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CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 1
By: Jaap Hoogland
SPX Cooling Technologies GmbH
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 2
SUMMARY
Seawater recooling systems
Technique required for seawater cooling towers– Heat calculation– Construction material
Environment– Drift loss– Salt emission
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 3
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 4
ONCE THROUGH COOLING
A sea water filtration station, consisting of one bar screen and two travelling basket filters Electro Chlorination station
Cooling water pump
Chiller
100 %
100 %
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 5
HELPER or DISCHARGE COOLING TOWER
A sea water filtration station, consisting of one bar screen and two travelling basket filters Electro Chlorination station
Cooling water pump
Chiller
Cooling towers complete with pump pits
98 %
100 %
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 6
SEAWATER COOLING TOWER PLANT
A sea water filtration station, consisting of one bar screen and two travelling basket filters
Electro Chlorination stationSuppletion water pump
Chiller
Cooling towers complete with pump pits
4 %
3 %
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 7
Technique required for seawater cooling towers
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 8
Main Components of a Wet Cooling Tower
fan stack with diffusor
fan with gearbox, shaft and motor
plenum
drift eliminatorwater distribution
spray area
cooling fill
rain area with air inlet
cold water basin with outlet to the main pump(s)
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 9
blow- down
evaporation,drift loss
(droplet emission)Drift loss (min. 0.0005 %)
Blow-down
Evaporation
Make-up
Cooling Water Circuit
Principle of Wet Cooling
heat exchanger
CHILLER PLANTCHILLER PLANT
% of Circuit Water Flow
City Water
TSE SEAWATER
Evaporation 1,2 % 1,2 % 1,2 %
Conc. Factor 5 2,5 1,4
Make-up 1,5 % 2,0 % 4,2 %
Blow down 0,3 % 0,8 % 3 %
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 10
Salts in the Cooling WaterWhat differentiates seawater cooling towers from fresh water towers is the existence of dissolved minerals (salts) in the cooling water. Therefore, establishing the impact of salts in the cooling water is the single most important technical feasibility concern.
The areas of concern were identified as
• thermal performance• salt concentration• salt emission (Drift) and• environmental impacts as far as• material resistance.
Designing Seawater Cooling Towers Salts in the cooling water
Make-up Circulatingwater water
Brackish Water mg/l mg/l @ 3 -4 cycles Total Dissolved Solids 8000 24 - 32000 Sulfate (SO4) 450 1350 - 1800 Chloride (Cl- ) 4500 13500 - 18000
Sea Water mg/l mg/l @ 1.2 - 1.4 cycles Total Dissolved Solids 35000 42 - 50000 Sulfate (SO4) 2800 3400 - 4000 Chloride (Cl- ) 20 24000 - 28000
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 11
Thermal Performance
Salt in the water has four basic effects on its use as a coolant, only one of those is major. Salt lowers the vapor pressure of water, thus the water does not evaporate as readily. This makes it less as a effective coolant and reduces tower performance.
For the above reasons tower performance decreases by approximately 1.1% for every 10,000 ppm of salts in the cooling water.
Designing Seawater Cooling Towers Thermal Performance
Impact of salts in water upon vapor pressure Fresh water Salt water 1)Water Temp. 35 35 [°C]Air Temp. 30,6 30,6 [°C]Air Relative Humidity 60 60 [%]Liquid Vapor Pressure 5,62 5,42 [kPa]Air Vapor Pressure 2,63 2,63 [kPa]Liquid-Air Vapor Pressure Difference 2,99 2,79 [kPa]Liquid-Air Vapor Pressure Difference (of Fresh Water Condition) 100 93,2 [%]Performance loss 2) -- 5,4 [%]
1) At salts concentration of 50,000 ppm2) Performance loss (approximated as 80% of change in VP difference) = 0,8 x (1-0,932)
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 12
Designing Seawater Cooling Towers Thermal Performance
Impact on Design / Size of the cooling tower
Rejected Heat = Flow x Density x Spec. Heat x Cooling Range (DT)
fresh water : density = 1000 kg/m³, specific heat = 4.18 kJ/(kg.K)
sea water: density = 1030 kg/m³ specific heat = 3.96 (@ salinity 45000 ppm)
⇒
flow (sea) / flow (fresh) = 1.03 (for the same cooling capacity) !!!
⇒
cooling tower size or power consumption increases
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 13
Computerised DesignOur modern and updated computer design programs are taking into account the salt content depending on density and temperature.Therefore the design of the cooling tower will take place "on point" and no other adds are necessary.Only modern computer design programs, based on huge experience and test results, are able to determinate all parameters correctly to guarantee the most feasable and economical cooling tower design regarding size and type.
Designing Seawater Cooling Towers 3 Computerised Design
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 14
Technique required for seawater cooling towers
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 15
Materials for• Structural components
• Mechanical part
• Thermo- hydraulic part
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 16
Construction materials• Concrete
• Timber
• FRP
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 17
The Cooling Tower Environment:
• The warm, saturated, oxygen-rich cooling tower environment promotes rapid corrosion of metallic components.
• Most construction materials are relatively unaffected by salt water
• Temperature level and pH-value has to maintained• Wood and plastic are as good as concrete
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 18
Impact on concrete constructions
React with cementMay react with aggregateReaction causes destruction of concrete matrix
Sulfates (SO4 )
Attack steel reinforcementAttack metallic hardwareRapid loss of cross section may occurCorrosion by products result in expansion and cracking of concrete
Chlorides (Cl-)
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 19
Desired Properties:
Low absorption/permeability to provide maximumprotection to reinforcement.
High resistance to sulfate attack.
Corrosion resistance
Resistance against biological attack
Temperature resistance
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 20
No problems with fill, drift eliminator, spray nozzles and fan if water quality is within the limits
Steel parts made of high grade stainless steel ("Duplex" 1.4462 [316 L], 1.4539) or special coated
Mechanical part should be protected with suitablecoating for salt water application
General Recommendations for thermo- hydraulic & mech. part:
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 21
Environment
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 22
Cooling Tower DriftCirculating water is distributed as droplets or films to maximise surface area
Exit air from cooling tower contains water vapor, drift dropletsand condensate droplets
Amount of content are mainly regulated by:
Drift eliminator design
Design of water distribution
Ambient psychometric and wind conditions
Water chemistry
Environment
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 23
Drift Loss Different Types of Drift Eliminators
0
0,001
0,002
0,003
0,004
0,005
0,006
1 Layer TC 187/44 1 Layer TC 187/33 CDX 0802 layers TC 187/33
Dri
ft L
oss
[% o
f wat
er fl
ow r
ate]
Cooling Tower Drift Loss (Standard Data)
Environment
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 24
TC 187/33E2 Layers
Drift Loss as a Function of the Droplet Size(Total Drift Loss = 0.0005% of water flow rate)
0
0,0005
0,001
0,0015
0,002
0,0025
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
Droplet Size [µm]
Drif
t Los
s [%
of w
ater
flow
rate
]
Environment
or 1 Layers
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 25
WaterqualityFeature Feature Feature Feature
Make-up system Own intake stationConnection to Grey water system
Connection to Grey water system
Connection to DEWA pipe system
Blow down system (drain) Own outlet station
Connection to sewage water system or irrigation system
Connection to sewage water system or irrigation system
Connection to sewage water system or irrigation system
Condensor system Titanium Standard material Standard material Standard material
Cooling tower
Titanium/Duplex hardware, special coating, FAND for larger plants
Standard material, low fouling fill Standard material Standard material
Water treatment system
ElectroChlorination, Bromation, hardness stabilizer Biocide, Corrosion inhibitor Biocide, Corrosion inhibitor Biocide, Corrosion inhibitor
Requirements of Cooling Circuit
Seawater Normal Grey water Polished Grey water Potable water
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 26
Central unit 125.000 TR 535,1 MW
Cooling tower design dataHot water temparature 105 °F 40,6 °CCold water temparature 95 °F 35,0 °CEntrance Wet bulb temperature 86 °F 30,0 °CEntrance Relative humidity 50% 50%Waterflow 375.000 USGPM 85.125 m³/hSalinity of the seawater 3,50% 3,50%drift loss 0,0005% 0,0005%CF used for seawater 1,4 1,4CF used for Normal Grey Water 2,5 2,5CF used for Polished Grey Water 5 5CF used for Potable water 5 5
Water use based on 80% operation Seawater 4.895.482.415 USGal/year 18.531.416 m³/yearWater use based on 80% operation Normal Grey water 2.331.594.847 USGal/year 8.826.046 m³/yearWater use based on 80% operation Polished Grey water 1.748.893.127 USGal/year 6.620.280 m³/yearWater use based on 80% operation Potable water 1.748.893.127 USGal/year 6.620.280 m³/year
Total drain amount 80% operation Seawater 3.496.210.320 USGal/year 13.234.595 m³/yearTotal drain amount 80% operation Normal Grey water 932.322.752 USGal/year 3.529.225 m³/yearTotal drain amount 80% operation Polished Grey water 349.621.032 USGal/year 1.323.459 m³/yearTotal drain amount 80% operation Potable water 349.621.032 USGal/year 1.323.459 m³/year
This is the amount produced by a city of around 180.000 peopleThis is the amount produced by a city of around 130.000 people
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 27
Environment
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 28
Critical Zone
Cooling Tower
Dispersion AreaPrevailing Wind
UseUse ofofWindroseWindrose
Environment
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 29
Relative Immission as a Function of the Distance from CTComparison between Round Type and Cell Type
0%
10%
20%
30%
40%
50%
60%
70%
0 100 200 300 400 500 600 700 800 900 1000Distance from CT [m]
C/C
max
cell 20 m acrossround 20 mcell 20 m averagecell 20 m alonground 60 m
wind
Environment
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 30
Salt Immission at Ground Level (Relative Concentration)as a Function of the Cooling Tower Heightand the Distance from the Cooling Tower
0102030405060708090
100
0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000Distance from the Cooling Tower [m]
15 m (cell)40 m60 m80 m
Environment
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 31
0
10
20
30
40
50
60
70
80
90
0,1 1 10 100
Distance from the coast [km] measured in Newport USA
Tota
l mas
s AS
SP
[µg/
m³]
source: AM S Journals Online, study Rossknecht , Elliot and Ramsey 1972
Environment
Cooling tower outlet will be arround 470-550 µg/m³
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 32
Objects of the Investigation
which will be referred to as:
Cooling tower conceptscell type cooling towers
case 1~50.000 TR
case 2~ 90.000 TR
Environment
circular cooling tower with forced draught fans
case 3~ 125.000 TR
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 33
Methods of the Investigation
Simulation of the flow in the surroundings of the cooling towers
calculated magnitudes:• velocity• pressure• temperature• mass ratio between wet air and dry air• relative humidity• flight path of salt water droplets
Environment
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 34
Boundary conditions of the calculationscell type cooling towers
Methods of the Investigation
windspeed
=
6 m/s
(at 10m height)profile
=
atmospheric boundary layerdirection
=
0°
and 90°temperature
=
5
°Cabs. humidity
=
0,43 % massratio
Environment
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 35
Salt emission
case 1, 50.000 TR winddirection = 0°
figure explaination:
colours
=
ratio local
salt
concentration
to salt
concentration
at the
outlet
of the
tower
[ unit
= % massratio](values
lower
than
100% represents
dillution)colourrange
=
red ≥
80%, blue
≤
20%
case 1, winddirection = 90°
increased
salt
concentration
close
to the
ground
50 storied bld
Results
Environment
Building needs to be at at least 400 m
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 36
case 2, 90.000 TR winddirection = 0° case 2, winddirection = 90°
increased
salt
concentration
close
to the
ground
Salt emissionfigure explaination:
colours
=
ratio local
salt
concentration
to salt
concentration
at the
outlet
of the
tower
[ unit
= % massratio](values
lower
than
100% represents
dillution)colourrange
=
red ≥
80%, blue
≤
20%
Results
Environment
50 storied bld
Building needs to be at at least 500 m
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 37
downwash
Case 3 ~ 125.000 TR
Salt emissionfigure explaination:
colours
=
ratio local
salt
concentration
to salt
concentration
at the
outlet
of the
tower
[ unit
= % massratio](values
lower
than
100% represents
dillution)colourrange
=
red ≥
80%, blue
≤
20%
Results
Environment
Nearest 50 Storied bld should be in approx. 400 m
50 storied bld
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 38
cold air
warm air
Cooling Fills
Water Distribution
Drift Eliminator
Arrangement of a Round Wet Cooling TowerArrangement of a Round Wet Cooling Tower
hot water inlet
cold water outlet
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 39
BuildingBuilding 75 m x 75 m x 38 m 75 m x 75 m x 38 m talltall ((aboveabove groundground))
125.000 TR central plant
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 40
Shell Shell couldcould bebe mademade of of frameworkframework structurestructure withwith claddingcladding
125.000 TR central plant
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 41
FloorsFloors forfor pumpspumps, , chillerschillers, , fansfans, and , and miscellaneousmiscellaneous
125.000 TR central plant
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 42
125.000 TR central plant
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 43
TheThe towertower cancan bebe divideddivided intointo 4 4 oror 8 8 sectorssectors
125.000 TR central plant
CW /Jaap Hoogland/ 16-10-2007 Seawater Cooling Tower Circuits 44
ThankThank youyou veryvery muchmuch forfor youryour attentionattention..
WeWe will will bebe pleasedpleased to to answeranswer youryour questionsquestions and and provideprovide anyany furtherfurther informationinformation youyou needneed..
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