Page 1© Copyright Cal Gavin 03/2007 www.calgavin.com
Up-grading performance of heat exchangers and
reducing fouling by retrofitting hiTRAN ® tube-side enhancement systems
www.calgavin.com
Heaters ● Coolers ● Condensers ● Vapourisers ● Reboilers ● Thermo-Syphon Reboilers ● Reactors ● Economisers ● Chillers ● Intercoolers ● Aftercoolers ● Oxidisers….
Page 2© Copyright Cal Gavin 03/2007 www.calgavin.com
Cal Gavin LimitedEstablished in 1980Research, development and manufacture of enhancement technology for heat exchangersSectors include -
Oil exploration, production and refiningGas production, transmission and treatmentPetrochemical and downstream processingPlastics, polymers and resinsPower generation, refrigeration and speciality chemicals
Process Intensification engineers
Page 3© Copyright Cal Gavin 03/2007 www.calgavin.com
Scope of Activities Include:
• De-bottlenecking – engineering solutions to overcome plant and process limitations
• Designing new enhanced exchangers• Simulating performance and upgrading existing exchangers (HTFS, HTRI, hiTRAN SP software)
Page 4© Copyright Cal Gavin 03/2007 www.calgavin.com
The Problem….
To improve matters we increase Reynolds number (velocity)…… but Pressure drop increases to the power 2 as velocity is increased, whereas heat transfer increases linearly.
In plain tubes, frictional drag at the wall and shear forces within the fluid cause maldistribution (parabolic velocity profile)A thermally inefficient laminar boundary layer results. Heat transfer relies on conduction (across the fluid) and convection (physical mixing)Even in turbulent flow a significant boundary layer exists (single and 2 phase flow regimes)
Page 5© Copyright Cal Gavin 03/2007 www.calgavin.com
Red dye:
A) Laminar flow
B) Pseudo turbulent flow
Blue dye:
Video presentation of flow (500 < Re < 8000)
• hiTRAN Matrix Elements remove the boundary layer and mix it with the bulk flow.
• Fluid from the centre is displaced in the direction of the wall
• Residence time of the fluid at the wall is considerably reduced.
• In plain tubes, even at Reynolds Numbers as high as 10,000, there is very little fluid mixing of the bulk flow with fluid at the wall.
Page 6© Copyright Cal Gavin 03/2007 www.calgavin.com
Flow with hiTRAN, 20mm tube diameter (Please be patient to load the video)
Page 7© Copyright Cal Gavin 03/2007 www.calgavin.com
mit Insert Plain tube
1.0
0.5
0.0
U/Umax
Flow velocity vectors of plain tube and immediately after the hiTRAN Element, measured with Laser PIV(Particle Image Velociometry – laminar flow)
Page 8© Copyright Cal Gavin 03/2007 www.calgavin.com
after hiTRAN Element Plain tube
1.0
0.5
0.0
U/Umax
Flow velocity vectors of plain tube and immediately after the hiTRAN Element, measured with Laser PIV(Particle Image Velociometry – laminar flow)
Page 9© Copyright Cal Gavin 03/2007 www.calgavin.com
Graphical representation of plain tube and hiTRAN matrix element performance range
1
10
100
1000
10 100 1000 10000 100000
Re [-]
heat
tran
sfer
fact
or [-
]
Page 10© Copyright Cal Gavin 03/2007 www.calgavin.com Page 1© Copyright Cal Gavin 03/2007 www.calgavin.com
Graphical representation of plain tube and hiTRAN matrix element performance, case study
1
10
100
10 100 1000 10000 100000
Re [-]
heat
tran
sfer
fact
or [-
]
0
0.2
0.4
0.6
0.8
1
pres
sure
dro
p [b
ar]
14*
3.8
20
1
2
2*
2 pass hiTRAN 8 pass plain
1 pass hiTRAN
hiTRAN tube pressure drop
plain tube pressure drop
1.2m/s0.3m/s
6.2m/s 42passes ~100 bar
200 400 1600 8200
Page 11© Copyright Cal Gavin 03/2007 www.calgavin.com
For New Exchangers…. hiTRAN Systems benefit any duty where the main heat transfer resistance is on the tubeside• Plot space and weight is restricted• Where single pass is only option• Close temperature approaches• Stability in transition region• Longer operation under most fouling conditions
Page 12© Copyright Cal Gavin 03/2007 www.calgavin.com
Upgrading existing exchangers• Higher heat loads• Higher / lower output temperatures• Lower energy requirements• Optimum use of existing hardware• Maintain performance with turn-down• Improved fluid distribution• Mitigation of reaction, crystallisation and deposition fouling
Page 13© Copyright Cal Gavin 03/2007 www.calgavin.com
Case study 1: Air Cooled Lube Oil Cooler
Enhanced
Plain Bore Finned Tube
• Requires only 1/3 of the plot area• Achieves the same heat duty at the same pressure drop• Uses less than ½ of the fan power• Allows flexibility to design within noise level limits• Lowest cost option
Page 14© Copyright Cal Gavin 03/2007 www.calgavin.com
Case study 2: Heavy Cycle Gas Oil Cooler
Enhanced
Plain Tube
•Requires less than ¼ of the effective heat transfer area•Achieves the same heat duty at the same pressure drop•Fluid residue time at the wall is reduced•Risk of thermal degradation fouling is lowered
Page 15© Copyright Cal Gavin 03/2007 www.calgavin.com
Reducing fouling with hiTran Systems
Most exchanger fouling is strongly affected by tube-wall temperature and the rate of shear (mixing) at the tube wall
• Increased shear keeps particles in flow
• Higher tube-side co-efficient : lowers wall temperature when heating fluids (reduces cracking of hydrocarbons) increases wall temperature when cooling (reduces crystallisation fouling e.g. wax
formation)
Page 16© Copyright Cal Gavin 03/2007 www.calgavin.com
Photographic Evaluation of hydro-dynamics
Talcum as suspension particles, 40 to 60 microns, 2500kg/m3
Constant Re no. of 750
• High shear rate at the wall causes homogenious distribution of particles
• Vortexes behind the wire loops causes high liquid mixing
Plain tube
hiTRAN tube
Page 17© Copyright Cal Gavin 03/2007 www.calgavin.com
Crude Oil fouling research [University of Bath]
F
oulin
g re
sist
ance
[m2 K
/ W
* 10
4 ]
Time [hr]
Tube with matrix Element velocity 0.5m/sTwall = 218 °C
Time [hr]
Tube without matrix Elementvelocity 0.5m/sTwall = 216 °C
Arabian light crude oil
Advantageous effects:• Lower tube-wall temperature for same duty• Reduction in fluid volume which is heated above bulk temperature• Reduction in wall fluid residence time• Suppression of nucleation at the surface• Increased shear rate at the wall (higher removal rate)
Page 18© Copyright Cal Gavin 03/2007 www.calgavin.com
Page 19© Copyright Cal Gavin 03/2007 www.calgavin.com
Liquid film htc’s are relatively high compared to vapour phase
Mechanisms of Condensation
Vapour
•Film heat transfer coefficients depend on:
–whether film is laminar, laminar/wavy or turbulent–thickness of the film
•Vapour phase heat/mass transfer coefficients depend on:
–vapour velocity/turbulence/mixing–vapour transport properties–concentration of condensable components
Vapour phase htc’s relatively low
Page 20© Copyright Cal Gavin 03/2007 www.calgavin.com
Enhancement of CondensersWire Matrix Elements enhance in-tube condensation by:• Film mixing • Film thinning• Film draining•Enhancing vapour phase
cooling•Increasing inter-phase mass transfer rates.
Typical applications:• Vent condensers• Vacuum condensers with inert components• Condensation of wide-boiling range mixtures• Reflux condensers
Page 21© Copyright Cal Gavin 03/2007 www.calgavin.com
Mechanisms of Boiling and the impact of Matrix Elements
(Reboilers) • Increased convective boiling rate• Shorter sub-cooled length
• Viscous liquids• Low temperature driving forces
Typical applications for:
• More even tube-side temperature distribution
Sub-cooled
Pla
in
tube
Enh
ance
d tu
be
Page 22© Copyright Cal Gavin 03/2007 www.calgavin.com
Where total vaporisation is required at high heat fluxes, enhancement is often applied to:
• Control film boiling• Mitigate mist carry-over• Enhance fluid distribution• Enhance wall wetting
LNG/LPG/Ethylene… vaporisersTypical applications:
Mechanism of Boiling and the impactof Matrix Elements – (vaporisers)
• Improve heat transfer in the superheated region
Page 23© Copyright Cal Gavin 03/2007 www.calgavin.com
Case Study 1. Tar Heaters - Cabot Carbon UK Carbon Black manufacture
Installation 1982 – Lummus / Cal Gavin Design
Feedstock mixture of cracked bottoms with coal tar residues – ”high fouling fluid”
12 Exchangers fitted – 2 pass design
Heated with thermal fluid (was steam) to 280C+
Plain tube fouled to shut-down in 2-3 months
hiTRAN System fitted - constant performance maintained
Elements replaced 3 times in 24 years
Higher temperature process in 2006
Page 24© Copyright Cal Gavin 03/2007 www.calgavin.com
Case study 2 Crude pre-heater - Wintershall Refinery (BP) - GermanyInstalation 1996 – 9 year operation
Vacuum residue tube side, Crude (preheat) shell-side
Process had a long history of fouling
Many un-planned shutdowns
Helical Baffle/hiTRAN installed – one shell only needed
(without enhancement 2 larger shells would be required)
Re-tubed in 2005, hiTRAN Elements removed and re-installed
Page 25© Copyright Cal Gavin 03/2007 www.calgavin.com
Case Study 3 Dalia FPSO – Total Oil, Angola oil-water separation process
• design capacity of 240,000 barrels per day of crude, two million barrels of storage capacity
• shell side 1073500kg/hr wet crude oil is heated from 50.5 °C to 60.7 °C
• tube side 802170kg/hr dry crude oil is cooled from 87.5 °C to 70.1°C
TEMA Type BES
Temp. shell in / out [°C] 50.5 / 60.7
Temp. tube in / out [°C] 87.5 / 70.1
Massflow shell / tube [kg/s] 298.2 / 222.8
Duty [MW] 7.94
Tube OD diameter [mm] 25.4
FPSO Dalia with installed Crude / Oil Interchangers on the Top deck
Page 26© Copyright Cal Gavin 03/2007 www.calgavin.com
Case study 3 Size comparison - Conventional / HELITRANplain /
single.Segmental.
hiTRAN® / helical baffle
gain
OHTC [W/m2K] 59.9 242.7 4x
Tube side:HTC [W/m2K] 95 770 8xdp [bar] 140 150Flow velocity [m/sec] 0.92 0.45 ½Reynolds [-] 1680 800 ½Residence time [sec] 102 27 ¼Shell siede HTC [W/m2K] 455 789 ~2dp [bar] 1.50 1.25Flow velocity [m/sec] 0.41 1.3 3Reynolds 250 635Wall temperatures [°C] 59.2 65.6GeometryShell in series [-] 3 1Shell in parallel [-] 3 2Total no. of Shells [-] 9 2 ~4Tube Flow path [m] 94.5 12.2 1/8Tube length [m] 5.25 6.096Total tube count [-] 16002 3640 ~¼Tube passes [-] 6 2Total HT area [m2] 6420 1704 ~¼Plot space [m2] 104.5 26.2 ¼Weight wet [kg] 401148 130716 1/3Exchanger costs [%] 100 35 ~1/3
Conventional HELITRAN
Page 27© Copyright Cal Gavin 03/2007 www.calgavin.com
Case study 4 Process Air-cooled Exchanger Upgrade Client: Reliance Industries, Surat, India Contractor: Bechtel Limited Exchanger: Product Fractionator Bottoms Cooler Fluid : Vacuum Gas Oil
Plant Problem -Plant Problem - Planned major upgrade - increased
throughput - change in feedstock Existing exchanger 65% under-
surfaced for new duty No space available for new
exchangers Limited pressure loss available
Page 28© Copyright Cal Gavin 03/2007 www.calgavin.com
HiTRANHiTRAN®® Enhancement Solution Enhancement Solution Keep frames and fans
Fit new 2 pass bundles with optimised hiTRAN ® System
instead of 6 pass plain tube design
Up-grade meets new duty plus 10% spare capacity
New duty achieved within allowable pressure drop
The BenefitsThe Benefits Reuse of existing bays, fans, structures - no modifications
No additional structures required
Proven heat transfer performance
Significant cost reduction
Page 29© Copyright Cal Gavin 03/2007 www.calgavin.com
“Texas Tower” Feed / Effluent Exchanger May 2007
1700 tubes - 12 metres vertical - 2 joined hiTRAN Elements / tube Benefits :-• increased product throughput • higher return temperature to furnace - increased energy efficiency • Increased plant profit!
Page 30© Copyright Cal Gavin 03/2007 www.calgavin.com
Texas Tower – RUHR OEL (BP AMERICA INC)
Benefits:
Retrofit upgrade delivers 15% increased throughput
0.8MW heat recovery
Reduction of 1700t/yr carbon emission recovery from fired heater
Direct reduction of energy input of 25 TJoule/year ( ~50000Euro/yr)
Page 31© Copyright Cal Gavin 03/2007 www.calgavin.com
Crude Desalter Exchanger
Fabricator: EIGSADesigner: Cal Gavin
LtdEnd User: PemexCountry: MexicoPlant: Dos Bocas
terminal
Plain tube - 20 shellshiTRAN - 8 ShellsTubeside: desalted
crudeShellside: wet crude
Page 32© Copyright Cal Gavin 03/2007 www.calgavin.com
Column Top Condenser
Fabricator: Doosan MecatecDesigner: DOW Chemicals +
Cal Gavin LtdEnd User: SinopecCountry: ChinaTwo new plants: Zhenhei and
TianjinnNote :Combined heat and mass
transfer- one stage effective
Small unit 7000 tubes - 5 metres dia
Large unit 9000 tubes – 7 metres dia
Page 33© Copyright Cal Gavin 03/2007 www.calgavin.com
Case Study 10
Retrofit heat recovery of feed/effluent exchanger
User: LUKOIL refineryLocation: Volgograd, RussianService: HydrocarbonExchanger: TEMA AES with Helical baffles 2 parallel trains of 3 horizontal stacked shells in seriesBenefits• Increased performance of
exchangers• Reduced maldistribution on tube-
side• Reduced energy consumption of
fired heater 2.2 MW (4.6 MW at new capacity)
• Fuel saving of $233,000 per year• Enables higher plant throughput• Increased plant profit!
Page 34© Copyright Cal Gavin 03/2007 www.calgavin.com
Thank you for your attention
Please tell us what improvements you would like to make to the operation of your plant.
Martin Gough – Cal Gavin Limited