By: Jaap Hoogland SPX Cooling Technologies GmbH. CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 1

Transcription

1 By: Jaap Hoogland SPX Cooling Technologies GmbH CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 1

2 SUMMARY Seawater recooling systems Technique required for seawater cooling towers Heat calculation Construction material Environment Drift loss Salt emission CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 2

3 CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 3

4 ONCE THROUGH COOLING Chiller 100 % 100 % Cooling water pump A sea water filtration station, consisting of one bar screen and two travelling basket filters Electro Chlorination station CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 4

5 HELPER or DISCHARGE COOLING TOWER Cooling towers complete with pump pits Chiller 98 % 100 % Cooling water pump A sea water filtration station, consisting of one bar screen and two travelling basket filters Electro Chlorination station CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 5

6 SEAWATER COOLING TOWER PLANT Cooling towers complete with pump pits Chiller 3 % 4 % A sea water filtration station, consisting of one bar screen and two travelling basket filters Suppletion water pump Electro Chlorination station CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 6

7 Technique required for seawater cooling towers CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 7

8 Main Components of a Wet Cooling Tower fan stack with diffusor fan with gearbox, shaft and motor plenum drift eliminator water distribution spray area cooling fill rain area with air inlet cold water basin with outlet to the main pump(s) CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 8

9 Principle of Wet Cooling Cooling Water Circuit evaporation, drift loss (droplet emission) Drift loss (min %) Blow-down Evaporation Make-up blowdown % of Circuit Water Flow City Water TSE SEA WATER Evaporation 1,2 % 1,2 % 1,2 % Conc. Factor 5 2,5 1,4 heat exchanger CHILLER PLANT Make-up 1,5 % 2,0 % 4,2 % Blow down 0,3 % 0,8 % 3 % CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 9

10 Designing Seawater Cooling Towers Salts in the cooling water Salts in the Cooling Water What 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. Make-up water Circulating water Brackish Water mg/l 3-4 cycles Total Dissolved Solids Sulfate (SO4) Chloride (Cl- ) Sea Water mg/l cycles Total Dissolved Solids Sulfate (SO4) Chloride (Cl- ) CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 10

11 Designing Seawater Cooling Towers Thermal Performance 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. Impact of salts in water upon vapor pressure Fresh water Salt water 1) Water Temp [ C] Air Temp. 30,6 30,6 [ C] Air Relative Humidity [%] 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) ,2 [%] Performance loss 2) -- 5,4 [%] 1) At salts concentration of 50,000 ppm 2) Performance loss (approximated as 80% of change in VP difference) = 0,8 x (1-0,932) CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 11

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 ppm) flow (sea) / flow (fresh) = 1.03 (for the same cooling capacity)!!! cooling tower size or power consumption increases CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 12

13 Designing Seawater Cooling Towers 3 Computerised Design Computerised Design Our 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. CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 13

14 Technique required for seawater cooling towers CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 14

15 Materials for Structural components Mechanical part Thermo- hydraulic part CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 15

16 Construction materials Concrete Timber FRP CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 16

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/ Seawater Cooling Tower Circuits 17

18 Impact on concrete constructions Sulfates (SO 4 ) React with cement May react with aggregate Reaction causes destruction of concrete matrix Chlorides (Cl - ) Attack steel reinforcement Attack metallic hardware Rapid loss of cross section may occur Corrosion by products result in expansion and cracking of concrete CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 18

19 Desired Properties: Low absorption/permeability to provide maximum protection to reinforcement. High resistance to sulfate attack. Corrosion resistance Resistance against biological attack Temperature resistance CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 19

20 General Recommendations for thermo- hydraulic & mech. part: 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" [316 L], ) or special coated Mechanical part should be protected with suitable coating for salt water application CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 20

21 Environment CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 21

22 Environment Cooling Tower Drift Circulating water is distributed as droplets or films to maximise surface area Exit air from cooling tower contains water vapor, drift droplets and condensate droplets Amount of content are mainly regulated by: Drift eliminator design Design of water distribution Ambient psychometric and wind conditions Water chemistry CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 22

23 Environment Cooling Tower Drift Loss (Standard Data) Drift Loss Different Types of Drift Eliminators 0,006 Drift Loss [% of water flow rate] 0,005 0,004 0,003 0,002 0, Layer TC 187/44 1 Layer TC 187/33 CDX layers TC 187/33 CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 23

24 Environment Drift Loss as a Function of the Droplet Size (Total Drift Loss = % of water flow rate) 2 Layers TC 187/33E 0,0025 or 1 Layers Drift Loss [% of water flow rate] 0,002 0,0015 0,001 0, Droplet Size [µm] CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 24

25 Requirements of Cooling Circuit Waterquality Seawater Normal Grey water Polished Grey water Potable water Feature Feature Feature Feature Make-up system Own intake station Connection 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 Water treatment system Titanium/Duplex hardware, special coating, FAND for larger plants ElectroChlorination, Bromation, hardness stabilizer Standard material, low fouling fill Standard material Standard material Biocide, Corrosion inhibitor Biocide, Corrosion inhibitor Biocide, Corrosion inhibitor CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 25

26 Central unit TR 535,1 MW Cooling tower design data Hot water temparature 105 F 40,6 C Cold water temparature 95 F 35,0 C Entrance Wet bulb temperature 86 F 30,0 C Entrance Relative humidity 50% 50% Waterflow USGPM m³/h Salinity of the seawater 3,50% This is the amount 3,50% drift loss 0,0005% 0,0005% produced This is the by amount a city of CF used for seawater 1,4 1,4 CF used for Normal Grey Water 2,5 around produced by a city people of 2,5 around people CF used for Polished Grey Water 5 5 CF used for Potable water 5 5 Water use based on 80% operation Seawater USGal/year m³/year Water use based on 80% operation Normal Grey water USGal/year m³/year Water use based on 80% operation Polished Grey water USGal/year m³/year Water use based on 80% operation Potable water USGal/year m³/year Total drain amount 80% operation Seawater USGal/year m³/year Total drain amount 80% operation Normal Grey water USGal/year m³/year Total drain amount 80% operation Polished Grey water USGal/year m³/year Total drain amount 80% operation Potable water USGal/year m³/year CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 26

27 Environment CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 27

28 Environment Use of Windrose Critical Zone Cooling Tower Prevailing Wind Dispersion Area CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 28

29 Environment 70% Relative Immission as a Function of the Distance from CT Comparison between Round Type and Cell Type C/Cmax 60% 50% 40% 30% wind cell 20 m across round 20 m cell 20 m average cell 20 m along round 60 m 20% 10% 0% Distance from CT [m] CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 29

30 Environment Salt Immission at Ground Level (Relative Concentration) as a Function of the Cooling Tower Height and the Distance from the Cooling Tower 15 m (cell) 40 m 60 m 80 m Distance from the Cooling Tower [m] CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 30

31 Environment Total mass ASSP [µg/m³] , source: AM S Journals Online, study Rossknecht, Elliot and Ramsey 1972 Distance from the coast [km] measured in Newport USA Cooling tower outlet will be arround µg/m³ CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 31

32 Environment Objects of the Investigation Cooling tower concepts which will be referred to as: case 1 ~ TR cell type cooling towers circular cooling tower with forced draught fans case 2 ~ TR case 3 ~ TR CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 32

33 Environment 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 CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 33

34 Environment Methods of the Investigation Boundary conditions of the calculations cell type cooling towers wind speed = 6 m/s (at 10m height) profile = atmospheric boundary layer direction = 0 and 90 temperature = 5 C abs. humidity = 0,43 % massratio CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 34

35 Environment Results Salt emission 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, TR winddirection = 0 case 1, winddirection = 90 Building needs to be at at least 400 m 50 storied bld increased salt concentration close to the ground CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 35

36 Environment Results Salt emission 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 2, TR winddirection = 0 case 2, winddirection = 90 Building needs to be at at least 500 m 50 storied bld increased salt concentration close to the ground CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 36

37 Environment Results Salt emission 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 3 ~ TR Nearest 50 Storied bld should be in approx. 400 m 50 storied bld downwash CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 37

38 Arrangement of a Round Wet Cooling Tower Water Distribution warm air hot water inlet Drift Eliminator Cooling Fills cold air cold water outlet CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 38

39 TR central plant Building 75 m x 75 m x 38 m tall (above ground) CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 39

40 TR central plant Shell could be made of framework structure with cladding CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 40

41 TR central plant Floors for pumps, chillers, fans,, and miscellaneous CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 41

42 TR central plant CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 42

43 TR central plant The tower can be divided into 4 or 8 sectors CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 43

44 Thank you very much for your attention. We will be pleased to answer your questions and provide any further information you need. CW /Jaap Hoogland/ Seawater Cooling Tower Circuits 44