Mechanical Engineering Department
ME332 Operation and Management of Power Plants
Prof. Osama A El Masry
Steam Condenser I
Prof. Osama El Masry
Direct Contact Condenser
This type of condenser is suitable where conditions permit condensation of exhaust
steam by direct contact with the cooling water.
The vacuum is created in the chamber by an air ejector. The cooling water is sprayed
into the chamber an the fine spray contacts the steam. The steam condenses and falls
to the bottom of the condenser chamber with the injection water. The condensed steam
and injection water is withdrawn using a centrifugal extraction pump
Barometric Condenser
Barometric Counter-Current
Condensers have no moving
parts. Little maintenance is
required and provision can
be
made
for
internal
inspection
of
the
unit.
Because of the
barometric leg, no water
removal pump is required
Barometric Condenser
Multi-Jet Barometric Condensers are generally employed where low cost water
is available in ample quantity. It is the simplest design of all barometric
condensers, and requires no auxiliary air pump or pre-cooler.
- Recommended for operation under fairly constant loads where there is
relatively little air leakage, and where water is not too scarce and does not need
to be recirculated.
Jet-Type Condenser
Multi-Jet Spray Type Barometric Condensers are generally employed where
large capacities are required and where wide fluctuations in water
temperature or steam load occur.
Surface Condensers
Surface condensers are the
most
commonly
used
condensers in modern power
plants. The exhaust steam
from the turbine flows on the
shell side (under vacuum)
of the condenser,
while the plant’s
circulating water
flows in the
tube side.
Surface Condensers
The source of the
circulating water can be
either a closed-loop (i.e.
cooling tower, spray
pond, etc.) or once
through (i.e. from a lake,
ocean, or river). The
condensed steam from the
turbine,
called
condensate, is collected in
the bottom of the
condenser, which is called
a
hot
well.
The
condensate
is
then
pumped back to the steam
generator to repeat the
cycle.
Surface Condensers
Surface Condensers
Surface condensers are basically a shell
and tube heat exchanger consisting of
water boxes for directing the flow of
cooling water to and from horizontal tubes.
The tubes are sealed into fixed tube sheets
at each end and are supported at
intermediate points along the length of the
tubes by tube support plates. Numerous
tubes present a relatively large heat transfer
and condensing surface to the steam.
During operation at a very high vacuum,
only a few kgs of steam are contained in
the steam space and in contact with the
large and relatively cold condensing
surface at any one instant.
 surface condenser have improved by cutting down the bundle to half and




making two smaller bundles beside each others to overcome the high pressure
drop problem .
Baffles are used to help the steam distribution and accelerate condensation
rate
The shell is fabricated from carbon steel plates and is stiffened as needed to
provide rigidity for the shell.
Intermediate plates are installed to serve as baffle plates that provide the
desired flow path of the condensing steam. The plates also provide support
that help prevent sagging of long tube lengths.
At the bottom of the shell, where the condensate collects, an outlet is
installed. In some designs, a sump (often referred to as the hot well) is
provided. Condensate is pumped from the outlet or the hot well for reuse as
boiler feed water.
Shell Outlet
Channel Inlet
Channel
Outlet
Shell Outlet
SINGLE SEGMENTAL TRANVERSE BAFFLES
 Tube sheets of sufficient thickness usually made of stainless steel is
provided, with holes for the tubes to be inserted and rolled. This is
to avoid eddies at the inlet of each tube giving rise to erosion, and to
reduce flow friction. To take care of length wise expansion of tubes
some designs have expansion joint between the shell and the tube
sheet allowing the latter to move longitudinally.
 Size: modern condensers use 7/8 or 1.0 in tube of 18 gauge
thickness
 Condensers may have up to four passes; one and two pass
condensers are the most common. In a single pass condenser, the
cooling water makes one passage from end to end, through the
tubes. Single pass condensers have an inlet waterbox on one end
and an outlet water box on the other end. Two pass condensers have
the cooling water inlet and outlet on the same water box at one end
of the condenser, with a return water box at the other end.
 A single pass condenser is commonly used where the water is supplied from
natural sources such as rivers or oceans. If the source of circulating water is at
all limited, a two pass condenser will probably be the best selection since a
single pass condenser requires more cooling water per square foot of condenser
surface and per kilowatt of electrical generation. Usually, a two pass condenser
is used with cooling towers or a cooling lake.
 Waterboxes: The tube sheet at each end with tube ends rolled, for each end of
the condenser is closed by a fabricated box cover known as a waterbox, with
flanged connection to the tube sheet or condenser shell. The waterbox is
usually provided with man holes on hinged covers to allow inspection and
cleaning. These waterboxes on inlet side will also have flanged connections for
cooling water inlet butterfly valves, small vent pipe with hand valve for air
venting at higher level, and hand operated drain valve at bottom to drain the
waterbox for maintenance. Similarly on the outlet waterbox the cooling water
connection will have large flanges, butterfly valves, vent connection also at
higher level and drain connections at lower level.

Condenser Temperature Profile
Change in Condenser Temperature Profile
Change in Turbine Load and Condenser
Pressure
Variation in Condenser Pressure
Air Cooled Condensers
Hood or Plenum
Fan Ring
Fan
Inlet
Nozzles
Return
Headers
Inlet
Headers
Outlet
Headers
Outlet
Nozzles
Tube Bundle
Drive Assembly
Supports
Dry Cooling
Steam ducted to air-cooled
condenser
Condensation inside finned
tubes - analogous to automobile
radiator
Cold water approaches
bulb temperature
dry
Steam Condensers
Water Cooled
Condensers
Air Cooled
Condensers
Internal Surfaces
External Surfaces
Tube Fouling
Deposition or
Particulates
Scaling or
Crystallization
Microbiological
Debris
Corrosion Products
Deposition or Particulates
Are fine particulates that settles on
the tube surface due to gravity
under low flow condition.
Natural sediment
Bio-growth
Coal dust
Crystalline solids
Scaling or Crystallization Fouling
•
Scale occurs when the saturation point of dissolved constituents in the
cooling water is exceeded.
•
Scale can provide sites for local under scale corrosion
Pitting under scale in stainless steel tube
Debris
Caused by any substance whose size is close to, or greater than, tube
internal diameter.
Examples :
•
•
Rocks
Cooling tower materials ( Plastic
fill , wood )
• Large pieces of rusted steel
• Aquatic animals ( Small fishes )
• Any other substance that enters
the circulating water can obstruct
cooling water flow
Tubewall
Tube Metal
Temperature
800ºF
785ºF
Deposit Layer
Film
766ºF Inside Tube Temperature
730ºF Film Temperature
700ºF
Fluid
600ºF
500ºF
520ºF Bulk Fluid
Temperature
Temperature Profile in Heat Transfer
Cleaning interior surfaces of tubes
Chemical
Off Line Cleaning
Mechanical
On Line Cleaning
Chemical treatment
•
Several chemicals, often in combination, are used to control condenser tube fouling.
Chemical treatment methods :
•
PH control ( lowering PH to 5.8 or 4 )
•
Scale inhibitors
•
Corrosion inhibitors ( Zinc & phosphates for carbon steel )
Utilized for recirculating cleaning system because of :
1) The concentration of dissolved constituents is significant, increasing the
threat of scaling and corrosion.
2) Once-through cooling systems often discharge directly into a river, lake,
or ocean where chemicals concentrations are restricted.
Disadvantages of chemical treatment:
•
Expensive.
•
Job duration is excessive.
•
Subsequent disposal of the chemicals requires serious consideration due to potential
environmental hazard.
Mechanical cleaning
Off line cleaning
High Pressure
Water
Molded Plastic
Cleaners ( Pigs )
Brushes
Metal Scrapers
Hydrodrilling
High pressure water :
•
The water is directed in a high pressure towards the tubes.
•
Disadvantages:
 The time taken to clean a condenser can become extended.
 Could damage tube sheet or tube coatings.
Pigs
•
They are molded plastic cleaners .
•
Quit popular for softest types of deposits such as mud , silt and microbiological fouling
Plastic tube cleaners
Brushes
•
Used to remove micro / macro fouling, soft organic scales, some corrosion by-products.
•
Useful for cleaning tubes with thin wall metal inserts or epoxy type coatings.
Metal Scrapers
•
Used for harder types of deposits such as calcium carbonate.
•
The blades are mounted on a spindle.
•
One end of the spindle is a serrated plastic disc that allows a jet of water to propel the
cleaners through the tube.
Metal U-tube Cleaners
How does this technique work?
•
Spring loaded tube cleaner (Bullets) are shot through fouled Condenser
tubes
using specially designed water guns at 1.5-2.5 MPa water pressure with velocities 3-6
m/s.
•
Tube cleaners exit at the end of the condensers, hitting a collection screen hung at the
other end.
•
These cleaners are collected, cleaned and used again. Normally a bullet can be used 10 to
15 times.
Water Gun & its pumping system
Hydrodrilling
•
Used to remove difficult deposits from the inside of tubes .
•
Hard deposits such as ( Calcium, sulfur and oxides).
•
Could be used on-site therefore eliminating the need for bundles to
be sent off-site for cleaning treatments.
•
Polishes tube internal diameter to as-new condition.
Advantages of Hydrodrilling
•
It uses a small a volume of water (2 to 3 GPM at 200 to 300 PSI) that
is filtered and
recycled through a booster pump.
•
Greater heat transfer efficiency.
•
Less scheduled cleaning time and cost.
Cleaning effects for a calcium carbonate scale:
Before
After
In-Line Mechanical Cleaning
•
The tube cleaning system consists of:
•
•
•
•
•
Balls that are slightly larger in diameter than the tubes.
Ball injection nozzle.
Ball strainer.
Ball recirculating pump.
Ball collector.
Sponged balls
Ball Strainer
Air Cooled Condensers
External surfaces fouling
Dirt, dust & debris
Insects & bird carcasses
Pollen & Leaves
Cleaning External Tubes Surfaces
Fire hose
High pressure
handlance
Automated cleaning
machine
Fire hose
•
Uses low pressurized water but with high volume flow rates.
•
Has low washing effect.
Advantages:
•
The galvanized surfaces of the tubes and fins are not damaged by this method.
Disadvantages:
•
•
Unit must be taken out of service and scaffolding erected.
Improvements are quite small, since only a portion of debris is removed, remainder
being compacted between tube fins
High pressure handlance
•
Low water consumption and a high water pressure
•
Latter can damage galvanized surfaces and/or snap off fins
•
Unit must be taken out of service and scaffolding erected
•
Again, improvements are quite small since only portion of debris is
removed, remainder being compacted between tube fins
Automated Cleaning Machine
•
60 GPM at 1,000-2,000 psi water pressure avoids fin and tube surface
damage.
•
Adjustable nozzle design, distance from surface and jet energy.
•
Water contains no additives.
•
Fouling removed effectively and uniformly.
•
No need to shut unit down or erect scaffolding.
•
Nozzle beam optimally matched to tube bundle geometry with a constant jet angle.
Forms of Automated Cleaning
Machine
Permanently
installed system
Semi-automatic
system
Portable service unit
Permanently installed system
The system is supplied for each side of the ACC & controlled automatically
Semi-automatic system
•
The guide rails are permanently installed.
•
The nozzle beam carriage being moved from section to section by the labour.
Portable service unit
The unit has a portable nozzle beam carriage and control unit
Cleaning Results
During cleaning
Fouled
Cleaned
Conclusion
Surfaces should be kept
clean to increase
generation capacity &
reduce the associated
costs.