Ca Looping: a New Technology forCa Looping: a New .... Ben Anthony... · Ca Looping: a New...

2010-05-10

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Ca Looping: a New Technology forCa Looping: a New Technology for CO2 Capture

E.J. “Ben” Anthony

G L d FBC & G ifi ti

60th IEA FBC Meeting, Gothenburg, Sweden

Group Leader FBC & GasificationCanmetENERGY, Natural Resources Canada

Anthropogenic Global Warming “The examples, so far as they go, demonstrate that comparatively unimportant variations in the composition of the air have avariations in the composition of the air have a very great influence…On the other hand, any doubling of the percentage of the carbon dioxide in the air would raise the temperature of the earth’s surface by 4˚…”- Professor Svante Arrhenius

Extract from pg. 52 of “Worlds in the Making”, Harper and Brothers Publishers, 1907.

We have known about global warming for over 100 years!

Increasingly there is a conviction that we need to have CCS ready within the next few decades!

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Technology ChoicesIf a 20-year cycle is realistic for deploying CCS, then the choices narrow down to:

P t b ti tPost-combustion captureOxy-firing technologyGasification

New technologies will be under severe pressure to seize significant market shareP iti CCS th t t b i t t dProposition: CCS processes that are not being tested at the pilot scale now have a limited future!

CaCO3/CaO Cycle Concept is Old Technology

Removal of CO2 by limeRemoval of CO2 by limeCalcination of CaCO3 to produce a fresh sorbent goes back over a century

DuMotay and Maréchal first patented the use of lime to aid gasification of carbon by steam in 1867In this respect, this technology has a similar history to fuel cells (William Grove–1837)

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The Concept was Explored in 1995/6

Professor Tadaaki Shimizu of Niigata University proposedNiigata University proposed various cycles using lime-based chemistry for CO2removal – The schematic comes from the 5th Int. Conf. on Circulating Fluidized Beds (Beijing,Fluidized Beds (Beijing, 1996)

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Ca Looping Cycles

Limestone is the obvious choice because it is one of the cheapest industrial chemicals (after water) and is environmentally benign Another big advantage of CaO/CaCO3 is that both processes are hot

Carbonator600-700°C

Regenerator850-920°C

CO2- freeflue gas

CaO

CaCO3

CO2- rich gas(for storage)

Purge CaO

both processes are hot enough to raise steam, i.e., both carbonator and calciner can serve as boilers

Flue gas heat freshCaCO3

Carbonation Reaction

CaO(s) + CO2(g) CaCO3(s) ΔH < 0Carbonation

Calcination100

on100

on

0.01

0.1

1

10

600 700 800 900 1000 1100

P co

2, e

q

Carbonati

on

Calcination

0.01

0.1

1

10

600 700 800 900 1000 1100

P co

2, e

q

Carbonati

on

Calcination

[ ] [ ]KT83087.079atmPlog CO210 −=

8

0.001

T (C)

0.001

T (C)

Thermodynamic equilibrium in the system CO2/CaO/CaCO3

[ ]KT

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Barelli et al., Energy 2008, 33 (4), 554-570.Sorbent Stoich. sorption

capacity (g CO2/g sorbent)

Regenerating temperature (°C)

Sorption capacity after 45 cycles(g CO2/g sorbent)

Natural CaCO3 0.79 900 0.316

CaCO3∙MgCO3 0.46 0.16

CaCO3∙3MgCO3 0.25 0.20

Synthetic Hydrotalcite, 0.029 400 Stablepromoted K2CO3/hydrotalcite

Li4SiO4 0.37 750 Stable to 100 cyclesLi2ZrO3 0.29 690

Na2ZrO3 0.24 790

Carbonation reaction

70

80

90

100

gree

[%]

Heterogeneous reaction with product layer formationDiffusion inproduct layer

(CaCO3)

0

10

20

3040

50

60

0 5 10 15 20 25 30 35 40

Time [min]

Car

boni

zatio

n de

g

CO2

CaO

CO2

CaCO3

10

Fast stage Slow stage

Reaction rate control Diffusion control

Application

CaO

The fast reaction period is the key for practical CO2 removal. This corresponds to filling of all the smaller pore spaces. Bench‐scale and other work has clearly established that the reaction is fast enough to be employed with a combustion system.

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Process Concept

CarbonationNew or Fuel Flue Gas

Heat

Vent

CaO (s) + CO2 (g) ↔ CaCO3 (s)

~ 600 ºCFluidized Bed

Calcination

900 ºC

Existing Combustor

CaCO3 CaO

SequesterFuel

Air 8% < CO2 < 15%

Heat

Vent

< 1 mol% CO2

Limestone

~ 900 ºCFluidized Bed

>90 mol% CO2Fuel

O2

Oxy-fuel CFBC

CO2 Looping Combustion

Strengths of the Technology

Low oxygen demand compared to oxy-fuel technologies (~1/3)Higher efficiency than low-temperature processes (e.g., amine – assuming adequate sorbent performance)Sulphur capture to low ppm levels inherent to process

CaO + SO2 + ½ O2 → CaSO4Long history of design and operation with air-blown fluid bed combustion allows rapid technology developmentrapid technology developmentOperating conditions are not extremeFluid bed combustion results in low NO production

CFBC, Vesuvius

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Challenges - Sulphation

45

50

55s

[mg]

Calcium aluminate pellet

25

30

35

40

0 50 100 150 200 250 300 350 400 450 500 550

Time [min]

Sam

ple

mas

s

behaviour. Conditions: sulphation/carbonation with 15% CO2, 3% O2, 0.5% SO2, and N2 balance for 30 min at 700°C; calcination under 100% N2 for 25 min at temperature 700‐950‐700°C.

Sulphation (CaO + SO2 + 1/2O2 = CaSO4)In the presence of SO2 some sorbent is chemically bound as CaSO4Product layer creates a shell around active CaO surfaceSolution: separate SO2 and CO2 capture

Ca Looping – for Gasification

Interestingly, CaS formation under gasification conditions, while it also reacts irreversibly, does not block carbonation, so it would be less difficult to use this cycle for gasification applicationsCaO (CaCO3) + H2S = CaS + H2O (+CO2)

CaS has a molar volume of 28.9 cm3/mol, CaSO4 of 46 cm3/molCaCO3 has molar volume of 37 cm3/mol, and CaO of 17 cm3/mol

Sun, P., Grace, J.R., Lim C.J. and Anthony, E.J., “Co-capture of H2S and CO2 in a Pressurized-Gasifier-Based Process”, Energy and Fuels 21, 836, 2007

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Limestone Performance in Looping Cycles Decays due to Sintering

The decay of CO2 carrying capacity with increasing calcination/carbonation 1.0

Emprical Model CurveCurran (1967)calcination/carbonation

cycles is a well known problem, shown in this figure – our TGA and CFBC results alongside data from other researchersSolution: improve sorbent

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

CO

2 Cap

acity

Curran (1967)Shimizu (1999)Silaban (1996)Barker (1973)Aihara (2001)HavelockCadominHavelock (Na2CO3, 4%)Havelock (NaCl, 0.5%)

15

Solution: improve sorbent performance or live with it Doping did not appear to work

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

Number of Cycles

Salvador, C., Lu, D., Anthony, E.J. and Abanades, J.C., “Enhancement of CaO for CO2 Capture in a FBC Environment”, Chemical Engineering Journal 96, 187, 2003

Alterations in Pore Structure

After initial calcination. After 30 carbonation/calcination cycles.

Grasa et al., ChemEng J 2008, 137, 561

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Slow carbonation stage

Fast carbonation stageg

Fast calcination stage ‐ going to completion

Sorbent Deactivation1st carbonation

a

1st carbonation

aSintering

b

30th carbonation

b

30th carbonation

2 μm2 μm 2 μm2 μmSorbent Decay

During calcination (CaCO3 → CaO)formation of CaO, having a pseudo‐lattice of calcium carbonate (rhombohedral)recrystallization to calcium oxide

Abanades, J., Alvarez, D., Energy & Fuels 17 (2003), 308‐315

recrystallization to calcium oxide lattice (face‐centred cubic)sintering to lower free energy lattice structure

Grasa, G.S., Abanades, J.C., Ind. Eng. Chem. Res. 2006, 45, 8846‐8851

∞

∞

++

−

= XkN

X

X N

11

1

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Steam Reactivation Appears to be a Promising Reactivation Method

Steam reactivation has been proposed for sorbent

70

80

90

100

ar ra

tio [%

] KR22, KR37 (0.075-0.150 mm)KR23, KR38 (0.300-0.425 mm)KR24, KR39 (0.600-0.750 mm)

for sorbent reactivation in FBCIt is clear that it also has a positive effect on carbonationA disadvantage is th t th t i l

0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40

Time [min]

Tota

l CO

2/C

aO m

ola

Before reactivation

After reactivation

19

that the materials become more fragile and more prone to attrition

Manovic, V. and Anthony, E.J., “Steam Reactivation of Spent CaO-based Sorbent for Multiple CO2 Capture Cycles”, Environmental Science and Technology 41, 1420, 2007.Sun, P., Grace, J.R., Lim, C.J. and Anthony, E.J. “Investigation of Attempts to Improve Cyclic CO2 Capture by Sorbent Hydration and Modifications”, Industrial and Engineering Chemistry Research 47, 2024, 2008.

Reactivation of Spent Material from a Looping Cycle Combustor

One result demonstrated by our 100

O i i l li tdemonstrated by our research is that material from a looping cycle combustor can be reactivated to provide near-quantitative sulphur capture 10

20

30

40

50

60

70

80

90

Sulp

hatio

n [%

]

Original limestoneCarbonator #4, spentHydrated, 15 minHydrated, 30 minHydrated, 60 min

20

sulphur captureThis would be advantageous for deep removal of SO2 from flue gases

00 20 40 60 80 100 120 140 160

Time [min]

Manovic, V. and Anthony, E.J., “SO2 Retention by Reactivated CaO-based Sorbent from Multiple CO2 Capture Cycles”, Environmental Science and Technology 41, 4435, 2007

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Experimental Equipment – TGA

Presence of SteamThe presence of steam increases the carbonation conversion by approximately 30% at the end of the 10th cycle in a study done by Symonds et al. at temperatures above 580ºCpIn a recent study on sulphation under oxy-fired conditions, evidence was advanced for the transient formation of Ca(OH)2, with an effect on carbonation (Wang et al., 2008)The addition of steam seems to result in the creation of larger porescreation of larger pores

Lu, D., Symonds, R., Macchi, A., Hughes, R., and Anthony, E.J., “CO2 Capture from Syngas viaCyclic Carbonation/Calcination for a Naturally Occurring Limestone (I): Modelling and Bench-Scale Tests”, Chemical Engineering Science, 64, 3536, 2009

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6

7

8

l%)

600

700

800

e (o C

)

Steam Addition

Symonds, R., Lu, D., Hughes,

The Effect of Steam

0

1

2

3

4

5

0 1000 2000 3000 4000

Time (s)

CO 2

Con

cent

ratio

n (v

ol

0

100

200

300

400

500

Ave

rage

Bed

Tem

pera

ture

Cut Steam

Symonds, R., Lu, D., Hughes, R., Anthony, E.J., and Macchi, A., “CO2 Capture from Simulated Syngas via Cyclic Carbonation/Calcination for a Naturally Occurring Limestone: Pilot Plant Testing”, I&ECR 48, 8431, 2009.

CO2 concentration and average bed temperature vs. time –Enhanced air calcination with SO2 addition – 8% CO2, balance air carbonation feed gas – 2nd cycle – Cadomin limestone.

Other Methods of Improving Sorbents – Self-reactivation

Recently we have shown that powdered materials in particular 100

N t t t 1000 CºCmaterials, in particular, can have their reactivity enhanced by deep sinteringHere are results for Kelly Rock (NS) samples (KR02) spent in 20 CO2 cycles in a tube

0102030405060708090

0 5 10 15 20 25 30Cycle Number

Car

bona

tion

[%]

No pretreatment 1000 oC800 oC 1100 oC900 oC 1200 oC

ºCºCºC

ºCºC

24

2 yfurnace, hydrated by steam and preheated for 24 h at different temperatures

y

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CaO-based Sorbent Pretreated in CO2 at High TemperatureSelf-reactivation also works with

607080

%]

Original limestone6h

larger particles –here are results for Kelly Rock limestone pretreated in CO2

t hi h

0102030405060

0 5 10 15 20 25 30 35 40 45Cycle Number

Car

bona

tion

[% 24h64h

25

at high temperature

Schematic Representation of Proposed Pore-Skeleton Model

Outward (soft) skeleton Inward (hard)

skeleton Pores Particle outer

surface area

A pore-skeleton model was initially proposed by Russian workers (Lysikov et al 2007)

-- Ion diffusion -- CO2 diffusion

(Lysikov et al., 2007)The model proposes that at temperatures above a 1000 ˚Cbelow 1200~1300˚C the sorbent morphology is not totally destroyed, but instead supports the development of a

Particle interior 2

-- Bulk mass transfer development of a softer external layer which permits increased carbonation

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We have also explained why our collaborator failed to see this phenomenonLa Blanca (Spanish 80 Original limestoneLa Blanca (Spanish limestone, 400-600 µm) pretreated in CO2 at 1000ºC.It can be seen that La Blanca fails to show improvements. There is no increase in activity and the

010203040506070

0 5 10 15 20 25 30 35 40 45Cycle Number

Car

bona

tion

[%]

Original limestone6h24h

27

ylevels are significantly below those for the original, untreated sample.High Na, low silica, low alumina were problematic

y

•.Manovic, V., Anthony, E.J. Abanades, C.J, and Grasa, G., “CO2 Looping Cycle Performance of a High-Purity Limestone after Thermal Activation/Doping", Energy and Fuels 22, 3258, 2008.

Influence of Na

20

30

40

50

60

Car

bona

tion

[%]

No doping 10%5%, No pretreatment 5%

2.5%

Conditions:TGAPretreated in N2 at 1000 ºC for 6 hIsothermal cycles at 800 °C

10

20

0 5 10 15 20 25 30Cycle Number

CCarbonation: 50% CO2, N2 bal.Calcination: 100% N2

SEM - Kelly Rock sorbent (original powder <50 µm) doped by 5% Na2CO3 powder – after 30 cycles

Na disrupts lattice resulting in mobile ions

Different application than sulphur capture:• sulphation is “1 cycle”• cumulative effect of sintering during CO2 cycles

Na addition not suitable for CaO looping for CO2 capture

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Influence of SiConditions:TGAPretreatment: 6 h at 1000ºC in 100% CO2calcination 850ºC in 100% N2carbonation at 850ºC in 100% CO2

20

30

40

50

60

70

80

Conv

ersi

on [%

]

Powdered L1 Powdered L22%, L1 2%, L1, pretreated5%, L1 5%, L1, pretreated2%, L2 2%, L2, pretreated5%, L2 5%, L2, pretreated

1.37% SiO2

SEM-EDX elemental analysis of surface area of Havelock limestone particle calcined at 950 ºC in 100% CO2

Pelletization with bentonite binder resulted in i d t hi h Si t t

Pellets (∼0.8 mm ) prepared from two Cadomin limestone samples (L1, L2) and Ca-bentonite (2%, 5%).

0

10

0 5 10 15 20 25 30 35Cycle

10.21% SiO2

poor conversion due to high Si content

Cause is enhanced sintering due to:• formation of CaO / SiO2 eutectic mixtures• low-melting point Ca-Si compounds

Influence of Al

25

30

35

40

45

50

Car

bona

tion

[%]

No doping10%5%2.5%

Conditions:TGAPretreatment. in N2 at 1100 ºC for 6 h

200 5 10 15 20 25 30

Cycle Number

Cycles isothermally at 800 °CCarbonation: 50% CO2, N2 balanceCalcination: 100% N2

SEM-EDX - Residue of powdered (<50 µm) La Blanca doped by 5% Al2O3 powder –after 30 cycles

Favorable influence of Al2O3

10 µm

• Increased activity – self-reactivation• Enhanced morphology• Noticed when synthetic sorbents were prepared

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Dual Fluidized Bed Pilot Facility – 75 kW

Dual-bed Experimental ConditionsTemperature:

Calcination @ 850-910°CCarbonation @ 500-700°CC @ 500 00 C

Gas stream: Calcination with air-blown combustion and oxy-fuel combustion: wood pellets, eastern bituminous coalCarbonation with gas mixture of 15% CO2 and 85% air

Sorbent:Limestone: Havelock, CadominSize: 0 4-1 0 mmSize: 0.4 1.0 mmBatch: 10-15 kg

Solid transfer rate:Max: 300 kg/hOperation: 30-60 kg/h

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Results from Pilot-scale System

20

24

s, %

CO2 level at inlet of carbonator

4

8

12

16

CO 2

Con

cent

ratio

n in

Offg

as

Capture

CO2 level at outlet of carbonator

0

4

3:00 PM 3:30 PM 4:00 PM 4:30 PM 5:00 PM 5:30 PM 6:00 PM

Running Time

C carbonator

CO2 Capture from Initial Cycles

95%

100%

80%

85%

90%

95%

CO2Ca

pture, %

70%

75%

40 50 60 70 80 90 100 110

Flue gas into the Carbonator, SLPM

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Pilot-scale Results

20

40

60

80

100

CO

2 C

once

ntra

tion,

%

offgas from CalcinerCarbonator

start oxy-fuel combustion

20

40

60

80

100

CO

2 C

once

ntra

tion,

%

offgas from CalcinerCarbonator

start oxy-fuel combustion

03:00 PM 3:30 PM 4:00 PM 4:30 PM 5:00 PM 5:30 PM 6:00 PM

Running Tim e

03:00 PM 3:30 PM 4:00 PM 4:30 PM 5:00 PM 5:30 PM 6:00 PM

Running Tim e

CanmetENERGY mini dual fluidized bed Ca looping facility

Effect of Temperature

CO2 Capture Pilot Plant

4

8

12

16

20

24

CO

2 Con

cent

ratio

n, %

100

200

300

400

500

600

700

800

900

1000

Tem

pera

ture

, °C

calciner temperature

carbonator temperature

offgas CO2 from carbonator

Optimized temperatures

03:30 PM 4:00 PM 4:30 PM 5:00 PM 5:30 PM 6:00 PM

Running Time

0

36

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In 2008/9, jointly demonstrated that thermal sintering was an effective method of enhancing reactivity – but does not resolve attrition

0.6

0.7

No thermal pre-treatment

6 h thermal pre treatment at 1100 deg C

0.1

0.2

0.3

0.4

0.5

Car

bona

tion

utili

zatio

n 6 h thermal pre-treatment at 1100 deg C

24 h thermal pre-treatment at 1100 deg C

00 200 400 600 800 1000 1200 1400

Number of calcination-carbonation cycles

Chen, Z., Song, H.S., Portillo, M., Lim, C.J., Grace, J.R. and Anthony, E.J., “Long-term Calcination/Carbonation Cycling and Thermal Pretreatment for CO2 Capture by Limestone and Dolomite”, Energy and Fuels 23, 1437, 2009

Attrition is a Problem80%

%

40%

60%

Fine

par

ticle

s in

cyc

lone

s, %

38

20%0 5 10 15 20 25 30

Number of cycles

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80%

100%tio

n

Attrition Resistance

20%

40%

60%

ive

unde

rsiz

e w

eigh

t fra

ct

Original limestone

Thermal pretreated for 6 h

1 impact after thermal pretreatment of 6 h

Thermal pretreated for 24 h

1 impact after thermal pretreatment of 24 h

0%0 200 400 600 800 1000 1200C

umul

ati

Particle size (μm)

39

Pelletization

.Sorbent is pulverized (<75 micron), combined with a binder, and then formed into a pellet of suitable size for FBC

Thermal treatment is necessary before injection into the FBCinto the FBC

Macropores improve mass transfer into particle

Spent sorbent can be re-activated and reused-recycled

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Pelletization Work – using Ca Aluminate Cements

Conventional binders enhance sintering, especially anything with K, Na or Si in it in significant amounts, but Al does not, g ,

Manovic, V. and Anthony, E.J., Screening of Binders for Pelletization of CaO-Based Sorbents for CO2 Capture”, E&F 23, 4797, 2009.

CO2 Capture Tests – Large # of Cycles

Porous sorbent structure with nano-sized pores/sub-grains stable along cycles is responsible for excellent CO2 capture

Pellets composed of hydrated lime and cement

Long-term CO2 carrying capacities of different sorbents during CO2 capture cycles. Conditions: isothermal at 800 ºC, carbonation in 50% CO2 (N2 balance) for 10 min, calcination in 100% N2 for 10 min.

High residual activity – 28%

Preliminary analyses showedthat sorbent costs could be<$10 sorbent/t CO2<$20/t avoided CO2

Manovic, V. and Anthony, E.J., “The Long-term Behavior of CaO-based Pellets Supported by Calcium Aluminate Cements in Long Series of CO2 Capture Cycles” I&ECR 48, 8906, 2009.

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Separate effects of high temperature and high CO2concentration during calcination steps on sorbent activity

Conditions: heating/cooling rate is 50ºC/min; carbonation for 10 min

Hydration and Extended Carbonation

Calcination/carbonation cycles of CD-CA-14 pellets enhanced by steam hydration. Calcination in 100% CO2 at 950 oC, carbonation in 20% CO2 (N2 balance) at 700 oC for 30 min, hydration after cycle 30, 120 and 143 in saturated steam at 100 oC for 5 min under atmospheric pressure, prolonged carbonation for 5 h in cycles 91, 241-6 and 301.

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60708090

100

n [%

]

A Perfect SO2 Sorbent?

The problemi i !

0102030405060

0 50 100 150 200 250 300 350 400Time [min]

Sulp

hatio

n

Limestone Hydrated lime

PP-CA-14 HP-CA-14

TGA sulphation of CD limestone – 1 mm pellets

is price!

TGA sulphation of CD limestone – 1 mm pelletsPrepared from CA-14, powdered CD limestone (PP-CA-14), and hydrated CD lime (HP-CA-14). 900˚C in synthetic flue gas

Manovic, V. and Anthony, E.J., “Sulphation Performance of CaO-based Pellets Supported by Calcium Aluminate Cements Designed for High-Temperature CO2 Capture”, accepted Energy & Fuels, ef-2009-00943h.R1.

Pilot Plants

Pilot plants are now operating at theUniversity of StuttgartUniversity of StuttgartSpanish Research Council

Or being brought into operation byThe University of Darmstadt

The largest and most important project is g p p jbeing developed under the FP 7 “CaOling”

2010-05-10

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30 kW twin CFB test facility at CSIC

Calciner CarbonatorT~ 900ºC T ~ 650ºC

Air + coal Flue gas

The 10 kWth IFK Calcium Looping DFB Facility

900 °C BFB R t

CaCO3 from cone valve

CO2 lean gas

600-700 °C CFB Carbonator with CaO/

CaCO3 bed height: 12.4 m, diameter: 70

mm

900 °C BFB Regeneratorheight: 3.2 m, diameter: 114 mm

CaCO3 CaO + CO2 ΔH = +178

CO2 rich gas suitable for storage

CaO + CO2 CaCO3 ΔH = -178 kJ/mol

10%-15% vol. CO2 in flue gas

CO2 ΔH +178 kJ/mol

C-fuel/ O2 & CO2

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CaOling Roadmap

Ca-based Looping Cycles: Conclusions• Dual-beds using limestone appear to be a workable high-

temperature in situ CO2 capture process

• CO capture decreases with increasing cycle numbers• CO2 capture decreases with increasing cycle numbers due to sorbent activity decay and particle attrition, but we believe the sorbent activity decay problem can be largely resolved

• Particle attrition is a major challenge, but again can be resolved

50

• Larger-scale pelletization runs are planned in the fall of 2010

• The first pilot plants are now coming on stream

2010-05-10

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Bibliography

Blamey, J., Anthony, E.J., Wang, J. and Fennell, P., “The Calcium Looping Cycle for Large-Scale CO2 Capture”, Progress in Energy and Combustion Science 36, 260-279, 2010.

THANK YOU FOR YOUR ATTENTIONTHANK YOU FOR YOUR ATTENTION.

QUESTIONS?

E-mail:[email protected] (Ben Anthony)

2010-05-10

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Coal to Electricity

•Order‐of‐Magnitude Economic Study•360 MWe Pressurized Fluid Bed Combustor•85% CO2 Capture

•Ca Looping Capture Cost: Cdn $23.70/tonne CO2

•MEA Capture Cost: Cdn $39‐$96/tonne CO2( f l )(range from 11 literature sources)

MacKenzie et al., Energy&Fuels 2007, 21, 920

Coal to ElectricityProcess COE, ¢/kWh η, % HHV

*Amine, subcritical 8.16 25.1

*Amine, supercritical 7.69 29.3

*Amine, ultra supercritical 7.34 34.1*Oxy-fuel 6.98 30.6

IGCC 6.51 31.2

Limestone (X = 0.1) 6.54 31.0

Dolomite (X = 0.14) 6.31 31.2

75CaO/25Ca12Al14O33 (X = 0.27) 6.35 32.8

Li et al., AIChEJ 2008, 54, 1912

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Coal to ElectricityUnits Existing

PlantOxy‐fuel Plant

Calcium Looping

Efficiency kWhe/kWh 43 32 35.6Efficiency kWhe/kWh 43 32 35.6

CO2 Capture % ‐‐‐ 95 86

CO2 Emission Factor kgCO2/kWhe 795 53 134

Cost of Electricity US$/kWhe 0.039 0.057 0.049

Avoided Cost US$/t CO2 ‐‐‐ 23.8 15.5

Abanades et al., EnvSciTech 2007,41,5523

CO2-based Looping Cycles

Generally such cycles can be written:Carbonation: MxO + CO2 = MxCO3 ExothermicCarbonation: MxO CO2 MxCO3 ExothermicRegeneration: MxCO3 = MxO + CO2 EndothermicAn obvious example of an element that could be used is Mg, in a cycle based on MgO/MgCO3, but the cheapest and most available material is CaOThere are also other reactions which might take advantage of the carbonation of CaO namely the

56

advantage of the carbonation of CaO, namely the reforming reaction:CH4 + 2H2O + CaO = 4H2 + CaCO3

Energy Systemsand TechnologyProf. Dr.-Ing. B. Epple

Petersenstrasse 3064287 Darmstadt / GermanyPhone: +49 6151 16 2191www.est.tu-darmstadt.de

TU Darmstadt

Chair for Energy Systems and Technology

CCS equipment

1


Carbonate Looping:„Post Combustion“

CarbonatorT=650°C

CalcinerT=900°C

Flue gas

Flue gas w/o CO2

CaCO3 T=650°C

CaO T=900°C

Coal

CO2

Air Reactor

1000°C

Fuel Reactor

950°CMe

MeO

O2, N2

N2 CO2, H2O

Chemical Looping:„Metalloxid-Oxyfuel “

O2

Fluidized bed based CCS Processes

Coal

2


Carbonate Looping Process

CaO

CaCO3

CO2 to compressionFluegas

minus CO2

Flue gas from power plant with CO2

Ashdeactivated lime

Make-up CaCO3

(limestone)

Oxygen

Coal

CARBONATOR650°C

CALCINER900°C

CO2 captureby CaO

CaO +CO2 CaCO3

Energy demand for O2 supply to calciner (~1/3 of an oxyfuel process) Carbonator: Capture of CO2 from flue gas by CaO Calciner: Release of CO2 (for subsequent storage)

CaCO3 CaO +CO2

3


EST – Test Rig Building

Dimensions:Cross Section: 14 m x 36 mHeight: 18 m

4


Brennkammer

Wärmetauscher

WassergekühltesSegment

Tisch und Wasserbad

Technische Daten Brennkammer

Verbrennung von Kohlenstaub, Biomasse und staubförmigen Ersatzbrennstoffen

0,75 mInnendurchmesser

1,3 mAußendurchmesser

7 mHöhe Brennraum (ohne Tisch)

1 MWThermische Leistung

Brenner

5


1 MW Brennkammer

Mitverbrennung von Staubförmiger Biomasse, Ersatzbrennstoffen

6


Carbonate Looping - Schema 1 MWth Technikumsanlage

FilterFilter

Filter Cyclone

Cyc

lone

Cal

cine

r

Car

bona

tor

Coa

l Com

bust

or

Heat Exchanger

Heat Exchanger

Air

Sta

ck

650°

C

900°

C

FD Fan Fan

ID Fan

Blower

ID Fan

Coal

Air

Ash

Flue gas

Flue gas

Fly ash

CaCO3

CaO

Option: Air

O2

CaCO3

Coal

CO2

Ash

CO2

Fly ash

Steam

CO2N2

Option

O2

7


CFB 600

Carbonate Looping: Used as CarbonatorChemical Looping: Used as Air Reactor

0.59 mInner diameter3 – 6 m/sGas velocity

1.3 mOuter diameter8 mHeightatmosphericOperating pressure650-1050°COperating temperature

Some data on CFB 600

The reactor is fully refractory lined.

8


CFB 400

Carbonate Looping: Used as CalcinerChemical Looping: Used as Fuel Reactor

0.4 mInner diameter3 – 6 m/sGas velocity

1.0 mOuter diameter11 mHeightatmosphericOperating pressure850-1000°COperating temperature

Some data on CFB 400

The reactor is fully refractory lined.

9


Interconnected fludized bedreactors

CFB 400

CFB 600

Flue gas heat exchanger CFB 600

Loop Seal CFB 600

Screw conveyor

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