Post on 18-Jul-2020
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
abad@icb.csic.es
Operational experience during coal combustion in
a 50 kWth Chemical Looping Combustion unit
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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?
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
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
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
abad@icb.csic.es
Thanks for your attention
Project: ENE 2013-45454-R- Reference: T06