operational experience during coal combustion in a 50 kwth...
TRANSCRIPT
![Page 1: Operational experience during coal combustion in a 50 kWth ...ieaghg.org/docs/General_Docs/6_Sol_Looping/2... · H 3.6 N 1.8 S 0.5 LHV (kJ/kg) 24930 Nominal thermal power: •20 kW](https://reader030.vdocuments.mx/reader030/viewer/2022011908/5f56a84dfc1c7b7b5e54769b/html5/thumbnails/1.jpg)
Politecnico Di Milano Milan, Italy
1st - 2nd September 2015
Alberto Abad
Raúl Pérez-Vega, Francisco García‐Labiano, Pilar Gayán, Luis F. de Diego, Juan Adánez
Combustion & Gasification Group
Instituto de Carboquímica (ICB-CSIC), Zaragoza, Spain
Operational experience during coal combustion in
a 50 kWth Chemical Looping Combustion unit
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A. iG-CLC: in-situ gasification of coal in the fuel reactor
B. CLOU: Chemical Looping with Oxygen Uncoupling
Coal
CO2 + H2ON2 (+O2)
MexOy
H2O(l)
CO2
Air
Reactor
Fuel
Reactor
MexOy-1
Condenser
Air
CLC: Direct coal feeding to the fuel reactor
H2O(v)
and/or
CO2
Ash
Two options
CO2
Introduction
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A. iG-CLC: Gasification of coal in the fuel reactor
Oxygen-Carrier
Coal
iG-CLC (solid fuel)
H2O and/or CO2
H2O
CO
H2
H2O
Char
Volatiles
Syngas-CLC (gas fuel)
Syngas
CO
H2
CO2
H2O
Coal
O2
CO2 H2O
Volatiles
CLOU (solid fuel)
CO2
CO2
Oxygen-Carrier
Char
CO2
H2O
CO2
H2O
Oxygen-Carrier
First, coal is dried and devolatized
Remaining solid char is gasified to give gaseous H2
and CO
Volatiles and Gasification Products react with oxygen-carrier as a gas-solid reaction
► Coal H2O + Volatile matter + Char
► Char + H2O H2 + CO
► Char + CO2 2 CO
► + n MexOy CO2 + H2O + n MexOy-1
Volatile matter
H2 + CO
H2O
CO2
Introduction
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B. CLOU: Chemical-Looping with Oxygen Uncoupling
Here, coal is also dried and devolatized
But the oxygen-carrier is able to release gaseous OXYGEN (O2)
Volatiles and Char react with OXYGEN (O2) as in common combustion with air
► Coal H2O + Volatile matter + Char
► + O2 CO2 + H2OVolatile matter
Char
Oxygen-Carrier
Coal
iG-CLC (solid fuel)
H2O and/or CO2
H2O
CO
H2
H2O
Char
Volatiles
Syngas-CLC (gas fuel)
Syngas
CO
H2
CO2
H2O
Coal
O2
CO2 H2O
Volatiles
CLOU (solid fuel)
CO2
CO2
Oxygen-Carrier
Char
CO2
H2O
CO2
H2O
Oxygen-Carrier
► 2 MexOy 2 MexOy-1 + O2
Introduction
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Coal
CO2 + H2ON2 (+O2)
MexOy
H2O(l)
CO2
Air
Reactor
Fuel
Reactor
MexOy-1
Condenser
Air
H2O(v)
and/or
CO2
Ash
CO2
Which is desirable in CLC?
High CO2
capture
efficiency
High
combustion
efficiency
A Carbon
Stripper is
necessary
To minimize
the use of an
Oxygen
Polishing Unit
Carbon
Stripper
C
CO2
MexOy-1 + C
+ CO + H2 + CH4 CO2
Oxygen
Demand
Oxygen
polishing
O2
WT = O2 for unburnt gases
O2 for coal combustion
WT
Introduction
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Coal reaction rate
CS efficiency
Coal
CO2 + H2ON2 (+O2)
MexOy
H2O(l)
CO2
MexOy-1
Condenser
Air
H2O(v)and/or
CO2Ash
CO2
Carbon
Stripper
C
CO2
+ CO + H2 + CH4 CO2Oxygen
polishing
O2
CO2 capture
efficiency
Oxygen
Demand
Availability of oxygen in FR
OC OC
coal coal
R m
m
W
Oxygen carrier reaction rate
OC to fuel ratio
Inventory of
solids in FR (kg/MW)
Residence time
of solids in FR
Solids circulation
Coal feeding rate
Amount of solids in FR
FR Temperature
Oxygen carrier
Type of coal
Gas velocity in CS
Introduction
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Objective
To optimize the design and operation
of the CLC process of coal
• The effect of operating conditions, such as temperature, solids
circulation rate, solids inventory and carbon stripper
efficiency on the CO2 capture and the Oxygen demand were
analyzed in a 50 kWth CLC unit burning coal
• Operating conditions were linked to fluid dynamics of the fuel
reactor for desing purposes
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ICB-CSIC-s50 facility
N2 Air
Air
H2OH2O
Loop Seal(LS-CS)
Loop Seal(LS-AF)
Air Reactor (AR)
Air Reactor exhaust gases
(N2 + O2)
Fuel Reactor exhaust gases
(CO2 + H2O)
Fuel Reactor (FR)
CarbonStripper
(CS)
DoubleLoop Seal
(LS-D)
Coal
ScrewFeeders
Solidscirculation
measurementdevices
Solidsreservoir
N2 / CO2
Oxygen carrier (100-300 mm):
ILMENITE: Fe2TiO5 / FeTiO3
Coal (200-300 mm):
South African Bituminous coal
Moisture 3.5
Ash 15.7
Volatile matter 25.5
Fixed carbon 55.3
C 66.3
H 3.6
N 1.8
S 0.5
LHV (kJ/kg) 24930
Nominal thermal power:
• 20 kWth for CLC of coal
• 50 kWth for CLOU
Main dimensions of the ICB-CSIC.s50 facility
FR AR CS Height (m) 4.00 4.80 0.71 Diameter bottom (m) 0.10 0.30 0.15 Diameter up (m) 0.08 0.10 -
Experimental
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Experimental
Experimental Series
I II III IV V
Operating condition unit 1 2 3 1 2 3 6 7 8 9 10
FR Temperature ºC 944 990 1006 964 982 990 905 963 970 991 962
Solids circulation rate kg/h 140 140 140 150 150 150 100 100 100 100 75
Thermal power kWth 17.5 17.5 17.5 13.5 13.5 13.5 12.5 12.5 12.5 12.5 6.9
Coal feeding rate kg/h 2.5 2.5 2.5 2.0 2.0 2.0 1.8 1.8 1.8 1.8 1.0
OC to fuel ratio () 1.1 1.1 1.1 1.5 1.5 1.5 1.1 1.1 1.1 1.1 1.5
FR solids inventory kg/MWth 253 306 443 522 525 481 680 535 506 466 722
CS gas velocity m/s 0.20 0.20 0.35 0.50 0.50 0.50 0.35 0.35 0.35 0.35 0.35
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Gas c
on
cen
trati
on
(vo
l.%
, d
ry,
N2 f
ree)
0
20
40
60
80
100
Tem
pera
ture
(ºC
)
0
200
400
600
800
1000
Time (min)
0 100 200 300
0
5
10
15
20
25
0
200
400
600
800
FR
AR
CO2
CO
CH4
CO2
O2
Temperature
Temperature
Heating period Coal combustion
H2
Gas c
on
cen
trati
on
(vo
l.%
)
Startingconditions
Results
Steady state
CO2 capture
efficiency
Oxygen
Demand
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FR Temperature (ºC)
880 900 920 940 960 980 1000 1020
CO
2 c
ap
ture
eff
icie
nc
y (
%)
50
60
70
80
90
100
CO2 capture
efficiency
• CO2 capture increased with fuel reactor temperature because a higher char conversion was reached
Results
Effect of fuel reactor temperature
Series I ( ): 17.5 kWth
Series II ( ): 17.5 kWth
Series III ( ): 13.5 kWth
Series IV ( ): 12.5 kWth
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FR Temperature (ºC)
880 900 920 940 960 980 1000 1020
CO
2 c
ap
ture
eff
icie
ncy (
%)
50
60
70
80
90
100
ugasCS = 0.2 m/s
+10 % in CO2 Capture
ugasCS = 0.35 m/s
CO2 capture
efficiency
Results
Series I ( ): 17.5 kWth
Series II ( ): 17.5 kWth
Effect of gas velocity in CS
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FR Temperature (ºC)
880 900 920 940 960 980 1000 1020
CO
2 c
ap
ture
eff
icie
nc
y (
%)
50
60
70
80
90
100
ugasCS = 0.5 m/s
+6 % in CO2 Capture
ugasCS = 0.35 m/s
ugasCS = 0.2 m/s
CO2 capture
efficiency
Results
Series I ( ): 17.5 kWth
Series II ( ): 17.5 kWth
Series III ( ): 13.5 kWth
Effect of gas velocity in CS
• The higher CS gas velocity led to the higher CO2 capture efficiency
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FR Temperature (ºC)
880 900 920 940 960 980 1000 1020
CO
2 c
ap
ture
eff
icie
nc
y (
%)
50
60
70
80
90
100
.mOC = 100 kg/h
mOC = 150 kg/h.
+7 % in CO2 Capture
CO2 capture
efficiency
Results
Series I ( ): 17.5 kWth
Series II ( ): 17.5 kWth
Series III ( ): 13.5 kWth
Series IV ( ): 12.5 kWth
Effect of solids circulation rate
• The decrease of the solids circulation rate had a positive effect on the CO2 capture
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FR Temperature (ºC)
960 975 990 1005
CO
2 c
ap
ture
eff
icie
ncy (
%)
50
60
70
80
90
100 .mOC = 100 kg/h
ugasCS = 0.35 m/s
mOC = 150 kg/h
ugasCS = 0.5 m/s
.
mOC = 150 kg/h
ugasCS = 0.35 m/s
.
.mOC = 75 kg/h
ugasCS = 0.35 m/s
CO2 capture
efficiency
Results
Series I ( ): 17.5 kWth
Series II ( ): 17.5 kWth
Series III ( ): 13.5 kWth
Series IV ( ): 12.5 kWth
Series V ( ): 6.9 kWth
Global evaluation
• Similar CO2 capture could be obtained varying the fuel reactor temperature, solids circulation rate and CS gas velocity
► Experiments selected
to evaluate
the oxygen demand
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FR Temperature (ºC)
880 900 920 940 960 980 1000 1020
Ox
yg
en
de
ma
nd
(%
)
0
2
4
6
8
10
12
14 = 1.1mOC = 450 kg/MW
= 1.1mOC = 470 kg/MW
= 1.5mOC = 480 kg/MW
- 2 % in Oxygen demand
Oxygen
Demand
Results
Effect of oxygen carrier to fuel ratio ()
• The oxygen carrier to fuel ratio has a relevant influence on the Oxygen Demand
Availability of oxygen in FR
OC OC
coal coal
R m
m
WOC to fuel ratio
Series I ( ): 17.5 kWth
Series II ( ): 17.5 kWth
Series III ( ): 13.5 kWth
Series IV ( ): 12.5 kWth
Series V ( ): 6.9 kWth
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FR Temperature (ºC)
880 900 920 940 960 980 1000 1020
Oxyg
en
dem
an
d (
%)
0
2
4
6
8
10
12
14 = 1.1mOC = 450 kg/MW
= 1.1mOC = 470 kg/MW
= 1.5mOC = 480 kg/MW
= 1.5mOC = 720 kg/MW
- 1 % in Oxygen demand
Oxygen
Demand
Results
Series I ( ): 17.5 kWth
Series II ( ): 17.5 kWth
Series III ( ): 13.5 kWth
Series IV ( ): 12.5 kWth
Series V ( ): 6.9 kWth
Effect of the solids inventory in FR
• In addition, a higher solids inventory in the fuel reactor improved the combustion efficiency of the process
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Operating variable
CO2 Capture Oxygen demandDesign
condition
FR temperature As high as possibleLow relevance in the interval 900-1000ºC
1000 ºC
Solids circulation rateAs low as possible
( > 1)As high as possible
= 1.5
Solids inventoryLow relevance in the
interval 300-700 kg/MWAs high as possible,
but conditioned by DP700 kg/MWth
Carbon stripper performance
Must be optimized Low relevance>98% separation
efficiency
Results
Selection of operating conditions
► Would it be possible to operate a
CFB with these requirements?
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Pre
ssu
re d
rop
(kP
a)
1
10
100
ug r
iser
(m/s
)
0.1
1
10
Cross Sectional Area (m2/MW
th)
0.01 0.1 1
So
lid
s f
lux (
kg
m-2
s-1
)
1
10
100
H2O/C = 0.1 - 0.2 - 0.5 - 1.0 - 2.0 - 5.0
mOC = 100 kg/MW 200
500
1000
2000
5000
2
5
10
= 1
Particle diameter ( m)
100 1000 10000
Gas v
elo
cit
y (
m/s
)
0.01
0.1
1
10
100
umf
ut
Bubbling
Spouted
Turbulent
Pneumatictransport Fast
fluidization
Results
Fluid dynamics & Design parameters
Adapted for ilmenite particles from Kunii & LevenspielChem. Eng. Sci. 1997, 52, 2471-2482
ug = 4 m/s
H2O/C=1
0.2 m2/MWth
700 kg/MWth
30 kPa
= 1.5
15 kg m-2 s-1
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Conclusions
• The effect of relevant operating conditions on the CO2 capture and
Oxygen demand of the iG-CLC process was determined in a CLC unit
• The value of several operating conditions for the design of a iG-CLC
unit was determined
• The operating conditions of the fuel reactor fit the fluid dynamics
requirements for CFB units
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Politecnico Di Milano Milan, Italy
1st - 2nd September 2015
Alberto Abad
Raúl Pérez-Vega, Francisco García‐Labiano, Pilar Gayán, Luis F. de Diego, Juan Adánez
Combustion & Gasification Group
Instituto de Carboquímica (ICB-CSIC), Zaragoza, Spain
Thanks for your attention
Project: ENE 2013-45454-R- Reference: T06