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Desalination of SeawaterKeerthi Gnanavel Blaine BensurChen Xu
Overview1.Background
2.Methodsa. Multiple Effect Distillation
b. Multi-stage Flash Distillation
c. Reverse Osmosis
3.Results
4.Summary and Conclusions
1.BackgroundPlaces where Desalination is common…
Hot, arid climates
India, Middle East, Some parts of Central US
Wherever transporting drinking water is expensive
2a. Multiple Effect Distillation (MED)Background
Classic Desalination Method
Tolerant to external conditions
Cost-Effective
Utilizes increased surface area to vaporize water (highly effective)
External condenser needed
MED Diagram
2b. Multi-stage Flash Distillation (MSF)Background
Tolerant to external conditions
Utilizes change in pressure to vaporize water
Product is fresh liquid water (no condenser needed)
Very little energy required
MSF Diagram
2c. Reverse OsmosisBackground
Relatively new Technology
Sensitive to conditions
Can be expensive
Has potential to be a promising method
RO Diagram
3. Results Product water
capacity50,600 m3/day = 2,108 m3/hr
Product water concentration
500 mg/solid solute
Pressure across membranes
Ranges from 800psi - 1000psi
pH of product water
~5
Annual Cost ~365,000 USD/m3
Product water output capacity
68,000 m3/day = 2,833 m3/hr
Product water salt content
<2ppm
Seawater feed temperature
Varies
Waste brine temperature
60oC
Concentration of brine
~1.5 x feed concentration
Brine heater steam requirements
130oC, ranges from 0.35 - 1 bar
Plant life ~25 years
Power consumption
Ranges from 1.5KWh - 15.0 KWh
Overall annual cost
~1 Million USD
Product water output
4500 m3/day = 187.5 m3/hr
Product water salt content
<50ppm
Seawater feed requirement
375 m3/hr
Seawater feed temperature
29oC
Waste brine temperature
40oC
Concentration of brine
~2 x feed concentration
Brine heater steam requirements
130oC, 2.8 bar
Performance ratio 9 kg water produced/kg steam input
Power consumption 500KWh (pumping) + 100KWh (lighting/other) = 600KWh
Overall annual cost 73.369 Million Indian Rupees = 1.1 Million USD
4. Summary and ConclusionsMED seems to be more effective given cost, power consumption,
product quantity, etc.
References1. Cohen-Tanugi, David, and Jeffrey C. Grossman. "Water Desalination across Nanoporous Graphene." Nano Letters Nano Lett. 12.7 (2012): 3602-608.
Web. (DOI: 10.1021/nl3012853) (NANO Graphene) (article)
2. Wade, Neil M. "Technical and Economic Evaluation of Distillation and Reverse Osmosis Desalination Processes." Desalination 93.1-3 (1993): 343-63. Web. (DOI: 10.10160011916493801132) (RO MED MF) (article)
3. Manolakos, D., G. Papadakis, S. Kyritsis, and K. Bouzianas. "Desalination." Experimental Evaluation of an Autonomous Low-temperature Solar Rankine Cycle System for Reverse Osmosis Desalination 203.1-3 (Feb 2007): 366-74. Print. (DOI: 10.1016/j.desal.2006.04.018) (RO)(article)
4. https://www.oas.org/dsd/publications/Unit/oea59e/begin.htm#Contents -URL Secretariat, General, comp. "2.1-2.5." Source Book of Alternative Technologies for Freshwater Augmentation in Latin America and the Caribbean. Osaka, Japan: UNEP, 1998. N. pag. Print.(RO)(print)
5. http://www.engr.uky.edu/~aseeched/SummerSchool/2007/session_handouts/Spreadsheets/3%20Spreadsheet%20Applications%20Across%20The%20Curriculum/3%20Documents/TripleEffect.pdf (MED)(paper-lecture)
6. Krishnan, Mangala Sunder, Professor, comp. "Modeling of Evaporators." Multiple Effect Evaporator System (n.d.): n. pag. Web. 10 Oct. 2015. <http://nptel.ac.in/courses/103107096/25>. (MED)(Paper-lecture)