Some Industrial Applications
Teo Chee Seng
17 Feb 2015
Types of Heat Exchangers
Typical Applications in Oil refinery
Cryogenic applications in LNG industry
Design
Operations
Vendors
Practical aspects
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
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
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
Efficiency of network has an impact on unit throughput and fuel consumption
o application of online chemical cleaning
o optimization of cleaning schedule
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
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LNG Tanks Vaporisers
HP Pumps
BOG Compressor
Second Metering Station etc.
Metering Station
BTU adjustment / odorisation
Recondenser
LNG Carrier
Flare / Vent
In-tank Pumps
Utilities
Typical LNG Receiving Terminal Flow Scheme
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ORV conceptional flow
Open Rack Vaporizer
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Banks of Air Cooled Heat Exchangers are used as condensers in baseload LNG liquefaction plants
http://www.gea-heatexchangers.com/products/finned-tube-heat-exchangers/air-fin-coolers-for-oil-and-gas/
Aluminium HX for enhanced heat transfer
Very specialised equipment for Air/NG liquefaction
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
Fixed Tubesheet (TEMA type BEM) ◦ Cheap and easy
construction ◦ Tubes fixed on
both ends; tube external not accessible for cleaning
U tube (TEMA type BEU) ◦ Good for large
differential Ts ◦ Limited internal
tube cleaning
Floating Head (TEMA type BES) ◦ Allow access to shell &
tube external for cleaning
◦ Good for large dTs ◦ Expensive
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) PCHE B) Plate Fin type Often applied for narrow
temperature differences and clean services like air, N2, natural gas etc
A B
Typical “task” for process engineer is to monitor the effectiveness of heat exchange network
WHY? ◦ Lower efficiency means increased firing in furnaces leading to
more burning more fuel and higher costs ◦ Efficiency reduces with time due to “fouling”
How to monitor? ◦ 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
Decide when to clean and what to clean!
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
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
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
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, non-intrusive monitoring and process monitoring via simulation
Movie on heat exchanger incident at the Tesoro refinery
https://www.htri.net/
http://www.tema.org/
Prices