Chemical-Looping Combustion Steam Cycle for Power
Generation using Coal Synthesized Gas
ICAER 2013
by
R J Basavaraj , Sreenivas Jayanti
Department of Chemical Engineering
Indian Institute of Technology Madras
Chennai -600 036, India
Paper ID 312
Outline of the presentation
2
• 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
Relevance of oxy-fuel combustion
3
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 appearsto offer advantages over oxy-fuelcombustion and solvent capture
4
The countries that will be under water when
the ice caps melt
Possible submergence of coastal areas of
India due to melting of icecaps
5Image 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
INDIA
Relevance of oxy-fuel combustion
6
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 appearsto offer advantages over oxy-fuelcombustion and solvent capture
Chemical-looping combustion
7
Me
MeO
Fuel
Reactor
Air
Reactor
CO2, H2ON2 + unreacted O2
Abbreviations “Me” and “MeO” will be used as general terms for reduced and
oxygenated carrier respectively.
nMe + mAir → nMeO + Depleted air 4MeO + CH4 (fuel) → 4Me + CO2 + 2H2O
Figure 1. Schematic of chemical looping combustion system
Air
Me O
Me O
Fuel
Cm Hn
C ox RedConventional heat of combustion, ΔH = ΔH + ΔH
Chemical-looping combustion:
Technical issues
• Oxygen carriers and support materials
• Reactor configuration
• Heat balance and optimization
• Thermodynamic analysis
8
Selection of O2 carriers for gaseous Fuels
Inert Support**:
• Al2O3, SiO2, TiO2 , ZrO2,
NiAl2O4 and MgAl2O4
• NiAl2O4 is selected as a support
9
Figure 3. Conversion of CH4 to CO2 as a function of temperature*
Active metal oxide*:
• NiO, CuO, Fe2O3, CoO and
Mn3O4
• Reactivity of the oxygen carriers
NiO > CuO > Mn2O3 > Fe2O3
• NiO is chosen
*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.
Fe3O4/Fe0.947 O
CoO/Co
NiO/Ni
Fe0.947O/Fe
Cu2O/Cu Mn3O4/MnO Fe2O3/Fe3O4
0
0.2
0.4
0.6
0.8
1
800 1000 1200 1400 1600
Co
nv
ersi
on
of
CH
4to
CO
2
T (K)
Reactor configurations being reported in the
literaturePlace Configuration Fuel ReferenceGaseous fuels
Chalmer University of Technology, Sweden Interconnected CFB-BFB NGLinderholm et al. Int. J. of Green
house Gas Control 2008;2:520-30.
Institute of Carboquimica, Spain Interconnected BFB-BFB CH4
Garcia et al. Fuel 2007;86:1036-45.
Xi' an Jiaotong University, China Interconnected CFB-BFBCoke
oven gas
Wang et al. Energ. Environ. Sci.
2010;3:1353-60
ALSTOM Power Boilers, France Interconnected CFB-BFB NGMattisson et al. Energy Procedia
2009;1:1557-64.
Korean Institute of Energy Research, Korea Interconnected CFB-BFBCH4,
CO, H2
Adanez et al. Ind Eng Chem Res
2006;45:6075-80.
Technical university Vienna, Austria DCFBCH4,
CO, H2
Kolbitsch group. Int J Greenhouse
Gas Control 2010;4:180-5.
Solid fuels
Chalmer University of Technology, Sweden Interconnected CFB-BFBCoal,
petcoke
Berguerand N, Lyngfelt A. Fuel
2008;87:2713-26.
Southeast university, China CFB-spouted bedcoal,
biomass
Shen et al. Energ Fuel 2009;23:
2498-505.
Ohio State University, USAInterconnected moving bed-
entrained bedCoal
Ohio State University. NETL project
NT005289
ALSTOM Windsor, Connecticut, USA Interconnected CFB-CFB Coal
Andrus H.E., Proc. 34th Int. Tech.
Conf. on Clean Coal & Fuel
Systems. Clearwater, Florida, USA;
2009.
10CFB-Circulating Fluidized Bed
BFB-Bubbling Fluidized Bed
DCFB-Dual Circulating Fluidized Bed
Progression of plant efficiency via advanced
steam conditions and plant Designs
11
T91
Clean Coal Combustion: Meeting the Challenge of Environmental and Carbon Constraints by ALSTOM (USA), 2010
1960 1980 2000 20202010
Material Development
-Efficiency (net) HHV
-Typical Steam Parameters
35-37%
37-38
41%- 43%
TARGET
48 - 50 %
Ni-based
Materials
Mature
Supercritical
3480/1005/1050 (psi/ F/ F)
2400/1005/1005
167/540/540
Up to
5400/1300/1325(psi/ F/ F)
4000/1110/1150(psi/ F/ F)
4000/1075/1110
(psi/ F/ F)
38-41%
Subcritical
Technology
Commercial
State of Art
Supercritical
UltraSupercritical
Advanced USC
Sliding
Pressure
Supercritical
Advanced
Austenitic
Materials
12Korian Institute of Energy Research, 2010
Future research direction
Reactor configurations being reported in the
recent literature
Figure 4. Process diagram of the double loop circulating fluidized bed reactor system
13Bischi et al. 2011, International Journal of Greenhouse Gas Control, 5(3), 467-474.
Syngas fueled CLC plant lay-out studies
14
Assumptions
1. Adiabatic reactors.
2. Complete oxidation and reduction reactions.
3. No reforming reaction's in fuel reactor and fuel is completely
converted to CO2 and H2O.
Composition* of coal synthesized gas
Species Formula Mole %
Hydrogen H2 45.7
Carbon
monoxideCO 19.6
Methane CH4 6.6
Carbon dioxide CO2 28.1
LHV 11.2 MJ/kg
*Winslow, A.M., 1977, International symposium on combustion, 16, 503–513.
Reactions and operating variables
Reaction of Ni/NiO on nickel-spinel (NiAl2O4) support*
15
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
o
o
2 1000
2 927
2 2
Air reactor:
2 ( ) 2 H 468 kJ/mol
Fuel reactor:
( ) ( ) H 48 kJ/mol
( ) ( )
C
C
Ni O g NiO
NiO CO g Ni CO g
NiO H g Ni H O g o
o
927
4 2 2 927
H 15 kJ/mol
4 ( ) 4 2 ( ) H 133 kJ/mol
C
CNiO CH g Ni H O CO g
*Adanez, J., et al., 2012, Progress in Energy and Combustion Science, 38(2), 215–282.
Reactors heat balance and supercritical
steam cycle
16
Pump
QExhaust
Power
Air reactor
Fuel reactor
QAir
QMeO
QDepleted air
QMe
QFuel
Water removal and
CO2 sequestration
Cooled depleted air
to atmosphere
Gas
Solids
Steam/water
TurbineQAR, Extract
QOx
QRed
Air in Me Ox Depleted air MeO AR, ExtractAir reactor: Q + Q + Q = Q + Q + Q
Fuel in MeO Red Exhaust MeFuel reactor: Q + Q - Q = Q + Q
Figure 5a. CLC reactor system heat balance
2
55 bar
14 bar
0.069 bar
600 C 600 C 600 C
T
S
CP
1 3 5
4
7
86
.. .
. ..Figure 5b. T-s diagram of supercritical, double
reheat 240 bar/600/600/600 C steam cycle*
Heat balance of 800 MWth Syngas fueled CLC plant
Preheated Fuel
T = 200°CQ = 20.25 MW
MeO (NiO : NiAl2O4)
QMeO= 402.85 MW
Temperature (°C) = 1000
MeO flow rate (kg/s) = 411.36
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
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
Air reactor
Preheated Air
T = 550°CQ = 130.90 MW
Q = 133.67 MW
Temperature (°C) = 798
Exhaust gas flow rate (kg/s) = 124.3
Fuel Reactor
Synthesis gas from coal
Temperature (°C) = 30
Fuel flow rate (kg/s) = 71.43
Me (Ni : NiAl2O4)
QMe= 237.62 MW
Temperature (°C) = 900
Me flow rate (kg/s) = 358.49
Exhaust [CO2 = 86.1 kg; H2O = 38.2 kg]
Q= 154.01 MW
Temperature (°C) = 900
Exhaust gas flow rate (kg/s) = 124.3
T = 1000°C
QOx = 773.2 MW
ΔH = -ve
T= 900°C
QRed = 26.8 MW
ΔH = -ve
Fuel-preheaterAir-preheater
Q AR, Extract = 537.08 MW
Q FR, Extract = 58.30 MW
QTotal, Extract = 595.38 MW
17
Preheated Fuel
T = 200°CQ = 20.25 MW
MeO (NiO : NiAl2O4)
QMeO= 349.09 MW
Temperature (°C) = 900
MeO flow rate (kg/s) = 411.36
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
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
Air reactor
Preheated Air
T = 513°CQ = 121.17 MW
Q = 135.33 MW
Temperature (°C) = 806
Exhaust gas flow rate (kg/s) = 124.3
Fuel Reactor
Synthesis gas from coal
Temperature (°C) = 30
Fuel flow rate (kg/s) = 71.43
Me (Ni : NiAl2O4)
QMe= 240.54 MW
Temperature (°C) = 908
Me flow rate (kg/s) = 358.49
Exhaust [CO2 = 86.1 kg; H2O = 38.2 kg]
Q= 155.63 MW
Temperature (°C) = 908
Exhaust gas flow rate (kg/s) = 124.3
QAR, Extract = 606.45 MW
T = 900°C
QOx = 773.2 MW
ΔH = -ve
T= 908°C
QRed = 26.8 MW
ΔH = -ve
Fuel-preheater Air-preheater
Optimised Heat Balance of syngas fueled 800 MWth CLC plant
18
Stream P, bar T, °C m, kg/s h, kJ/kg
A1 1.0132 30 238.85 0
A2 1.0132 513 238.85 507.33
A3 1.0132 900 185.97 964.68
A4 1.0132 327 185.97 313.46
A5 1.0132 70 185.97 41.54
F1 1.0132 30 71.43 0
F2 1.0132 200 71.43 283.51
E1 1.0132 908 124.30 1252.03
E2 1.0132 807 124.30 1088.78
E3 1.0132 80 124.30 59.09
E4 1.0132 40 124.30 11.67
E5 1.05 40 38.20 18.73
E6 1.05 40 86.09 8.54
E7 110 35 86.09 4.26
S1 243.12 39 116.73 184.82
S2 243.12 252 116.73 1096.48
S3 243.12 39 46.12 184.82
S4 243.12 252 46.12 1096.48
S5 240 252 162.85 1096.48
S6 240 600 162.85 3502.91
S7 55 305 162.85 2922.83
S8 55 600 162.85 3662.80
S9 14 332 162.85 3117.56
S10 14 600 162.85 3695.40
S11 0.069 39 162.85 2573.72
S12 0.069 39 46.12 2573.72
S13 0.069 39 116.73 2573.72
M1 1.01325 900 411.36 848.61
M2 1.01325 908 358.49 670.97
Thermodynamic analysis of CLC power
plant and supercritical steam cycle
19
E4
Four stage compressor with
intercooling
E6
Air
preheater
Fuel
preheater
M1
M2
S8
S6
A3
E1
Air reacto
r
Fuel reacto
r
S10
S7
HP
S9
MP
LP
S11
F2
A4
S3
E2
E5
S13
S12S4
S2
F1
A5
A2
A1
S1
E3Flue gas conditioner
E7
HE1
HE3
HE2
S5
Pump 1 Pump 2
Condensate
preheater 1
Condensate
preheater 2
Stream
A- Air
E- Exhaust
F- Fuel
M- Metal/Metal oxide
S- Water/steam
HP- High pressure
MP- Medium pressure
LP- Low pressure
255 bar
14 bar
0.069 bar
600 C 600 C 600 C
T
S
CP
1 3 5
4
7
86
. . .
. ..T-s diagram of supercritical,double
reheat 240 bar/600/600/600 C
steam cycle*
CP-Critical point
*El-Wakil.; Mohamed, M. Power Plant Technology, New York, 2010, PP. 40-71.
CLC power plant lay-out configuration
20Figure 7. General arrangement for gaseous chemical-looping combustion.
CFB- Circulating Fluidized Bed
BFB- Bubbling Fluidized Bed
21
Possible carbon capture and sequestration options*
*Intergovernmental Panel on Climate Change (IPCC)-2005
Overall energy analysis
22
CLC steam cycle power plant: 240 bar/600/600/600 C
Fuel Syngas Revised Syngas
AR Temperature, C 1000 900
FR Temperature, C 900 908
AR cooling heat capacity, MWth 537 606
FR cooling heat capacity, MWth 58 0
HP turbine, MWe 94 94
MP turbine, MWe 88 88
LP turbine, MWe 182 182
Total production, MWe 365 365
CO2 compression, MWe 31 31
Water pumping, MWe 5 5
Total power consumption, MWe 36 36
Total useful output, MWe 329 329
Thermal input, MWth 800 800
Gross efficiency 45.74 45.74
Net efficiency 41.22 41.22
AR: Air reactor, FR: Fuel reactor, HP: High pressure , MP: Medium pressure and LP: Low pressure
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
Chemical-looping reactor Design (Cont…)
24*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.
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
ParameterBFB Fuel
Reactor
CFB Air
Reactor
Gas flow (kg/s) 71.43 238.85
Gas density at reactor temperature (kg/m3) 0.3848 0.3011
Gas velocity (m/s) 2.10 4.7
Oxidation area (m2) 87.14 170.31
Diameter of column (m) 10.54 14.73
Length of column (m) 1.50 45
Density of metal (kg/m3) 2420 2420
Average solid fraction 0.40 0.0011
Hold up mass (kg) 126533 20669
Mass flow of metal/metal oxide at reactor exit (kg/s) 358 411.36
Average solids residence time (s) 353 50
25
(Cont…) Chemical-looping reactor design
Fluidization regimes†
26
Bubbling fuel reactor
10-2
10-1
10-3
1
10
1 10 102
Circulating fluidized
bed air reactor
Syngas Lay-out AR
Syngas Lay-out FR
Air reactor Fuel reactor
dp, m dp* u, m/s u* dp, m dp* u, m/s u*
0.0002 2.91 4.7 2.01 0.0002 4.23 2.1 1.06
† Kunii D, Levenspiel O. 1991, Fluidization Engineering. 2nd Ed. Washington: Butterworth-Heinemann.
Heat transfer area
27
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
1
Fluidized bed to surface heat transfer coefficient
(neglecting radiation effect) is given by the
Zabrodsky’sEquation* (W/m2K)
2Botterill Recommendationfor effective heat
transfer* (W/m2K)
3Heat transfer co-efficient on fluid side
( W/m2K)
4 Overall heat transfer co-efficient (W/m2K)
5 Heat exchanger surface area (m2)
*Simeon NO. Fluidized Bed Combustion. Basel: Eastern Hemisphere; 2004.
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.
28
Stack
Air
CO
CH
4
Gas Analyser: O2, N2
Gas Analyser: H2, CH4, CO, CO2
Fluidized
bed reactorElectric coil heating
arrangement
Moisture Trap
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
THANK YOU
30
31
Geological Storage of CO2
• IPCC (2005)
Potential storage sites spread all over the world
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