Comparison of iron-, nickel- and copper-based oxygen carriers for chemical-looping combustion

Transcription

1 Comparison of iron-, nickel- and copper-based oxygen carriers for chemical-looping combustion Yu-Jhan Jian, Ching-Ying Huang, Yau-Pin Chyou*

2 CONTENTS Background Experimental Results and Discussion Summary INER ( ) History: founded since 1968 and currently under the administration of Atomic Energy Council (AEC). Mission: the sole national research institute, dedicated to energy technologies R&D and promotion for peaceful applications of nuclear science in Taiwan. Location: in Longtan, Taoyuan County, ~30 miles SW away from Taipei (about 1 hour drive), in scenic and historic suburban surroundings close to the Shihmen Reservoir. Longtan Taiwan Source: 2

3 Research Fields Radiation Application Technology Nuclear Safety Technology Environmental and Energy Technology Plasma Engineering Fuel Cell (SOFC, DMFC) Biomass-energy (Bio-ethanol Production ) Renewable Energy (Wind, Solar) Clean Carbon as Sustainable Energy (CaSE) System design & optimization Advanced process development Carbon capture & reutilization Solar Photovoltaics Attrition System Thermogravity Analyzer Temperature Sorption Analyzer Cellulosic Alcohol Process Wind Power Laboratory CO 2 Capture Reactor 3

4 Carbon Management Issues BACKGROUND (1-4) Undeniable Truth: Fossil fuels will remain the mainstay of energy production in the 21 st century. Anthropogenic GHG (CO 2 predominant) emissions exceed Carbon Cycle limit, causing climate change issues Taiwan 2030 Unit: Gt Carbon/yr World 2030 ETP 2014 YPC / INER_CaSE - 4

5 Background - CLP Chemical Looping Process (CLP) Features CLP is a novel technology with great potential for CO 2 Capture/separation. It implements metal oxide as solid oxygen carrier to replace ASU. Chemical Looping Combustion An oxy-combustion technology, which efficiently produces high-purity CO 2. Source: DOE/NETL Carbon Dioxide Capture and Storage RD&D Roadmap, Dec. 2010, Potential to efficiently mitigates NO x emission. Chemical Looping Reforming A method for partial oxidation of hydrocarbon fuels, to produce syngas. It integrates steam reforming process, suitable for production of hydrogen and separation of CO 2. Chemical-looping Reforming, (CLR) 5

6 Background - CLC Chemical looping Combustion CLC is a novel technology It use metal oxide as solid oxygen carrier to replace ASU. Between fuel reactor and air reactor there is no mixing, so it could produce high purity CO 2. Fuel reactor: C n H m + (2n+1/2m)MeO nco 2 + 1/2mH 2 O + (2n+1/2m)Me Air Reactor: Me + 1/2O 2 MeO Chemical-looping Combustion, (CLC) 6

7 Background - CLR Chemical looping Reforming It can be described as a method for partial oxidation of hydrocarbon fuels. It can produce a syngas, suitable for production of hydrogen and separation of CO 2. Fuel reactor: C n H m + nh 2 O nco + (n+1/2m)h 2 C n H m + nmeo nco + 1/2mH 2 + nme C n H m + nco 2 2nCO + 1/2mH 2 Air Reactor: Chemical-looping Reforming, (CLR) Me + 1/2O 2 MeO 7

8 Background - Oxygen carrier material 8

9 Background - Oxygen carrier material High reactivity & conversion (X > 0.8 in 1 min) 9

10 Experimental procedure Oxygen carrier-deposition-precipitation methods Support drying 12hrs Nitrate metal mixing Al 2 O 3 support and then 1M caustic soda water was slowly added to adjust the ph. Maturity of 1 hrs Filtering and washing several times TGA analysis reduction Temperature (800 C/900 C) Gas (20%CH 4 ) oxidation Temperature (800 C/900 C) Gas (Air) Drying and Calcined 800 C/950 C 6hrs Oxygen carrier (40wt% MeO x /support) Reduction-oxidation cycle test Property analysis (BET, ICP, XRD) 10

11 Test Facility and operating condition TGA system: Weight of oxygen carrier:~20mg Reaction temperature:800 C/900 C Gas sources: Reduction gas:20%ch 4 Oxidation gas:air Purge:N 2 Flow rate:20ml/min

12 Results and Discussion (1/5) Table 1 shows the MeO loading and surface area of various fresh oxygen carriers. It revealed that metal oxide recovery of various oxygen carriers have been more than 93%, close to the nominal value. The BET surface area of oxygen carriers was around m 2 /g. This characteristic could be beneficial for increased gas-solid contacting opportunity. Table 1: MeO loading and surface area of various fresh oxygen carriers Oxygen carrier MeOx loading Sintering temperature BET surface area (%) ( o C) (m 2 /g) Cu-based Fe-based Ni-based Oxygen carrier MeO loading Sintering temperature BET surface area (%) ( o C) (m 2 /g) Cu-based Fe-based Ni-based

13 Results and Discussion (2/5) In order to estimate the theoretical oxygen ratio of the various oxygen carriers, XRD was performed for the phase identification of the fresh oxygen carriers. The XRD patterns of 40 wt%cuo/al 2 O 3, 40 wt%fe 2 O 3 /Al 2 O 3 and 40 wt%nio/al 2 O 3 calcined at 950 o C and 800 o C are shown in Figure 1. The crystal phases of 40 wt%cu-based and Fe-based oxygen carriers mainly contained CuO, Fe 2 O 3 and Al 2 O 3. Among them, the support did not react with MeO at high calcination temperature and still maintained alumina phase. The NiO interacted with Al 2 O 3 after high temperature calcination of the Ni-based oxygen carrier. 40wt%-CuO/Al2O3(Cal.800 o C,6hr) 40wt%-Fe2O3/Al2O3(Cal.950 o C,6hr) 40wt%NiO/Al 2 O 3 (Cal.950 o C,6hr) Intensity (a.u) CuO Al2O3 Intensity (a.u) Al2O3 Intensity (a.u) NiO CuAl2O4 Fe2O3 NiAlO Theta 2 Theta 2 Theta Figure 1:XRD analysis for Cu-, Fe-, Ni-based oxygen carriers (Cal. 950 C/800 C, 6hrs) 13

14 Data Evaluation Oxygen ratio (R o ): It describes the maximum oxygen of the oxygen carrier could be transferred between the air and the reducing (fuel) during reaction. R o (oxygen ratio)= mox mred m ox m ox : mass of metal-oxide; m red : mass of reduced metal-oxide R o Fe2O3/Fe3O4 Fe2O3/FeO Fe2O3/Fe NiO/Ni CuO/Cu Cu2O/Cu Theoretical oxygen ratio, Ro, for the different pairs of metals/metal oxides

15 Results and Discussion (3/5) Comparisons of Cu-based, Fe-based, and Ni-based oxygen carriers include the weight changes of the various oxygen carriers after the 1st redox reaction, which are shown in Figure 2. It is found from the slope of the TG changing curve that the rates of the redox reaction of various oxygen carriers were very fast. The redox reaction of the Cu-based and Ni-based oxygen carriers were finished within 5 minutes, although the Fe-based oxygen carrier was finished within 10 minutes. It is revealed that the weight losses for the reduction reaction of Cu-based, Fe-based, and Ni-based oxygen carriers were 0.082, and 0.083, respectively. 102 Cu-based oxygen carrier 100 Fe-based oxygen carrier 102 Ni-based oxygen carrier TG (%) 96 TG (%) TG (%) Time (min) Time (min) Time (min) Figure 2 : The weight loss of the Cu-based, Fe-based and Ni-based oxygen carriers for 1 st redox reaction 15

16 Results and Discussion (4/5) Comparisons of the present experimental results with those reported in literature are shown in Table 2. The experimental oxygen ratios (Ro) of the Ni-based and Cu-based oxygen carriers are close to the theoretical counterparts, while the oxygen ratio of the iron-based oxygen carrier has a little different with theoretical counterpart. The difference between the experimental oxygen ratio and the theoretical counterpart of the Fe-based oxygen carrier was very large. Presumably, a possible reason is that the Fe 2 O 3 was not completely reduced to Fe, or formation carbon deposition. Oxygen carrier Ni-based Cu-based Fe-based Table 2 : Comparison of the characteristics of oxygen carriers Source MeO loading (%) Experimental R * o Theoretical R ** o Reference [12] INER Reference [12] INER Reference [12] INER * Given by Reference [12] & this study (INER) ** Calculated in this study based on Reference [10,11]

17 Results and Discussion (5/5) Comparisons of the Cu-based, Fe-based, and Ni-based oxygen carriers for 10 redox cycles conducted are shown in Figure 3. The literature reported that Fe 2 O 3 to Fe 3 O 4 is the only reduction in the iron oxide system that is able to convert methane completely to carbon dioxide and water at high temperatures. Thus, for reduction to a lower iron oxide, such as FeO and Fe, it is not possible to have full gas conversion in fuel reactor [13]. So in multiple-cycle tests of the Fe 2 O 3 /Al 2 O 3 oxygen carrier, we used the first stage to do test. It indicated that all oxygen carriers have very good redox reactivity and stability. The oxygen ratios of the copper-, iron- and nickel-based oxygen carriers were maintained at 0.082, and 0.083, respectively. 100 Cu-based 101 Fe-based 100 Ni-based TG (%) TG (%) TG(%) Time (min) Time (min) Time(min) Figure 3 : The oxygen ratio of the Cu-based, Fe-based and Ni-based oxygen carriers for 10 redox cycles conducted with alternately 20%CH 4 or air. 17

18 Conclusion (1) 1. From the BET analysis, the surface areas of nickel-, copper- and iron-based oxygen carriers were 69-79m 2 /g. 2. By ICP-OES analysis, the metal oxide recovery of the copper-, iron-, and nickel-based oxygen carriers have been more than 93%. The crystal phases of 40 wt% copper-based and iron-based oxygen carriers mainly contained CuO, Fe 2 O 3, and Al 2 O 3. The crystal phase of nickel-based carriers was NiAl 2 O 4 and Al 2 O 3 by XRD analysis. 3. If the iron-based oxygen carrier reduced to Fe, the oxygen ratio could be reached , which was more than the copper- and nickel-based oxygen carriers. However, in practical application, the iron-based oxygen carrier was only able to convert methane completely to carbon dioxide and water in the first reduction stage. 4. After the 10th redox cycling tests, it was found that the stabilities of the copper-, iron- and nickel-based oxygen carriers were very good. There was no significant degradation of the oxygen ratio of oxygen carriers observed. 18

19 Acknowledgements Financial support Governmental R&D budget allocated to the Institute of Nuclear Energy Research (INER), Atomic Energy Council (AEC), Bureau of Energy (BoE), Ministry of Economic Affairs (MoEA) of Taiwan, ROC. 19

20 CaSE Research INER (2) Clean Carbon as Sustainable Energy (CaSE ) System design & optimization Process design for polygen, CCR systems CFD for gasification mechanism Fluidized-bed gasifier as benchmark platform Advanced process development HT gas clean-up (Particulate Filtration, AGR) WGS-MR for CO 2 /H 2 separation Trace element removal Carbon capture & reutilization Pre-combustion capture Oxy-combustion capture (CLP, Oxyfuel) 1 kw CLC Reactor CO 2 Capture Reactor Laboratory 20 HP-HT AGR Reactor Fluidized-Bed Reactor GMBF Hot Model