NEW TECHNOLOGIES FOR THE USE OF WASTE ENERGY FOR DESALINATION

Transcription

1 NEW TECHNOLOGIES FOR THE USE OF WASTE ENERGY FOR DESALINATION

2 DESALINATION PROCESS System A System B H 2 O NaCl H 2 O + NaCl Energy Entropy of System A < Entropy of System B Energy in above equation can be the following Dissolution Heat Osmotic Pressure Boiling Point Elevation

3 ENERGY REQUIRED FOR REVERSE OSMOSIS Osmosis is a natural process where molecules of a solvent tends to pass through a semi permeable member from a lesser concentration to a higher concentration until the concentration on both sides are equal Reverse Osmosis for sea water requires a pressure of a minimum of 280 m WC to start the process.

4 ENERGY REQUIRED FOR THERMAL DESALINATION Boiling Point Elevation: Pure Water at 1 atm pressure boils at 100 o C. Addition of salts increases the boiling point depending on the concentration. This increase in boiling point is called Boiling Point Elevation (BPE) Sea water at ppm boils at ~101.4 o C

5 DESALINATION PROCESS COST OF ENERGY Depends on amount & value of energy RO requires electrical energy Thermal requires heat, value of which depends on temperature

6 DESALINATION PROCESS WITH RENEWABLE ENERGY PRESENT STATUS Intermittent supply calls for designs with higher rating Collection of energy calls for expensive equipments. Economically not viable Should be subsidized by government, considering environmental advantage.

7 DESALINATION PROCESS WITH RENEWABLE ENERGY IN THE NEAR FUTURE Unlimited availability & environmental friendly aspect helps possible dependency on sun & wind based energy. With storage becoming feasible ON-OFF operation can be avoided & investment made optimal. Traditional design to be optimized such as start-up time, fouling, crevice corrosion. Etc.

8 DESALINATION PROCESS WITH WASTE ENERGY Cost of waste energy is rated zero (40% of total cost saved) Recovery equipment cost to be contained within a desired level. Amortization cost of investment 40% operation cost 20% Zero cost of energy has significant impact on reduction of cost of water.

9 DESALINATION PROCESS WITH WASTE ENERGY - Waste Energy is typically thermal - Economically exploited by thermal desalination plants MED becomes more viable than RO. Additionally this has other advantages of higher availability & more friendly operation - Also available in large quantity, normally at low temperature with possibility of extraction at lower efficiency level - Applicable to large industries like power plants, steel plants & refineries.

10 LOW TEMPERATURE FLASH DESALINATION HEAT FROM COOLING WATER REJECT

11 LTF/MED DESALINATION WITH FLUE GAS WASTE HEAT - SIMHADRI

12 THERMAL DESAL BASED ON WASTE HEAT ARE THEY EXPENSIVE - Thermal Desalination generally expensive due to usage of high grade material having resistant to corrosion - Cost depends on efficiency of the plant. - With Waste Energy the plant can be optimized for lower efficiency & hence lower cost level with minimum number of effects. - Final total cost also should include energy recovery system depending on whether it is Waste Flue gas heat Discharged cooling water pumping energy. Condenser cooling water reject temperature.

13 POTABLE WATER FROM THERMAL POWER PLANTS HOW DOES IT HELP? - Significant potential exists in recovering PP waste water through desalination process utilizing waste energy to safe drinking water (mineral water). - Techno economical feasibility established - PP of 2000 MW capacity can produce MLD - Country's requirement of drinking / cooking mineral water ~ MLD - 50% of total mineral (drinking / cooking ) can be met with.

14 COST OF DESALINATION WATER A REVIEW A. COST OF ENERGY : AROUND 40% - Is a function of quantity & specific cost of energy - Electrical energy is most expensive - Recovered waste heat energy is of NO VALUE - RO Plants require low energy but high cost - Thermal plants require more energy but of lower or nil cost.

15 REVIEW OF COST B. COST OF INVESTMENT : AROUND 40% - Is a function of interest rate& amortization time (5 30 years) - RO Plant typically require lower investment but need to be checked case by case w.r.t. quality of sea water & the extent of pre-treatment required. - Thermal power plant require higher investment but ensures longer and trouble free working life.

16 REVIEW OF COST C. RUNNING COST : AROUND 20% - Accounts for chemicals, manpower maintenance and spare parts. - RO plants require more chemicals High skill chemical team more spares (including replacement membranes Thermal plants are recognized to ensure highest degree of availability with minimum running cost. - The final cost of desalinated Water (RO or Thermal) range from Rs /m 3.

17 DESAL PROCESS WITH RECOVERED WASTE ENERGY VS RENEWABLE ENERGY - Both are environmental friendly as both of them do not useful. - RO cannot be operated with Waste Energy and Solar PV or Wind Energy only to be exploited. - RO plants require far more Chemicals & hence less friendly. - Thermal plant can be operated with either recovered waste energy or renewable energy (only from solar collections)

18 EXPERIENCE ON DESALINATION PLANT WITH SOLAR OR RECOVERED WASTE ENERGY - New specific features of desalination plants for exploiting low cost energy (either solar or waste) already studied & tested enough by a few companies - GB Saline Water Solutions is a front runner in the implementation of new technologies devoted to the exploitation of either solar or waste energy - Pilot plants and small scale industrial plants already commissioned and now in successful operation thus proving the reliability of the progress.

19 TEMPERATURE GRAPH FROM SIMHADRI

20 DISTILLATE CONDUCTIVITY GRAPH FROM SIMHADRI

21 DISTILLATE QUANTITY GRAPH FROM SIMHADRI