1. S. Fukada, Y. Edao, N. Hayashi
OECD-NEA Meeting on Nuclear Production of Hydrogen, April , Chicago
Heat-pump cycle by hydrogen-absorbing alloys to assist high-temperature gas-cooled reactor in producing hydrogen
S. Fukada, Y. Edao, N. Hayashi
Department of Advanced Energy Engineering Science, Kyushu University, Japan

2. Center-Of-Excellence program of Kyushu University
OECD-NEA Meeting on Nuclear Production of Hydrogen, April , Chicago
Center-Of-Excellence program of Kyushu University
Fig. 1 Hydrogen project in Kyushu University

3. On overall thermal efficiency of HTGR
OECD-NEA Meeting on Nuclear Production of Hydrogen, April , Chicago
On overall thermal efficiency of HTGR
Generation of electricity by gas turbine
Heat-to-electricity
hmax=1-TL/ TH Carnot cycle
〜50%
Thermal efficiency and cost are important factors
PEM electrolysis
utilization
Thermo-chemical water splitting
Heat-to-H2
〜90%
HTGR
〜45%
Electricity-to-H2

4. OECD-NEA Meeting on Nuclear Production of Hydrogen, April 16 2009, Chicago
High-temperature H2 utilization system comprised of HTGR, H2 production plant, heat pump, H2 storage bed, ceramic fuel cell
Fig. 2 High-temperature H2 utilization system which was presented in 3rd OECD/NEA exchange meeting on nuclear production of hydrogen

5. Characteristics of Nuclear Production of H2 by I-S cycle
OECD-NEA Meeting on Nuclear Production of Hydrogen, April , Chicago
Characteristics of Nuclear Production of H2 by I-S cycle
After the Bunsen exothermic reaction
Three different temperatures according to endothermic reaction
SO2 + I2 + 2H2O→2HI + H2SO4 – DH oC
H2SO4(aq)→H2O(g) + SO3(g) + DH °C
SO3(g)→SO2(g) + 0.5O2(g) + DH °C +)
2HI→H2 + I2 + DH3 300oC
H2O = H O2 + DH0
DH0 = DH1 + DH2 + DH3 – DH4

6. Thermodynamic of hydride: M + (n/2)H2 = MHn + DH
OECD-NEA Meeting on Nuclear Production of Hydrogen, April , Chicago
y-intercept DS
Thermodynamic of hydride: M + (n/2)H2 = MHn + DH
Equilibrium pressure
ZrH DH= -163kJ/mol-H2
LiH DH= -157kJ/mol-H2
LaH DH= -200kJ/mol-H2
ZrV2H4.8 DH= -200kJ/mol-H2
DS=0.110〜0.13 kJ/mol-H2K independent of alloys or metals
Fig. 3 Van’t Hoff plot for hydrogen-absorbing alloys

7. Equilibrium pressure of Zr(V1-XFeX)2 alloys
OECD-NEA Meeting on Nuclear Production of Hydrogen, April , Chicago
Equilibrium pressure of Zr(V1-XFeX)2 alloys
ZrV2
ZrFe2
Zr(V1-XFeX)2
ZrV2H4.8 DH= -200kJ/mol-H2
pH2=10-8atm
ZrFe2H2 DH=0
pH2=100atm
Arbitral alloy
ZrV2 + ZrFe2 also composes C15-Laves phase hydride.
Fig. 4 DH or pH2 depend on composition of C15-Laves phase of Zr(V1-XFeX)2

8. Chemical heat pump to enhance heat utilization of HTGR
OECD-NEA Meeting on Nuclear Production of Hydrogen, April , Chicago
Chemical heat pump to enhance heat utilization of HTGR TM
MaH2→Ma+H2
utilization of heat H2
Heat
gas turbines 〜
Mb+H2→MbH2 TH TH TL
Tin
=TL
Tout=TH (He gas coolant) TL
HTGR
TM2
2HI→H2+I2
2SO3→2SO2+O2 TH
300oC
TM1
900oC
TM3
B+b/2H2 ⇄ BHb+H H2 H2
TM1
H2SO4→H2O+SO3
AHb+H ⇄A+b/2H2
Bunsen reaction
2H2O+SO2+I2 →2HI+H2SO4
TM3
TM2
500oC
TM2
chemical heat pump
Fig. 5 Chemical heat-pump system matched to temperature of I-S cycle and HTGR

9. TM1
TM2 TL TH
pA,M2 pH
pB,M2 pL t1 t2 t3 t4 t5 t6
Equilibrium pressure
H/M H2
Hydrogen-to-alloy atomic ratio
AHa or BHa’
AHb or BHb’
TM3
Alloy B
Alloy A
pM3

10. Fig. 6 Heat pump cycle on van’t Hoff plot
OECD-NEA Meeting on Nuclear Production of Hydrogen, April , Chicago
Fig. 6 Heat pump cycle on van’t Hoff plot
Log(p)
Two alloy beds Zr(V1-XFeX)2 are placed in parallel. TM
Heat supply
MaH2→Ma+H2
pA,M
MaH2→Ma+H2 H2 H2
Heat
Heat extract
PB,H
Mb+H2→MbH2
Mb+H2→MbH2 TH
pB,M
MbH2→Mb+H2 H2
Heat extract
Heat supply
pA,L
Ma+H2→MaHX
Alloy B
Alloy A
900oC
300oC-500oC
1/T
1/TH
1/TM
1/TL
H2SO4→H2O+SO3
2SO3→2SO2+O2
Reactor heat
2HI→H2+I2

11. Experiment of heat generation in ZrV1.9Fe0.1 alloys
OECD-NEA Meeting on Nuclear Production of Hydrogen, April , Chicago
Experiment of heat generation in ZrV1.9Fe0.1 alloys
Set-up procedures
Synthesize ZrV1.9Fe0.1 alloy from Zr, V and Fe
Set up absorption/desorption apparatus
Activate ZrV1.9Fe0.1 alloy particles
Introduce H2 under constant flow rate
Measure temperature in ZrV1.9Fe0.1 alloy bed
Whether or not the alloy can absorb and desorb H2 at the high temperature of I-S cycle?
Fig. 7 Experimental apparatus for basic study of Ze-V-Fe alloys heat pump

12. Temperature elevation of ZrV1.9Fe0.1 alloy particle bed
OECD-NEA Meeting on Nuclear Production of Hydrogen, April , Chicago
Temperature elevation of ZrV1.9Fe0.1 alloy particle bed
time
Experimental procedures
Desorb ZrV1.9Fe0.1 particle bed
Heat up to T0
Temperature increment
Cut off electricity of furnace (stop heating)
Supply H2 under constant W
Measure T inside ZrV1.9Fe0.1 particle bed
q0:maximum amount of hydrogen absorbed
Calculation was presented in IJHE.
Fig. 8 Temperature elevation vs. H2 absorbed amount

13. Temperature elevation during H2 absorption
OECD-NEA Meeting on Nuclear Production of Hydrogen, April , Chicago
Temperature elevation during H2 absorption W
When W<3.5L/min,
DT depends on W.
When W>3.5L/min,
DT is independent of W.
Temperature increment
This is because DH due to hydrogenating is consumed for gas heating.
The temperature increment is observed at the I-S cycle temperature
Fig. 9 Temperature elevation vs. temperature of introduced H2

14. H2 Desorption from ZrV1.9Fe0.1 alloy bed by heating
OECD-NEA Meeting on Nuclear Production of Hydrogen, April , Chicago
H2 Desorption from ZrV1.9Fe0.1 alloy bed by heating
ZrV1.9Fe0.1 can desorb H2 only by pressure difference between two beds without any external force.
The alloy can constitute heat-ump cycle without any external mechanical pump
Heat supply rate is constant.
Fig. 10 He desorption rate and temperature as a function of time

15. OECD-NEA Meeting on Nuclear Production of Hydrogen, April 16 2009, Chicago
Conclusions
A chemical heat pump system is proposed to enhance the reactor heat of HTGR for hydrogen producing.
The heat pump system is operated among three different temperatures of the I-S cycle to enhance heat utilization efficiency.
It was found that ZrV1.9Fe0.1 can absorb H2 at 650oC and it can heat up DT=100oC.
It was found that the alloy can desorb H2 only by pressure difference between two beds without any external force.

16. OECD-NEA Meeting on Nuclear Production of Hydrogen, April 16 2009, Chicago
Acknowledgement
This research was performed under the Center-of-Excellence (COE) program supported by the Ministry of Education, Culture, Sports, Science and Technology., which program name is “A challenge of reliable hydrogen-related technology”. Our research group belongs to Hydrogen Technology Research Center of Kyushu University:
We would like to express our gratitude to all the students who belong to our laboratory.