Electrodialysis Reversal with Capacitive Electrodes

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1 Electrodialysis Reversal with Capacitive Electrodes AIChE 2013 Desalination and Water Management for rural Communities John Barber, GE P&W Hai Yang, GE GRC

2 Outline Tech Review Electrodialysis Reversal (EDR) and Capacitive Deionization (Cap DI) Carbon Electrode (CE) Application to EDR CE/EDR Field studies Conclusions/Customer Benefits 2

3 EDR is the most robust and highest recovery wastewater desalination technology. 10+ year membrane life High turbidities Chlorine tolerance Silica tolerance 3

4 Platinum $/Oz Main Driver - Raw Material Costs Pt $/oz (corrected for Consumer Price Index) ounce of Pt per electrode kg AC per electrode, $12/kg EDR start Raw material price difference per electrode > $1,000 4

5 Capacitive Deionization Technology Technology Concept Key Features of Cap DI Salt removed via electrical field Ion Removal Energy stored during desalination Energy recovered in regeneration Energy Recovery Potential Advantages for EDR Low cost Less scaling, long life no gas generation 5

6 Why is current density important? Electrode Design For Capacitive electrodes ions are stored at the surface. solution + Θ + Θ Θ Θ + + Θ carbon The amount of ions that can be stored (charge or q ele ) is proportional to surface area and carbon mass. + System Design The number of ions we need to store is dependent on the current and reversal time. Reversal time (t) = 20 min. Current range (I) =1 to 15mA/cm 2 q cycle = I x t Requirement: q ele > q cycle q ele carbon mass Carbon mass electrode thickness 6

7 #sites Non-Faraday Current Density Over 80% of the installed base that was surveyed operate below 5mA/cm 2 Field trials covered sites that operated up to 7.5mA/cm field trials All stages 1st stage 2nd stage 3rd stage 4th stage lab trials Current Density (ma/cm2) 7

8 Electrode capacity onset of water electrolysis ph of electrode streams vs. time for applying 2.75mA/cm 2 current density ph of electrode streams vs. time for applying 5.5mA/cm 2 current density Charge = 3,100 C Charge = 2,500 C Kinetic factors play a role in charge holding capacity of electrode. Within typical current operating window, water electrolysis can be mitigated by adjusting reversal times. 8

9 Pilot Sites Site, Stage (Country/ State) Lewis, 1 st (AZ) Aripe, 1 st (ES) Barranco Seco, 1 st (ES) Gela, 3 rd (IT) North City, 1 st and 2 nd (SD) Foss, 2 nd (OK) ATLL, 1 st and 2 nd (ES) Water Type Run time/yr Well 4,015 Well 8,500 Waste 5,200 Waste 6,500 Waste 350 Surface 8,400 Surface 4,600 Cl2 (ppm) Feed TDS Feed Hard Current Density ma/cm 2 Reversal time (min) Temp Dominant Anion Estimated Platinum electrode life Cl 19, HCO3 20, Cl 14, Cl 0.5C , SO4 2 NH2Cl to 5 15? 27-5 SO , HCO3 13,000 to 30,000 15,000 to 25,000 9

10 NFEDR Pilot Electrode and End-block E-Spacer thickness 2X inter-membrane Flow rate = 0.65 gpm 10

11 Pilot Performance Indicators 1) Chamber Pressure drop Hardness scale development Mechanical stability 2) Current efficiency IX coating functionality Membrane integrity 3) Electrode voltage Hardness scale development Stability of carbon surface activity 11

12 Pressure drop Lewis Aripe BS Instability corresponded to scaling cleaning frequency adjusted. 12

13 Current efficiency Lewis Aripe BS CE can only be accurate evaluated during POS polarity Instability corresponded to scaling cleaning frequency adjusted. 13

14 Cost Savings Analysis Site # stacks Acid consumption $/year (% reduction) Electrode replacement $/year (% reduction) Lewis 18 $2,200 (83%) $6,200 (37%) Aripe 24 N/A* $23,100 (43%) BS 32 $2,700 $15,000 (75%) (40%) Impact of Water costs $/kgal Total production /year in kgal and ($ saved) $ ($8.6k) $ ($24k) $ ($18k) 14

15 Conclusions/Benefits Scaling issue seen in all pilots abated with tuning acid cleanings Use of Capacitive Carbon Electrode in EDR: a) Reduces operating costs - Reduced Electrode replacement costs - Reduced Acid usage b) Eliminates H 2, O 2, and Cl 2 gas production - EHS benefits c) Eliminates fluctuation in precious metal costs. 15

16 Acknowledgements Coating Chemistry Russ MacDonald, GE W&P Lab Trials Wei Lu, GE GRC Zhixun Liu, GE GRC Pilot Trials Joe Aldridge, GE W&P Jonatan Hernandez, GE W&P 16

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