Some Industrial Applications
Teo Chee Seng
17 Feb 2015
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Types of Heat Exchangers
Typical Applications in Oil refinery
Cryogenic applications in LNG industry
Design
Operations
Vendors
Practical aspects
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HXs can be broadly divided by the following
applications
◦ Heat exchange eg. Cold crude oil versus hot column
residue
◦ Boilers eg. Steam reboilers, distillation column
reboilers
◦ Cooler eg. Water coolers, air fin coolers
◦ Chillers eg. Chilled water coolers
◦ Cryogenic eg. Propane refrigeration coolers, air
separation HXs
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Shell and Tube (S&T) HXs are the majority
Water coolers – trim coolers or rundown
coolers
Air cooled HXs – distillation column
condensers
Steam heaters – reboilers or preheater
Hot oil heaters – closed loop process heating
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Heat transfer through S&T HXs
Design of heat exchange network is optimised
by matching temperature level considering
o application of pinch technology in design
o spiral heat inserts; special baffles
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Efficiency of network has an impact on unit
throughput and fuel consumption
o application of online chemical cleaning
o optimization of cleaning schedule
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Plate exchangers in LNG plants, air separation
units
Spool wound heat exchangers in LNG liquefaction
plants
Printed circuit exchangers in offshore platforms
Propane “kettles” characterized by narrow
temperature approaches
In LNG terminals, LNG is vaporised into natural
gas using vaporisers (ORVs or SCVs)
◦ ORV – Open Rack Vaporisers
◦ SCV – Submerged Combustion Vaporisers
Typical LNG Receiving Terminal Flow Scheme
Flare /
Vent
Second
Metering
Station etc.
BOG
Compressor
Recondenser
LNG Tanks
Vaporiser
s
LNG Carrier
In-tank
Pumps
HP
Pumps
Utilities
Metering
Station
BTU adjustment /
odorisation
9
ORV conceptional flow
10
Open Rack Vaporizer
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12
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Banks of Air Cooled Heat Exchangers are
used as condensers in baseload LNG
liquefaction plants
http://www.geaheatexchangers.com/products/finnedtube-heat-exchangers/air-fin-coolers-foroil-and-gas/
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Aluminium HX for enhanced
heat transfer
Very specialised equipment
for Air/NG liquefaction
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Service – fouling / corrosive?
Temperature difference / approach
Allowable/available pressure drop
O&M philosophy
Applicable codes and regulations
CAPEX / OPEX
Note the
lower
OHTC for
gas-gas
HX
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Fixed
Tubesheet
(TEMA type
BEM)
◦ Cheap and easy
construction
◦ Tubes fixed on
both ends; tube
external not
accessible for
cleaning
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U tube (TEMA
type BEU)
◦ Good for large
differential Ts
◦ Limited internal
tube cleaning
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Floating Head (TEMA
type BES)
◦ Allow access to shell &
tube external for
cleaning
◦ Good for large dTs
◦ Expensive
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Kettle Reboiler
◦ Meant for vaporising
medium either heating
eg. Distillation column
bottom reboilers or
chilling like propane
refrigerant
◦ Vapour space allows
liquid and gas
separation
A
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A) PCHE
B) Plate Fin type
Often applied for narrow
temperature differences
and clean services like air,
N2, natural gas etc
B
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Typical “task” for process engineer is to monitor the
effectiveness of heat exchange network
WHY?
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How to monitor?
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Decide when to clean and what to clean!
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◦ Lower efficiency means increased firing in furnaces leading to
more burning more fuel and higher costs
◦ Efficiency reduces with time due to “fouling”
◦ Trending the overall heat transfer coefficient of individual HXs or
groups of HXs
◦ There is no OHTC meter! OHTC has to be back calculated based
on temperatures and flowrates
◦ An alternative is to monitor the fouling factors – essentially the
same principle as OHTC
◦ “normalisation” to the right flowrates and temperature is
important as differernt flowrates and temperature can have
significant effect on OHTC calculations
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Key process parameters to monitor are
o Furnace Inlet Temperature
o Individual exchanger heat transfer coefficient
trends
o Individual exchanger delta P
Pix showing tube internal cleaning of the tube bundle
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For water coolers and air coolers, there are often
no flowmeters and temperature meters on the
air/water side
Monitoring is often by setting a “baseline” eg
after a maintenance shutdown when equipment
is clean
Troubleshooting is often via hand held meters
like an IR meter to gauge the temperature of the
process / portable ultrasonic flowmeters for
water flow measurement
Comparison against design values often give
good clues to current performance – process
models on rating mode is very useful
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S&T HXs equipment are no longer considered
specialized equipment and there are many
vendors in the world
Brazed aluminum plate exchangers are more
“specials” – Chart industries/Linde are two of
the leading vendors
Printed circuit HX is a special small form
factor compact HX offered by Heatric
SWHE – specialised HX offered by APCI/Linde
for cryogenic applications
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Heat exchangers are crucial pieces of equipment
in maintaining unit throughput and optimizing
fuel efficiency
O&M know how and considerations like space
requirements, cleaning schedule, valving
arrangements, flushing, fouling etc need to be
considered in the initial design
Relevant experience is important in choice of HX
to be applied
Trend is towards more online cleaning, nonintrusive monitoring and process monitoring via
simulation
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Movie on heat exchanger incident at the
Tesoro refinery
https://www.htri.net/
http://www.tema.org/
Prices