water-water duty?

Rf for S&T on PHE: 1,0 10-4 m2C/W A normal kClean for PHE: 6000 W/ m2C

4f

CleanService

106000

1Rk

1k

1 +=+= kService= 3750 W/ m2C

What does this correspond to in K-value margin?

%603750

37506000100100arg ===service

serviceclean

kkkinM

Much too high margin Too many plate Less turbulence Fouling ! Maybe not competitive?

Fouling What is fouling? Something that:

Reduces the heat transfer

Increases the pressure drop

Something that destroys the plate material

Something that leads to maldistribution

5 types of fouling Major debris

Biological growth

Scaling

Sedimentation

Burn-on

Fouling - major debris What is major debris?

Large objects and particles that get stuck in the HE Example, rocks, branches, coca-cola cans, fish

To avoid major debris clogging the HE use Widegap heat exchangers Spiral heat exchangers Design with high shear stress to avoid clogging & fouling Strainers (large mesh) Filters (fine mesh)

Fouling - biological growth What is biological growth?

Micro organisms that grow on the heat transfer surface

Example, algae, bacteria

To avoid major debris clogging the HE use Chock poisoning

Chlorinating

Cleaning In Place (CIP)

Environmental problems

Cleaning In Place

Why use cleaning In Place? Removes fouling without opening Increases lifetime for heat exchangers Minimises downtime Cost effective

What is Cleaning In Place? A chemical agent is circulated in

the HE to dissolve fouling Important parameters

Concentration of the chemical Temperature of the chemical Time of circulation Mechanical action (turbulence)

Fouling - scaling What is scaling?

Many fluids contains dissolved salts

When the fluid is heated or cooled the salts solubility changes

The salt precipitates on the heat transfer surface

Normal solubility Increased solubility at higher temperature

Most common

Precipitates when cooled down

Be careful when cooling

Example, sugar in water

Solubility

Temperature

Sugar

Fouling - scaling Reversed solubility

Reduced solubility at higher temperature

Precipitates when heated up

Be careful when heating

Solubility

Temperature

Sugar

CaCO3

Common problem Cooling water with CaCO3 and Ca(PO4)2 Avoid cooling water outlet temperatures above 45-50C

Design with high shear stress () Recommend water treatment

Regularly apply CIP

Fouling - sedimentation What is sedimentation?

Fine particles that settles on the heat transfer surface

Reduces the k-value and the HE does not perform

Difficult to remove in filter

Hard to dissolve with chemicals (CIP)

How to avoid it? Design with high turbulence / shear stress

Utilise pressure drop

Use H-theta plates

Back-flushing can be an option

Fouling - burn on What is burn on?

Breakdown or polymerisation of molecules that stick to the plate

Example, when you boil milk on the stove it burns easily

Common in food and organic applications

Caused by too high temperatures

How to avoid it? Design with high turbulence / shear stress

Utilise pressure drop

Use H-theta plates

Check what wall temperature can be allowed

Apply co-current flow to reduce wall temperature

Fouling in PHE vs S&T PHE is considered to foul less than a S&T

Baffles

High turbulence High shear stress Less fouling Low wall temperatures due to efficient heat transfer

Less risk of scaling and crystallisation Material is selected to avoid corrosion

(S&T have corrosion allowance)

No zones of low velocity

Fouling in PHE vs S&T

Examples, Heat Transfer Research Institute (HTRI) HTRI study of typical fouling in cooling tower water

PHE S&TFlow velocity (m/s) 0.45 1.8 m/sShear stress (Pa) ca 60 ca 15

Result: Fouling in PHE was 50-70% lower

PHE Higher turbulence at a lower velocity Less fouling

A common wrong beliefA A commoncommon wrongwrong beliefbelief

PHEs require a higher pressure drop than S&TStatement from Perrys Chemical Engineers Handbook (7thedition):

These narrow gaps and high number of contact points which change fluid flow direction, combine to create a very high turbulence between the plates. This means high individual-heat-transfer coefficient (up to 14200 W/m2C), but also very high pressure drop per length as well. To compensate, the channel plate length are usually short, most under 2 and few over 3 metersin length. In general, the same pressure drop as conventional exchangers are used without loss of the enhanced heat transfer.

This length, 2 to 3 meters, in Compabloc is even lower: max 750 mm...

Normal flowReversed flow

Backflushing Flow direction is reversed Flushes the debris out of the port and back to the source

Alfa Laval Port Filter A simple solution without separate filter Cylindrical perforated tube Protects at the inlet port Available on most M-serie PHEs Mounted and dismantled from pressure plate Requires

Hole in pressure plate Lining Inspection cover

Remove inspection cover Pull out and empty

Alfa Laval FiltersNormal operation

Flushing

Back flushing

Advantages Easy to install - Saves space

No extra pump capacity

No disturbance of operation during flushing

Low pressure drop

High reliability

Low flushing pressure

Easy and quick service

Good corrosion resistance