sulfur and ferrite-based thermochemical cycles for water...
TRANSCRIPT
Slight 1
Sulfur and ferrite-based thermochemical cycles for water splitting
Martin Roeb
SFERA WinterSchool 2011, Zurich, March 24th 2011
Slide 2
Outline
Ferrite based thermochemical cycle: HYDROSOL
Materials
System Model
Prototypes and tests
Pilot plants
Scale-up, economics
Sulphur based thermochemical cycle: HycycleS
Materials
Prototypes
Modelling
Scale-up
Summary
SFERA Winter School Solar Fuels & Materials Page 36
Slide 3
1. Ferrite based thermochemical cycle
Slide 4
The HYDROSOL CONSORTIA
HYDROSOL
APTL (GR)
DLR (D)
Heliotech (DK)
Johnson Matthey (GB)
HYDROSOL-2
APTL (GR)
DLR (D)
STC (DK)
Johnson Matthey (GB)
CIEMAT (ES)
HYDROSOL-3D
APTL (GR)
DLR (D)
CIEMAT (ES)
Total (F)
Hygear (NL)
SFERA Winter School Solar Fuels & Materials Page 37
Slide 5
Thermochemical Cycle using Mixed Iron Oxides: Reaction Scheme
2. Step: Regeneration
1. Step: Water Splitting
H2O + MOred MOox + H2
MOox MOred + ½ O2
Net reaction: H2O H2 + ½ O2
Typical redox materials:
ZnFe2O4, NiZnFe2O4, MnFe2O4 CoFe2O4
Slide 6
H2
H2O
O
O
O
OH
HOH
HH
H
O H
HMOreduced MOoxidized
MOreduced MOoxidized
The HYDROSOL process concept
1200 °C
800-900 °C
SFERA Winter School Solar Fuels & Materials Page 38
Slide 7
The HYDROSOL Process
Basic Features
Use of solar radiation absorbing ceramic honeycomb structures
Synthesis of active water-splitting redox nanomaterials with non-conventional techniques
Fixing/coating of the redox materials on the channels of the honeycomb
Advantages
No circulation of (hot) solid reactants
Product separation straightforward
No movable components at high temperatures
Slide 8
Objectives of HYDROSOL-2
to design and build a solar Hydrogen pilot plant (100 kWth) based on thermo-chemical water-splitting, carried out on monolithic ceramic honeycombs coated with active redox materials
To set the stage for further scale-up of the HYDROSOL technology and its effective coupling with solar thermal concentration systems, in order to exploit and demonstrate all potential advantages
To develop and identify redox materials most suitable for this cycle
To develop and verify suitable process strategies, in particular control strategies
To develop a fully scalable receiver-reactor to carry out the reactions involved
SFERA Winter School Solar Fuels & Materials Page 39
Slide 9
Objective: Integration in a Solar Tower System
Solar tower
Heliostats
“MODULAR” DESIGNAny final size from the
same initial pieces
Slide 10
Materials development
and characterisation
SFERA Winter School Solar Fuels & Materials Page 40
Slide 11
Consideration of Thermodynamics
Phase analysis
Efficiency
Yield
Pre-SelectionPre-SelectionPre-Selection
Slide 12
Phase analysis (calculated with FACTsage)
Reduction of CoFe2O4
Spinel
CoO - Monoxide
FeO
- Mon
oxid
e
Fe2O3 - Monoxide
O2
Reduktionstemperatur [°C]
Sto
ffm
eng
e [m
ol]
1000 1100 1200 1300 1400 15000,00
0,10
0,20
0,30
0,40
0,50
0,60
0,70
0,80
0,90
1,00
SFERA Winter School Solar Fuels & Materials Page 41
Slide 13
Yield (calculated)
Simulation of mixed oxides type MFe2O4 (M=Co, Ni, Mn, Mg)
Oxidation Treg = 1500°CH
ydro
gen
yie
ld[m
ol
per
mo
l fe
rrit
e]
Slide 14
Ellingham-Diagram: Transition Metals
300 600 900 1200 1500 1800 2100600
500
400
300
200
100
0
100
200
G0=RT
lnp(O
2)[kJp
er0.5molO
2]
Basic reactions0.5C+0.5O
2>0.5CO
2
C+0.5O2>CO
CO+0.5O2>CO
2
H2+0.5O
2>H
2O
melting/sublimationMetaloxide reactions
3FeO+0.5O2>Fe
3O
4
2Fe3O
4+0.5O
2>3Fe
2O
3
0.5Hf+0.5O2>HfO
2
NiO+2FeO+0.5O2>NiFe
2O
4
Zn+0.5O2>ZnO
0.4Ta+0.5O2>0.2Ta
2O
5
3CoO+0.5O2>Co
3O
4
NbO+0.5O2>NbO
2
2NbO2+0.5O
2>Nb
2O
5
V2O
3+0.5O
2>2VO
2
2Mn3O
4+0.5O
2>3Mn
2O
3
3MnO+0.5O2>Mn
3O
4
T [°C]
1022
1018
1014
1010
106
102
102
106
p(O
2)[bar]
ca 6.0 N2
SFERA Winter School Solar Fuels & Materials Page 42
Slide 15
Ellingham-Diagram: Desired Material
300 600 900 1200 1500 1800 2100600
500
400
300
200
100
0
100
200
basic reactions0.5C+0.5O
2>0.5CO
2
C+0.5O2>CO
CO+0.5O2>CO
2
H2+0.5O
2>H
2O
melting/sublimationperfect materialCe
6O
11+0.5O
2>6CeO
2
~ CeO1.83
NiO+2FeO+0.5O2>NiFe
2O
4
G0=RT
lnp(O
2)[kJp
er0.5molO
2]
T [°C]
1022
1018
1014
1010
106
102
102
106
p(O
2)[bar]
ca 6.0 N2
Slide 16
Reaction Schemes employed for Mixed Iron Oxides synthesis
2k Fe + (1-k) Fe2O3 + x MnO + (1-x) ZnO + 1.5 z O2 (MnxZn1-x)Fe2O4
Solid phase self-propagating high-temperature synthesis (SPSHS)
Liquid phase self-propagating high-temperature synthesis (LPSHS/GC)
2Fe(NO3)3 + x Mn(NO3)2 + (1-x) Zn(NO3)2 + 3 C6O7H8 + 8 NH3 + 9.5 O2
(MnxZn1-x)Fe2O4 + 18 CO2 + 8 N2 + 24H2O
Aerosol spray pyrolysis synthesis (ASP)
2Fe(NO3)3 + x Mn(NO3)2 + (1-x) Zn(NO3)2 + (3 C6O7H8 + 8 NH3 ) + 9.5 O2
(MnxZn1-x)Fe2O4 + 18 CO2 + 8 N2 + 24H2O
Solid state synthesis (SSS)
Fe2O3 + x MnCO3 (Mn3O4) (NiO) + (1-x) ZnO (Mnx (Ni)x Zn1-x)Fe2O4 + x CO2
SFERA Winter School Solar Fuels & Materials Page 43
Slide 17
Materials characterization: specific surface area
SSS
1-2 m2/g
LPSHS/GC
20-40 m2/g
SPSHS
4-5 m2/g
ASP
80-120 m2/g
Slide 18
10 20 30 40 50 60 70 80
1100oC/5hrs
1000oC/5hrs
900oC/5hrs
800oC/5hrs
700oC/5hrs
+
++
o
++
****
**
o o
Diffraction angle (two theta)
Inte
nsity
(arb
itrar
y un
its)
oo
oo o o
o Mn0.5Zn0.5FeO from SHS
raw
o:(Mn,Zn)Fe2O4
: Fe2O3
*: ZnO+: FeO
Fe3O4as-synth. 700oC 800oC 900oC 1000oC 1100oC Fe2O3
Mn0.5Zn0.5FeO
Phase and color evolution during calcination in air
SFERA Winter School Solar Fuels & Materials Page 44
Slide 19
Continuous Hydrogen productionsmall monolith SiSiC coated with YSZ/ Mn-2Fe-O (SHS)
0,0
0,2
0,4
0,6
0,8
1,0
0 10000 20000 30000 40000Time (s)
H2
(% in
N2)
Tests with coated monoliths: Testing of Mn-Fe-O mixed oxide with respect to cyclic H2 production (800 oC)
Slide 20
700 800 9000
1
2
3
4
5
6
7
8
9
10
m
mol
es H
2 p
rodu
ced/
g o
f red
ox
mat
eria
l
Water splitting temperature (oC)
ASP SHS GC
ASP-synthesized materials exhibit the highest H2 yield, followed by the SHS- and GC-produced ones.
For a given synthesis route, there is no significant variation of the amount of H2 produced, within 700-900oC.
Stoichiometry:Zn-Fe oxide material
Hydrogen yield (experiment)
SFERA Winter School Solar Fuels & Materials Page 45
Slide 21
Kinetics of water splitting
Slide 22
Experimental Set-Up
N2
H2O(g)H2O(fl)
H2O+N2
H2+N2
H2O(fl)
Water Splitting
SFERA Winter School Solar Fuels & Materials Page 46
Slide 23
Experimental Set-Up
Slide 24
H2 production curve
Water vapour input
14:50 15:00 15:10 15:20 15:30 15:40 15:50
0
1
2
3
4
5
6
con
cen
tra
tion
c in
%
time of day % O2 % H2 % CO2
H2
peak H2 production
SFERA Winter School Solar Fuels & Materials Page 47
Slide 25
Reaction Model
Reaction Rate Controlling Steps:
1. Film diffusion
2. Internal diffusion
3. Chemical reaction
product layer
gas film
unreacted core
bulk gas
Shrinking Core Model
core surface
H2O
Unreacted solidPartly reacted solid
Slide 26
Shrinking Core Model
Shrinking Core Model derives different approaches for
Xsolid: conversion of solid phase
Xsolid = f(t)
film diffusion internal diffusion chemical reaction
1 solidt k X2 3
2 solid solidt k 1 3 1 X 2 1 X 1 3
3 solidt k 1 1 x
Literature: Levenspiel, O., Chemical Reaction Engineering, 3rd. Edition, New York, Wiley, 1999
SFERA Winter School Solar Fuels & Materials Page 48
Slide 27
Analysis of Water Splitting Step
Conversion vs. Time
Fit function2 3 1 3
1 solid 2 solid solid 3 solidt k X k 1 3 1 X 2 1 X k 1 1 x
0,0
0,1
0,2
0,3
0,4
0,5
0,6
0 400 800 1200 1600 2000
Conversion Curve Fit
time in s
conv
ersi
on fe
rrite
Xfe
r
T = 800 °C
T = 900 °C
T = 1000 °C
T = 1100 °C
T = 1190 °C
Slide 28
Analysis of Water Splitting Step
Results from Shrinking Core Model Curve Fit
Reaction is mainly limited by internal diffusion
Possible film diffusion limitation at about 1200 °C
TSplitting k1 k2 k3
800 0 6312974 0
900 0 800484 0
990 0 210547 0
1100 0 33721 0
1190 1308 7037 0
SFERA Winter School Solar Fuels & Materials Page 49
Slide 29
Milestones of Materials Development
Field evaluation of coated monoliths
0 5 10 15 20 25 30 35 400
2
4
6
8
10
12
14
16
18
5. day4. day3. day2. day
mdo
t,H
2 in
10
-5 g
/s
Time in h
1. day
50-cycles of solar water-splitting
Key milestone
Water-splittingon redox coated
honeycombs
Redoxmaterialcoated SiSiChoneycombs
SEM analysis for the investigation of the quality of
coating and the effect of solar water splitting
Hyd
roge
n Y
ield
Slide 30
Reactor concept and
reactor design
SFERA Winter School Solar Fuels & Materials Page 50
Slide 31
1200° C
1200° C
Reactor for continuous hydrogen production
Reactor with two modules
10 kW two-chamber system
Two different alternating processes:
• Production: 800°C, water steam, nitrogen, exothermic
• Regeneration: 1200°C, nitrogen, endothermic
Transient steps like
• Switching between half cycle
• Start-up / Shutdown
Closed system: quartz window
Four-way-valve
800° C
800° C
H2+N2
O2+N2
O2+N2
H2+N2
Slide 32
HYDROSOL:Continously operating reactor during exposure to sunlight
SFERA Winter School Solar Fuels & Materials Page 51
Slide 33
2004:First solar thermochemical
2 production
2008:Pilot reactor (100 kW)
2005:Continuous STC 2 production
Hydrosol technology scale-up
DLR solar furnace
PSA solar tower
Slide 34
Pilot plant installation
and testing
SFERA Winter School Solar Fuels & Materials Page 52
Slide 35
Scale-up: 100kW-pilot-plant
Slide 36
Process strategy for thermal cycling
distance from tower
Focal length of heliostats
Focus 1 (east): Groups 1, 2, 3, 4
Focus 2 (west): Groups 5, 6, 7, 8 x
Switch-over groups (east and west): 0, 9, 10, 11y
Reserve group (east and west): R
Tower
1112
1314
15
2223 24 25
26
21 27
3334 35 36
37
32 38
31 39
4344
4546
47
42 48
41 49
6364
6566
6762
68
6169
8384
8586
87
82
81
51
52
5354 55
56
57
58
71
72
7374 75
76
77
78
91
92
9394 95
96
97
98
B1
B2
B3 B4B5
B6
A1
A2
A3A4
A5
A6
A7
C2C3
C4 C5 C6 C7C8
C9
C1 CA
59 m
67 m
77 m
89 m
97 m
104 m
113 m
122 m
133 m
143 m
156 m
169 m
67 m
136 m
115 m
162 m
97 m
5
6
7
8
1
3
2
4
9
11
10
0
R
SFERA Winter School Solar Fuels & Materials Page 53
Slide 37
Experiments – Solar Flux
Flux Measurement at test operation FluxMaxboth Modules= 115kW/m2
Slide 38
Experiments: Thermal cycling
Slide 38
SFERA Winter School Solar Fuels & Materials Page 54
Slide 39
Parametric study – mass flow
Slide 40
Parametric study – heliostats
SFERA Winter School Solar Fuels & Materials Page 55
Slide 41
First Hydrogen Production
West- Module
East- Module
West- Module
East- Module Heating
Slide 42
Hydrogen production in experimental series in July 2009
0
1
2
3
4
5
6
7
8
9
10:1
4:2
5:00
10:2
3:3
5:20
10:3
2:4
4:07
10:4
1:5
2:96
10:5
1:0
2:50
11:0
0:1
1:62
11:0
9:2
0:68
11:1
8:2
9:71
11:2
7:3
9:00
11:3
6:4
8:32
11:4
6:0
5:43
11:5
6:0
1:18
12:0
5:5
4:21
12:1
5:3
9:75
12:2
5:3
4:45
12:3
5:2
5:87
12:4
5:1
6:01
12:5
5:0
9:93
13:0
5:2
7:85
13:1
5:3
8:89
13:2
5:4
9:78
13:3
6:2
5:34
13:4
6:3
9:26
13:5
7:0
8:35
14:0
7:4
4:28
14:1
7:4
5:50
14:2
8:1
3:50
14:3
8:4
3:34
14:4
8:3
8:73
14:5
9:0
9:28
15:0
9:4
8:46
15:2
0:1
5:14
15:3
0:5
4:76
15:4
1:3
4:09
15:5
2:1
1:10
16:0
2:5
0:15
16:1
3:2
9:14
16:2
3:5
9:71
16:3
4:3
8:90
16:4
5:1
3:87
16:5
4:5
6:40
c(H
2) [%
]
09:36 14:24 19:12
0
200
400
600
800
1000
1200
31-07-2008
Tem
pera
ture
[°C
]
Time [hh:mm]
Left Hand Side - Exhaust Right Hand Side - Exhaust
SFERA Winter School Solar Fuels & Materials Page 56
Slide 43
Hydrogen production on June 18th 2010
Slide 44
Hydrogen production on June 17th 2010
SFERA Winter School Solar Fuels & Materials Page 57
Slide 45
Hydrogen production on June 21st/22nd 2010
13 kg/h steam6.5 kg/h
Slide 46
Modelling of reactor and process
SFERA Winter School Solar Fuels & Materials Page 58
slide 47
Model of Solar Furnace Reactor
Monolith
monolith
slice of themonolith ring of the
slice
Absorber model
slide 48
Overall Model of Solar Furnace Reactor
Model incluces:Irradiation and conduction
among the individual absorberelements
Intrusion of solar irradiationinto the absorber channels
Solar power input: gaussian distribution
Irradiation losses throughthe reactor front window
Thermal losses through thehousing
SFERA Winter School Solar Fuels & Materials Page 59
slide 49
Hydrogen Production
H2 and O2 production
pro
du
ctio
n r
ate
[kg
/s]
0
5.0·10-6
1.0·10-5
1.5·10-5
2.0·10-5
2.5·10-5
3.0·10-5
3.5·10-5
time [s]0 2000 4000 6000 8000 10000 12000 14000
production rate H2 production rate O2 Tmax
tem
pera
ture
[°C
]
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
Peak hydrogen production decreases
slide 50
Ferrite Composition
Oxygen uptake capacity of ferrite
oxy
ge
n u
pta
ke c
ap
aci
ty [
mo
le O
2/g
ferr
ite]
0.0027
0.0028
0.0029
0.0030
0.0031
0.0032
0.0033
0.0034
0.0035
time [s]0 2000 4000 6000 8000 10000 12000 14000
oxygen uptake capacity, central front element oxygen uptake capacity, rear side element Tmax
tem
pera
ture
[°C
]
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
Low temperatures at the absorber rearside
poor regeneration
SFERA Winter School Solar Fuels & Materials Page 60
slide 51
Scale-up
slide 52
Flow sheet of HYDROSOL process
SPLT 3Q=-0
RECREGQ=28
N2T NK
M X2
H2OTNK
SPLT 1Q=-0
SPLT 2Q=7
RECSPLTQ=299
M X1
CHOKE1
COM PW=5643
COOLX1Q=-35
HEATX3Q=5
M X3
HEATX1Q=35
COOLX3Q=-5
COOL2Q=-8
COOL3Q=-8
HEATX5Q=17
MIXER
H20T REAT
CHOKE3
HEATX4Q=4
COOLX4Q=-4
CHOKE2
COOLX5Q=-17
800
6421
700
263
300
18
23
300
8
24
98
56
9
1100
1
8
1100
119
4
60
1
17
60
1
16
95
022
60
71
28
60
71
6
95
119
27
-180
119
14
-170
63 30
-170
56 29
317
89
2
98
56
26
265
119
13
136
119
35
357
100
71
33
100
71
38
325
71105
34
-120
119
12
150
8
39
60
71 20
H2O
O2
H2
N2
Deioni-sation
Puri fi ca tion (PSA)
1to 6bar
200 to 1 bar
1,5 to 1bar
99
56
31
60
1
32
1 to 0,3bar6 to 1.5 bar
287
18
41
100
119
42444
-170
56
45
300
26
1517
40
SFERA Winter School Solar Fuels & Materials Page 61
Slide 53
Economics
29%
18%13%
10%
30%
14%10%
8%
44%24%
Heliostats Tower Receiver Components Support systems
Hydrosol1 MW*)
Hydrosol50 MW
Hybrid-SulphurCycle
WaterElectrolysis
Total investment 1.46 1.07 2.03 0.18 €/kgH2
Operational costs 13.02 5.73 2.64 6.32 €/kgH2/year
By-product credits 23,277 3,484,955 3,140,705 2,069,475 €/a
Hydrogen production costs 15.38 6.75 5.35 5.80 €/kgH2
Aswan Seville
Slide 54
Hydrosol 3D
The principal objective of HYDROSOL-3D is the in-detail preparation of a plant for solar thermo-chemical hydrogen production from water via the HYDROSOL technology, in a 1 MW scale on a solar tower.HYDROSOL-3D focuses on the next step towards commercialization and involves all activities necessary to prepare the erection of a HYDROSOL-technology-based 1 MW solar demonstration plant.In this respect HYDROSOL-3D is concerned with the complete pre-design and design of the whole plant including the solar hydrogen reactor and all necessary upstream and downstream units needed to feed in the reactants and separate the products and the calculation of the necessary plant erection and hydrogen supply costs.
SFERA Winter School Solar Fuels & Materials Page 62
Slide 55
Process variation: synfuels
Slide 56
CO2 reduction using metal oxides
2-step synthesis of CO using multi-valent metal oxides
1. Step: Reduction
MOoxidiert MOreduziert + ½ O2
2. Step: Oxidation oder CO2 splitting
MOreduziert + CO2 MOoxidiert + CO
SFERA Winter School Solar Fuels & Materials Page 63
Slide 57
2. Sulphur Based Thermochemical Cycles
Slide 58
Sulphur-Iodine Process
WaterH2O
OxygenO2
Heat800–1200 °C
HydrogenH2
Examples of Sulphur based thermochemical cycles
Electrolysis (90°C)
HH22SOSO44 + H+ H2 2 SOSO22 + 2 H+ 2 H22O O
HH22HH22OO
OO22
HH22SOSO44
SOSO22
WWäärmerme
800800°°C C –– 12001200°°CC
HH22SOSO44 HH22O + SOO + SO33
SOSO33 SOSO22 + + ½½OO22
+ H+ H22OO
HH22SOSO44 + H+ H2 2 SOSO22 + 2 H+ 2 H22O O
HH22HH22OO
OO22
HH22SOSO44
SOSO22
800800°°C C –– 12001200°°CC
HH22SOSO44 HH22O + SOO + SO33
SOSO33 SOSO22 + + ½½OO22
+ H+ H22OO
HeatHeat
Electrolysis (90°C)
HH22SOSO44 + H+ H2 2 SOSO22 + 2 H+ 2 H22O O
HH22HH22OO
OO22
HH22SOSO44
SOSO22
WWäärmerme
800800°°C C –– 12001200°°CC
HH22SOSO44 HH22O + SOO + SO33
SOSO33 SOSO22 + + ½½OO22
+ H+ H22OO
HH22SOSO44 + H+ H2 2 SOSO22 + 2 H+ 2 H22O O
HH22HH22OO
OO22
HH22SOSO44
SOSO22
800800°°C C –– 12001200°°CC
HH22SOSO44 HH22O + SOO + SO33
SOSO33 SOSO22 + + ½½OO22
+ H+ H22OO
HeatHeat
Hybrid Sulphur Cycle
SFERA Winter School Solar Fuels & Materials Page 64
Slide 59
Project Overview: HycycleS
Deutsches Zentrum für Luft- und Raumfahrt e.V. / DLR
Commissariat à l’Energie Atomique
Aerosol and Particle Technology Laboratory / CERTH-CPERI
EC - Joint Research Center
Ente per le Nuove tecnologie, l'Energia e l'Ambiente / ENEA
Empresarios Agrupados
ETH Zürich
Boostec Industries
The University of Sheffield
The Consortium
Deutsches Zentrum für Luft- und Raumfahrt e.V. / DLR
Commissariat à l’Energie Atomique
Aerosol and Particle Technology Laboratory / CERTH-CPERI
EC - Joint Research Center
Ente per le Nuove tecnologie, l'Energia e l'Ambiente / ENEA
Empresarios Agrupados
ETH Zürich
Boostec Industries
The University of Sheffield
The Consortium Main topics:Suitability of construction and catalyst materials for H2SO4decomposition section
Material and design of H2SO4 decomposer (as heat exchanger)
Material and design of H2SO4 decomposer (as solar receiver-reactor)
Materials and design of SO2/O2 separator(membranes for enhancingthe performance of SO3
decomposition)
HycycleS - Materials and components for Hydrogen production by sulphur based thermochemical cyclesEU FP7 - ENERGY Duration: January 2008 – March 2011
Slide 60
Solar reactor development, testing and simulation
SFERA Winter School Solar Fuels & Materials Page 65
Slide 61
Objective
Development of a solar receiver-reactor (multi-chamber concept)Evaporation and decomposition of sulphuric acidVolumetric receiver-reactor concept
Testing in DLR solar furnaceVariation of operating conditions and configurationAnalysis of different catalyst systems
DLR solar furnaceHYTHEC receiver-reactor
Slide 62
H2SO4 decomposition in 2 steps
1. Evaporation of liquid sulphuric acid (400°C)
SiSiC foam
SiSiC honeycomb
Absorbers:
2. Decomposition (reduction) of sulphurtrioxide (850°C)
H2SO4 (aq) H2SO4 (g) + H2O (g)
SFERA Winter School Solar Fuels & Materials Page 66
Slide 63
Procedure of technology development
1. Preliminary design of a multi-chamber concept
2. numerical analysis: FEM, Dymola, CT and continuum model
3. Finalization of the design
4. Construction and assembling of the reactor
5. Initial operation followed by first testing series
6. Optimisation of the set-up followed by second testing series
7. Further optimisation and testing (if necessary)
Slide 64
Design of multi-chamber solar reactor
Front view ofevaporator and decomposer
Rear view
H2SO4
SO3 + H2O
SO2 + O2 + H2OSolar radiation(focus 2)
Solar radiation(focus 1) honeycomb
foam
SFERA Winter School Solar Fuels & Materials Page 67
Slide 65
HycycleS solar reactor
H2SO4 SO3 + H2O
SO3 SO2 + ½ O2
Construction materials
Solar absorbers
SiSiC foam
SiSiC honeycomb
Piping
High-alloyed steel
Catalyst materials
Coated on SiSiC honeycomb
850°C
400°C
Slide 66
Assembling of the solar reactor
SFERA Winter School Solar Fuels & Materials Page 68
Slide 67
Solar furnace of DLR in Cologne
57 m2 heliostat159 concentrator mirrors
experiment
22 kW max. power
Slide 68
Power regulation of the two chambers
Segment shutter with 14 lamellae on each side
SFERA Winter School Solar Fuels & Materials Page 69
Slide 69
Receiver-Reactor during operation
Slide 70
Testing and qualification of the receiver-reactor
09:30 10:00 10:30 11:00 11:30 12:00 12:30
0
200
400
600
800
foa
m te
mpe
ratu
re [°
C]
time [hh:mm]
middle right bottom left outlet gas
0
2
4
6
8
10
vol
ume
rate
H2S
O4 [m
l/min
]
11:15 11:30 11:45 12:00 12:150
20
40
60
80
100 volume rate decomposition rate
deco
mpo
sitio
n r
ate
[%]
time [hh:mm]
0
1
2
3
4
5 v
olum
e ra
te H
2S
O4 [m
l/min
]
Con
vers
ion
[%]
Temperature of the evaporator Performance of the SO3 decomposer
SFERA Winter School Solar Fuels & Materials Page 70
Slide 71
Conversion of SO3: experiment and equilibrium
2
3
3
SO ;ausSO
SO ;ein
VU
V
Slide 72
Reactor efficiencies
1 2 3 4 5 6 70
20
40
60
net,evap (SiSiC for decomp.)
net,evap
(Fe2O
3 for decomp.)
[%
]
VH2SO4
[ml/min]1 2 3 4 5 6 7
0
5
10
15
20
25
net,decomp (SiSiC for decomp.)
net,decomp
(Fe2O
3 for decomp.)
[%]
VH2SO4
[ml/min]
evaporator decomposer
SFERA Winter School Solar Fuels & Materials Page 71
Slide 73
Reactor efficiencies
0 1 2 3 4 5 6 70
10
20
30
40
50
reactor
net
[%]
VH2SO4
[ml/min]
Total reactor
Slide 74
Energy Losses
Net power evaporator
17%
Net power decomposer
8%
Sensible heat16%
Loss evaporator-window
7%
Loss decompser-
window31%
Loss housing12%
Rest9%
15 %net,decomp
39 %net,evap
82 %Conversion
852 °CThc,mean
6 ml/minVH2SO4
Fe2O3Catalyst
1141 WPS,decomp
870 WPS,evap
15 %net,decomp
39 %net,evap
82 %Conversion
852 °CThc,mean
6 ml/minVH2SO4
Fe2O3Catalyst
1141 WPS,decomp
870 WPS,evap
SFERA Winter School Solar Fuels & Materials Page 72
Slide 75
System Model of the Decomposer
Slide 76
Discretisation of the Absorber
7 Ring elements x10 Slices
70 elements
20 cellsper elementfor chemical reactionmodelling
SFERA Winter School Solar Fuels & Materials Page 73
Slide 77
, ,cond a radialQ
, ,cond b radialQ, ,rad b radialQ
, ,rad a radialQ
convectionQ , ,cond d axialQ, ,cond c axialQ
Symmetry axis of absorber
solarQ
Heat balance of solid volume elements
Heat balance of gas volume elements
Kinetic model of SO3 reduction
3
3
2 2
2 2
[ ] , [ 1]
, [ 1] , [ 1]
SO
SO O
n
i SO out i gas
n n
back SO out i gas O out i gas
v k x c
k x c x c
reaction0 in in out out convectionm h m h Q Q
, , , , , ,
, , , , , ,
0 p cond a radial cond b radial cond c axial
cons d axial rad a radial rad b radial solar convection
Tm c Q Q Q
t
Q Q Q Q Q
0
10
20
30
40
50
60
70
80
0 2 4 6 8 10 12 14 16 18 20
Total Volume Flow in m3/h
Re
act
or
Effi
cie
ncy
in %
Simulation
Experiment
Simulation of the SO3 Decomposer
Slide 78
Modelling of Radiation
0
100
200
300
400
500
600
700
800
900
-0,125 -0,075 -0,025 0,025 0,075 0,125
Radius in m
So
lar
Flu
x D
en
sit
y in
kW
/m2
Vertical Cut
Horizontal Cut
Average
Approx. Gauss
0,001
0,01
0,1
1
0 20 40 60 80 100 120 140
Absorber Depth in mm
Fra
cti
on
of
So
lar
Po
we
r (l
og
ari
thm
ic)
, , ,TR TR conus TR window TR ambienceQ Q Q Q
, 12
4 4
GrenzTR ambient Absorber ambient
S Absorber Absorber ambient
Q a
C A T T
Heat losses: Thermal radiation
Thermal radiation through quartz window
SFERA Winter School Solar Fuels & Materials Page 74
Slide 79
Validation: conversion and reactor efficiency
0
5
10
15
20
25
30
35
40
45
0 1 2 3 4 5 6
Total Volume Flow in Nm3/h
Re
ac
tor
Eff
icie
nc
y in
%
Simulation
Experiment40
50
60
70
80
90
100
900 950 1000 1050 1100 1150 1200 1250
Operating Temperature in °C
Co
nv
ers
ion
in %
Experiment
Simulation
2 4 3,reactor
H SO dissociation SO decomposition sensible heatnet reactor
solar solar
Q Q QQ
P P
Slide 80
Efficiency of the SO3-decomposition
Tinlet = 450 °C, w = 96 %, lAbsorber = 0.15 m
0
10
20
30
40
50
60
0 50 100 150 200 250 300 350 400 450 500
Solar Flux Density in kW/m2
Eff
icie
nc
y in
%
Conversion = 50 %
Conversion = 80 %
Tinlet = 450 °C, w = 96 %, lAbsorber = 0.15 m
0
5
10
15
20
25
30
0 1 2 3 4 5 6 7 8 9
Mass Flow Rate in g/s
Eff
icie
nc
y in
%
61 kW/m²,1000 W
123 kW/m², 2000 W
307 kW/m², 5000 W
491 kW/m², 8000 W
two different fixed minimum conversions
SFERA Winter School Solar Fuels & Materials Page 75
Slide 81
Case studies: Gradient of Solar Flux
Tinlet = 350 °C, w = 96 %, lAbsorber = 0.15 m, Mass Flow = 2 g/s
600
700
800
900
1000
1100
1200
0 1 2 3 4 5 6 7
Radius in cmT
em
pe
ratu
re in
°C
Case 1
Case 2
Case 3
Case 1: The prototype test reactor as used in the solar furnace(Gaussian flux profile)
Case 2: Like case 1 but with an ideal homogeneous distribution of the solar flux density.
Case 3: Adiabatic absorber element of a large receiver-reactoron a solar tower.
Slide 82
Higher Conversion in a Large Scale Receiver-Reactor
T in = 350 °C, w = 96 %, Mass Flow = 2 g/s, l Absorber = 0.15 m
0
10
20
30
40
50
60
70
80
90
100
700 800 900 1000 1100 1200 1300 1400 1500 1600
Operating Temperature in °C
Co
nve
rsio
n in
%
Test Reactor
Absorber Module (Solar Tower)
SFERA Winter School Solar Fuels & Materials Page 76
Slide 83
Case Studies: Efficiency
Tinlet = 350 °C, w = 96 %, lAbsorber = 0.15 m, Mass Flow = 2 g/s
30
35
40
45
50
55
60
65
70
75
10 20 30 40 50 60 70 80 90 100
Conversion in %
Eff
icie
nc
y in
%
Case 1
Case 2
Case 3
Tinlet = 350 °C, w = 96 %, lAbsorber = 0.15 m, Mass Flow = 2 g/s
10
12
14
16
18
20
22
24
26
28
600 700 800 900 1000 1100 1200 1300 1400 1500 1600
Operating Temperature in °C
Eff
icie
nc
y in
%
Case 1
Case 2
Case 3
Slide 84
Model of the evaporator (ETH)
SFERA Winter School Solar Fuels & Materials Page 77
Slide 85
Foam characterization by CT and digitalisation
SiSiC sample (uncoated, 20ppi dnom = 1.27mm):
photo micronCT 3D rendered
5mm 5mm
submicronCT
0.1mm
no internal porosity
Slide 86
Characterisation of the foam
Geometrical Characterisation
Radiative Characterisation
Convective Characterisation
Heat Transfer Characterisation
Mass Transfer Characterisation
SFERA Winter School Solar Fuels & Materials Page 78
Slide 87
Continuum model based on Energy conservation, solid and fluid
Mass- & Species conservation, fluid
Momentum conservation, fluid
will be able to predict: optimum and maximal mass flow of acid
Variations in:position of acid inlet
porosity and nominal diameter of foam
solar input
…
lead to a deeper understanding of the process and its optimization for maximum solar-to-chemical energy conversion efficiency
Development of a continuum model
Slide 88
Validation of model using experimental data from solar furnace campaigns
SFERA Winter School Solar Fuels & Materials Page 79
Slide 89
Temperature maps and flow regimes of the foam vaporiser
Slide 90
Influence of process parameters on reactor’s energetic and chemical efficiency and mean outlet temperature
SFERA Winter School Solar Fuels & Materials Page 80
Slide 91
Scale-up
Slide 92
Implementation in to a Solar Tower
SFERA Winter School Solar Fuels & Materials Page 81
Slide 93
Summary
Volumetric Receiver-Reactors well suited for thermochemical hydrogenproduction
Observed yield close to therodynamic limits
Efficiency of the reactor can still be drastically improved (Slow kinetics, high re-radiation losses)
Materials: Optimum solutions by far not yet reached for redox materials, catalysts, construction materials
A bunch of capable reactor and process models developed and nowavaiable for a broad variety of purposes and applications
The more one gets into the details of process design, the higher are theproduction cost
Slide 94
Acknowledgements
The authors acknowledge the co-funding of the European Commission for the projects HYTHEC, HycycleS, HYDROSOL, HYDROSOL-2 and HYDROSOL-3D.
Many thanks for your attention!
SFERA Winter School Solar Fuels & Materials Page 82