This document summarizes a presentation on chemical looping combustion (CLC) technology for power generation using coal synthesized gas. CLC uses oxygen carriers to transfer oxygen from air to fuel, allowing for inherent separation of carbon dioxide during combustion. The presentation outlines CLC technology, selection of oxygen carriers and reactor configurations reported in literature. It also provides analysis of a syngas-fueled CLC system layout and thermodynamic modeling of an optimized 800 MWth plant integrated with a supercritical steam cycle. The optimized design achieves higher efficiencies through increased steam temperatures.

1. ICAER 2013
Chemical-Looping Combustion Steam Cycle for Power
Generation using Coal Synthesized Gas
Paper ID 312
by
R J Basavaraj , Sreenivas Jayanti
Department of Chemical Engineering
Indian Institute of Technology Madras
Chennai -600 036, India

2. Outline of the presentation
• Chemical-looping combustion (CLC) technology
• Selection of oxygen carriers / support material, reactor configuration
• Analysis of syngas CLC system and lay-out studies
• Chemical-looping reactors, and heat exchangers, design
• Current focus
• Conclusions
2

3. Relevance of oxy-fuel combustion
Rise in global warming -Increase in CO2
level, ~388 ppm in 2010, the highest for 650000
years; Surface temperature rise of 0.74+0.18 C
over the 20th century
Possibility of reduction of CO2
from concentric sources – coal-fired
power plants, steel plants, cement kilns, steel
industries, refineries ..
Post combustion CO2 removal
– Chemical looping combustion appears
to offer advantages over
combustion and solvent capture
oxy-fuel
3

4. The countries that will be under water when
the ice caps melt
4

5. Possible submergence of coastal areas of
India due to melting of icecaps
INDIA
Image downloaded from the net around the time of announcement of a new nuclear power plant and energy
price rises in the UK recently. http://i.imgur.com/lHfiCD5.jpg
5

6. Relevance of oxy-fuel combustion
Rise in global warming -Increase in CO2
level, ~388 ppm in 2010, the highest for 650000
years; Surface temperature rise of 0.74+0.18 C
over the 20th century
Possibility of reduction of CO2
from concentric sources – coal-fired
power plants, steel plants, cement kilns, steel
industries, refineries ..
Post combustion CO2 removal
– Chemical looping combustion appears
to offer advantages over
combustion and solvent capture
oxy-fuel
6

7. Chemical-looping combustion
CO2, H2O
N2 + unreacted O2
4MeO + CH4 (fuel) → 4Me + CO2 + 2H2O
nMe + mAir → nMeO + Depleted air
Air
Reactor
MeO
Me
Me
Me
Air
O
O
Cm
Hn
Fuel
Reactor
Fuel
Figure 1. Schematic of chemical looping combustion system
Abbreviations “Me” and “MeO” will be used as general terms for reduced and
oxygenated carrier respectively.
Conventional heat of combustion, ΔH C = ΔH ox + ΔH Red
7

8. Chemical-looping combustion:
Technical issues
•
•
•
•
Oxygen carriers and support materials
Reactor configuration
Heat balance and optimization
Thermodynamic analysis
8

9. Selection of O2 carriers for gaseous Fuels
Cu2O/Cu
Mn3O4/MnO
Fe2O3/Fe3O4
1
NiO/Ni
CoO/Co
Active metal oxide*:
• NiO, CuO, Fe2O3, CoO and
Mn3O4
• NiO is chosen
Inert Support**:
• Al2O3, SiO2, TiO2 , ZrO2,
NiAl2O4 and MgAl2O4
• NiAl2O4 is selected as a support
Conversion of CH4 to CO2
• Reactivity of the oxygen carriers
NiO > CuO > Mn2O3 > Fe2O3
0.8
Fe3O4/Fe0.947 O
0.6
0.4
Fe0.947O/Fe
0.2
0
800
1000
1200
1400
1600
T (K)
Figure 3. Conversion of CH4 to CO2 as a function of temperature*
*Hossain, M. M., & de Lasa, H. I, 2008, Chemical Engineering Science, 63(18), 4433–4451.
**Ryu, H., et al., 2003, Korean J. Chem. Eng., 20(1), 157–162.
9

10. Reactor configurations being reported in the
literature
Place
Configuration
Fuel
Reference
Gaseous fuels
Chalmer University of Technology, Sweden
Interconnected CFB-BFB
NG
Institute of Carboquimica, Spain
Interconnected BFB-BFB
CH4
Linderholm et al. Int. J. of Green
house Gas Control 2008;2:520-30.
Garcia et al. Fuel 2007;86:1036-45.
Xi' an Jiaotong University, China
Interconnected CFB-BFB
Coke
oven gas
Wang et al. Energ. Environ. Sci.
2010;3:1353-60
ALSTOM Power Boilers, France
Interconnected CFB-BFB
Mattisson et al. Energy Procedia
2009;1:1557-64.
Korean Institute of Energy Research, Korea
Interconnected CFB-BFB
Technical university Vienna, Austria
DCFB
NG
CH4,
CO, H2
CH4,
CO, H2
Coal,
petcoke
coal,
biomass
Berguerand N, Lyngfelt A. Fuel
2008;87:2713-26.
Coal
Ohio State University. NETL project
NT005289
Coal
Andrus H.E., Proc. 34th Int. Tech.
Conf. on Clean Coal & Fuel
Systems. Clearwater, Florida, USA;
2009.
Adanez et al. Ind Eng Chem Res
2006;45:6075-80.
Kolbitsch group. Int J Greenhouse
Gas Control 2010;4:180-5.
Solid fuels
Chalmer University of Technology, Sweden
Interconnected CFB-BFB
Southeast university, China
CFB-spouted bed
Ohio State University, USA
Interconnected moving bedentrained bed
ALSTOM Windsor, Connecticut, USA
Interconnected CFB-CFB
CFB-Circulating Fluidized Bed
BFB-Bubbling Fluidized Bed
DCFB-Dual Circulating Fluidized Bed
Shen et al. Energ Fuel 2009;23:
2498-505.
10

11. Progression of plant efficiency via advanced
steam conditions and plant Designs
TARGET
48 - 50 %
41%- 43%
Up to
5400/1300/1325(psi/ F/ F)
38-41%
37-38
-Efficiency (net) HHV
-Typical Steam Parameters
Advanced USC
35-37%
4000/1110/1150(psi/ F/ F)
3480/1005/1050 (psi/ F/ F)
2400/1005/1005
167/540/540
Subcritical
Technology
Sliding
Mature
Pressure
Supercritical Supercritical
Material Development
4000/1075/1110
(psi/ F/ F)
UltraSupercritical
Commercial
State of Art
Supercritical
Ni-based
Materials
T91 Advanced
Austenitic
Materials
1960
1980
2000
2010
Clean Coal Combustion: Meeting the Challenge of Environmental and Carbon Constraints by ALSTOM (USA), 2010
2020
11

12. Future research direction
Korian Institute of Energy Research, 2010
12

13. Reactor configurations being reported in the
recent literature
Figure 4. Process diagram of the double loop circulating fluidized bed reactor system
Bischi et al. 2011, International Journal of Greenhouse Gas Control, 5(3), 467-474.
13

14. Syngas fueled CLC plant lay-out studies
Assumptions
1.
2.
3.
Adiabatic reactors.
Complete oxidation and reduction reactions.
No reforming reaction's in fuel reactor and fuel is completely
converted to CO2 and H2O.
Composition* of coal synthesized gas
Species
Hydrogen
Carbon
monoxide
Methane
Formula
H2
Mole %
45.7
CO
19.6
CH4
6.6
Carbon dioxide
CO2
28.1
LHV 11.2 MJ/kg
*Winslow, A.M., 1977, International symposium on combustion, 16, 503–513.
14

15. Reactions and operating variables
Reaction of Ni/NiO on nickel-spinel (NiAl2O4) support*
Air reactor:
2 Ni O2 ( g )
2 NiO
H1000oC
468 kJ/mol
Fuel reactor:
NiO CO( g )
Ni CO2 ( g )
H927oC
48 kJ/mol
NiO H 2 ( g )
Ni H 2O( g )
H927oC
15 kJ/mol
H927oC
133 kJ/mol
4 NiO CH 4 ( g )
4 Ni 2 H 2O CO2 ( g )
Variables
Operating Temperature : Air reactor (1000 C) and Fuel reactor (900 C)
Reactor system operating pressure: 1atm
Particle Composition by weight: 60% NiO + 40% NiAl2O4
Average Particle size: 200 micron; Sphericity: 0.99
*Adanez, J., et al., 2012, Progress in Energy and Combustion Science, 38(2), 215–282.
15

16. Reactors heat balance and supercritical
steam cycle
T
600 C
1
Power
QAR, Extract
Air reactor
600 C 600 C
3
5
Turbine
QDepleted air
QAir
Cooled depleted air
to atmosphere
QOx
.
CP
4
2
Solids
Gas
Steam/water
QMeO
QMe
.
.
55 bar
14 bar
Pump
QRed
QFuel
QExhaust
Fuel reactor
Water removal and
CO2 sequestration
.
8
7
0.069 bar
.
6
Figure 5a. CLC reactor system heat balance
S
Figure 5b. T-s diagram of supercritical, double
reheat 240 bar/600/600/600 C steam cycle*
Air reactor: Q Air in + Q Me + QOx = Q Depleted air + Q MeO + Q AR, Extract
Fuel reactor: QFuel in + QMeO - QRed = QExhaust + QMe
16

17. Heat balance of 800 MWth Syngas fueled CLC plant
Depleted Air [N2 =183.19 kg; O2 = 2.78 kg]
Q= 201.82 MW
Temperature (°C) = 1000
Depleted air flow rate (kg/s) = 185.97
Air reactor
T = 1000°C
QOx = 773.2 MW
ΔH = -ve
Exhaust [CO2 = 86.1 kg; H2O = 38.2 kg]
Q= 154.01 MW
Temperature (°C) = 900
Exhaust gas flow rate (kg/s) = 124.3
MeO (NiO : NiAl2O4)
QMeO= 402.85 MW
Temperature (°C) = 1000
MeO flow rate (kg/s) = 411.36
Q AR, Extract = 537.08 MW
Q FR, Extract = 58.30 MW
Fuel Reactor
T= 900°C
QRed = 26.8 MW
ΔH = -ve
QTotal, Extract = 595.38 MW
Preheated Air
T = 550°C
Q = 130.90 MW
Me (Ni : NiAl2O4)
QMe= 237.62 MW
Temperature (°C) = 900
Me flow rate (kg/s) = 358.49
Air-preheater
Preheated Fuel
T = 200°C
Q = 20.25 MW
Fuel-preheater
Q = 133.67 MW
Temperature (°C) = 798
Exhaust gas flow rate (kg/s) = 124.3
Q = 70.92 MW
Temperature (°C) = 390
Depleted air flow rate (kg/s) = 185.97
Air
Temperature (°C) = 30
Air flow rate (kg/s) = 238.85
Synthesis gas from coal
Temperature (°C) = 30
Fuel flow rate (kg/s) = 71.43
17

18. Optimised Heat Balance of syngas fueled 800 MWth CLC plant
Depleted Air [N2 =183.19 kg; O2 = 2.78 kg]
Q= 179.41 MW
Temperature (°C) = 900
Depleted air flow rate (kg/s) = 185.97
Air reactor
T = 900°C
QOx = 773.2 MW
ΔH = -ve
Preheated Air
T = 513°C
Q = 121.17 MW
MeO (NiO : NiAl2O4)
QMeO= 349.09 MW
Temperature (°C) = 900
MeO flow rate (kg/s) = 411.36
QAR, Extract = 606.45 MW
Exhaust [CO2 = 86.1 kg; H2O = 38.2 kg]
Q= 155.63 MW
Temperature (°C) = 908
Exhaust gas flow rate (kg/s) = 124.3
Fuel Reactor
T= 908°C
QRed = 26.8 MW
ΔH = -ve
Me (Ni : NiAl2O4)
QMe= 240.54 MW
Temperature (°C) = 908
Me flow rate (kg/s) = 358.49
Air-preheater
Preheated Fuel
T = 200°C
Q = 20.25 MW
Fuel-preheater
Q = 135.33 MW
Temperature (°C) = 806
Exhaust gas flow rate (kg/s) = 124.3
Q = 58.3 MW
Temperature (°C) = 327
Depleted air flow rate (kg/s) = 185.97
Air
Temperature (°C) = 30
Air flow rate (kg/s) = 238.85
Synthesis gas from coal
Temperature (°C) = 30
Fuel flow rate (kg/s) = 71.43
18

19. 19
Thermodynamic analysis of CLC power
E1
plant and supercritical steam cycle
A3
S5
S6
Stream P, bar
T, °C m, kg/s h, kJ/kg
A1
1.0132 30
238.85 0
600 C 600238.85 C507.33
C 600
A2
1.0132 513
M1
1
3
5
HP
A3
1.0132 900
185.97 964.68
Stream
A4
1.0132 327
185.97 313.46
A- Air
S7
A5
1.0132 70
185.97 41.54
E- Exhaust
S8
F1
1.0132 30
71.43
0
HE2
F- Fuel
F2
1.0132 200
71.43
283.51
MP
M- Metal/Metal oxide
M2
E1
1.0132 908
124.30 1252.03
S- Water/steam
CP
4
E2
1.0132 807
124.30 1088.78
HP- High pressure
S9
2
S10
E3
1.0132bar 80
124.30 59.09
MP- Medium pressure
55
HE3
LP- Low pressure
E4
1.0132 40
124.30 11.67
LP
14
E5
1.05 bar 40
38.20
18.73
F2
E6
1.05
40
86.09
8.54
S11
E7
110
35
86.09
4.26
A2
S1
243.12 39
116.73 184.82
S2
243.12 252
116.73 1096.48
E2
Air
Fuel
8
0.069 bar
S3
243.12 39
46.126
184.82
preheater
preheater
7
S4
243.12 252
46.12
1096.48
S5
240
252
162.85 1096.48 S
F1
A4
A1
S6
240
600
162.85 3502.91
Condensate
Condensate
S13
preheater 2
preheater 1
S7
55
305
162.85 2922.83
S4
S1
S12
S8
55
600
162.85 3662.80
S3
Pump 2
Pump 1
S9
14
332
162.85 3117.56
S2
E3
Flue gas conditioner
S10
14
600
162.85 3695.40
E4
S11
0.069 39
162.85 2573.72
E5
A5
CP-Critical point
Four stage compressor with E6
S12
0.069 39
46.12
2573.72
intercooling
S13
0.069 39
116.73 2573.72
E7
M1
1.01325 900
411.36 848.61
M2
1.01325 908
358.49 PP. 40-71.
*El-Wakil.; Mohamed, M. Power Plant Technology, New York, 2010, 670.97
HE1
T
Fuel reactor
Air reactor
. ..
.
.
T-s diagram of supercritical,double
reheat 240 bar/600/600/600 C
steam cycle*

20. CLC power plant lay-out configuration
CFB- Circulating Fluidized Bed
BFB- Bubbling Fluidized Bed
Figure 7. General arrangement for gaseous chemical-looping combustion.
20

21. Possible carbon capture and sequestration options*
*Intergovernmental Panel on Climate Change (IPCC)-2005
21

22. Overall energy analysis
CLC steam cycle power plant: 240 bar/600/600/600 C
Fuel
AR Temperature, C
FR Temperature, C
AR cooling heat capacity, MWth
FR cooling heat capacity, MWth
HP turbine, MWe
MP turbine, MWe
LP turbine, MWe
Total production, MWe
CO2 compression, MWe
Water pumping, MWe
Total power consumption, MWe
Total useful output, MWe
Thermal input, MWth
Gross efficiency
Net efficiency
Syngas
1000
900
537
58
94
88
182
365
31
5
36
329
800
45.74
41.22
Revised Syngas
900
908
606
0
94
88
182
365
31
5
36
329
800
45.74
41.22
AR: Air reactor, FR: Fuel reactor, HP: High pressure , MP: Medium pressure and LP: Low pressure
22

23. Chemical-looping combustion system:
layout design Issues
• Chemical-looping reactor design
PFR Factors
 Particle Residence Time
 Fluidization Regimes in Reactor System
 Reaction Kinetics
• Heat transfer area
23

24. Chemical-looping reactor Design (Cont…)
1
Fuel flow (kg/s)
2
Air flow (kg/s)
3
Area of reactor (Air /Fuel)
4
Solids holdup in the CFB air reactor (kg)
5
Solids holdup in BFB fuel reactor (kg)
6
Average solid fraction in CFB air reactor
7 Average solid residence time
t = solids holdup/solids flow rate
*Naqvi R. 2006, Analysis of Natural Gas-Fired Power Cycles with CLC for CO2 Capture. Doctoral Theses: NUST.
#Kunii D, Levenspiel O. 1991, Fluidization Engineering. 2nd Ed. Washington: Butterworth-Heinemann.
24

25. (Cont…) Chemical-looping reactor design
BFB Fuel
Reactor
Gas flow (kg/s)
71.43
Gas density at reactor temperature (kg/m3)
0.3848
Gas velocity (m/s)
2.10
Oxidation area (m2)
87.14
Diameter of column (m)
10.54
Length of column (m)
1.50
Density of metal (kg/m3)
2420
Average solid fraction
0.40
Hold up mass (kg)
126533
Mass flow of metal/metal oxide at reactor exit (kg/s) 358
Average solids residence time (s)
353
Parameter
CFB Air
Reactor
238.85
0.3011
4.7
170.31
14.73
45
2420
0.0011
20669
411.36
50
25

26. Fluidization regimes†
dp, m
Air reactor
dp* u, m/s
u*
0.0002
2.91
2.01
4.7
dp, m
Fuel reactor
dp* u, m/s
u*
0.0002
4.23
1.06
2.1
Circulating fluidized
bed air reactor
10
1
10-1
Bubbling fuel reactor
10-2
Syngas Lay-out AR
Syngas Lay-out FR
10-3
1
10
102
† Kunii D, Levenspiel O. 1991, Fluidization Engineering. 2nd Ed. Washington: Butterworth-Heinemann.
26

27. Heat transfer area
1
Fluidized bed to surface heat transfer coefficient
(neglecting radiation effect) is given by the
Zabrodsky’sEquation* (W/m2K)
2
Botterill
Recommendationfor effective heat
transfer* (W/m2K)
3
Heat transfer co-efficient on fluid side
( W/m2K)
4
Overall heat transfer co-efficient (W/m2K)
5
Heat exchanger surface area (m2)
Heat exchanger
Q, kW
U, kW/m2K
∆TLMTD, K
A , m2
Air-preheater
121173
0.110
340
3240
Fuel-preheater
20250
0.112
742
248
Embedded Heat exchanger 1
391885
0.216
452
4015
Embedded Heat exchanger 2
120504
0.166
431
1685
Embedded Heat exchanger 3
94101
0.177
420
1266
*Simeon NO. Fluidized Bed Combustion. Basel: Eastern Hemisphere; 2004.
27

28. Current focus
• Studies are in progress to develop a Dual-fuel CLC power plant
layout for natural gas as well as syngas without affecting steam side
load.
• Catalyst NiO:NiAl2O4 (60:40 by mass) is prepared. Experimental
studies on fuel reactivity.
Electric coil heating
arrangement
Fluidized
bed reactor
Moisture Trap
Gas Analyser: O2, N2
Stack
Gas Analyser: H2, CH4, CO, CO2
CH4
CO
Air
28

29. Conclusions
• From the energy balance and thermodynamic analysis of syngas fuelled 800
MWth CLC system, a power plant layout is made.
• Thermodynamic calculations show that CLC-steam cycle is capable of
achieving overall net cycle efficiency up to 41.22%. This efficiency includes
100% carbon capture.
• The aerodynamics, particles residence time of the CLC reactor system has
been studied. Enough heat transfer area is provided in heat exchanger so that
required amount of heat transfer to takes place.
• The proposed lay-out is designed in such a way that CLC plant operates at
atmospheric pressure on the fuel side and generates supercritical steam (240
bar/600/600/600oC) on the steam side to run a steam turbine while
maintaining a high overall thermal efficiency and a net electrical output of
330 MWe.
29

30. THANK YOU
30

31. Geological Storage of CO2
• IPCC (2005)
Potential storage sites spread all over the world
31