Enhanced Performance of Ca-Al-O Modified Fe 2 O 3 O 2 -Carrier for CO 2 Capture & H 2 Production in CLC

Transcription

1 Enhanced Performance of Ca-Al-O Modified Fe 2 O 3 O 2 -Carrier for CO 2 Capture & H 2 Production in CLC Mohammad Ismail, PhD student Supervisor: Stuart A. Scott Department of Engineering, University of Cambridge 6 th High Temperature Solid Looping Cycles Network Meeting, 1-2 September, 2015

2 Outline Basics of CLC - H 2 Production Experimental: a). Oxygen Carrier Preparation Methods b). Fluidized bed & TGA set up Characterization of the prepared Oxygen Carriers Performance Study for CO 2 capture & H 2 Production Comparison of support materials Conclusion

3 Chemical Looping Combustion & Hydrogen Production Lean air Fe 2 O 3 CO 2 Heat Air reactor Fuel reactor Air H 2, CO or CH 4 Fe 3 O 4

4 Chemical Looping Combustion & Hydrogen Production Lean air Fe 2 O 3 CO 2 Heat Air reactor Fuel reactor Air Fe 3 O 4 Steam reactor FeO/Fe H 2, CO or CH 4 H 2 H 2 O

5 Oxygen Carrier (OCs) Selection Oxides of Ni, Fe, Cu, Mn and Co are potential OCs We selected Fe 2 O 3 because- # Cheap # Environmental friendly # Non-toxic # Phase transitions favours both looping & H 2 production

6 Additives for Fe 2 O 3 Oxygen Carrier Granulated Fe 2 O 3 is stable up to 10 cycles, but reduction to Fe results in rapid deactivation. 1 Addition of Al, Cr and Mg to Fe 2 O 3 showed higher reactivity over more cycles 2. We already reported that addition of CaO to Fe 2 O 3 improves stability of OCs in H 2 production 3. We Prepared Mixed Oxide O 2 -Carriers Containing Fe 2 O 3 + CaO + Al 2 O 3 1 Bohn et. al. (2008). Ind. Eng. Chem. Res 47, Bohn et. al. (2010). Energy Fuels, 24, , 3 Ismail et. al. (2014). Energy Procedia, 63, 87-97

7 Aims of the Study To develop stable Fe-Ca-Al-O OCs by different methods (e.g., wet mixing & co-precipitation methods) To characterize the fresh and cycled OCs by physicochemical means. Study of the CO 2 capture & H 2 production capacity of the developed OCs. To make a comparative study of the support materials: (i.e., CaO, Al 2 O 3, CaO+ Al 2 O 3 at different ratio)

8 Composition P. Pressure Diagram of Fe-Ca-Al-O system Log (p O ) for Fe-Al 2 system for Compete reduction at 900 o C is CA =Al 6 Ca 3 O 12 CA 2 =Al 4 CaO 7 Log (p O ) for Fe-Ca 2 system for Compete reduction at 900 o C is CA 6 =AlCa 0.83 O 1.6 C 3 A =AlCa 1.5 O 3 F60CA2 F60CA1 Fig: C - P diagram at 900 o C with 0.5 mole of Fe & varied amount of Ca & Al

9 Oxygen Carriers (OCs) Preparation

10 OCs Preparation: Wet Mixing & Co-precipitation Methods Wet Mixing Method Fe 2 O 3 + Ca(OH) 2 + Al(OH) 3 Mixing with DI water (6:1 ratio) at 50 o C, 24h Drying ( ~80 o C) + o C, 6h Sieve ( µm) 1M NaOH + 1M Na 2 CO 3 Co-Precipitation Method Fe(NO 3 ) 3 + Ca(NO 3 ) 2 + Al(NO 3 ) 3 solution, 1M Co-precipitation at ph =10 Wash to remove Na Drying ( ~80 o C) o C, 6h Sieving for µm sized OCs

11 Summary of the Prepared OCs Composition Particles names F60CA1WM, F75CA1WM, F60CA2WM, F75CA2WM, F60CA1COP F75CA1COP F60CA2COP F75CA2COP Fe 2 O 3 in the particles 60 wt.% 75 wt.% 60 wt.% 75 wt.% Mass Ratio of CaO to Al 2 O 3 in the support Named as CA1 Named as CA1 Named as CA2 Named as CA2 WM: Wet mixing method, COP: Co-precipitation method For comparison, we also made 5 other OCs: FC0 (pure Fe 2 O 3 ), F60A40COP, F75A25COP, F60C40COP, F75C25COP

12 Summary of the Prepared OCs Composition Particles names F60CA1WM, F75CA1WM, F60CA2WM, F75CA2WM, F60CA1COP F75CA1COP F60CA2COP F75CA2COP Fe 2 O 3 in the particles 60 wt.% 75 wt.% 60 wt.% 75 wt.% Mass Ratio of CaO to Al 2 O 3 in the support Named as CA1 Named as CA1 Named as CA2 Named as CA2 WM: Wet mixing method, COP: Co-precipitation method For comparison, we also made 5 other OCs: FC0 (pure Fe 2 O 3 ), F60A40COP, F75A25COP, F60C40COP, F75C25COP

13 Characterization of the Fresh Oxygen Carriers Table: Comparison between the phases identified in XRD pattern & obtained from Phase diagram OCs Phases predicted Phases detected by XRD CA1 C 3 A, C 12 A 7 CA, C 3 A, C 12 A 7 CA2 CA, C 12 A 7 CA, C 12 A 7 F60CA1WM CaAlFe 4 O 10, CA 2, CA 6 CaAlFe 4 O 10, CA, C 3 A,CA 2, CA 6, C 12 A 7, CF, C 2 F F60CA1COP CaAlFe 4 O 10, CA, C 3 A, CA 2, CA 6, C 12 A 7, CF, C 2 F, Al 2 O 3 F60CA2WM CaAlFe 4 O 10, CA 2, CF CaAlFe 4 O 10, CA, C 3 A, CA 2, C 12 A 7, CF, C 2 F F60CA2COP CaAlFe 4 O 10, CA, C 3 A, CA 2, C 12 A 7, CF, C 2 F, Al 2 O 3 F75CA1WM CaAlFe 4 O 10, CA 6, Fe 2 O 3 CaAlFe 4 O 10, CA, C 3 A, CA 2, C 12 A 7, CF, C 2 F, Fe 2 O 3 F75CA1COP CaAlFe 4 O 10, CA, C 3 A, CA 2, C 12 A 7, CF, C 2 F, Fe 2 O 3 F75CA2WM CaAlFe4O10, CA 2, CF CaAlFe 4 O 10, CA, C 3 A, CA 2, C 12 A 7, CF, C 2 F, Fe 2 O 3 F75CA2COP CaAlFe 4 O 10, CA, C 3 A, CA 2, C 12 A 7, CF, C 2 F, Fe 2 O 3

14 Experimental Setup of Fluidized Bed Reactor: Gas sampling probe Tube reactor Electric furnace Drying tube containing CaCl 2 Thermocouple s Gas Pump Vent Gas Analyzer * Length: 70.0 cm * I.D: ~2.0 cm * Bed material: 10 ml Al 2 O 3 (~400 μm) 0.5 g of sample Fluidized bed of sample & alumina Solenoid Valve Distributor * U/U mf 7.0 * Gas analyser: NDIR gas analyser (EL3020, ABB) CO 2 N 2 Air Gas cylinders CO Reactor for H 2 Production: Length :14 cm & i.d: 1.6 cm

15 Results of Experiments in Fluidized Bed (FB) CO 2 was used instead of Steam: K p for CO 2 CO and H 2 O H 2 is almost the same at 850 C To avoid complexity of operation Concentration profile of off gases from FB experiment, 1 st & 2 nd cycles of F75CA1 at 900 C

16 Comparison of Cycling Expt. for H 2 & CO 2 Production in FB 1 CO 2 Oxidation for CO Production 0.95 Solid Conversion, X H 2 / X CO2 / X CO Reduction, CO-steam-air cy Reduction, CO-CO₂-air cy Oxidation, CO-steam-air cy Oxidation, CO-CO₂-air cy OCs: F60CA1COP Steam oxidation for H 2 Production Cycle number Fig: Redox cycles: 1. a) CO reduction (8 min) b) Steam oxidation (5 min) c) air oxidation (5 min) in FBR-1 2. a) CO reduction (8 min) b) CO 2 oxidation (5 min) c) air oxidation (5 min) in FBR-2

17 CO 2 yield im m.mol /g. of sample Fluidized Bed Redox Cycling Exp. Results cy-1 cy-3 cy-10 cy-20 Theoritical Max. Yield FC0 F75CA1WM F75CA1COP F75CA2COP F60CA1WM F60CA1COP F60CA2WM F60CA2COP Different Oxygen Carriers 20 redox cycles of FCA Particles: 8 min reduction in 10 vol% CO, 5 min oxidation in 20 vol% CO 2 and 5 min air ox

18 CO 2 yield im m.mol /g. of sample Fluidized Bed Redox Cycling Exp. Results cy-1 cy-3 cy-10 cy-20 Theoritical Max. Yield FC0 F75CA1WM F75CA1COP F75CA2COP F60CA1WM F60CA1COP F60CA2WM F60CA2COP Different Oxygen Carriers 20 redox cycles of FCA Particles: 8 min reduction in 10 vol% CO, 5 min oxidation in 20 vol% CO 2 and 5 min air ox

19 CO 2 yield im m.mol /g. of sample Fluidized Bed Redox Cycling Exp. Results cy-1 cy-3 cy-10 cy-20 Theoritical Max. Yield FC0 F75CA1WM F75CA1COP F75CA2COP F60CA1WM F60CA1COP F60CA2WM F60CA2COP Different Oxygen Carriers 20 redox cycles of FCA Particles: 8 min reduction in 10 vol% CO, 5 min oxidation in 20 vol% CO 2 and 5 min air ox

20 CO 2 yield im m.mol /g. of sample Fluidized Bed Redox Cycling Exp. Results cy-1 cy-3 cy-10 cy-20 Theoritical Max. Yield FC0 F75CA1WM F75CA1COP F75CA2COP F60CA1WM F60CA1COP F60CA2WM F60CA2COP Different Oxygen Carriers 20 redox cycles of FCA Particles: 8 min reduction in 10 vol% CO, 5 min oxidation in 20 vol% CO 2 and 5 min air ox

21 CO 2 yield im m.mol /g. of sample Fluidized Bed Redox Cycling Exp. Results cy-1 cy-3 cy-10 cy-20 Theoritical Max. Yield FC0 F75CA1WM F75CA1COP F75CA2COP F60CA1WM F60CA1COP F60CA2WM F60CA2COP Different Oxygen Carriers 20 redox cycles of FCA Particles: 8 min reduction in 10 vol% CO, 5 min oxidation in 20 vol% CO 2 and 5 min air ox

22 CO 2 yield im m.mol /g. of sample Fluidized Bed Redox Cycling Exp. Results cy-1 cy-3 cy-10 cy-20 Theoritical Max. Yield FC0 F75CA1WM F75CA1COP F75CA2COP F60CA1WM F60CA1COP F60CA2WM F60CA2COP Different Oxygen Carriers 20 redox cycles of FCA Particles: 8 min reduction in 10 vol% CO, 5 min oxidation in 20 vol% CO 2 and 5 min air ox

23 Conversion vs Time during Reduction Cycles in FBR 1 1 Reduction Conversion, X red (a) F60CA1COP: stable conversion Cy-1 Cy-2 Cy-10 Cy-20 Reduction Conversion, X red (b) F60CA1WM: Attrition occurs Cy-1 Cy-2 Cy-10 Cy-20 Reduction Conversion, X red Time in sec (c) F60CA2COP: Gradual deactivation Cy-1 Cy-2 Cy-10 Cy-18 Reduction Conversion, X red Time in sec (d) F75CA1COP: Rapid deactivation Cy-1 Cy-2 Cy-10 Cy Time in sec Time in sec

24 Redox cycles in TGA: 80min reduction in H 2, 40min Oxidation in air, 900 o C 1 (a) Reduction 1 (b) Oxidation Solid conversion, X red FC0 F60CA1COP F60CA2COP F75CA1COP Solid conversion, X ox FC0 F60CA1COP F60CA2COP F75CA1COP Cycle number Cycle number Fig: a) 80min reduction in 5 vol% H 2, b) 40min Oxidation in air, in TGA at 900 o C

25 Reactivity (conversion.) comparison of the OCs 1.1 (a) Expt. in FBR 1 (b) Expt. in TGA Solid Conversion, X red F60A40COP F60C40COP Solid conversion, X red F60CA1COP F60CA2COP 0.5 F75A25COP F75C25COP F75CA1COP Cycle number Fig- (a): Conversion in FB during 8 min reduction by CO Cycle number Fig-(b): Conversion in TGA during 80 min red by H 2

26 SEM Image of Fresh and FB cycled Fe 2 O 3 Fig: SEM images of surfaces of a) fresh Fe 2 O 3, b) 20 cycled air oxidized Fe 2 O 3

27 SEM Images of Ca-Al-Fe-O Fresh and cycled OCs (a) 2 µm (b) 2 µm (c) 2 µm SEM images of surfaces of fresh a) F60CA1WM, b) F60CA1COP & c) F75CA1COP (d) 2 µm (e) 2 µm (f) 2 µm (d), (e) and (f) after 20 cycles in FBR at 900 o C

28 Reduction mechanism of the fresh OCs in TGA A: Reduction of CaAlFe 4 O 10 & CF to Spinel + C 4 WF 4 B: Reduction of spinel + C 4 WF 4 to C 2 F followed by Fe + Ca-aluminates Fig: Rate of mass change against normalised mass for fresh FCA OCs during TPR in H 2.

29 Conclusions CaO+Al 2 O 3 containing Fe 2 O 3 OCs showed better performance than a) Pure Fe 2 O 3 b) Individual CaO or Al 2 O 3 supported Fe 2 O 3 Co-precipitation method provides most stable particles compared to Wet mixing method. In all cases, particles containing 60 wt.% of Fe 2 O 3 showed more stablility in reactivity over cycles. The overall reaction mechanism of Ca-Al-Fe-O OCs is complex and still under study.

30 Acknowledgements Dr. Stuart A. Scott PhD Supervisor Professor Clare Grey and Dr. Matthew Dunstan Felix Donat, PhD student Islamic Development Bank

31 Thanks for your kind attention Any Question?