1. Operation, Modeling and Analysis of the Reverse Water Gas Shift Process Jonathan Whitlow Florida Institute of Technology NASA/ASEE Summer Faculty Program August 1, 2001

2. Overview of Presentation Description of RWGS Process Gas Chromatograph Composition Analysis Presentation and Analysis of Operating Data Problems Encountered with RWGS Operation Description and Evaluation of Matlab Models Conclusions and Recommendations

3. RWGS Photo

4. CO 2 Condenser Catalytic Reactor Membrane Separator 2 2 2 O 2 in Q F 1 W 23 4 R Electrolysis Recycle Compressor 2 2 O 2 H H CO H H H Q out H O 2 2 RWGS Process Flow Diagram

5. RWGS Flow Schematic

6. Composition Analysis Analysis is Key to Mass Balance Models Insufficient Calibration for use of Mass Spectrophotometer Gas Chromatograph utilized for Analysis – TCD for CO and CO 2 – HID for H 2

7. Carbon Dioxide GC Calibration

8. Carbon Monoxide GC Calibration

9. Hydrogen GC Calibration

10. Summary of RWGS Operating Data

11. July 3 Reactor Temperatures (Electrolysis On)

12. July 19 Reactor Temperatures

13. July 3 CO Vent {R9} Flow (Electrolysis On)

14. July 18 CO Vent {R9} Flow PC1 Set Point = 53 psia

15. July 19 CO Vent {R9} Flow Feed Flow=1.3 slpm CO 2 & H 2

16. July 27 CO Vent {R9} Flow Feed Flow=1.1 slpm CO 2 & H 2

17. July 3 Membrane  P (Electrolysis On)

18. July 18 Membrane  P PC1 Set Point = 53 psia

19. July 19 Membrane  P Feed Flow=1.3 slpm CO 2 & H 2

20. July 27 Membrane  P Feed Flow=1.1 slpm CO 2 & H 2

21. July 3 Recycle {R12} Flow & Membrane Feed (R8) (Electrolysis On)

22. July 18 Recycle {R12} PC1 Set Point = 53 psia

23. July 19 Recycle {R12} & Membrane Feed (R8) Flow Feed Flow=1.3 slpm CO 2 & H 2

24. July 27 Membrane Feed (R8) Flow Feed Flow=1.1 slpm CO 2 & H 2

25. RWGS July 18 Mass Balance Summary

26. RWGS July 18 Operation Summary

27. RWGS July 19 Mass Balance Summary

28. RWGS July 19 Operation Summary

29. RWGS July 27 Mass Balance Summary

30. RWGS July 27 Operation Summary

31. RWGS Operation Summary

32. Problems Encountered in RWGS Operation Water Level Control is a Major Process Disturbance Non Uniform Temperature Across Reactor Catalyst Bed Temperature T2 had to be controlled by adjusting T3 Set Point Solenoid Valves (SV13 & SV14) tied to RWGS Interlocks Stuck Shut (Replaced with Coupling) Calibration on Flow Sensors is Inaccurate Some of the Redundant Sensors don’t work (P7 & R11) Electrolysis use is Limited by High Water Conductivity

33. RWGS Model Development (Mass Balance Algorithm)

34. Equilibrium favors left side of reaction unless very high temperatures are achieved CO 2 + H 2 CO + H 2 O @400 Centigrade K = [CO][H 2 O] = 0.086 [CO 2 ][H 2 ] RWGS Reactor

35. Reactor analysis assumes that equilibrium conversion is achieved. Conversion is found by solving a quadratic equation. RWGS Reactor

36. Condenser Condenser is used to remove water from the reactor exit stream Ideal cases are assumed in modeling the condenser  Raoult’s Law for water in vapor phase Partial Pressure = Vapor Pressure  Henry’s Law for dissolved gases in liquid phase Solubility is a function of temperature in pure H 2 O

37. Model Representation for N Stage Counter-Current Membrane Feed Permeate V N-1 y j,N-1 V k+1 y j,k+1 V N y j,N L N+1 x j,N+1 L k+2 x j,k+2 L k+1 x j,k+1 V k y j,k L k x j,k L 2 x j,2 L 1 x j,1 V k-1 y j,k-1 V 1 y j,1 V 0 y j,0 m j,N m j,k-1 m j,k m j,1 Residue Sweep Stage NStage k+1Stage kStage 1 L N x j,N

38. Summary of Membrane Modeling

39. Conclusions High Conversion of H 2 can be Achieved with Proper Operating Conditions Modifications are needed to Improve Operation and Analysis of RWGS with Electrolysis Further Experimental Testing is Needed to Better Characterize RWGS Process Membrane Model is Valid, Further Work is Needed to Refine and Validate the rest of RWGS Models

40. Recommended Modifications Make Modifications to Sampling System Evaluate Other Methods for H 2 Analysis –Calibrate Mass Spec –GC using TCD with Argon Carrier Install Low Pressure Drop Bleed Valves for Water Level Control Recalibrate Flow Sensors Around Membrane (R8 & R12) Control Reactor Temperature with T2 Add Integral Action to Pressure & Temperature Controller

41. Further Experimental Tests Examine Additional Steady States at Different System Pressures/Membrane  P (@ Constant Temperature & Feed Ratio) Examine Additional Steady States at Different Feed Rates (@ Constant Temperature & Feed Ratio) Examine Effects of Varying Reactor Temperature Examine Effects of Varying Fresh Feed Ratios