A SCW Flow Apparatus for Material Testing and

A SCW Flow Apparatus for Material Testing and Electrochemical Measurements Steven Rogak Akram Alfantazi Edouard Asselin University of British Columbia May 12, 2009 IAPWS/COG Workshop 1 of 20

Outline • Background: Supercritical Water Oxidation (SCWO) experiments in flow systems – Fouling – Heat transfer – Corrosion • Just starting: Sensor development for supercritical water (fouling and corrosion for relatively clean water) May 12, 2009 IAPWS/COG Workshop 2 of 20

SCWO Pilot Plant • 1990’s Supercritical Water Oxidation (SCWO) waste destruction “ready to move from chemist’s lab to engineering” • UBC-NORAM pilot plant built 1997 -1998 for – waste destruction pilot plant tests – heat transfer measurements (eg. H 2 O/O 2) – fouling measurements • Corrosion experiments: unintended bonus! May 12, 2009 IAPWS/COG Workshop 3 of 20

1. 5 Kg/min 600 C 25 MPa May 12, 2009 IAPWS/COG Workshop 4 of 20

Fouling in SCWO • Salts (ppm % conc. ) insoluble in low-density water precipitate; can form hard or soft deposits (surface growth or bulk nucleation) Sodium carbonate growth on heated tube wall May 12, 2009 IAPWS/COG Workshop 5 of 20

Corrosion in SCWO of “Redwater” • Ammonium sulphate solution (high p. H at room temperature) destroys Alloy 625 preheater in hours (in presence of oxygen) • Literature give no indication that this would happen! May 12, 2009 IAPWS/COG Workshop 6 of 20

Corroded Tube Cross Sections May 12, 2009 IAPWS/COG Workshop 7 of 20

What did we learn from SCWO? • Tough technical challenges! • Viable only in niche applications (may not justify huge R&D programs) • Practical experimental techiques for SCWO might benefit Gen IV (SCWR), where the large “payoff” may justify the effort. May 12, 2009 IAPWS/COG Workshop 8 of 20

Sensors for monitoring chemistry in the SCWR • NSERC CRD with AECL; • Team: – – – Akram Alfantazi (Materials Eng. ) Steve Rogak (Mechanical Eng. ) Walter Merida (Mechanical Eng. ) Edouard Asselin (Materials Eng. ) Glenn Mcrae (AECL) • Feb 2009 start; 3 years x $100 K • Recruiting students and learning more about SCWR reactor requirements May 12, 2009 IAPWS/COG Workshop 9 of 20

Broad Objectives • Develop reliable reference electrodes • Measure corrosion potentials, p. H, complex impedance • Detect fouling and/or in-stream solids May 12, 2009 IAPWS/COG Workshop 10 of 20

UBC SCW Flow Systems • Big system (discussed earlier) – Realistic flow regimes for pilot studies (heat transfer) – Expensive to operate • Small system (<0. 1 kg/min) – low tube velocities, but can integrate special materials and test sections easily May 12, 2009 IAPWS/COG Workshop 11 of 20

UBC SCWO • Put pictures here May 12, 2009 IAPWS/COG Workshop 12 of 20

UBC SCW Electrochemical Cell • Unfinished idea from Ed Asselin’s Ph. D thesis: electrochemistry cell for the flow system. • Design completed by Ed’s student; ready to be tested this summer. May 12, 2009 IAPWS/COG Workshop 13 of 20

Non-flow reference electrode • Used by Ed Asselin in Ph. D • Potential drift from KCl diffusion through plug • ~300 m. V bias from thermodiffusion (Oh et al 2004) May 12, 2009 IAPWS/COG Workshop 14 of 20

Flow Loop & Flow-Through Reference Electrode FTRE May 12, 2009 IAPWS/COG Workshop 15 of 20

Uncertainty in RE Potential 1. Liquid Junction Potential (ELJP) – few m. V 2. Thermal Liquid Junction Potential (ETJP) – 300 m. V? May 12, 2009 IAPWS/COG Workshop 16 of 20

Working/Counter Electrode • Design Consideration – Electrical isolation of the electrodes from the cell body – Sealing/Leakage: what material to use? 27 February 2021 IAPWS/COG Workshop 17 of 20

Working/Counter Electrode May 12, 2009 IAPWS/COG Workshop 18 of 20

Ideas for work this summer • EIS for coated and uncoated working electrodes (precursor to fouling detection) • Sensitivity of reference electrode to flow, concentration and temperature differences May 12, 2009 IAPWS/COG Workshop 19 of 20

Conclusions • SCWO has technical problems analogous to the proposed SCWR – we can offer something! • SCWR contaminants are dilute and have slow effects – some new challenges (for us). • Many, diverse corrosion and fouling problems in existing and proposed SCWR plants – where should we start? May 12, 2009 IAPWS/COG Workshop 20 of 20

FEM Safety Factor 5000 PSI/500°C – 316 SS May 12, 2009 IAPWS/COG Workshop 21 of 20

Liquid Junction Potential (ELJP) • Henderson Equation: Case 1 Reference Solution 0. 01 M KCl Case 2 Test Solution : 1 M Na 2 SO 4 Reference Solution 0. 01 M KCl ELJP = -10. 7 m. V Test Solution : 0. 1 M Na 2 SO 4 Case 3 Reference Solution 0. 01 M KCl Test Solution : 0. 05 M Na 2 SO 4 ELJP =-3. 74 m. V ELJP =- 5. 35 m. V May 12, 2009 IAPWS/COG Workshop 22 of 20

Thermal Junction Potential Thermal junction potential = combined effect of heat and ion flux Depends on electrode configuration and flow rates (if any) Soret Effect (Thermal Diffusion) Concentration Gradient Migration of Ion Diffusion Potential Internal Electric Field Thermal Junction May 12, 2009 IAPWS/COG Workshop 23 of 20