Ammonia as Hydrogen Carrier

Transcription

1 Hydrogen ü Primary fuel source for fuel cell ü Low volume density ü Difficulty in storage and transportation Ammonia as Hydrogen Carrier Ammonia ü High H 2 density ü Carbon-free ü High boiling point ü Ease in liquefaction and transportation ü Hydrogen production via decomposition reaction H 2 + N 2 ΔHº = +46 kj mol 1 Table H 2 density and boiling point of liquid H 2,, and C 7 H 14 (Methylcyclohexane) H 2 density (kg-h 2 / m 3 -liq. ) Boiling point (ºC) Liquid H C 7 H 14 (Methylcyclohexane)

2 2

3 Ø Hydrogen-fueled SOFC Ø Direct ammonia-fueled SOFC e - H 2 H 2 O N 2 - Anode Electrolyte Cathode 2 N H 2 H H 2 O + 2 e - 1/2 +2 e - - 3

4 Hydrogen carrier & energy conversion technology ØAmmonia as a promising hydrogen carrier: High H 2 density, Carbon-free, Low production cost, High boiling point, Ease in liquefaction and transportation, etc. H 2 density (kg-h 2 / m 3 -liq. ) Boiling point (ºC) ΔH r (kj/mol-h 2 ) Liquid H C 7 H 14 (Methylcyclohexane) N 2 +3H C 7 H 14 C 7 H 8 +3H 2 Kyoto Univ. PEFC PAFC SOFC Fuel cells AMFC Molten Alkali FC MCFC MeOH Hydrocarbons NH3 Reforming / decomposition Temperature Temperature (ºC) / ºC Fig. Operating temperature ranges of fuel cells and catalytic reformers 4

5 Operation type of ammonia fueled cell R: decomposition reactor,c:fuel cell chamber,s:sofc stack E x t e r n a l Decomposition Indirect Internal Decomposition Direct Internal Decomposition Ø decomp. reactor installed on the flow line Ø Optimized operation of each reactor Ø Large energy loss Ø Large system size Ø Stationary application Ø Reactor installed in the FC chamber Ø System design with effective heat management Ø Either stationary or mobile application Ø decomp. reactor unnecessary Ø decomp. And anode reaction proceed on the electrode Ø Simplified system Ø Multifunctional electrode Ø Heat management Ø Either stationary or mobile application 5

6 Durability of Catalyst for Cracking Catalyst: 5wt.% SrO 40wt.% Ni/Y 2 O 3 (Pretreated at 600ºC in 50%H 2 /Ar) Supply gas: 100% ; Space velocity = 2,400 h 1 Durability test: 700ºC Activity evaluation: 515ºC, 565ºC Fig. Time course of ammonia conversion at 515 and 565ºC for the SrO Ni/ Y 2 O 3 catalyst under the stability test at 700ºC with an S.V. of 2,400 h 1.

7 Ammonia-fueled Solid Oxide Fuel Cell System SOFC u System 1 Autothermal cracking cracking 3 2 Direct supply 1 2 H 2 + N 2 e - e - e e - Gas in u System 2 oxidation NH1 3 cracking 2 H 2 N N 2 + H 2 O Heat - - u System 3 Autothermal cracking H 2 N 2 H 2 O - - It is important to develop the catalyst and control the reaction conditions!! Gas out

8 To SOFC stack H 2 +N 2 +steam Ammonia + air Start-up Heater C a t a l y s t honeycomb Outline of the reactor set-up for auto-thermal ammonia cracking 8

9 Electrical Heating Air Supplying (ATR) 600 Ammonia supplying Temperature / C Honeycomb center temp. ATR outlet temp Time / sec Start-up characteristics of auto-thermal ammonia cracker designed for 1 kw SOFC system. Start-up time was ca. 130 sec. 9

10 Ammonia-fueled Solid Oxide Fuel Cell System SOFC u System 1 Direct supply e - e - Gas in e - - e - - u System 2 cracking 3 2 NH 1 3 cracking 2 H 2 + N 2 H 2 N 2 Heat - u System 3 Electrochemical H 2 oxidation H 2 + H 2 O + 2e Autothermal cracking H 2 N 2 H 2 O Gas out

11 Cell & Material Table Configuration of the anode-supported cell Layer Composition Thickness / µm Diameter / mm Anode support layer NiO/Zr -based material Anode functional layer NiO/Zr -based material Electrolyte layer Zr -based material Cathode layer Perovskite-type oxide material

12 Performance of -fueled SOFC Stack with 10 single cells Fig. I V and I P characteristics of the SOFC stack at 770ºC. Anode gas: 75% H 2 25% N 2,, cracked, and autothermally cracked ; Cathode gas: Air.

13 SOFC single cell Photograph of 1 kw SOFC stack consisting of 30 single cells supplied with ammonia 13

14 1kW SOFC stack evaluation set-up 14

15 Voltage / V Power / W H 2 + N 2 Current / A Current-voltage (I-V) and current power (I-P) characteristics of ammonia-fueled SOFC stack. First demonstration of 1 kw-class SOFC directly supplied with ammonia. 15

16 Voltage / V Efficiency [%] Fuel Utilization [%] Dependence of voltage and DC efficiency on fuel utilization of ammoniafueled SOFC stack at current of 45 A. High DC generation efficiency over 50% was attained. (e.g., Efficiency was 54.7% at fuel utilization = 85%, current = 45 A, and power = 950 W) DC generation efficiency is defined as DC power divided by lower heating value for ammonia combustion. 16

17 Summary ü The rapid start-up less than 130 sec was possible with the autothermal cracker. ü The SOFC stack with 30 single cells fueled with exhibited 1 kw power at ca. 750ºC. ü The DC generation efficiency of 1 kw class SOFC stack was 50% or higher. Acknowledgment This work was supported by the Council for Science, Technology and Innovation (CSTI) Cross-ministerial Strategic Innovation Promotion Program (SIP) energy carrier (Funding agency: JST).