3rd oxyfuel combustion conference ponferrada, … oxyfuel combustion conference ponferrada, spain...

3rd Oxyfuel Combustion Conference yPonferrada, SpainTechnical session 3c

Clarification of gasification behavior of gsolid fuel char prepared under CO atmosphereCO2 atmosphere

Tokyo Institute of Techonology

Kiyomi SHIMOMURA*Kiyomi SHIMOMURA , Hirotatsu WATANABE, Ken OKAZAKI

Energy Phenomena Laboratory

Today’s contents 2

Background Research purpose Experiment

– Sample and setup– Experiment condition

Result and Discussion– Pyrolysis experiment

h f– Char gasification experiment

Conclusion


Today’s contents 3





Conclusion


Background 4

CO2 ≈ 13%Air combustion

FuelH2OO2N2

N2

2Boiler

Air

FuelFlue gastreatment

O2/CO2 combustion

Flue gas composition

Boiler

ASUAir O2

FuelFlue gastreatment

N2H2OO2N

CO2

CO2 ≈ 95%2 2

ASU 2

Flue gas composition

N22

l li

※ASU : Air Separation Unit

Flue gas recycling（Mainly CO2 ） Easy to treat/handle CO2

(Eg. Carbon capture & Storage)


Research purpose 5

Because CO2 is highly concentrated in O2/CO2 combustion→ The pyrolysis process of solid fuel undergoes in CO2 atmosphere.py y p g 2 p

→ The mechanism of production of char in pyrolysis process is considered

to be different, which causes the difference of char property.to be different, which causes the difference of char property.Possible changes:• Reaction between CO2 and alkali metal

(Influence on catalytic effect of alkali metal[1])

• Increase of specific surface area[2](enhancement of gasification reaction)

R hInvestigate the influence of these properties on char gasification → Clarify the effect of CO2 in char

Research purpose

gasification

[2] Renu Kumar Rathnam et. al., Fuel Processing Technology,2009,6,797–802[1] McKee, D. W, Marcel Dekker, New York, 1981, 16, 1‐118


6





Conclusion


Sample & Setup 7

Table: proximate analysis &ash contents (ICP‐AES) flowmeter Reaction tube

Alkali lignin [wt%]

Volatile matters 46.4heater

sample

Volatile matters 46.4Fixed carbon 23.1

Water 11.8

CO2

Thermometric pointPt cell

Ash 18.2

Ash Na 55.0 thermobalancePressure meterAr

[mg/g] K 1.03

PC

Air compressor

Alkali lignin was employed to PC

Vacuum pump

Fig. Thermobalance

Alkali lignin was employed to extract the effect of alkali metal in CO2 environment


Experiment method （Pyrolysis) 8

Pyrolysis exp.Gas CO2 or ArGas flow rate 0 8 ℓ/minGas flow rate 0.8 ℓ/minHeating rate 1 K/sFinal temp. 700oCSample mass 40mg

The chars were analyzed by FT-IR, N2 BET analysis and SEM images to investigate the influence of CO2on char properties.


9Experiment method (Char gasification)

Pyrolysis GasificationGas CO2 or Ar AirSwitching

CO2 or Ar AirGas flow rate 0.8 ℓ/min 0.8 ℓ/minHeating rate 1 K/s -

Final temp 700oC 700oC, 750oC,800oC, 850oC, 900oC, 950oC, Final temp. 700oC , , , , , ,1100oC,1150oC, 1200oC

pyrolysisswithcing

gasification

i

X

Wdt/dWdt/dX

＝gasification rate600700800900

25.00

30.00

35.00

[mg]

Temperat

35

30

25

20X：Char conversion ratio W：Weight

gasification rate

200300400500

5 00

10.00

15.00

20.00

Wei

ght

ture [ oC]

20

15

10

5 char

0100

0.00

5.00

0 500 1000Time [sec]

5

0Pyrolysis (700oC) and Gasification (900oC)

Arrhenius plot (X=0.5)


10





Conclusion


11Result and Discussion (Pyrolysis)

Reaction between CO2 and alkali metal

FT‐IR1450 cm-1 880 cm-1

lignin‐char‐CO2 = lignin char made in CO2

lignin‐char‐Ar = lignin char made in Ar

u.] Wavelength of 1450cm‐1 and 880cm‐1

are assigned to the peaks for carbonate

Na2CO3

tens

ity [a

.u are assigned to the peaks for carbonate ion[1].

Carbonate was formed in lignin char

500100015002000

Int g

which was prepared in CO2atmosphere. This result matches with our previous research[3].

Wavelength [cm-1]

[3] Watanabe, H. et al., Proceedings of the Combustion Institute, 2013, 34, 2339‐2345

with our previous research .

[1] McKee, D. W, Marcel Dekker, New York, 1981, 16, 1‐118


12Result and Discussion (Pyrolysis)

Surface area of char

SEM 10μm

Specific surface area [m2/g]

N2 BET analysis

Specific surface area [m2/g]lignin‐char‐CO2 392lignin‐char‐Ar 0 73

Lignin‐char‐CO2 Lignin‐char‐Ar

lignin char Ar 0.73

Drastic development of pores in lignin-char-CO2 is considered to be2

The char prepared in CO2 atmosphere has more porous surface

lignin char CO2 is considered to be caused by char-CO2 reaction.

The char prepared in CO2 atmosphere has more porous surface and larger surface area than that prepared in Ar atmosphere


13





Conclusion


14Result and Discussion (Char gasification)

lignin-char-CO2 = lignin char made in CO2

lignin-char-Ar = lignin char made in ArGasification rate of lignin char

lignin char Ar lignin char made in Ar

5 5Zone II Zone I Zone I = Kinetic controlled

i-5.5

.5 [s

-1]

↑

regionZone II = Internal diffusion

controlled region

-6.5

ndX

/dt x

=0

▲lignin‐char‐CO2

↑950oC

↑1200oC

700oC↓ i

X

Wdt/dWdt/dX

-7.5 6 7 8 9 10 11

ln ▲lignin char CO2×lignin‐char‐Ar

X：char conversion ratio W：Weight

＝gasification rate

6 7 8 9 10 11104/T [K-1]

Fig. Arrhenius plot of ligninchar gasification in air environment

ratio W：Weight







i-5.5

.5 [s

-1]

↑


controlled region

-6.5

ndX

/dt x

=0


↑950oC

↑1200oC

700oC↓ i

X

Wdt/dWdt/dX

-7.5 6 7 8 9 10 11




6 7 8 9 10 11104/T [K-1]


ratio W：Weight


Result and Discussion (Char gasification) 16

Zone I (Kinetic controlled region):

A h l

600

800

40

50

] o C]

Pyrolysis GasificationAt the temperature lower than 750oC, lignin char prepared in CO2 (lignin‐char CO ) didn’t gasify

400

600

20

30

eigh

t [m

g]

pera

ture

[lignin-char -CO2char‐CO2) didn t gasify, while the lignin char prepared in Ar (lignin‐char‐Ar) gasified.

Carbonate formation in ligin char prepared in

20010

20

We

Tem

p

lignin-char-Ar

Ar) gasified.

ligin char prepared in CO2 inhibited char gasification at lower

( 750oC)

00750 1250 1750 2250

Time [s]temperature (<750oC).Gasification reaction at 700oC


Result and Discussion (Char gasification) 17

Zone I (Kinetic controlled region):How the carbonate inhibit gasification reaction?g• P. J. van Eyk et al.[4] reported that Na works as a catalyst by repeating the following redox reaction.

(‐CNa)+1/2O2 → (‐CONa) ・・・・oxidation(‐CONa)+C → (‐CNa) +CO ・・・・reduction

• (‐CNa) plays important role in char gasification reaction.

• In pyrolysis in CO2 environment, it can be assumed that Na py y 2 ,reacts with CO2 to form Na2CO3 so that Na cannot act as the specie which can contribute to the catalytic reaction shown above especially at lower temperatureabove, especially at lower temperature.

[4] van Eyk, P. J. et al., Combustion and Flame, 2011, 158, 2512‐2523







i-5.5

.5 [s

-1]

↑


controlled region

-6.5

ndX

/dt x

=0


↑950oC

↑1200oC

700oC↓ i

X

Wdt/dWdt/dX

-7.5 6 7 8 9 10 11




6 7 8 9 10 11104/T [K-1]


ratio W：Weight



Zone II (Internal diffusion controlled region):Lignin char made in CO had higher gasification rate than that of char‐ Lignin char made in CO2 had higher gasification rate than that of char

made in Ar.SEM 10μm

During pyrolysis in CO2, both micro and macro pores of char developed more drastically

ligninchar CO ligninchar Ar

developed more drastically. → It makes gasification agents to diffuse more easily.

ligninchar‐CO2 ligninchar‐Ar

More porous morphology and larger specific surface area of char made in CO2 enhanced gas transport leading to increase of gasification rate.


20





Conclusion


21Conclusion

Properties of lignin char in CO2:– The lignin char prepared in CO2 environment contained carbonateThe lignin char prepared in CO2 environment contained carbonate and it had more porous surface and larger specific surface area.

Char gasification behavior of lignin char:– Zone I (Kinetic controlled region):

Carbonate formation inhibited char gasification, by changing Na form in charform in char.

– Zone II (Internal diffusion controlled region): More porous morphology and larger specific surface area of char p p gy g pdue to char‐CO2 gasification enhanced gas transport leading to increase of gasification rate.

CO2 in pyrolysis of lignin plays different roles in char gasification process, according to the rate limiting factors.


Thank you for your kind attention


Characteristics of lignin


Lignin (proximate & ultimate analysis) 24/14

lignin [wt%]

Ultimate analysislignin [wt%]

Proximate analysis

g [ ]C 46.5H 4.49

g [ ]Volatile matters 46.4Fixed carbon 23.1

W 11 8N 0.08S 2.51

Water 11.8Ash 18.2

O 28.19Ash 18.2

Ash composition of lignin [mg/g] (ICP-AES)Lignin Ion-exchanged ligninLignin Ion exchanged lignin

N a 55.0 10.5K 1.03 0.25


P l i i tPyrolysis experiment


26Result (Pyrolysis)

FTIR analysis1440 cm-1 880 1

Pyrolysis of lignin (biomass)

Weight 10%UP

1440 cm 1 880 cm-1

.u.]

tens

ity [a

.In

t

300 430 600 800T t [oC] 500100015002000

Wavelength [cm-1]

Li i h d i COligninchar-CO2 = lignin char made in CO2

Temperature [oC]

Lignin‐char prepared in CO2contains carbonateNa2CO3

ligninchar-Ar = lignin char made in Ar


実験結果：ligninチャー 27C123 東工大下村聖実

FTIRl CO l AN COli i CO li i A

1440 cm-1 880 cm-1coal-CO2 coal-ArNa2CO3lignin-CO2 lignin-Ar

1440 cm-1 880 cm-1

ity [a

.u.]

sity

[a.u

.]

Inte

nsi

Inte

ns

500100015002000Wavelength [cm-1]

500100015002000Wavelength [cm-1]

[3] Watanabe, H. et al., Proceedings of the Combustion Institute 2012

lignin Coal


G ifi ti i tGasification experiment

Energy Phenomena LaboratoryExperiment method（Gasification） 29（Gasification）

Pyrolysis

Keep @ 700oCfor 3min.

GasificationPyrolysisCO2 or Ar

@ 1K/s to 700oC Switching gas

GasificationAir

700oC – 1200oC

Experiment condition

Switching gasCO2 or Ar→ Air

Pyrolysis GasificationGas CO2 or Ar AirSwitching

Experiment condition

Gas flow rate 0.8 ℓ/min 0.8 ℓ/minHeating rate 1 K/s -

700oC 750oC 800oC 850oC 900oCFinal temp. 700oC 700 C, 750 C,800 C, 850 C, 900 C, 950oC, 1100oC,1150oC, 1200oC

Sample mass 40mg -


Result: Gasification profile 30

lignin 700oC(CO2) → 900oC（Air）

dWWdt/dW .X.X

X1010

pyrolysis

swithcinggasification

i

X

Wdt/dWdt/dX

dtX

700800900

30.00

35.00

g]

Temp

35

30

25 i


＝gasification rate400500600

15.00

20.00

25.00

eigh

t [m

g erature [ o

Wi

25

20

15

At each temperature,

ratio W：Weight

100200300

5.00

10.00 We oC

]10

5

0 gasification rate at X=0.5 was compared.

00.00 0 500 1000

Time [sec]

0


Ad d di iAdvanced discussion


Why carbonate inhibit gasification 32/14

The key reaction for Na to work as a catalyst in char gasification[4](‐CNa)+1/2O2 → (‐CONa) ・・・・oxidation( CNa) 1/2O2 → ( CONa) oxidation(‐CONa)+C → (‐CNa) +CO ・・・・reduction

When Na CO was formed in the pyrolysis process in CO

Pyrolysis Gasification

When Na2CO3 was formed in the pyrolysis process in CO2atmosphere, the Na loose chance to act as a catalyst

Ar ‐CNa(‐CNa) + 1/2O2 → (‐CONa) (‐CONa) + C → (‐CNa) + CO

y y

CO N CO

‐COONa

CO2 ‐Na2CO3

[4] van Eyk, P. J. et al., Combustion and Flame, 2011, 158, 2512‐2523


Discussion 33

Zone IIt has already revealed that carbonate (mainly Na2CO3) is formed in the lignin char

Lignincha

It has already revealed that carbonate (mainly Na2CO3) is formed in the lignin char made in CO2 (Ligninchar-CO2).

Lignin gr

Na2CO3,…

gR-COONa

NaCl, NaOH, …CO2

, ,

Different formations of Na seems to have different effects on gasification at gtemperature lower than 750oC.→ Analyze the formation of Na

GOAL:To clarify the order of activeness as catalyst of gasification at lower temperature(-750oC) with respect to the formation of Na.

s8

s8 これを、図式化したほうがよかった。触媒の活性度を、グラフみたいにして、NaCl > Na2CO2 > NaOHとかみたいに。shimomura, 18/06/2013


B k dBackground


CO2 separatation cost and energy 35/13

cost$55/tonne of CO2

$35/tonne of CO2

O2/CO2 Air

O2/CO2 Air (by chemical absorption）

O2/CO2 AirASU Power [MWe] 86 -CO2 Separation Unit Power [MWe] 53 40H t d t [MW ] 340

energy

D. Singh et al. / Energy Conversion and Management 44 (2003) 3073-3091

Heat duty [MWth] - 340Cooling duty [MWth] 142 430


Background：CCS 36

CCS: Carbon Capture and Storage

C t

Capture Storage Transport Compress

Storage

Compress

Capture

TransportStorage

PowerPower Plant

CompressCO2 CO2


Objective 37

O f l C b ti

How the enriched CO2 affects oxyfuel combustion?

(C li t d t l )Oxyfuel Combustion

Pyrolysis

(Complicated to analyze)

Pyrolysis Emission of volatiles and formation of char Very important step, which also affects the following steps in combustion The effect of CO in pyrolysis process of oxyfuel combustion is still unknown

Gasification

The effect of CO2 in pyrolysis process of oxyfuel combustion is still unknown

The char formed in pyrolysis process is gasified Gasification behavior of char strongly dependent on char property

Objective:Objective: To clarify the effect of CO2 in pyrolysis process by investigating char property and char gasification behavior


Background 38

Pyrolysis：1000~1700

JCOAL:http://www.jcoal.or.jp/cshandbook/dlfiles/c3‐4.pdf

Combustion phenomenon of coal particle

Pyrolysis：‐Emission of volatile mattersF ti f h

flame

volatiles Air

End of emission of volatiles

‐ Formation of char

Ignition

ture

volatilesCombustion of char

e tempe

rat

fly ash

Gasification：

Particle

Rapid increase of particle temperature

Gasification：Gasification of char by gasifying agents (O2 ,CO2)

Air+coal

pulverized coal

Distance from burner


Background 39

Pyrolysis：1000~1700

Combustion phenomenon of coal particle O2/CO2 combustionPyrolysis：

‐Emission of volatile mattersF ti f h

flame

volatiles Air

End of emission of volatiles

‐ Formation of char

Ignition

ture

volatilesCombustion of char

CO2

e tempe

rat

fly ash

Gasification：

CO2

2

CO2

Particle

Rapid increase of particle temperature

Gasification：Gasification of char by gasifying agents (O2 ,CO2)

Air+coal

2

pulverized coal

Distance from burner

3rd oxyfuel combustion conference ponferrada, … oxyfuel combustion conference ponferrada, spain...

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