Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process
Antonio Coppola, Fabio Montagnaro, Piero Salatino and Fabrizio Scala
Antonio Coppola, Fabio Montagnaro, Piero Salatino and Fabrizio Scala
This work has been carried out in the framework of the European Commission –Research Fund for Coal and Steel Contract no. RFCR-CT-2010-00013 (CAL-MOD)
This work has been carried out in the framework of the European Commission –Research Fund for Coal and Steel Contract no. RFCR-CT-2010-00013 (CAL-MOD)
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Calcium-Looping is a post-combustion technology whichuses lime to capture carbon dioxide from flue gas
CaO+CO2→CaCO3CaCO3→CaO+CO2
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Calcium-Looping: Main Issues
Decay of CO2 Capture Capacity of the sorbent:
Sintering
Presence of SO2 in the flue gasCaO + SO2 + ½O2 → CaSO4
Cycle
2 4 6 8 10 12 14
Cap
ture
Cap
acity
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Calcium-Looping: Main Issues
Attrition/Fragmentation Phenomena
Primary Fragmentation
Secondary Fragmentation
Attrition by Abrasion
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Operating conditions in the calcinerunder oxy-firing conditions:
High CO2 concentration (> 70%) High temperature (> 900°C) Presence of SO2 (from coal combustion)
What is the effect of these conditions on CO2capture capacity and sorbent attrition?
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
SorbentsSample Origin SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O SO3 TiO2 LOI Sum
Massicci Italy 1.11 0.37 0.14 54.53 0.44 0.06 0.02 0.00 0.02 43.13 99.81
Schwabian Alb Germany 3.51 0.50 0.18 53.64 0.51 0.08 0.02 0.00 0.02 41.94 100.39
EnBW Germany 0.30 0.13 0.08 56.01 0.26 0.00 0.02 0.00 0.01 43.50 100.31
Xirorema Sand Greece 0.83 0.26 0.36 55.13 0.56 0.00 0.01 0.00 0.02 42.87 99.22
Tarnow Opolski Poland 1.73 0.34 0.39 54.04 0.94 0.00 0.02 0.00 0.02 42.64 100.11
Czatkowice Poland 3.91 0.39 0.31 52.88 0.99 0.00 0.02 0.00 0.03 41.43 99.96
Limestone particle size = 0.4-0.6 mm
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Experimental apparatus(1) gas preheating/premixing section; (2) electrical furnaces; (3) ceramic insulator; (4) gas distributor; (5) thermocouple; (6) fluidization column; (7) two-exit head; (8) sintered brass filters; (9) hopper; (10) SO2 scrubber; (11) stack; (12) cellulose filter; (13) membrane pump; (14) gas analyzers; (15) personal computer; (16) manometer; (17) mass flow meter/controller.40 mm ID
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Effect of temperature and CO2 in the calciner Attrition of an Italian limestone during calcium looping cycles for CO2capture was studied in a lab-scale FB apparatus. Batch experiments under alternating calcination-carbonation conditions (5 cycles) were carried out.Attrition processes were characterized by following the modifications of bed sorbent PSD and the elutriation rates of fines throughout conversion over repeated cycles.
Calcination/Carbonation Condition 1 Condition 2 Condition 3Duration [min] 15/15 35/15 20/15
Temperature [ C] 850/700 850/700 900/700Inlet CO2 [%v/v]
(balance air) 0/16 20/16 44/16
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Results: CO2 capture capacity
Cycle #1 2 3 4 5
Cap
ture
cap
acity
[gC
O2/i
nitia
l gC
aCO
3]
0,00
0,05
0,10
0,15
0,20
0,25
0,30Condition 1Condition 2Condition 3
• Highest capacity: Condition 1 (calcination in air);• Slightly lower capacity: Condition 2 (calcination in CO2);• Lowest capacity: Condition 3 (calcination in CO2 at higher temperature – 900°C).
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Results: PSD changes after 5th cycle
d [m]0 100 200 300 400
PSD
[ m
-1]
0.00
0.01
0.02
0.03
0.04
0.05Condition 1Condition 2Condition 3
d [m]
26.5
82.5
146.0
196.0
231.0
275.0
327.5
377.5
500.0
PSD
[ m
-1]
0.0
0.2
0.4
0.6
0.8
1.0Condition 1Condition 2Condition 3
• Tests carried out under the three experimental conditions showed the same qualitative trend.
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Results: Elutriation rate in Condition 1
T im e [m in ]0 1 5 3 0 4 5 6 0 7 5 9 0 1 0 5 1 2 0 1 3 5 1 5 0
E [g
/min
]
0 ,0 0
0 ,0 2
0 ,0 4
0 ,0 6
0 ,0 8
0 ,1 0
Calc
inat
ion
Carb
onat
ion
2 n d c y c le 3 rd c y c le 4 th c y c le 5 th c y c le1 s t c y c le
• Fines elutriation rate decreases with the number of cycles;• In each cycle the elutriation rate shows an initial peak, caused by a combination of rounding off, thermal shock and rapid release of CO2 (only during calcination).
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Condition 1
1 2 3 4 5
E tot [g
]
0,001
0,01
0,1
1Calcination Carbonation
Condition 2
1 2 3 4 50,001
0,01
0,1
1
Condition 3
Cycle #1 2 3 4 5
E tot [g
]
0,001
0,01
0,1
1
A
B
C
E tot [g
]
Results: Total amount of elutriated fines
• The largest amount of fines was obtained in the tests carried out in Condition 1;• Fines generation was much smaller under Condition 2 (20% CO2 during calcination);• When the calcination temperature was increased at 900°C (Condition 3), a larger amount of fines was collected.
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Calcination at high CO2 concentration:explorative tests (Massicci limestone)
Time, min
0 50 100 150 200 250 300
CO
2, %
69.6
69.8
70.0
70.2
70.4
70.6
70.8
71.0
71.2
69.2
69.4
69.6
69.8
70
70.2
70.4
70.6
70.8
71
71.2
0 500 1000 1500 2000
CO
2, %
Time, s
930°C
940°C
CO2 = 70%
T = 940°C
Inlet concentration
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Tests under high temperature and CO2 in the calciner
Five calcination/carbonation cycles were carried out under all experimental conditions;
An initial amount of 20 g of fresh limestone, sieved in the range 0.4-0.6 mm was fed to a bed consisting of 150 g of silica sand in the range 0.85-1.0 mm;
The fluidizing velocities were 0.7 and 0.6 m/s in the calcination and in the carbonation stages, respectively;
The progress of calcination/carbonation was followed by measuring the CO2concentration at the exhaust;
The duration of each stage was such that calcination/carbonation was complete; After each step the bed was discharged, the limestone was separated from the
sand by sieving, and its PSD was measured; During the runs the rate of fines generation was determined by measuring the
amount of fines elutriated from the reactor by means of the brass filters.
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Experimental conditions
Materials: Limestones
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Results: CO2 Capture Capacity - CC
0,00
0,05
0,10
0,15
0,20
0,25Massicci
0,00
0,05
0,10
0,15
0,20 Schwabian Alb
0,00
0,05
0,10
0,15
0,20 EnBW
0,00
0,05
0,10
0,15
0,20 Xirorema Sand
0,00
0,05
0,10
0,15
0,20 Tarnow Opolski
1 2 3 4 50,00
0,05
0,10
0,15
0,20 Czatkowice
CO
2 cap
ture
cap
acity
, gC
O2/g
CaC
O30
Cycle #
SO2 = 1500 ppm
0.00
0.05
0.10
0.15
0.20
0.25Massicci
0.00
0.05
0.10
0.15
0.20 Schwabian Alb
0.00
0.05
0.10
0.15
0.20 EnBW
0.00
0.05
0.10
0.15
0.20 Xirorema Sand
0.00
0.05
0.10
0.15
0.20 Tarnow Opolski
1 2 3 4 50.00
0.05
0.10
0.15
0.20 Czatkowice
CO
2 cap
ture
cap
acity
, gC
O2/g
CaC
O30
Cycle #
No SO2 • Typical decay for all limestones(with and without SO2);
• The residual CC - without SO2 -is 0.02-0.07 gCO2/gCaCO3° -lower values then Blamey et al. (2010) (0.1-0.2 gCO2/gCaCO3°) ;
• Higher decay of CC with SO2(0.004-0.07 gCO2/gCaCO3°);
• The presence of SO2 does notalter the relative ranking of the six limestones:
1. EnBW;2. Xirorema Sand;3. Czatkowice;4. Tarnow Opolski;5. Schwabian Alb;6. Massicci:
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Results: Ca conversion to sulfate
• Typical decay for all limestones(with and without SO2);
• The residual CC - without SO2 -is 0.02-0.07 gCO2/gCaCO3° -lower values then Blamey et al. (2010) (0.1-0.2 gCO2/gCaCO3°) ;
• Higher decay of CC with SO2(0.004-0.07 gCO2/gCaCO3°);
• The presence of SO2 does notalter the relative ranking of the six limestones:
1. EnBW;2. Xirorema Sand;3. Czatkowice;4. Tarnow Opolski;5. Schwabian Alb;6. Massicci:Cycle #
0 1 2 3 4 5
Cal
cium
con
vers
ion
to s
ulfa
te, %
0
5
10
15
20
25
30
MassicciSchwabian AlbEnBWXirorema SandTarnow OpolskiCzatkowice
SO2 = 1500 ppm
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Results: Particle Size Distribution - PSD
Particle size, m
0 100 200 300 400 500
Cum
ulat
ive
unde
rsiz
e di
strib
utio
n, -
0,0
0,2
0,4
0,6
0,8
1,0MassicciSchwabian AlbEnBWXirorema SandTarnow OpolskiCzatkowice
No SO2
Particle size, m
0 100 200 300 400 500
Cum
ulat
ive
unde
rsiz
e di
strib
utio
n, -
0,0
0,2
0,4
0,6
0,8
1,0MassicciSchwabian AlbEnBWXirorema SandTarnow OpolskiCzatkowice
SO2 = 1500 ppm
Particle size, m
0 100 200 300 400
PSD
, mm
-1
0
1
2
3
4
5MassicciSchwabian AlbEnBWXirorema SandTarnow OpolskiCzatkowice
No SO2
Particle size, m
0 100 200 300 400
PSD
, mm
-1
0
1
2
3
4
5
MassicciSchwabian AlbEnBWXirorema SandTarnow OpolskiCzatkowice
SO2 = 1500 ppm
• Similar shape for alllimestones;
• Slight differences in the amount of the producedfragments;
• The presence of SO2 appearsto reduce the extent of fragmentation.
• Ranking:1. EnBW;2. Massicci;3. Tarnow Opolski;4. Xirorema Sand;5. Czatkowice;6. Schwabian Alb.
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
0.000
0.005
0.010
0.015
0.020Massicci
0.000
0.005
0.010
0.015 Schwabian Alb
0.000
0.005
0.010
0.015 EnBW
Ave
rage
elu
tria
tion
rate
, g/m
in
0.000
0.005
0.010
0.015 Xirorema Sand
0.000
0.005
0.010
0.015 Tarnow Opolski
Cycle #1 2 3 4 5
0.000
0.005
0.010
0.015 CalcinationCarbonation
Czatkowice
SO2 = 1500 ppm
0.000
0.005
0.010
0.015
0.020Massicci
0.000
0.005
0.010
0.015 Schwabian Alb
0.000
0.005
0.010
0.015 EnBW
Ave
rage
elu
tria
tion
rate
, g/m
in
0.000
0.005
0.010
0.015 Xirorema Sand
0.000
0.005
0.010
0.015 Tarnow Opolski
Cycle #1 2 3 4 5
0.000
0.005
0.010
0.015 CalcinationCarbonation
Czatkowice
No SO2
Results: Total amount of elutriated finesIn general, the amount of elutriated fines:• decreases with the number of
cycles;• is approximately the same
during tha calcination and the carbonation stage – Scala et al. 1997;
• is slightly lower when SO2 ispresent.
• Ranking:1. Czatkowice;2. EnbW;3. Tarnow Opolski;4. Schwabian Alb;5. Xirorema Sand;6. Massicci
The estimated limestone loss rate is 0.3-0.5 %/h - Charitos and coworkers (2010) found a valueof 2%/h
Istituto di Ricerche sulla Combustione
The effect of an oxyfiring environment on the calcination stage of a Ca-looping process2nd International Workshop on Oxyfuel FBC Technology – Stuttgart, Germany – June 28-29, 2012
Università degli Studi diNapoli Federico II
Conclusions• Results showed that the CO2 capture capacity decreased with the cycles. The presence of a high CO2
concentration during calcination (70%) and a high calcination temperature (940°C) determined asignificant decrease of the sorbent capacity for all the cycles, most likely due to the enhancement ofparticle sintering.
• The analysis of the PSD of bed material over repeated calcination/carbonation cycles indicated thatparticle fragmentation was limited for all the limestones.
• The fines elutriation rate was relatively large only during the first cycle and decreased with thenumber of cycles, since the combined chemical-thermal treatment affected the particle structuremaking it increasingly hard.
• The presence of SO2 had a detrimental effect on the CO2 capture capacity of all limestones, whileattrition was only slightly affected by the presence of SO2.
• The residual CO2 capture capacity after the first few cycles is of the order of 0.05 and 0.01gCO2/gCaCO3 without and with the presence of SO2, respectively.
• The average limestone loss rate by elutriation can be estimated to be of the order of 0.5%/h underrealistic conditions, and should not represent a process limitation.
• The overall ranking of the six limestones tested in this work (combining the capture capacity andattrition performance) was, from the best to the worst: EnBW, Czatkowice, Xirorema Sand, TarnowOpolski, Schwabian Alb and Massicci.
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