Optimum Design of a Solar Desalination Process IPRO 304-e

Transcription

1 Optimum Design of a Solar Desalination Process IPRO 304-e Team Members: Advisors: Anne Kulka, Natasha Lagunova, Bill Mustain, Lina Nilsson, Rajarshi Parai, Ronak Patel, Shannon Phillips, Erin Sawardecker, Îryna Sokhan, Beth Volberding, Jennifer Walden Professors Hamid Arastoopour, Said Al-Hallaj, Nader Aderangi, Javad Abbasian

2 Project Background Global Water Shortages Project Focus

3 Process Schematic Recycle SOLAR COLLECTOR Warm Air Incoming salt water EVAPORATOR CONDENSER Brine Product fresh water Cold Air

4 Project Outline Solar heater Evaporator Condenser Cost and sustainability Conclusion

5 Solar Collector Convert solar energy Constant exit temperature F(t), Twin Tb Solar (t) F(t), Twout Minimize wasted energy

6 January Insolation 2 Insolation (J/hr*m) 4.0E E E E E E E E E Time (hrs)

7 Solar Collector Convert solar energy Constant exit temperature Minimize wasted energy F(t), Twin Tb Solar (t) F(t), Twout

8 Solar Unit

9 No insolation losses No convective or radiative heat losses At start-up T bulk =T win No temperature gradient in bulk Quasi steady-state heat transfer coefficient Assumptions

10 Mathematical Model Bulk heating dtb Vb Cpbρb = dt A b * Solar ( t) Bulk temperature V b C pb dt ρb dt b = A b * Solar( t) ha( Tb T ln) Exit water temperature 0 = CpwρwF( t)*( Twin Tout) + ha( Tb T ln)

11 Total Daily Flow Flow (m3/sec) Time (sec)

12 Evaporator Design Salt water enters, sprayed in tiny drops Pure water evaporates, leaves as water vapor Concentrated salt water exits Air flows countercurrent Salt Water Conc. Salt Water Sprayer Humid Air Dry Air

13 Evaporator Design Salt Water T=90C M=18,400 lb/h Height 14 ft Diameter 2.2 ft Humid Air T=85C M=3100 lb/h Brine T=45C M=17,000 lb/h Evaporator Schematic Dry Air T=35C M=1700 lb/h

14 Evaporator Design Select tower diameter Solve for height and cost Heat transfer properties Mass balance Adjust diameter to optimize cost and feasibility Results Diameter: 2.2 ft Height: 14.5 ft Stainless steel

15 Condenser Design General Information Transformation of water vapor to liquid by mechanical means Circulating Water T=30C M=20630 lb/h Diameter, 2.0 ft Spray Nozzle Types Shell and tube condenser Spray condenser Spray Condenser 1. Water inlet 2. Spray 3. Incondensables outlet 4. Inlet of humid vapor 5. Condensate outlet H=11.5 ft Pure Water T=70C M=1400 lb/h Dry Air T=35C M=1700 lb/h Circulating Water T=70C M=20630 lb/h Humid Air T=85C M=3100 lb/h

16 Condenser Design Specific Design Considerations Co-current flow Condensed water recycle stream used for spray water Extra water only for start up Additional heat exchanger needed Preheat salt water while cooling spray water Parameter Minimum Height Diameter Optimal Value ft (3.5m) 2.0 ft (61 cm)

17 Condenser Design Calculations Volumetric air flow rate = ft 3 /hr Mass air flow rate = 1731 lb m /hr Volumetric flow rate of circulating water = ft 3 /hr Mass flow rate of circulating water = lb m /hr Mass flow rate of produced water: m water produced = v circulating water c λ o pl T water =1432lb m / hr

18 Heat Exchanger

19 Cost Analysis Used Seider s Process Design Cylindrical process vessels and heat exchanger models Principal equipment cost (C P ) estimated C & E : height & diameter HE : heat exchange area Materials factor (F M ) Carbon steel Stainless steel Titanium Compare costs

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21 Comparative Costs & Investment Investment for project Our Investment: Heat Exchanger $41, Condenser: Carbon Steel $98, Evaporator: Stainless Steel $390, Miscellaneous Materials $10, Total $540,607.66

22 Cost in the long run? Life of unit: 25 years Water producing days: liters 180day 25years = liters day year Price of our water (worst case scenario) January flow ½ year production time $540, = liters $0.02 / liter

23 Feasibility & Sustainability Typical person uses 250 liters/day Single person: $5/day or $160/month Current costs are lower in U.S. Q: Is this technology sustainable? Green energy Minimal impact on environment Raw material plentiful Cost still too high A: Yes, with water conservation and further development to make unit more cost effective

24 Production: 5,670 L/day for test case Prohibitively expensive Model development and cost reduction Conclusion

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