The effect of an oxyfiring environment on the calcination ...oxyfbc.eu-projects.de/Portals/29/OxyFBC/14_Scala_IRC - Pres-Scala-Oxy-Stuttgart.pdf · Calcium-Looping is a post-combustion

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)




Calcium-Looping is a post-combustion technology whichuses lime to capture carbon dioxide from flue gas

CaO+CO2→CaCO3CaCO3→CaO+CO2




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




Calcium-Looping: Main Issues

Attrition/Fragmentation Phenomena

Primary Fragmentation

Secondary Fragmentation

Attrition by Abrasion




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?




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




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




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




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).




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.




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).




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.




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




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.




Experimental conditions

Materials: Limestones




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:




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




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.




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




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.

Documents

The effect of an oxyfiring environment on the calcination ...oxyfbc.eu-projects.de/Portals/29/OxyFBC/14_Scala_IRC - Pres-Scala-Oxy-Stuttgart.pdf · Calcium-Looping is a post-combustion